LTC6804-1/LTC6804-2
Multicell Battery Monitors
Features
Description
Measures Up to 12 Battery Cells in Series
nn Stackable Architecture Supports 100s of Cells
nn Built-In isoSPI™ Interface:
1Mbps Isolated Serial Communications
Uses a Single Twisted Pair, Up to 100 Meters
Low EMI Susceptibility and Emissions
nn 1.2mV Maximum Total Measurement Error
nn 290µs to Measure All Cells in a System
nn Synchronized Voltage and Current Measurement
nn 16-Bit Delta-Sigma ADC with Frequency Programmable 3rd Order Noise Filter
nn Engineered for ISO26262 Compliant Systems
nn Passive Cell Balancing with Programmable Timer
nn 5 General Purpose Digital I/O or Analog Inputs:
Temperature or other Sensor Inputs
Configurable as an I2C or SPI Master
nn 4μA Sleep Mode Supply Current
nn 48-Lead SSOP Package
The LTC®6804 is a 3rd generation multicell battery stack
monitor that measures up to 12 series connected battery
cells with a total measurement error of less than 1.2mV. The
cell measurement range of 0V to 5V makes the LTC6804
suitable for most battery chemistries. All 12 cell voltages
can be captured in 290µs, and lower data acquisition rates
can be selected for high noise reduction.
nn
Multiple LTC6804 devices can be connected in series,
permitting simultaneous cell monitoring of long, high voltage battery strings. Each LTC6804 has an isoSPI interface
for high speed, RF-immune, local area communications.
Using the LTC6804-1, multiple devices are connected in
a daisy-chain with one host processor connection for all
devices. Using the LTC6804-2, multiple devices are connected in parallel to the host processor, with each device
individually addressed.
Additional features include passive balancing for each cell,
an onboard 5V regulator, and 5 general purpose I/O lines.
In sleep mode, current consumption is reduced to 4µA.
The LTC6804 can be powered directly from the battery,
or from an isolated supply.
Applications
Electric and Hybrid Electric Vehicles
Backup Battery Systems
nn Grid Energy Storage
nn High Power Portable Equipment
nn
nn
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered and isoSPI is a
trademark of Linear Technology Corporation. All other trademarks are the property of their
respective owners. Protected by U.S. patents, including 8908799, 9182428, 9270133.
Typical Application
+
2.0
1.5
IMA
+
+
•
•
IPB
LTC6804-1
IMB
IPA
IMA
+
IPB
LTC6804-1
IMB
IPA
CELL VOLTAGE = 3.3V
5 TYPICAL UNITS
1.0
0.5
0
–0.5
–1.0
–1.5
•
•
MPU
SPI
•
•
+
MEASUREMENT ERROR (mV)
12S1P
Total Measurement Error
vs Temperature of 5 Typical Units
IPB
LTC6804-1
IMB
ILP
IPA
•
•
+
–2.0
–50 –25
75
50
25
TEMPERATURE (°C)
0
100
125
680412 TA01b
IP
LTC6820
IMA
IM
680412 TA01a
For more information www.linear.com/LTC6804-1
680412fc
1
LTC6804-1/LTC6804-2
Table of Contents
Features...................................................... 1
Applications................................................. 1
Typical Application ......................................... 1
Description.................................................. 1
Absolute Maximum Ratings............................... 3
Pin Configuration........................................... 3
Order Information........................................... 4
Electrical Characteristics.................................. 4
Pin Functions............................................... 17
Block Diagram.............................................. 18
Operation................................................... 20
State Diagram..........................................................20
LTC6804 Core State Descriptions............................20
isoSPI State Descriptions........................................ 21
Power Consumption................................................ 21
ADC Operation......................................................... 21
Data Acquisition System Diagnostics......................26
Watchdog and Software Discharge Timer...............30
I2C/SPI Master on LTC6804 Using GPIOS............... 31
Serial Interface Overview.........................................35
4-Wire Serial Peripheral Interface (SPI)
Physical Layer.........................................................36
2-Wire Isolated Interface (isoSPI) Physical Layer....36
2
Data Link Layer........................................................44
Network Layer.........................................................44
Programming Examples..........................................54
Simple Linear Regulator..........................................58
Improved Regulator Power Efficiency......................58
Fully Isolated Power................................................. 59
Reading External Temperature Probes..................... 59
Expanding the Number of Auxiliary
Measurements.........................................................60
Internal Protection Features.....................................60
Filtering of Cell and GPIO Inputs..............................60
Cell Balancing with Internal Mosfets........................62
Cell Balancing with External MOSFETS................... 62
Discharge Control During Cell Measurements.........62
Power Dissipation and Thermal Shutdown..............63
Method to Verify Balancing Circuitry.......................63
Current Measurement with a Hall Effect Sensor......66
Current Measurement with a Shunt Resistor...........66
Using the LTC6804 with Less Than 12 Cells............ 67
Package Description...................................... 76
Revision History........................................... 77
Typical Application........................................ 78
Related Parts............................................... 78
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Absolute Maximum Ratings
(Note 1)
Total Supply Voltage V+ to V–.....................................75V
Input Voltage (Relative to V–)
C0.......................................................... –0.3V to 0.3V
C12......................................................... –0.3V to 75V
C(n)......................................–0.3V to MIN (8 • n, 75V)
S(n)......................................–0.3V to MIN (8 • n, 75V)
IPA, IMA, IPB, IMB .....................–0.3V to VREG + 0.3V
DRIVE Pin................................................. –0.3V to 7V
All Other Pins............................................ –0.3V to 6V
Voltage Between Inputs
V+ to C12.............................................................–5.5V
C(n) to C(n – 1)......................................... –0.3V to 8V
S(n) to C(n – 1)......................................... –0.3V to 8V
C12 to C8................................................ –0.3V to 25V
C8 to C4.................................................. –0.3V to 25V
C4 to C0.................................................. –0.3V to 25V
Current In/Out of Pins
All Pins Except VREG, IPA, IMA, IPB, IMB, S(n)...10mA
IPA, IMA, IPB, IMB..............................................30mA
Operating Temperature Range
LTC6804I..............................................–40°C to 85°C
LTC6804H........................................... –40°C to 125°C
Specified Temperature Range
LTC6804I..............................................–40°C to 85°C
LTC6804H........................................... –40°C to 125°C
Junction Temperature............................................ 150°C
Storage Temperature.............................. –65°C to 150°C
Lead Temperature (Soldering, 10sec).................... 300°C
Pin Configuration
LTC6804-1
LTC6804-2
TOP VIEW
V+
1
C12
2
S12
TOP VIEW
48 IPB
V+
1
48 A3
47 IMB
C12
2
47 A2
3
46 ICMP
S12
3
46 A1
C11
4
45 IBIAS
C11
4
45 A0
S11
5
44 SDO (NC)*
S11
5
44 SDO (IBIAS)*
C10
6
43 SDI (NC)*
C10
6
43 SDI (ICMP)*
S10
7
42 SCK (IPA)*
S10
7
42 SCK (IPA)*
C9
8
41 CSB (IMA)*
C9
8
41 CSB (IMA)*
S9
9
40 ISOMD
S9
9
40 ISOMD
C8 10
39 WDT
C8 10
39 WDT
S8 11
38 DRIVE
S8 11
38 DRIVE
C7 12
37 VREG
C7 12
37 VREG
S7 13
36 SWTEN
S7 13
36 SWTEN
C6 14
35 VREF1
C6 14
35 VREF1
S6 15
34 VREF2
S6 15
34 VREF2
C5 16
33 GPIO5
C5 16
33 GPIO5
S5 17
32 GPIO4
S5 17
32 GPIO4
C4 18
31 V–
C4 18
31 V–
S4 19
30 V–**
29 GPIO3
S4 19
30
V–**
C3 20
29 GPIO3
C3 20
S3 21
28 GPIO2
S3 21
28 GPIO2
C2 22
27 GPIO1
C2 22
27 GPIO1
S2 23
26 C0
S2 23
26 C0
C1 24
25 S1
C1 24
25 S1
G PACKAGE
48-LEAD PLASTIC SSOP
G PACKAGE
48-LEAD PLASTIC SSOP
TJMAX = 150°C, θJA = 55°C/W
*THE FUNCTION OF THESE PINS DEPENDS ON THE CONNECTION OF ISOMD
ISOMD TIED TO V–: CSB, SCK, SDI, SDO
ISOMD TIED TO VREG: IMA, IPA, NC, NC
**THIS PIN MUST BE CONNECTED TO V–
TJMAX = 150°C, θJA = 55°C/W
*THE FUNCTION OF THESE PINS DEPENDS ON THE CONNECTION OF ISOMD
ISOMD TIED TO V–: CSB, SCK, SDI, SDO
ISOMD TIED TO VREG: IMA, IPA, ICMP, IBIAS
**THIS PIN MUST BE CONNECTED TO V–
680412fc
For more information www.linear.com/LTC6804-1
3
LTC6804-1/LTC6804-2
Order Information
http://www.linear.com/product/LTC6804-1#orderinfo
TUBE
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
SPECIFIED TEMPERATURE RANGE
LTC6804IG-1#PBF
LTC6804IG-1#TRPBF
LTC6804G-1
48-Lead Plastic SSOP
–40°C to 85°C
LTC6804HG-1#PBF
LTC6804HG-1#TRPBF
LTC6804G-1
48-Lead Plastic SSOP
–40°C to 125°C
LTC6804IG-2#PBF
LTC6804IG-2#TRPBF
LTC6804G-2
48-Lead Plastic SSOP
–40°C to 85°C
LTC6804HG-2#PBF
LTC6804HG-2#TRPBF
LTC6804G-2
48-Lead Plastic SSOP
–40°C to 125°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Parts ending with PBF are RoHS and WEEE compliant.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/. Some packages are available in 500 unit reels through
designated sales channels with #TRMPBF suffix.
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. The test conditions are V+ = 39.6V, VREG = 5.0V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
ADC DC Specifications
Measurement Resolution
ADC Offset Voltage
(Note 2)
ADC Gain Error
(Note 2)
Total Measurement Error (TME) in
Normal Mode
l
0.1
mV/bit
l
0.1
mV
l
0.01
0.02
%
%
C(n) to C(n – 1), GPIO(n) to V– = 0
±0.2
C(n) to C(n – 1) = 2.0
±0.1
C(n) to C(n – 1), GPIO(n) to V– = 2.0
l
C(n) to C(n – 1) = 3.3
C(n) to C(n – 1), GPIO(n) to V– = 3.3
±0.2
l
C(n) to C(n – 1) = 4.2
C(n) to C(n – 1), GPIO(n) to V– = 4.2
±0.3
l
C(n) to C(n – 1), GPIO(n) to V– = 5.0
Sum of Cells, V(CO) = V–
mV
±1.4
mV
±1.2
mV
±2.2
mV
±1.6
mV
±2.8
mV
±1
l
Internal Temperature, T = Maximum
Specified Temperature
4
mV
±0.8
±0.2
mV
±0.75
±5
%
°C
VREG Pin
l
±0.1
±0.25
%
VREF2 Pin
l
±0.02
±0.1
%
Digital Supply Voltage VREGD
l
±0.1
±1
%
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. The test conditions are V+ = 39.6V, VREG = 5.0V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
Total Measurement Error (TME) in
Filtered Mode
C(n) to C(n – 1), GPIO(n) to V– = 0
MIN
±0.1
l
C(n) to C(n – 1) = 3.3
C(n) to C(n – 1), GPIO(n) to V– = 3.3
±0.2
l
C(n) to C(n – 1) = 4.2
C(n) to C(n – 1), GPIO(n) to V– = 4.2
±0.3
l
C(n) to C(n – 1), GPIO(n) to V– = 5.0
Sum of Cells, V(CO) = V–
±0.2
l
mV
±1.4
mV
±1.2
mV
±2.2
mV
±1.6
mV
±2.8
mV
mV
±0.75
%
°C
VREG Pin
l
±0.1
±0.25
%
VREF2 Pin
l
±0.02
±0.1
%
Digital Supply Voltage VREGD
l
±0.1
±1
C(n) to C(n – 1), GPIO(n) to V– = 0
±2
%
mV
C(n) to C(n – 1), GPIO(n) to V– = 2.0
l
±4
mV
C(n) to C(n – 1), GPIO(n) to V– = 3.3
l
±4.7
mV
C(n) to C(n – 1), GPIO(n) to V– = 4.2
l
±8.3
mV
Sum of Cells, V(CO) = V–
±10
±0.3
l
Internal Temperature, T = Maximum
Specified Temperature
IL
±0.8
±5
C(n) to C(n – 1), GPIO(n) to V– = 5.0
Input Range
UNITS
mV
±1
Internal Temperature, T = Maximum
Specified Temperature
Total Measurement Error (TME) in
Fast Mode
MAX
±0.1
C(n) to C(n – 1) = 2.0
C(n) to C(n – 1), GPIO(n) to V– = 2.0
TYP
mV
±1
±5
%
°C
VREG Pin
l
±0.3
±1
%
VREF2 Pin
l
±0.1
±0.25
%
Digital Supply Voltage VREGD
l
±0.2
±2
%
C(n), n = 1 to 12
l C(n – 1)
C(n – 1) + 5
V
5
V
0
C0
l
GPIO(n), n = 1 to 5
l
Input Leakage Current When Inputs C(n), n = 0 to 12
Are Not Being Measured
GPIO(n), n = 1 to 5
l
10
±250
nA
l
10
±250
nA
Input Current When Inputs Are
Being Measured
0
C(n), n = 0 to 12
±2
GPIO(n), n = 1 to 5
Input Current During Open Wire
Detection
µA
±2
l
70
100
µA
130
µA
680412fc
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5
LTC6804-1/LTC6804-2
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. The test conditions are V+ = 39.6V, VREG = 5.0V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
3.1
3.2
3.3
UNITS
Voltage Reference Specifications
VREF1
VREF2
1st Reference Voltage
VREF1 Pin, No Load
1st Reference Voltage TC
VREF1 Pin, No Load
3
ppm/°C
1st Reference Voltage Hysteresis
VREF1 Pin, No Load
20
ppm
1st Reference Long Term Drift
VREF1 Pin, No Load
2nd Reference Voltage
VREF2 Pin, No Load
VREF2
l
20
Pin, 5k Load to V–
l
2.990
l
2.988
V
ppm/√kHr
3
3.010
3
3.012
V
V
2nd Reference Voltage TC
VREF2 Pin, No Load
10
ppm/°C
2nd Reference Voltage Hysteresis
VREF2 Pin, No Load
100
ppm
2nd Reference Long Term Drift
VREF2 Pin, No Load
60
ppm/√kHr
General DC Specifications
IVP
V+ Supply Current
(See Figure 1: LTC6804 Operation
State Diagram)
State: Core = SLEEP, isoSPI = IDLE
VREG = 0V
3.8
6
µA
VREG = 0V l
3.8
10
µA
VREG = 5V
1.6
3
µA
VREG = 5V l
1.6
5
µA
18
32
50
µA
l
10
32
60
µA
0.4
0.55
0.7
mA
l
0.375
0.55
0.725
mA
VREG = 5V
2.2
4
µA
VREG = 5V l
2.2
6
µA
35
60
µA
State: Core = STANDBY
State: Core = REFUP or MEASURE
IREG(CORE)
VREG Supply Current
(See Figure 1: LTC6804 Operation
State diagram)
State: Core = SLEEP, isoSPI = IDLE
State: Core = STANDBY
10
6
35
65
µA
0.2
0.45
0.7
mA
0.15
0.45
0.75
mA
10.8
11.5
12.2
mA
l
10.7
11.5
12.3
mA
l
State: Core = REFUP
l
State: Core = MEASURE
IREG(isoSPI)
Additional VREG Supply Current if
isoSPI in READY/ACTIVE States
Note: ACTIVE State Current
Assumes tCLK = 1µs, (Note 3)
LTC6804-2: ISOMD = 1,
RB1 + RB2 = 2k
LTC6804-1: ISOMD = 0,
RB1 + RB2 = 2k
LTC6804-1: ISOMD = 1,
RB1 + RB2 = 2k
LTC6804-2: ISOMD = 1,
RB1 + RB2 = 20k
6
READY
l
3.9
4.8
5.8
mA
ACTIVE
l
5.1
6.1
7.3
mA
READY
l
3.7
4.6
5.6
mA
ACTIVE
l
5.7
6.8
8.1
mA
READY
l
6.5
7.8
9.5
mA
ACTIVE
l
10.2
11.3
13.3
mA
READY
l
1.3
2.1
3
mA
ACTIVE
l
1.6
2.5
3.5
mA
LTC6804-1: ISOMD = 0,
RB1 + RB2 = 20k
READY
l
1.1
1.9
2.8
mA
ACTIVE
l
1.5
2.3
3.3
mA
LTC6804-1: ISOMD = 1,
RB1 + RB2 = 20k
READY
l
2.1
3.3
4.9
mA
ACTIVE
l
2.7
4.1
5.8
mA
680412fc
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LTC6804-1/LTC6804-2
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. The test conditions are V+ = 39.6V, VREG = 5.0V unless otherwise noted.
SYMBOL
VREG
PARAMETER
CONDITIONS
V+ Supply Voltage
TME Specifications Met (Note 6)
VREG Supply Voltage
TME Supply Rejection < 1mV/V
DRIVE output voltage
Sourcing 1µA
Sourcing 500µA
VREGD
Digital Supply Voltage
Discharge Switch ON Resistance
VCELL = 3.6V
MIN
TYP
MAX
l
11
40
55
V
l
4.5
5
5.5
V
l
5.4
5.2
5.6
5.6
5.8
6.0
V
V
l
5.1
5.6
6.1
V
l
2.7
3.0
3.6
V
10
25
l
Thermal Shutdown Temperature
150
UNITS
Ω
°C
VOL(WDT)
Watchdog Timer Pin Low
WDT Pin Sinking 4mA
l
0.4
V
VOL(GPIO)
General Purpose I/O Pin Low
GPIO Pin Sinking 4mA (Used as Digital Output)
l
0.4
V
Measure 12 Cells
l
2120
2335
2480
µs
Measure 2 Cells
l
365
405
430
µs
Measure 12 Cells and 2 GPIO Inputs
l
2845
3133
3325
µs
Measurement + Calibration Cycle
Time When Starting from the
REFUP State in Filtered Mode
Measure 12 Cells
l
183
201.3
213.5
ms
Measure 2 Cells
l
30.54
33.6
35.64
ms
Measure 12 Cells and 2 GPIO Inputs
l
244
268.4
284.7
ms
Measurement + Calibration Cycle
Time When Starting from the
REFUP State in Fast Mode
Measure 12 Cells
l
1010
1113
1185
µs
Measure 2 Cells
l
180
201
215
µs
Measure 12 Cells and 2 GPIO Inputs
l
1420
1564
1660
µs
Skew Time. The Time Difference
between C12 and GPIO2
Measurements, Command =
ADCVAX
Fast Mode
l
189
208
221
µs
Normal Mode
l
493
543
576
µs
Skew Time. The Time
Difference between C12 and C0
Measurements, Command = ADCV
Fast Mode
l
211
233
248
µs
Normal Mode
l
609
670
711
µs
100
300
µs
ADC Timing Specifications
tCYCLE
(Figure 3)
tSKEW1
(Figure 6)
tSKEW2
(Figure 3)
Measurement + Calibration Cycle
Time When Starting from the
REFUP State in Normal Mode
tWAKE
Regulator Start-Up Time
VREG Generated from Drive Pin (Figure 28)
l
tSLEEP
Watchdog or Software Discharge
Timer
SWTEN Pin = 0 or DCTO[3:0] = 0000
l
tREFUP
(Figure 1,
Figures 3 to 7)
Reference Wake-Up Time
State: Core = STANDBY
l
State: Core = REFUP
l
fS
ADC Clock Frequency
SWTEN Pin = 1 and DCTO[3:0] ≠ 0000
1.8
2
0.5
2.7
l
3.0
2.3
3.5
3.3
2.2
sec
120
min
4.4
ms
0
ms
3.5
MHz
0.8
V
SPI Interface DC Specifications
VIH(SPI)
SPI Pin Digital Input Voltage High
Pins CSB, SCK, SDI
l
VIL(SPI)
SPI Pin Digital Input Voltage Low
Pins CSB, SCK, SDI
l
VIH(CFG)
Configuration Pin Digital
Input Voltage High
Pins ISOMD, SWTEN, GPIO1 to GPIO5, A0 to A3
l
VIL(CFG)
Configuration Pin Digital
Input Voltage Low
Pins ISOMD, SWTEN, GPIO1 to GPIO5, A0 to A3
l
V
2.7
V
1.2
V
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7
LTC6804-1/LTC6804-2
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. The test conditions are V+ = 39.6V, VREG = 5.0V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
ILEAK(DIG)
Digital Input Current
Pins CSB, SCK, SDI, ISOMD, SWTEN,
A0 to A3
l
MIN
TYP
MAX
±1
UNITS
µA
VOL(SDO)
Digital Output Low
Pin SDO Sinking 1mA
l
0.3
V
2.1
V
V
isoSPI DC Specifications (See Figure 16)
VBIAS
Voltage on IBIAS Pin
READY/ACTIVE State
IDLE State
l
1.9
IB
Isolated Interface Bias Current
RBIAS = 2k to 20k
l
0.1
AIB
Isolated Interface Current Gain
VA ≤ 1.6V IB = 1mA
IB = 0.1mA
l
l
18
18
VA
Transmitter Pulse Amplitude
VA = |VIP – VIM|
l
VICMP
Threshold-Setting Voltage on ICMP VTCMP = ATCMP • VICMP
Pin
l
ILEAK(ICMP)
Input Leakage Current on ICMP Pin VICMP = 0V to VREG
Leakage Current on IP and IM Pins IDLE State, VIP or VIM = 0V to VREG
l
ATCMP
Receiver Comparator Threshold
Voltage Gain
VCM = VREG/2 to VREG – 0.2V, VICMP = 0.2V to 1.5V
l
VCM
Receiver Common Mode Bias
IP/IM Not Driving
RIN
Receiver Input Resistance
Single-Ended to IPA, IMA, IPB, IMB
l
27
ILEAK(IP/IM)
2.0
0
20
20
0.2
l
0.4
0.5
1.0
mA
22
24.5
mA/mA
mA/mA
1.6
V
1.5
V
±1
µA
±1
µA
0.6
V/V
(VREG – VICMP/3 – 167mV)
35
43
V
kΩ
isoSPI Idle/Wakeup Specifications (See Figure 21)
VWAKE
Differential Wake-Up Voltage
tDWELL = 240ns
l
200
mV
tDWELL
Dwell Time at VWAKE Before Wake
Detection
VWAKE = 200mV
l
240
ns
tREADY
Startup Time After Wake Detection
l
tIDLE
Idle Timeout Duration
l
4.3
10
µs
5.5
6.7
ms
120
150
180
ns
200
ns
40
50
60
ns
70
ns
isoSPI Pulse Timing Specifications (See Figure 19)
t1/2PW(CS)
Chip-Select Half-Pulse Width
l
tINV(CS)
Chip-Select Pulse Inversion Delay
l
t1/2PW(D)
Data Half-Pulse Width
l
tINV(D)
Data Pulse Inversion Delay
l
SPI Timing Requirements (See Figure 15 and Figure 20)
tCLK
SCK Period
t1
(Note 4)
l
1
µs
SDI Setup Time before SCK Rising
Edge
l
25
ns
t2
SDI Hold Time after SCK Rising
Edge
l
25
ns
t3
SCK Low
tCLK = t3 + t4 ≥ 1µs
l
200
ns
t4
SCK High
tCLK = t3 + t4 ≥ 1µs
l
200
ns
t5
CSB Rising Edge to CSB Falling
Edge
l
0.65
µs
t6
SCK Rising Edge to CSB Rising
Edge
(Note 4)
l
0.8
µs
t7
CSB Falling Edge to SCK Rising
Edge
(Note 4)
l
1
µs
8
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Electrical Characteristics
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. The test conditions are V+ = 39.6V, VREG = 5.0V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
isoSPI Timing Specifications (See Figure 19)
t8
SCK Falling Edge to SDO Valid
l
60
ns
t9
SCK Rising Edge to Short ±1
Transmit
(Note 5)
l
50
ns
t10
CSB Transition to Long ±1 Transmit
l
60
ns
t11
CSB Rising Edge to SDO Rising
l
200
ns
tRTN
Data Return Delay
l
430
525
ns
tDSY(CS)
Chip-Select Daisy-Chain Delay
l
150
200
ns
tDSY(D)
Data Daisy-Chain Delay
l
300
360
ns
tLAG
Data Daisy-Chain Lag (vs ChipSelect)
l
0
35
70
ns
t6(GOV)
Data to Chip-Select Pulse Governor
l
0.8
1.05
µs
(Note 5)
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: The ADC specifications are guaranteed by the Total Measurement
Error specification.
Note 3: The ACTIVE state current is calculated from DC measurements.
The ACTIVE state current is the additional average supply current into
VREG when there is continuous 1MHz communications on the isoSPI ports
with 50% data 1’s and 50% data 0’s. Slower clock rates reduce the supply
current. See Applications Information section for additional details.
Note 4: These timing specifications are dependent on the delay through
the cable, and include allowances for 50ns of delay each direction. 50ns
corresponds to 10m of CAT-5 cable (which has a velocity of propagation of
66% the speed of light). Use of longer cables would require derating these
specs by the amount of additional delay.
Note 5: These specifications do not include rise or fall time of SDO. While
fall time (typically 5ns due to the internal pull-down transistor) is not a
concern, rising-edge transition time tRISE is dependent on the pull-up
resistance and load capacitance on the SDO pin. The time constant must
be chosen such that SDO meets the setup time requirements of the MCU.
Note 6: V+ needs to be greater than or equal to the highest C(n) voltage for
accurate measurements. See the graph Top Cell Measurement Error vs V+.
680412fc
For more information www.linear.com/LTC6804-1
9
LTC6804-1/LTC6804-2
Typical Performance Characteristics
Measurement Error
vs Temperature
35
CELL VOLTAGE = 3.3V
5 TYPICAL UNITS
1.5
0.5
0
–0.5
–1.0
30
260°C, 1 CYCLE
25
20
15
10
5
–1.5
–2.0
–50 –25
75
50
25
TEMPERATURE (°C)
0
100
0
25 50
–125 –100 –75 –50 –25 0
CHANGE IN GAIN ERROR (ppm)
125
Measurement Error vs Input,
Normal Mode
MEASUREMENT ERROR (mV)
MEASUREMENT ERROR (mV)
0
–0.5
–1.0
–1.5
3
INPUT (V)
4
1.0
0.5
0
–0.5
–1.0
–2.0
5
0
–2
–4
–6
0
1
2
3
INPUT (V)
4
–10
5
9
0.8
0.8
8
0.7
0.7
7
PEAK NOISE (mV)
10
0.6
0.5
0.4
0.3
0.1
1
0
0
10
0
1
3
2
INPUT (V)
4
5
3
2
680412 G07
4
4
0.1
5
3
2
INPUT (V)
5
0.2
4
1
6
0.2
3
2
INPUT (V)
0
Measurement Noise vs Input,
Fast Mode
0.9
1
10 ADC MEASUREMENTS
AVERAGED AT EACH INPUT
680412 G06
1.0
PEAK NOISE (mV)
PEAK NOISE (mV)
2
0.9
0
3000
4
1.0
0.3
2500
6
Measurement Noise vs Input,
Filtered Mode
0.4
1000 1500 2000
TIME (HOURS)
680412 G05
Measurement Noise vs Input,
Normal Mode
0.5
500
–8
680412 G04
0.6
0
8
–1.5
2
5
10
1.5
0.5
1
10
Measurement Error vs Input,
Fast Mode
2.0
1.0
0
15
Measurement Error vs Input,
Filtered Mode
10 ADC MEASUREMENTS
AVERAGED AT EACH INPUT
1.5
20
680412 G03
MEASUREMENT ERROR (mV)
2.0
25
0
75
CELL VOLTAGE = 3.3V
8 TYPICAL PARTS
680412 G02
680412 G01
–2.0
Measurement Error LongTerm Drift
30
1.0
NUMBER OF PARTS
MEASUREMENT ERROR (mV)
Measurement Error Due to IR
Reflow
MEASUREMENT ERROR (ppm)
2.0
TA = 25°C, unless otherwise noted.
5
680412 G08
0
0
1
3
2
INPUT (V)
4
680412 G09
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Typical Performance Characteristics
Measurement Gain Error
Hysteresis, Hot
25
Measurement Gain Error
Hysteresis, Cold
30
TA = 85°C TO 25°C
TA = –45°C TO 25°C
–10
15
10
5
NOISE REJECTION (dB)
NUMBER OF PARTS
20
15
10
5
0
0
–50 –40 –30 –20 –10
10 20
CHANGE IN GAIN ERROR (ppm)
0
10 20 30
–40 –30 –20 –10 0
CHANGE IN GAIN ERROR (ppm)
30
–40
2.0
–50
1.0
–55
0
–0.5
–10
–65
–70
C=0
C = 10nF
C = 100nF
C = 1µF
–15
1
100
10
1000
INPUT RESISTOR, R (Ω)
–40
1k
100k
10k
FREQUENCY (Hz)
1M
–70
100
10M
10
680412 G16
10k
100k
1M
68412 G15
Top Cell Measurement Error vs V+
6
4
2
0
–2
–4
C=0
C = 100nF
C = 1µF
C = 10µF
–6
–10
1
10M
FREQUENCY (Hz)
1.0
TIME BETWEEN MEASUREMENTS > 3RC
8
–8
10000
1k
680412 G14
MEASUREMENT ERROR (mV)
–5
–10
–30
GPIO Measurement Error
vs Input RC Values
0
VREG(DC) = 5V
VREG(AC) = 500mVP-P
1 BIT CHANGE < –70dB
–60
–90
100
Cell Measurement Error
vs Input RC Values
1M
–50
680412 G13
5
1k
10k
100k
INPUT FREQUENCY (Hz)
–20
–60
–85
–2.0
4.5 4.6 4.7 4.8 4.9 5.0 5.1 5.2 5.3 5.4 5.5
VREG (V)
CELL MEASUREMENT ERROR (mV)
0
–80
VIN = 2V
VIN = 3.3V
VIN = 4.2V
10
100
Measurement Error VREG PSRR
vs Frequency
–75
NORMAL MODE CONVERSIONS
DIFFERENTIAL RC FILTER ON EVERY C PIN.
EXPECT CELL-TO-CELL AND
PART-TO-PART VARIATIONS
IN ERROR IF R > 100Ω AND/OR C > 10nF
10
ADC MODE:
NORMAL
FILTERED
15kHz
2kHz
FAST 680412 G12
3kHz
PSRR (dB)
0.5
PSRR (dB)
MEASUREMENT ERROR (mV)
1.5
15
–50
–70
40
V+DC = 39.6V
V+AC = 5VP-P
1 BIT CHANGE < –90dB
VREG GENERATED FROM
DRIVE PIN, FIGURE 28
–45
20
–40
Measurement Error V+ PSRR
vs Frequency
Measurement Error vs VREG
–1.5
–30
680412 G11
680412 G10
–1.0
–20
–60
CELL 12 MEASUREMENT ERROR (mV)
NUMBER OF PARTS
Noise Filter Response
0
25
20
–20
TA = 25°C, unless otherwise noted.
10
1000 10000 100000
100
INPUT RESISTANCE, R (Ω)
680412 G17
C12-C11 = 3.3V
C12 = 39.6V
0.8
0.6
0.4
0.2
0
–0.2
–0.4
–0.6
–0.8
–1.0
36
38
40
V+ (V)
42
44
680412 G18
680412fc
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11
LTC6804-1/LTC6804-2
Typical Performance Characteristics
Cell Measurement Error
vs Common Mode Voltage
Cell Measurement CMRR
vs Frequency
0
C12-C11 = 3.3V
V+ = 39.6V
MEASUREMENT ERROR (mV)
0.2
0
–0.2
–0.4
–30
–40
–50
–60
–0.6
–70
–0.8
–80
10
0
20
C11 VOLTAGE (V)
1k
3
SLEEP SUPPLY CURRENT =
V+ CURRENT + VREG CURRENT
15
25
45
35
V+ (V)
55
65
70
50
2440
2420
12.25
11.00
5
15
25
45
35
V+ (V)
55
65
75
680412 G25
12
MEASUREMENT TIME (µs)
MEASURE MODE SUPPLY CURRENT (mA)
12.50
11.25
30
35
STANDBY SUPPLY CURRENT =
V+ CURRENT + VREG CURRENT
5
15
25
45
35
V+ (V)
55
65
125°C
85°C
25°C
–45°C
REFUP SUPPLY CURRENT =
V+ CURRENT + VREG CURRENT
900
850
75
12 CELL NORMAL MODE TIME
SHOWN. ALL ADC MEASURE
TIMES SCALE PROPORTIONALLY
2400
2380
2360
2340
2320
VREG = 5V
VREG = 4.5V
VREG = 5.5V
2300
2280
–50 –25
75
50
25
TEMPERATURE (°C)
0
40
950
5
15
25
45
35
V+ (V)
55
100
125
680412 G26
65
75
680412 G24
Internal Die Temperature
Measurement Error vs Temperature
Measurement Time vs Temperature
125°C
85°C
25°C
–45°C
MEASURE MODE SUPPLY CURRENT =
+ CURRENT + V
V
REG CURRENT
25
20
V+ (V)
680412 G23
Measure Mode Supply Current
vs V+
11.75
15
1000
60
40
75
12.00
10
5
REFUP Supply Current vs V+
125°C
85°C
25°C
–45°C
680412 G22
11.50
–1.0
680412 G21
REFUP SUPPLY CURRENT (µA)
4
STANDBY SUPPLY CURRENT (µA)
SLEEP SUPPLY CURRENT (µA)
80
125°C
85°C
25°C
–45°C
5
–0.5
Standby Supply Current vs V+
5
2
0
680412 G20
Sleep Supply Current vs V+
6
0.5
–2.0
10M
1M
100k
10k
FREQUENCY (Hz)
680412 G19
7
1.0
–1.5
–90
100
30
MEASUREMENT ERROR OF
CELL 1 WITH 3.3V INPUT.
VREG GENERATED FROM
DRIVE PIN, FIGURE 28
1.5
–20
0.4
–1.0
VCM(IN) = 5VP-P
NORMAL MODE CONVERSIONS
–10
0.6
Measurement Error vs V+
2.0
TEMPERATURE MEASUREMENT ERROR (DEG)
0.8
REJECTION (dB)
CELL 12 MEASUREMENT ERROR (mV)
1.0
TA = 25°C, unless otherwise noted.
10
8
5 TYPICAL UNITS
6
4
2
0
–2
–4
–6
–8
–10
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
680412 G27
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Typical Performance Characteristics
VREF2 vs Temperature
3.003
VREG GENERATED FROM
150 DRIVE PIN, FIGURE 28
3.000
2.999
–400
–600
V+ = 39.6V
–800
2.998
50
25
75
0
TEMPERATURE (°C)
100
125
–1000
0.01
VREG = 5V
125°C
85°C
25°C
–45°C
1
0.1
3.0
VREF2 (V)
100
50
0
–200
15
5
25
–50
5.25
65
2.5
2.0
VREF2
1.5
CSB
50
25
0
–25
–50
–75
0
–5
8 TYPICAL PARTS
75
5
5.5
1ms/DIV
680412 G32
–100
500
0
VREG (V)
1000
1500
2000
2500
680412 G33
VREF2 Hysteresis, Hot
VREF2 Hysteresis, Cold
16
TA = 85°C TO 25°C
VREF2 Change Due to IR Reflow
30
TA = –45°C TO 25°C
14
15
10
260°C, 1 CYCLE
25
12
NUMBER OF PARTS
NUMBER OF PARTS
NUMBER OF PARTS
20
10
8
6
20
15
10
4
5
5
2
0
–125
3000
TIME (HOURS)
680412 G31
25
75
580412 G30
RL = 5k
CL = 1µF
0
125°C
85°C
25°C
–45°C
55
45
35
V+ (V)
VREF2 Long-Term Drift
0.5
5
125°C
85°C
25°C
–45°C
100
1.0
CSB
CHANGE IN VREF2 (ppm)
10
VREF2 Power-Up
3.5
4.75
–50
680412 G29
RL = 5k
4.5
0
IOUT (mA)
VREF2 VREG Line Regulation
–150
50
–150
680412 G28
–100
100
–100
CHANGE IN VREF2 (ppm)
2.997
–50 –25
CHANGE IN VREF2 (ppm)
CHANGE IN VREF2 (ppm)
VREF2 (V)
200
–200
3.001
150
VREF2 V+ Line Regulation
VREF2 Load Regulation
0
V+ = 39.6V
5 TYPICAL PARTS
3.002
TA = 25°C, unless otherwise noted.
–75
25
75
125
–25
CHANGE IN REF2 (ppm)
175
680412 G34
0
0
50
–250 –200 –150 –100 –50
CHANGE IN REF2 (ppm)
100
680412 G35
0
–700
–500
–300
–100
100
CHANGE IN REF2 (ppm)
300
680412 G36
680412fc
For more information www.linear.com/LTC6804-1
13
LTC6804-1/LTC6804-2
Typical Performance Characteristics
Discharge Switch On-Resistance
vs Cell Voltage
Drive Pin Load Regulation
0
40
35
30
25
20
15
125°C
85°C
25°C
–45°C
10
5
0
1
2
4
3
CELL VOLTAGE (V)
V+ = 39.6V
–20
–40
–60
125°C
85°C
25°C
–45°C
–80
–100
0.01
5
0.1
3.5
3.0
–5
125°C
85°C
25°C
–45°C
–10
–15
1
5
15
25
45
35
V+ (V)
55
3
VREF1 Power-Up
3.155
CL = 1µF
75
VREF1 vs Temperature
5 TYPICAL
3.154
3.153
2.5
2.0
3.152
VREF1
1.5
1.0
2
65
680412 G39
VREF1 (V)
VREF1 (V)
VREG
0.5
3.151
3.150
3.149
3.148
1
VREG: CL = 1µF
VREG GENERATED FROM
DRIVE PIN, FIGURE 28
0
–1
3.147
3.146
0
–5
680412 G40
100µs/DIV
CSB
5
CSB
VDRIVE AND VREG (V)
5
VDRIVE
0
680412 G38
Drive and VREG Pin Power-Up
4
5
ILOAD (mA)
680412 G37
6
Drive Pin Line Regulation
10
CHANGE IN DRIVE PIN VOLTAGE (mV)
ON-RESISTANCE OF INTERNAL
DISCHARGE SWITCH MEASURED
WITH 100Ω. EXTERNAL DISCHARGE
RESISTOR BETWEEN S(n) and C(n)
45
CHANGE IN DRIVE PIN VOLTAGE (mV)
DISCHARGE SWITCH ON-RESISTANCE (Ω)
50
TA = 25°C, unless otherwise noted.
1ms/DIV
680412 G41
3.145
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
680412 G42
Internal Die Temperature
Increase vs Discharge Current
isoSPI Current (READY)
vs Temperature
45
40
35
30
25
12 CELLS DISCHARGING
20
15
10
5
1 CELL
DISCHARGING
0
80
40
20
0
60
INTERNAL DISCHARGE CURRENT (mA PER CELL)
680412 G43
14
LT6804-1
ISOMD = VREG
8
6 CELLS DISCHARGING
14
IB = 1mA
7
6
LT6804-2
ISOMD = VREG
5
4
–50
50
0
75
25
TEMPERATURE (°C)
LTC6804-1
10
8
LTC6804-2
6
4
2
LT6804-1, ISOMD = 0
–25
ISOMD = VREG
IB = 1mA
12
isoSPI CURRENT (mA)
9
isoSPI CURRENT (mA)
INCREASE IN DIE TEMPERATURE (°C)
50
isoSPI Current (READY/ACTIVE)
vs isoSPI Clock Frequency
100
125
680412 G44
0
WRITE
READ
0
200
400
600
800
isoSPI CLOCK FREQUENCY (kHz)
1000
680412 G45
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Typical Performance Characteristics
IBIAS Voltage vs Temperature
2.010
2.01
2.00
1.99
–25
75
0
25
50
TEMPERATURE (°C)
100
125
23
2.005
CURRENT GAIN (mA/mA)
IB = 1mA
3 PARTS
1.98
–50
2.000
1.995
1.990
200
0
600
800
400
BIAS CURRENT (µA)
680412 G46
20
19
50
0
75
25
TEMPERATURE (°C)
100
IB = 100µA
4.5
4.0
3.5
3.0
2.5
125
IB = 1mA
0
0.5
1.0
1.5
PULSE AMPLITUDE (V)
WAKE-UP PULSE AMPLITUDE, VWAKE (mV)
0.52
0.50
0.48
0.46
0.4
600
800
400
BIAS CURRENT (µA)
0.6 0.8 1.0 1.2
ICMP VOLTAGE (V)
1000
2.0
0.54
0.52
VICMP = 1V
0.50
VICMP = 0.2V
0.48
0.46
0.44
2.5
3.5
4.0
4.5
5.0
3.0
COMMON MODE VOLTAGE (V)
1.4
5.5
680412 G51
Typical Wake-Up Pulse Amplitude
(Port A) vs Dwell Time
0.54
0.2
200
680412 G50
3 PARTS
0
0
isoSPI Comparator Threshold
Gain (Port A/Port B) vs Common
Mode
5.0
isoSPI Comparator Threshold
Gain (Port A/Port B) vs ICMP
Voltage
0.44
VA = 0.5V
VA = 1.0V
VA = 1.6V
0.56
680412 G49
0.56
19
680412 G48
COMPARATOR THRESHOLD GAIN (V/V)
DRIVER COMMON MODE (V)
IB = 1mA
COMPARATOR THRESHOLD GAIN (V/V)
CURRENT GAIN (mA/mA)
IB = 100µA
–25
20
18
1000
5.5
21
21
isoSPI Driver Common Mode
Voltage (Port A/Port B) vs Pulse
Amplitude
23
22
22
408912 G47
isoSPI Driver Current Gain
(Port A/PortB) vs Temperature
18
–50
isoSPI Driver Current Gain
(Port A/PortB) vs Bias Current
IBIAS Voltage Load Regulation
IBIAS PIN VOLTAGE (V)
IBIAS PIN VOLTAGE (V)
2.02
TA = 25°C, unless otherwise noted.
1.6
300
GUARANTEED
WAKE-UP REGION
250
200
150
100
50
0
680412 G52
300
150
450
WAKE-UP DWELL TIME, tDWELL (ns)
600
680412 G53
680412fc
For more information www.linear.com/LTC6804-1
15
LTC6804-1/LTC6804-2
Typical Performance Characteristics
TA = 25°C, unless otherwise noted.
Write Command to a Daisy-Chained
Device (ISOMD = 0)
CSB
5V/DIV
SDI
5V/DIV
PORT A
IPA-IMA
1V/DIV
(PORT A)
SCK
5V/DIV
SDO
5V/DIV
IPB-IMB
2V/DIV
(PORT B)
Write Command to a Daisy-Chained
Device (ISOMD = 1)
IPB-IMB
1V/DIV
(PORT B)
1µs/DIV
ISOMD = V–
BEGINNING OF A COMMAND
680412 G54
1µs/DIV
ISOMD = VREG
BEGINNING OF A COMMAND
Data Read-Back from a Daisy-Chained
Device (ISOMD = 0)
CSB
5V/DIV
SDI
5V/DIV
PORT A
SDO
5V/DIV
16
Data Read-Back from a Daisy-Chained
Device (ISOMD = 1)
IPA-IMA
1V/DIV
(PORT A)
SCK
5V/DIV
IPB-IMB
2V/DIV
(PORT B)
680412 G55
IPB-IMB
1V/DIV
(PORT B)
1µs/DIV
ISOMD = V–
END OF A READ COMMAND
680412 G56
1µs/DIV
ISOMD = VREG
END OF A READ COMMAND
680412 G57
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Pin Functions
C0 to C12: Cell Inputs.
Serial Port Pins
LTC6804-1
(DAISY-CHAINABLE)
S1 to S12: Balance Inputs/Outputs. 12 N-MOSFETs are
connected between S(n) and C(n – 1) for discharging cells.
V+: Positive Supply Pin.
V–:
Negative Supply Pins. The
together, external to the IC.
V–
pins must be shorted
VREF2: Buffered 2nd reference voltage for driving multiple
10k thermistors. Bypass with an external 1µF capacitor.
VREF1: ADC Reference Voltage. Bypass with an external
1µF capacitor. No DC loads allowed.
GPIO[1:5]: General Purpose I/O. Can be used as digital
inputs or digital outputs, or as analog inputs with a measurement range from V– to 5V. GPIO [3:5] can be used
as an I2C or SPI port.
SWTEN: Software Timer Enable. Connect this pin to VREG
to enable the software timer.
PORT B
(Pins 45
to 48)
PORT A
(Pins 41
to 44)
LTC6804-2
(ADDRESSABLE)
ISOMD = VREG
ISOMD = V–
ISOMD = VREG
ISOMD = V–
IPB
IPB
A3
A3
IMB
IMB
A2
A2
ICMP
ICMP
A1
A1
IBIAS
IBIAS
A0
A0
(NC)
SDO
IBIAS
SDO
(NC)
SDI
ICMP
SDI
IPA
SCK
IPA
SCK
IMA
CSB
IMA
CSB
CSB, SCK, SDI, SDO: 4-Wire Serial Peripheral Interface
(SPI). Active low chip select (CSB), serial clock (SCK),
and serial data in (SDI) are digital inputs. Serial data out
(SDO) is an open drain NMOS output pin. SDO requires
a 5k pull-up resistor.
DRIVE: Connect the base of an NPN to this pin. Connect
the collector to V+ and the emitter to VREG.
A0 to A3: Address Pins. These digital inputs are connected
to VREG or V– to set the chip address for addressable serial commands.
VREG: 5V Regulator Input. Bypass with an external 1µF
capacitor.
IPA, IMA: Isolated 2-Wire Serial Interface Port A. IPA
(plus) and IMA (minus) are a differential input/output pair.
ISOMD: Serial Interface Mode. Connecting ISOMD to
VREG configures Pins 41 to 44 of the LTC6804 for 2-wire
isolated interface (isoSPI) mode. Connecting ISOMD to
V– configures the LTC6804 for 4-wire SPI mode.
IPB, IMB: Isolated 2-Wire Serial Interface Port B. IPB
(plus) and IMB (minus) are a differential input/output pair.
WDT: Watchdog Timer Output Pin. This is an open drain
NMOS digital output. It can be left unconnected or connected with a 1M resistor to VREG. If the LTC6804 does not
receive a wake-up signal (see Figure 21) within 2 seconds,
the watchdog timer circuit will reset the LTC6804 and the
WDT pin will go high impedance.
IBIAS: Isolated Interface Current Bias. Tie IBIAS to
V– through a resistor divider to set the interface output
current level. When the isoSPI interface is enabled, the
IBIAS pin voltage is 2V. The IPA/IMA or IPB/IMB output
current drive is set to 20 times the current, IB, sourced
from the IBIAS pin.
ICMP: Isolated Interface Comparator Voltage Threshold
Set. Tie this pin to the resistor divider between IBIAS
and V– to set the voltage threshold of the isoSPI receiver
comparators. The comparator thresholds are set to 1/2
the voltage on the ICMP pin.
680412fc
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17
LTC6804-1/LTC6804-2
Block Diagram
LTC6804-1
V+
IPB
C12
IMB
1
48
2
47
VREGD POR
S12
VREG
ICMP
3
46
C11
4
S11
5
C10
6
C12
C11
C10
C9
C8
C7
P
6-CELL
MUX
IBIAS
+
45
ADC2
M
DIGITAL
FILTERS
C6
S10
7
C9
8
S9
SERIAL I/O
PORT B
16
–
C5
C4
C3
C2
C1
C0
P
6-CELL
MUX
+
M
43
SCK/(IPA)
16
–
44
SDI/(NC)
LOGIC
AND
MEMORY
SERIAL I/O
PORT A
ADC1
SDO/(NC)
42
CSB/(IMA)
41
ISOMD
9
40
C8
10
WDT
S8
11
DRIVE
C7
12
S7
13
39
38
12 BALANCE FETs
S(n)
VREGD
SOC
VREG
C(n – 1)
P
C6
14
S6
15
C5
16
S5
17
C4
18
S4
19
C3
20
S3
21
AUX
MUX
M
37
SOFTWARE
TIMER
SWTEN
36
VREF1
35
VREF2
34
REGULATORS
GPIO5
V+
33
LDO2
GPIO4
DRIVE
LDO1
VREG
V+
VREGD
POR
DIE
TEMPERATURE
2ND
REFERENCE
32
V–
31
V–*
30
GPIO3
1ST
REFERENCE
29
GPIO2
28
C2
22
GPIO1
S2
23
C0
C1
24
S1
27
26
25
680412 BD1
18
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Block Diagram
LTC6804-2
V+
A4
C12
A3
1
48
2
47
VREGD POR
S12
VREG
A2
3
46
C11
4
S11
5
C10
6
C12
C11
C10
C9
C8
C7
P
6-CELL
MUX
A1
+
45
ADC2
M
DIGITAL
FILTERS
C6
S10
7
C9
8
S9
SERIAL I/O
ADDRESS
16
–
C5
C4
C3
C2
C1
C0
P
6-CELL
MUX
+
M
43
SCK/(IPA)
16
–
44
SDI/(ICMP)
LOGIC
AND
MEMORY
SERIAL I/O
PORT A
ADC1
SDO/(IBIAS)
42
CSB/(IMA)
41
ISOMD
9
40
C8
10
WDT
S8
11
DRIVE
C7
12
S7
13
39
38
12 BALANCE FETs
S(n)
VREGD
SOC
VREG
C(n – 1)
P
C6
14
S6
15
C5
16
S5
17
C4
18
S4
19
C3
20
S3
21
AUX
MUX
M
37
SOFTWARE
TIMER
SWTEN
36
VREF1
35
VREF2
34
REGULATORS
GPIO5
V+
33
LDO2
GPIO4
DRIVE
LDO1
VREG
V+
VREGD
POR
DIE
TEMPERATURE
2ND
REFERENCE
32
V–
31
V–*
30
GPIO3
1ST
REFERENCE
29
GPIO2
28
C2
22
GPIO1
S2
23
C0
C1
24
S1
27
26
25
680412 BD2
680412fc
For more information www.linear.com/LTC6804-1
19
LTC6804-1/LTC6804-2
Operation
State Diagram
The operation of the LTC6804 is divided into two separate
sections: the core circuit and the isoSPI circuit. Both sections have an independent set of operating states, as well
as a shutdown timeout.
LTC6804 Core State Descriptions
SLEEP State
The reference and ADCs are powered down. The watchdog
timer (see Watchdog and Software Discharge Timer) has
timed out. The software discharge timer is either disabled
or timed out. The supply currents are reduced to minimum
levels. The isoSPI ports will be in the IDLE state.
If a WAKEUP signal is received (see Waking Up the Serial
Interface), the LTC6804 will enter the STANDBY state.
returns to the SLEEP state. If the software discharge timer
is disabled, only the watchdog timer is relevant.
REFUP State
To reach this state the REFON bit in the Configuration Register Group must be set to 1 (using the WRCFG command,
see Table 36). The ADCs are off. The reference is powered
up so that the LTC6804 can initiate ADC conversions more
quickly than from the STANDBY state.
When a valid ADC command is received, the IC goes to the
MEASURE state to begin the conversion. Otherwise, the
LTC6804 will return to the STANDBY state when the REFON
bit is set to 0, either manually (using WRCFG command)
or automatically when the watchdog timer expires. (The
LTC6804 will then move straight into the SLEEP state if
both timers are expired).
MEASURE State
STANDBY State
The reference and the ADCs are off. The watchdog timer
and/or the software discharge timer is running. The DRIVE
pin powers the VREG pin to 5V through an external transistor.
(Alternatively, VREG can be powered by an external supply).
When a valid ADC command is received or the REFON bit is
set to 1 in the Configuration Register Group, the IC pauses
for tREFUP to allow for the reference to power up and then
enters either the REFUP or MEASURE state. If there is no
WAKEUP signal for a duration tSLEEP (when both the watchdog and software discharge timer have expired) the LTC6804
The LTC6804 performs ADC conversions in this state. The
reference and ADCs are powered up.
After ADC conversions are complete the LTC6804 will
transition to either the REFUP or STANDBY states, depending on the REFON bit. Additional ADC conversions
can be initiated more quickly by setting REFON = 1 to take
advantage of the REFUP state.
Note: Non-ADC commands do not cause a Core state transition. Only an ADC conversion or diagnostic commands
will place the Core in the MEASURE state.
CORE LTC6804
isoSPI PORT
SLEEP
IDLE
WD TIMEOUT
OR SWT TIMEOUT
(tSLEEP)
WAKEUP
SIGNAL
(tWAKE)
STANDBY
REFON = 0
REFON = 1
(tREFUP)
REFUP
ADC
COMMAND
WAKEUP SIGNAL
(CORE = SLEEP)
(tWAKE)
IDLE TIMEOUT
(tIDLE)
WAKEUP SIGNAL
(CORE = STANDBY)
(tREADY)
READY
ADC COMMAND
(tREFUP)
CONVERSION
DONE (REFON = 0)
NO ACTIVITY ON
isoSPI PORT
MEASURE
TRANSMIT/RECEIVE
ACTIVE
CONVERSION DONE
(REFON = 1)
NOTE: STATE TRANSITION
DELAYS DENOTED BY (tX)
680412 F01
Figure 1. LTC6804 Operation State Diagram
20
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Operation
isoSPI State Descriptions
Note: The LTC6804-1 has two isoSPI ports (A and B), for
daisy-chain communication. The LTC6804-2 has only one
isoSPI port (A), for parallel-addressable communication.
IDLE State
The isoSPI ports are powered down.
When isoSPI port A receives a WAKEUP signal (see Waking Up the Serial Interface), the isoSPI enters the READY
state. This transition happens quickly (within tREADY) if
the Core is in the STANDBY state because the DRIVE and
VREG pins are already biased up. If the Core is in the SLEEP
state when the isoSPI receives a WAKEUP signal, then it
transitions to the READY state within tWAKE.
READY State
The isoSPI port(s) are ready for communication. Port
B is enabled only for LTC6804-1, and is not present on
the LTC6804-2. The serial interface current in this state
depends on if the part is LTC6804-1 or LTC6804-2, the
status of the ISOMD pin, and RBIAS = RB1 + RB2 (the
external resistors tied to the IBIAS pin).
If there is no activity (i.e., no WAKEUP signal) on port A
for greater than tIDLE = 5.5ms, the LTC6804 goes to the
IDLE state. When the serial interface is transmitting or
receiving data the LTC6804 goes to the ACTIVE state.
ACTIVE State
The LTC6804 is transmitting/receiving data using one or
both of the isoSPI ports. The serial interface consumes
maximum power in this state. The supply current increases
with clock frequency as the density of isoSPI pulses
increases.
Power Consumption
The LTC6804 is powered via two pins: V+ and VREG. The
V+ input requires voltage greater than or equal to the top
cell voltage, and it provides power to the high voltage
elements of the core circuitry. The VREG input requires
5V and provides power to the remaining core circuitry
and the isoSPI circuitry. The VREG input can be powered
through an external transistor, driven by the regulated
DRIVE output pin. Alternatively, VREG can be powered by
an external supply.
The power consumption varies according to the operational states. Table 1 and Table 2 provide equations to
approximate the supply pin currents in each state. The V+
pin current depends only on the Core state and not on the
isoSPI state. However, the VREG pin current depends on
both the Core state and isoSPI state, and can therefore be
divided into two components. The isoSPI interface draws
current only from the VREG pin.
IREG = IREG(CORE) + IREG(isoSPI)
Table 1. Core Supply Current
STATE
SLEEP
IV+
IREG(CORE)
VREG = 0V
3.8µA
0µA
VREG = 5V
1.6µA
2.2µA
STANDBY
32µA
35µA
REFUP
550µA
450µA
MEASURE
550µA
11.5mA
In the SLEEP state the VREG pin will draw approximately
2.2µA if powered by a external supply. Otherwise, the V+
pin will supply the necessary current.
ADC Operation
There are two ADCs inside the LTC6804. The two ADCs
operate simultaneously when measuring twelve cells. Only
one ADC is used to measure the general purpose inputs.
The following discussion uses the term ADC to refer to
one or both ADCs, depending on the operation being
performed. The following discussion will refer to ADC1
and ADC2 when it is necessary to distinguish between the
two circuits, in timing diagrams, for example.
ADC Modes
The ADCOPT bit (CFGR0[0]) in the configuration register
group and the mode selection bits MD[1:0] in the conversion command together provide 6 modes of operation for
the ADC which correspond to different over sampling ratios
(OSR). The accuracy of these modes are summarized in
Table 3. In each mode, the ADC first measures the inputs,
and then performs a calibration of each channel. The
names of the modes are based on the –3dB bandwidth
of the ADC measurement.
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21
LTC6804-1/LTC6804-2
Operation
Table 2. isoSPI Supply Current Equations
isoSPI STATE
IDLE
READY
DEVICE
LTC6804-1/LTC6804-2
LTC6804-1
LTC6804-2
ACTIVE
LTC6804-1
ISOMD
CONNECTION
N/A
VREG
V–
VREG
V–
VREG
IREG(isoSPI)
0mA
2.8mA + 5 • IB Note: IB = VBIAS/(RB1 + RB2)
1.6mA + 3 • IB
1.8mA + 3 • IB
0mA
V–
LTC6804-2
Write: 2.8mA + 5 •IB + ( 2 •IB + 0.4mA ) •
1µs
tCLK
Read: 2.8mA + 5 •IB + ( 3 •IB + 0.5mA ) •
1µs
tCLK
1.6mA+ 3 •IB + ( 2 •IB + 0.2mA ) •
VREG
Write: 1.8mA + 3 •IB + ( 0.3mA ) •
1µs
tCLK
1µs
tCLK
Read: 1.8mA + 3 •IB + (IB + 0.3mA ) •
V–
1µs
tCLK
0mA
Table 3. ADC Filter Bandwidth and Accuracy
MODE
–3dB FILTER BW
–40dB FILTER BW
TME SPEC AT 3.3V, 25°C
TME SPEC AT 3.3V,–40°C, 125°C
27kHz (Fast Mode)
27kHz
84kHz
±4.7mV
±4.7mV
14kHz
13.5kHz
42kHz
±4.7mV
±4.7mV
7kHz (Normal Mode)
6.8kHz
21kHz
±1.2mV
±2.2mV
3kHz
3.4kHz
10.5kHz
±1.2mV
±2.2mV
2kHz
1.7kHz
5.3kHz
±1.2mV
±2.2mV
26Hz (Filtered Mode)
26Hz
82Hz
±1.2mV
±2.2mV
Note: TME is the total measurement error.
Mode 7kHz (Normal):
Mode 26Hz (Filtered):
In this mode, the ADC has high resolution and low TME
(total measurement error). This is considered the normal
operating mode because of the optimum combination of
speed and accuracy.
In this mode, the ADC digital filter –3dB frequency is
lowered to 26Hz by increasing the OSR. This mode is
also referred to as the filtered mode due to its low –3dB
frequency. The accuracy is similar to the 7kHz (Normal)
mode with lower noise.
Mode 27kHz (Fast):
In this mode, the ADC has maximum throughput but has
some increase in TME (total measurement error). So this
mode is also referred to as the fast mode. The increase
in speed comes from a reduction in the oversampling
ratio. This results in an increase in noise and average
measurement error.
22
Modes 14kHz, 3kHz and 2kHz:
Modes 14kHz, 3kHz and 2kHz provide additional options to
set the ADC digital filter –3dB frequency at 13.5kHz, 3.4kHz
and 1.7kHz respectively. The accuracy of the 14kHz mode
is similar to the 27kHz (fast) mode. The accuracy of 3kHz
and 2kHz modes is similar to the 7kHz (normal) mode.
680412fc
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LTC6804-1/LTC6804-2
Operation
The conversion times for these modes are provided in
Table 5. If the core is in STANDBY state, an additional
tREFUP time is required to power up the reference before
beginning the ADC conversions. The reference can remain
powered up between ADC conversions if the REFON bit
in Configuration Register Group is set to 1 so the core is
in REFUP state after a delay tREFUP. Then, the subsequent
ADC commands will not have the tREFUP delay before
beginning ADC conversions.
1.0
PEAK NOISE (mV)
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
ADC Range and Resolution
The C inputs and GPIO inputs have the same range and
resolution. The ADC inside the LTC6804 has an approximate
range from –0.82V to 5.73V. Negative readings are rounded
to 0V. The format of the data is a 16-bit unsigned integer
where the LSB represents 100µV. Therefore, a reading of
0x80E8 (33,000 decimal) indicates a measurement of 3.3V.
Delta-Sigma ADCs have quantization noise which depends
on the input voltage, especially at low over sampling ratios
(OSR), such as in FAST mode. In some of the ADC modes,
the quantization noise increases as the input voltage approaches the upper and lower limits of the ADC range.
For example, the total measurement noise versus input
voltage in normal and filtered modes is shown in Figure 2.
The specified range of the ADC is 0V to 5V. In Table 4, the
precision range of the ADC is arbitrarily defined as 0.5V
to 4.5V. This is the range where the quantization noise
is relatively constant even in the lower OSR modes (see
Figure 2). Table 4 summarizes the total noise in this range
for all six ADC operating modes. Also shown is the noise
NORMAL MODE
FILTERED MODE
0.9
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
ADC INPUT VOLTAGE (V)
680412 F02
Figure 2. Measurement Noise vs Input Voltage
free resolution. For example, 14-bit noise free resolution
in normal mode implies that the top 14 bits will be noise
free with a DC input, but that the 15th and 16th least
significant bits (LSB) will flicker.
ADC Range vs Voltage Reference Value:
Typical Delta-Sigma ADC’s have a range which is exactly
twice the value of the voltage reference, and the ADC
measurement error is directly proportional to the error
in the voltage reference. The LTC6804 ADC is not typical. The absolute value of VREF1 is trimmed up or down
to compensate for gain errors in the ADC. Therefore, the
ADC total measurement error (TME) specifications are
superior to the VREF1 specifications. For example, the
25°C specification of the total measurement error when
measuring 3.300V in 7kHz (normal) mode is ±1.2mV and
the 25°C specification for VREF1 is 3.200V ±100mV.
Table 4. ADC Range and Resolution
SPECIFIED
RANGE
PRECISION
RANGE2
MAX NOISE
NOISE FREE
RESOLUTION3
27kHz (Fast)
±4mVP-P
10 Bits
14kHz
±1mVP-P
12 Bits
±250µVP-P
14 Bits
±150µVP-P
14 Bits
2kHz
±100µVP-P
15 Bits
26Hz (Filtered)
±50µVP-P
16 Bits
MODE
7kHz (Normal)
3kHz
FULL RANGE1
–0.8192V to
5.7344V
0V to 5V
0.5V to 4.5V
LSB
100µV
FORMAT
Unsigned 16 Bits
1. Negative readings are rounded to 0V.
2. PRECISION RANGE is the range over which the noise is less than MAX NOISE.
3. NOISE FREE RESOLUTION is a measure of the noise level within the PRECISION RANGE.
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23
LTC6804-1/LTC6804-2
Operation
Measuring Cell Voltages (ADCV Command)
tREFUP
The ADCV command initiates the measurement of the
battery cell inputs, pins C0 through C12. This command
has options to select the number of channels to measure
and the ADC mode. See the section on Commands for the
ADCV command format.
Figure 3 illustrates the timing of ADCV command which
measures all twelve cells. After the receipt of the ADCV
command to measure all 12 cells, ADC1 sequentially
measures the bottom 6 cells. ADC2 sequentially measures
the top 6 cells. After the cell measurements are complete,
each channel is calibrated to remove any offset errors.
SERIAL
INTERFACE
MEASURE
C10 TO C9
CALIBRATE
C10 TO C9
ADC1
MEASURE
C4 TO C3
CALIBRATE
C4 TO C3
t1M
t1C
680412 F04
Figure 4. Timing for ADCV Command Measuring 2 Cells
Table 6. Conversion Times for ADCV Command Measuring Only 2
Cells in Different Modes
CONVERSION TIMES (in µs)
Figure 4 illustrates the timing of the ADCV command that
measures only two cells.
Table 6 shows the conversion time for ADCV command
measuring only 2 cells. t1C indicates the total conversion
time for this command.
SERIAL
INTERFACE
ADC2
t0
Table 5 shows the conversion times for the ADCV command measuring all 12 cells. The total conversion time is
given by t6C which indicates the end of the calibration step.
tREFUP
ADCV + PEC
MODE
t0
t1M
t1C
27kHz
0
57
201
14kHz
0
86
230
7kHz
0
144
405
3kHz
0
260
521
2kHz
0
493
754
26Hz
0
29,817
33,568
tCYCLE
tSKEW2
ADCV + PEC
ADC2
MEASURE
C7 TO C6
MEASURE
C8 TO C7
MEASURE
C12 TO C11
CALIBRATE
C7 TO C6
CALIBRATE
C8 TO C7
CALIBRATE
C12 TO C11
ADC1
MEASURE
C1 TO C0
MEASURE
C2 TO C1
MEASURE
C6 TO C5
CALIBRATE
C1 TO C0
CALIBRATE
C2 TO C1
CALIBRATE
C6 TO C5
t1M
t0
t2M t5M
t6M
t1C
t2C t5C
t6C
680412 F03
Figure 3. Timing for ADCV Command Measuring All 12 Cells
Table 5. Conversion Times for ADCV Command Measuring All 12 Cells in Different Modes
CONVERSION TIMES (in µs)
MODE
t0
t1M
t2M
t5M
t6M
t1C
t2C
t5C
t6C
27kHz
0
57
103
243
290
432
568
975
1,113
14kHz
0
86
162
389
465
606
742
1,149
1,288
7kHz
0
144
278
680
814
1,072
1,324
2,080
2,335
3kHz
0
260
511
1,262
1,512
1,770
2,022
2,778
3,033
2kHz
0
493
976
2,425
2,908
3,166
3,418
4,175
4,430
26Hz
0
29,817
59,623
149,043
178,850
182,599
186,342
197,571
201,317
24
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LTC6804-1/LTC6804-2
Operation
Under/Overvoltage Monitoring
Whenever the C inputs are measured, the results are compared to undervoltage and overvoltage thresholds stored
in memory. If the reading of a cell is above the overvoltage
limit, a bit in memory is set as a flag. Similarly, measurement results below the undervoltage limit cause a flag to
be set. The overvoltage and undervoltage thresholds are
stored in the configuration register group. The flags are
stored in the status register group B.
Auxiliary (GPIO) Measurements (ADAX Command)
The ADAX command initiates the measurement of the
GPIO inputs. This command has options to select which
GPIO input to measure (GPIO1-5) and which ADC mode.
The ADAX command also measures the 2nd reference.
There are options in the ADAX command to measure each
GPIO and the 2nd reference separately or to measure all 5
GPIOs and the 2nd reference in a single command. See the
section on commands for the ADAX command format. All
auxiliary measurements are relative to the V– pin voltage.
This command can be used to read external temperature
tREFUP
SERIAL
INTERFACE
by connecting the temperature sensors to the GPIOs.
These sensors can be powered from the 2nd reference
which is also measured by the ADAX command, resulting
in precise ratiometric measurements.
Figure 5 illustrates the timing of the ADAX command
measuring all GPIOs and the 2nd reference. Since all
the 6 measurements are carried out on ADC1 alone, the
conversion time for the ADAX command is similar to the
ADCV command.
Measuring Cell Voltages and GPIOs (ADCVAX
Command)
The ADCVAX command combines twelve cell measurements with two GPIO measurements (GPIO1 and GPIO2).
This command simplifies the synchronization of battery
cell voltage and current measurements when current sensors are connected to GPIO1 or GPIO2 inputs. Figure 6
illustrates the timing of the ADCVAX command. See the
section on commands for the ADCVAX command format.
The synchronization of the current and voltage measurements, tSKEW1, in FAST MODE is within 208µs.
tCYCLE
tSKEW
ADAX + PEC
ADC2
MEASURE
GPIO1
ADC1
MEASURE
GPIO2
t1M
t0
MEASURE
2ND REF
t2M t5M
CALIBRATE
GPIO1
t6M
CALIBRATE
GPIO2
t1C
CALIBRATE
2ND REF
t2C t5C
t6C
680412 F05
Figure 5. Timing for ADAX Command Measuring All GPIOs and 2nd Reference
Table 7. Conversion Times for ADAX Command Measuring All GPIOs and 2nd Reference in Different Modes
CONVERSION TIMES (in µs)
MODE
t0
t1M
t2M
t5M
t6M
t1C
t2C
t5C
t6C
27kHz
0
57
103
243
290
432
568
975
1,113
14kHz
0
86
162
389
465
606
742
1,149
1,288
7kHz
0
144
278
680
814
1,072
1,324
2,080
2,335
3kHz
0
260
511
1,262
1,512
1,770
2,022
2,778
3,033
2kHz
0
493
976
2,425
2,908
3,166
3,418
4,175
4,430
26Hz
0
29,817
59,623
149,043
178,850
182,599
186,342
197,571
201,317
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LTC6804-1/LTC6804-2
Operation
tREFUP
SERIAL
INTERFACE
tCYCLE
tSKEW1
tSKEW1
ADCVAX + PEC
ADC2
MEASURE
C7 TO C6
MEASURE
C8 TO C7
MEASURE
C9 TO C8
ADC1
MEASURE
C1 TO C0
MEASURE
C2 TO C1
MEASURE
C3 TO C2
t1M
t0
t2M
MEASURE
GPIO1
t3M
MEASURE
GPIO2
t4M
MEASURE
C10 TO C9
MEASURE
C11 TO C10
MEASURE
C12 TO C11
CALIBRATE
MEASURE
C4 TO C3
MEASURE
C5 TO C4
MEASURE
C6 TO C5
CALIBRATE
t5M
t6M
t7M
t8M
t8C
680412 F06
Figure 6. Timing of ADCVAX Command
Table 8. Conversion and Synchronization Times for ADCVAX Command in Different Modes
SYNCHRONIZATION
TIME (µs)
CONVERSION TIMES (in µs)
MODE
t0
t1M
t2M
t3M
t4M
t5M
t6M
t7M
t8M
t8C
tSKEW1
27kHz
0
57
106
155
216
265
326
375
424
1,564
208
14kHz
0
86
161
237
320
396
479
555
630
1,736
310
7kHz
0
144
278
412
553
687
828
962
1,096
3,133
543
3kHz
0
260
511
761
1,018
1,269
1,526
1,777
2,027
4,064
1009
2kHz
0
493
976
1,459
1,949
2,432
2,923
3,406
3,888
5,925
1939
26Hz
0
29,817
59,623
89,430
119,244
149,051
178,864
208,671
238,478
268,442
119234
Table 8 shows the conversion and synchronization time
for the ADCVAX command in different modes. The total
conversion time for the command is given by t8C.
Data Acquisition System Diagnostics
The battery monitoring data acquisition system is comprised of the multiplexers, ADCs, 1st reference, digital
filters, and memory. To ensure long term reliable performance there are several diagnostic commands which can
be used to verify the proper operation of these circuits.
tREFUP
SERIAL
INTERFACE
Measuring Internal Device Parameters (ADSTAT
Command)
The ADSTAT command is a diagnostic command that
measures the following internal device parameters: sum
of all cells (SOC), internal die temperature (ITMP), analog
power supply (VA) and the digital power supply (VD).
These parameters are described in the section below. All
6 ADC modes are available for these conversions. See the
section on commands for the ADSTAT command format.
Figure 7 illustrates the timing of the ADSTAT command
measuring all 4 internal device parameters.
tCYCLE
tSKEW
ADSTAT + PEC
ADC2
MEASURE
SOC
ADC1
t0
MEASURE
ITMP
t1M
MEASURE
VD
t2M t3M
CALIBRATE
SOC
t4M
CALIBRATE
ITMP
t1C
CALIBRATE
VD
t2C t3C
t4C
680412 F07
Figure 7. Timing for ADSTAT Command Measuring SOC, ITMP, VA, VD
26
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Operation
Table 9 shows the conversion time of the ADSTAT command measuring all 4 internal parameters. t4C indicates
the total conversion time for the ADSTAT command.
Sum of Cells Measurement: The sum of all cells measurement
is the voltage between C12 and C0 with a 20:1 attenuation.
The 16-bit ADC value of sum of cells measurement (SOC)
is stored in status register group A. Any potential difference between the CO and V– pins results in an error in the
SOC measurement equal to this difference. From the SOC
value, the sum of all cell voltage measurements is given by:
Sum of all Cells = SOC • 20 • 100µV
Internal Die Temperature: The ADSTAT command can
measure the internal die temperature. The 16-bit ADC
value of the die temperature measurement (ITMP) is
stored in status register group A. From ITMP the actual
die temperature is calculated using the expression:
Internal Die Temperature (°C) = (ITMP) • 100µV/
(7.5mV)°C – 273°C
Power Supply Measurements: The ADSTAT command is
also used to measure the analog power supply (VREG) and
digital power supply (VREGD).
The 16-bit ADC value of the analog power supply measurement (VA) is stored in Status Register Group A. The 16-bit
ADC value of the digital power supply measurement (VD)
is stored in status register group B. From VA and VD, the
power supply measurements are given by:
Analog power supply measurement (VREG) = VA • 100µV
Digital power supply measurement (VREGD) = VD • 100µV
The nominal range of VREG is 4.5V to 5.5V. The nominal
range of VREGD is 2.7V to 3.6V.
Issuing an ADSTAT command with CHST = 100 runs an
ADC measurement of just the digital supply (VREGD). This
is not recommended following an ADCV command. With
large cell voltages, running the ADSTAT command with
CST = 100 following an ADCV command with CH = 000
(all cells) can cause the LTC6804 to perform a power on
reset. If using the ADSTAT command with CHST = 100,
it is necessary to run an ADCV command with CH = 001
prior to running the ADSTAT command with CHST = 100.
This charges the high voltage multiplexer to a low potential before the VREGD measurement is executed. To save
time, this sacrificial ADCV command run prior to running
the VREGD measurement can be executed in FAST mode
(MD = 01).
Accuracy Check
Measuring an independent voltage reference is the best
means to verify the accuracy of a data acquisition system.
The LTC6804 contains a 2nd reference for this purpose.
The ADAX command will initiate the measurement of the
2nd reference. The results are placed in auxiliary register
group B. The range of the result depends on the ADC
measurement accuracy and the accuracy of the 2nd reference, including thermal hysteresis and long term drift.
Readings outside the range 2.985 to 3.015 indicate the
system is out of its specified tolerance.
MUX Decoder Check
The diagnostic command DIAGN ensures the proper operation of each multiplexer channel. The command cycles
through all channels and sets the MUXFAIL bit to 1 in
status register group B if any channel decoder fails. The
MUXFAIL bit is set to 0 if the channel decoder passes the
Table 9. Conversion Times for ADSTAT Command Measuring SOC, ITMP, VA, VD
CONVERSION TIMES (in µs)
MODE
t0
t1M
t2M
t3M
t4M
t1C
t2C
t3C
t4C
27kHz
0
57
103
150
197
338
474
610
748
14kHz
0
86
162
237
313
455
591
726
865
7kHz
0
144
278
412
546
804
1,056
1,308
1,563
3kHz
0
260
511
761
1,011
1,269
1,522
1,774
2,028
2kHz
0
493
976
1,459
1,942
2,200
2,452
2,705
2,959
26Hz
0
29,817
59,623
89,430
119,237
122,986
126,729
130,472
134,218
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Operation
test. The MUXFAIL bit is also set to 1 on power-up (POR)
or after a CLRSTAT command.
test signal passes through the digital filter and is converted to a 16-bit value. The 1-bit test signal undergoes
the same digital conversion as the regular 1-bit pulse
from the modulator, so the conversion time for any self
test command is exactly the same as the corresponding
regular ADC conversion command. The 16-bit ADC value
is stored in the same register groups as the regular ADC
conversion command. The test signals are designed to
place alternating one-zero patterns in the registers. Table
10 provides a list of the self test commands. If the digital
filters and memory are working properly, then the registers
will contain the values shown in Table 10. For more details
see the section Commands.
The DIAGN command takes about 400µs to complete if the
core is in REFUP state and about 4.5ms to complete if the
core is in STANDBY state. The polling methods described
in the section Polling Methods can be used to determine
the completion of the DIAGN command.
Digital Filter Check
The delta-sigma ADC is composed of a 1-bit pulse density modulator followed by a digital filter. A pulse density
modulated bit stream has a higher percentage of 1s for
higher analog input voltages. The digital filter converts
this high frequency 1-bit stream into a single 16-bit word.
This is why a delta-sigma ADC is often referred to as an
oversampling converter.
ADC Clear Commands
LTC6804 has 3 clear commands – CLRCELL, CLRAUX
and CLRSTAT. These commands clear the registers that
store all ADC conversion results.
The self test commands verify the operation of the digital
filters and memory. Figure 8 illustrates the operation of
the ADC during self test. The output of the 1-bit pulse
density modulator is replaced by a 1-bit test signal. The
The CLRCELL command clears cell voltage register group
A, B, C and D. All bytes in these registers are set to 0xFF
by CLRCELL command.
PULSE DENSITY
MODULATED
BIT STREAM
MUX
ANALOG
INPUT
1-BIT
MODULATOR
DIGITAL
FILTER
1
SELF TEST
PATTERN
GENERATOR
16
RESULTS
REGISTER
TEST SIGNAL
680412 F08
Figure 8. Operation of LTC6804 ADC Self Test
Table 10. Self Test Command Summary
COMMAND
SELF TEST
OPTION
27kHz
14kHz
7kHz
3kHz
2kHz
26Hz
CVST
ST[1:0]=01
0x9565
0x9553
0x9555
0x9555
0x9555
0x9555
ST[1:0]=10
0x6A9A
0x6AAC
0x6AAA
0x6AAA
0x6AAA
0x6AAA
AXST
STATST
28
RESULTS REGISTER
GROUPS
OUTPUT PATTERN IN DIFFERENT ADC MODES
ST[1:0]=01
0x9565
0x9553
0x9555
0x9555
0x9555
0x9555
ST[1:0]=10
0x6A9A
0x6AAC
0x6AAA
0x6AAA
0x6AAA
0x6AAA
ST[1:0]=01
0x9565
0x9553
0x9555
0x9555
0x9555
0x9555
ST[1:0]=10
0x6A9A
0x6AAC
0x6AAA
0x6AAA
0x6AAA
0x6AAA
C1V to C12V
(CVA, CVB, CVC, CVD)
G1V to G5V, REF
(AUXA, AUXB)
SOC, ITMP, VA, VD
(STATA, STATB)
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Operation
The CLRAUX command clears auxiliary register group
A and B. All bytes in these registers are set to 0xFF by
CLRAUX command.
The CLRSTAT command clears status register group A and
B except the REVCODE and RSVD bits in status register
group B. A read back of REVCODE will return the revision
code of the part. All OV flags, UV flags, MUXFAIL bit, and
THSD bit in status register group B are set to 1 by CLRSTAT command. The THSD bit is set to 0 after RDSTATB
command. The registers storing SOC, ITMP, VA and VD
are all set to 0xFF by CLRSTAT command.
time to create a large enough difference for the algorithm
to detect an open connection. This can be accomplished
by running more than two ADOW commands in steps 1
and 2, or by using filtered mode conversions instead of
normal mode conversions. Use Table 11 to determine how
many conversions are necessary:
Table 11
Number of ADOW Commands Required in
Steps 1 and 2
EXTERNAL C PIN
CAPACITANCE
Open-Wire Check (ADOW Command)
The ADOW command is used to check for any open wires
between the ADCs in the LTC6804 and the external cells.
This command performs ADC conversions on the C pin
inputs identically to the ADCV command, except two
internal current sources sink or source current into the
two C pins while they are being measured. The pull-up
(PUP) bit of the ADOW command determines whether the
current sources are sinking or sourcing 100µA.
The following simple algorithm can be used to check for
an open wire on any of the 13 C pins (see Figure 9):
1) Run the 12-cell command ADOW with PUP = 1 at least
twice. Read the cell voltages for cells 1 through 12 once
at the end and store them in array CELLPU(n).
2) Run the 12-cell command ADOW with PUP = 0 at least
twice. Read the cell voltages for cells 1 through 12 once
at the end and store them in array CELLPD(n).
3) Take the difference between the pull-up and pull-down
measurements made in above steps for cells 2-12:
CELL∆(n) = CELLPU(n) – CELLPD(n).
4) For all values of n from 1 to 11: If CELL∆(n+1) < –400mV,
then C(n) is open. If the CELLPU(1) = 0.0000, then C(0)
is open. If the CELLPD(12) = 0.0000, then C(12) is open.
The above algorithm detects open wires using normal mode
conversions with as much as 10nF of capacitance remaining
on the LTC6804 side of the open wire. However, if more
external capacitance is on the open C pin, then the length
of time that the open wire conversions are ran in steps 1
and 2 must be increased to give the 100µA current sources
NORMAL MODE
FILTERED MODE
≤10nF
2
2
100nF
10
2
1µF
100
2
C
1+ROUNDUP(C/10nF)
2
V+
1
+
2
+
4
+
6
+
8
+
10
+
12
+
14
+
16
+
18
+
20
+
22
+
V+
C12
100µA
C11
PUP = 1
C10
26
ADC2
6-CELL
MUX
C9
PUP = 0
C8
100µA
C7
C6
24
LTC6804
V+
C6
V–
V–
V+
V+
C5
100µA
C4
PUP = 1
C3
C2
ADC1
6-CELL
MUX
PUP = 0
C1
100µA
C0
V–
30
V–
31
V–
680412 F09
Figure 9. Open-Wire Detection Circuitry
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Operation
Thermal Shutdown
Watchdog and Software Discharge Timer
To protect the LTC6804 from overheating, there is a thermal
shutdown circuit included inside the IC. If the temperature
detected on the die goes above approximately 150°C, the
thermal shutdown circuit trips and resets the configuration register group to its default state. This turns off all
discharge switches. When a thermal shutdown event has
occurred, the THSD bit in status register group B will go
high. This bit is cleared after a read operation has been
performed on the status register group B (RDSTATB
command). The CLRSTAT command sets the THSD bit
high for diagnostic purposes, but does not reset the
configuration register group.
When there is no wake-up signal (see Figure 21) for more
than 2 seconds, the watchdog timer expires. This resets
configuration register bytes CFGR0-CFGR3 in all cases.
CFGR4 and CFGR5 are reset by the watchdog timer when
the software timer is disabled. The WDT pin is pulled high
by the external pull-up when the watchdog time elapses.
The watchdog timer is always enabled and is reset by a
qualified wake-up signal.
Revision Code and Reserved Bits
To enable the software timer, SWTEN pin needs to be tied
high to VREG (Figure 10). The discharge switches can
now be kept ON for the programmed time duration that is
determined by the DCTO value written to the configuration
register. Table 12 shows the various time settings and the
corresponding DCTO value. Table 13 summarizes the status
of the configuration register group after a watchdog timer
or software timer event.
The status register group B contains a 4-bit revision code
and 2 reserved bits. If software detection of device revision
is necessary, then contact the factory for details. Otherwise,
the code can be ignored. In all cases, however, the values
of all bits must be used when calculating the packet error
code (PEC) on data reads.
The software discharge timer is used to keep the discharge
switches turned ON for programmable time duration. If
the software timer is being used, the discharge switches
are not turned OFF when the watchdog timer is activated.
LTC6804
DCTEN
TIMEOUT
EN
SW TIMER
CLK
OSC 16Hz
VREG
1
DCTO > 0 SWTEN
RST
2
(POR OR WRCFG DONE OR TIMEOUT)
RST1
(RESETS DCTO, DCC)
WDTRST && ~DCTEN
WDT
RST2
(RESETS REFUP, VUV, VOV)
WDTPD
WATCHDOG
TIMER
CLK
RST
OSC 16Hz
WDTRST
(POR OR VALID COMMAND)
680412 F10
Figure 10. Watchdog and Software Discharge Timer
Table 12. DCTO Settings
DCTO
0
1
2
3
4
5
6
7
8
9
A
B
C
D
E
F
Time Min
Disabled
0.5
1
2
3
4
5
10
15
20
30
40
60
75
90
120
30
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Operation
Table 14
Table 13
SWTEN = 0, DCTO = XXXX
WATCHDOG TIMER
SOFTWARE TIMER
Resets CFGR0-5
When It Activates
Disabled
DCTO
(READ VALUE)
TIME LEFT (MIN)
0
Disabled (or) Timer Has Timed Out
1
0 < Timer ≤ 0.5
2
0.5 < Timer ≤ 1
3
1 < Timer ≤ 2
4
2 < Timer ≤ 3
Unlike the watchdog timer, the software timer does not
reset when there is a valid command. The software timer
can only be reset after a valid WRCFG (write configuration
register) command. There is a possibility that the software
timer will expire in the middle of some commands.
5
3 < Timer ≤ 4
6
4 < Timer ≤ 5
7
5 < Timer ≤ 10
8
10 < Timer ≤ 15
9
15 < Timer ≤ 20
If software timer activates in the middle of WRCFG command, the configuration register resets as per Table 14.
However, at the end of the valid WRCFG command, the
new data is copied to the configuration register. The new
data is not lost when the software timer is activated.
A
20 < Timer ≤ 30
B
30 < Timer ≤ 40
SWTEN = 1, DCTO = 0000
SWTEN = 1, DCTO ! = 0000
Resets CFGR0-5
When It Activates
Disabled
Resets CFGR0-3
When It Activates
Resets CFGR4-5
When It Fires
If software timer activates in the middle of RDCFG command, the configuration register group resets as per
Table 14. As a result, the read back data from bytes CRFG4
and CRFG5 could be corrupted.
I2C/SPI Master on LTC6804 Using GPIOS
The I/O ports GPIO3, GPIO4 and GPIO5 on LTC6804-1 and
LTC6804-2 can be used as an I2C or SPI master port to
communicate to an I2C or SPI slave. In the case of an I2C
master, GPIO4 and GPIO5 form the SDA and SCL ports of
the I2C interface respectively. In the case of a SPI master,
GPIO3, GPIO5 and GPIO4 become the chip select (CSBM),
clock (SCKM) and data (SDIOM) ports of the SPI interface
respectively. The SPI master on LTC6804 supports only
SPI mode 3 (CHPA = 1, CPOL = 1).
C
40 < Timer ≤ 60
D
60 < Timer ≤ 75
E
75 < Timer ≤ 90
F
90 < Timer ≤ 120
The GPIOs are open drain outputs, so an external pull-up
is required on these ports to operate as an I2C or SPI
master. It is also important to write the GPIO bits to 1 in
the CFG register group so these ports are not pulled low
internally by the device.
COMM Register
LTC6804 has a 6-byte COMM register as shown in Table 15.
This register stores all data and control bits required for
I2C or SPI communication to a slave. The COMM register
contains 3 bytes of data Dn[7:0] to be transmitted to or
received from the slave device. ICOMn [3:0] specify control actions before transmitting/receiving the data byte.
FCOMn [3:0] specify control actions after transmitting/
receiving the data byte.
Table 15. COMM Register Memory Map
REGISTER
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COMM0
RD/WR
ICOM0[3]
ICOM0[2]
ICOM0[1]
ICOM0[0]
D0[7]
D0[6]
D0[5]
D0[4]
COMM1
RD/WR
D0[3]
D0[2]
D0[1]
D0[0]
FCOM0[3]
FCOM0[2]
FCOM0[1]
FCOM0[0]
COMM2
RD/WR
ICOM1[3]
ICOM1[2]
ICOM1[1]
ICOM1[0]
D1[7]
D1[6]
D1[5]
D1[4]
COMM3
RD/WR
D1[3]
D1[2]
D1[1]
D1[0]
FCOM1[3]
FCOM1[2]
FCOM1[1]
FCOM1[0]
COMM4
RD/WR
ICOM2[3]
ICOM2[2]
ICOM2[1]
ICOM2[0]
D2[7]
D2[6]
D2[5]
D2[4]
COMM5
RD/WR
D2[3]
D2[2]
D2[1]
D2[0]
FCOM2[3]
FCOM2[2]
FCOM2[1]
FCOM2[0]
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Operation
Table 16. Write Codes for ICOMn[3:0] and FCOMn[3:0] on I2C Master
CONTROL BITS
ICOMn[3:0]
FCOMn[3:0]
CODE
ACTION
DESCRIPTION
0110
START
Generate a START Signal on I2C Port Followed By Data Transmission
0001
STOP
Generate a STOP Signal on I2C port
0000
BLANK
Proceed Directly to Data Transmission on I2C Port
0111
No Transmit
Release SDA and SCL and Ignore the Rest of the Data
0000
Master ACK
Master Generates an ACK Signal on Ninth Clock Cycle
1000
Master NACK
Master Generates a NACK Signal on Ninth Clock Cycle
1001
Master NACK + STOP
Master Generates a NACK Signal Followed by STOP Signal
Table 17. Write Codes for ICOMn[3:0] and FCOMn[3:0] on SPI Master
CONTROL BITS
ICOMn[3:0]
FCOMn[3:0]
CODE
ACTION
DESCRIPTION
1000
CSBM low
Generates a CSBM Low Signal on SPI Port (GPIO3)
1001
CSBM high
Generates a CSBM High Signal on SPI Port (GPIO3)
1111
No Transmit
Releases the SPI Port and Ignores the Rest of the Data
X000
CSBM low
Holds CSBM Low at the End of Byte Transmission
1001
CSBM high
Transitions CSBM High at the End of Byte Transmission
If the bit ICOMn[3] in the COMM register is set to 1 the
part becomes an I2C master and if the bit is set to 0 the
part becomes a SPI master.
Table 16 describes the valid write codes for ICOMn[3:0]
and FCOMn[3:0] and their behavior when using the part
as an I2C master.
Table 17 describes the valid codes for ICOMn[3:0] and
FCOMn[3:0] and their behavior when using the part as
a SPI master.
Note that only the codes listed in Tables 16 and 17 are
valid for ICOMn[3:0] and FCOMn[3:0]. Writing any other
code that is not listed in Tables 16 and 17 to ICOMn[3:0]
and FCOMn[3:0] may result in unexpected behavior on
the I2C and SPI ports.
COMM Commands
Three commands help accomplish I2C or SPI communication to the slave device: WRCOMM, STCOMM, RDCOMM
WRCOMM Command: This command is used to write data
to the COMM register. This command writes 6 bytes of
data to the COMM register. The PEC needs to be written
32
at the end of the data. If the PEC does not match, all data
in the COMM register is cleared to 1’s when CSB goes
high. See the section Bus Protocols for more details on a
write command format.
STCOMM Command: This command initiates I2C/SPI communication on the GPIO ports. The COMM register contains
3 bytes of data to be transmitted to the slave. During this
command, the data bytes stored in the COMM register are
transmitted to the slave I2C or SPI device and the data
received from the I2C or SPI device is stored in the COMM
register. This command uses GPIO4 (SDA) and GPIO5
(SCL) for I2C communication or GPIO3 (CSBM), GPIO4
(SDIOM) and GPIO5 (SCKM) for SPI communication.
The STCOMM command is to be followed by 24 clock
cycles for each byte of data to be transmitted to the slave
device while holding CSB low. For example, to transmit 3
bytes of data to the slave, send STCOMM command and
its PEC followed by 72 clock cycles. Pull CSB high at the
end of the 72 clock cycles of STCOMM command.
During I2C or SPI communication, the data received from
the slave device is updated in the COMM register.
680412fc
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LTC6804-1/LTC6804-2
Operation
RDCOMM Command: The data received from the slave
device can be read back from the COMM register using the
RDCOMM command. The command reads back 6 bytes of
data followed by the PEC. See the section Bus Protocols
for more details on a read command format.
Table 18 describes the possible read back codes for
ICOMn[3:0] and FCOMn[3:0] when using the part as an I2C
master. Dn[7:0] contains the data byte either transmitted
by the I2C master or received from the I2C slave.
In case of the SPI master, the read back codes for
ICOMn[3:0] and FCOMn[3:0] are always 0111 and 1111
respectively. Dn[7:0] contains the data byte either transmitted by the SPI master or received from the SPI slave.
Table 18. Read Codes for ICOMn[3:0] and FCOMn[3:0] on I2C
Master
CONTROL
BITS
ICOMn[3:0]
FCOMn[3:0]
CODE
DESCRIPTION
0110
Master Generated a START Signal
0001
Master Generated a STOP Signal
0000
Blank, SDA Was Held Low Between Bytes
0111
Blank, SDA Was Held High Between Bytes
0000
Master Generated an ACK Signal
0111
Slave Generated an ACK Signal
1111
Slave Generated a NACK Signal
0001
Slave Generated an ACK Signal, Master
Generated a STOP Signal
1001
Slave Generated a NACK Signal, Master
Generated a STOP Signal
Figure 11 illustrates the operation of LTC6804 as an I2C
or SPI master using the GPIOs.
LTC6804-1/LTC6804-2
I2C/SPI
SLAVE
STCOMM
RDCOMM
GPIO
PORT
COMM
REGISTER
PORT A
WRCOMM
Any number of bytes can be transmitted to the slave in
groups of 3 bytes using these commands. The GPIO ports
will not get reset between different STCOMM commands.
However, if the wait time between the commands is greater
than 2 seconds, the watchdog will timeout and reset the
ports to their default values.
To transmit several bytes of data using an I2C master, a
START signal is only required at the beginning of the entire
data stream. A STOP signal is only required at the end of
the data stream. All intermediate data groups can use a
BLANK code before the data byte and an ACK/NACK signal
as appropriate after the data byte. SDA and SCL will not
get reset between different STCOMM commands.
To transmit several bytes of data using SPI master, a
CSBM low signal is sent at the beginning of the 1st data
byte. CSBM can be held low or taken high for intermediate
data groups using the appropriate code on FCOMn[3:0].
A CSBM high signal is sent at the end of the last byte of
data. CSBM, SDIOM and SCKM will not get reset between
different STCOMM commands.
Figure 12 shows the 24 clock cycles following STCOMM
command for an I2C master in different cases. Note that
if ICOMn[3:0] specified a STOP condition, after the STOP
signal is sent, the SDA and SCL lines are held high and
all data in the rest of the word is ignored. If ICOMn[3:0]
is a NO TRANSMIT, both SDA and SCL lines are released,
and rest of the data in the word is ignored. This is used
when a particular device in the stack does not have to
communicate to a slave.
Figure 13 shows the 24 clock cycles following STCOMM
command for a SPI master. Similar to the I2C master, if
ICOMn[3:0] specified a CSBM HIGH or a NO TRANSMIT
condition, the CSBM, SCKM and SDIOM lines of the SPI
master are released and the rest of the data in the word
is ignored.
680412 F11
Figure 11. LTC6804 I2C/SPI Master Using GPIOs
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33
LTC6804-1/LTC6804-2
Operation
tCLK
t4
t3
(SCK)
START
NACK + STOP
BLANK
NACK
START
ACK
SCL (GPIO5)
SDA (GPIO4)
SCL (GPIO5)
SDA (GPIO4)
SCL (GPIO5)
SDA (GPIO4)
STOP
SCL (GPIO5)
SDA (GPIO4)
NO TRANSMIT
SCL (GPIO5)
SDA (GPIO4)
680412 F12
Figure 12. STCOMM Timing Diagram for an I2C Master
tCLK
t4
t3
(SCK)
CSBM LOW
CSBM HIGH ≥ LOW
CSBM (GPIO3)
SCKM (GPIO5)
SDIOM (GPIO4)
CSBM LOW ≥ HIGH
CSBM LOW
CSBM (GPIO3)
SCKM (GPIO5)
SDIOM (GPIO4)
CSBM HIGH/NO TRANSMIT
CSBM (GPIO3)
SCKM (GPIO5)
SDIOM (GPIO4)
680412 F13
Figure 13. STCOMM Timing Diagram for a SPI Master
34
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LTC6804-1/LTC6804-2
Operation
Timing Specifications of I2C and SPI master
The timing of the LTC6804 I2C or SPI master will be
controlled by the timing of the communication at the
LTC6804’s primary SPI interface. Table 19 shows the
I2C master timing relationship to the primary SPI clock.
Table 20 shows the SPI master timing specifications.
Table 19. I2C Master Timing
TIMING RELATIONSHIP
TIMING
I2C MASTER
TO PRIMARY SPI
SPECIFICATIONS AT
PARAMETER
INTERFACE
tCLK = 1µs
Max 500kHz
SCL Clock Frequency
1/(2 • tCLK)
t3
Min 200ns
tHD; STA
tCLK
Min 1µs
tLOW
tCLK
Min 1µs
tHIGH
tCLK + t4*
Min 1.03µs
tSU; STA
t 4*
Min 30ns
tHD; DAT
t3
Min 1µs
tSU; DAT
tCLK + t4*
Min 1.03µs
tSU; STO
3 • tCLK
Min 3µs
tBUF
*Note: When using isoSPI, t4 is generated internally and is a minimum of
30ns. Also, t3 = tCLK – t4. When using SPI, t3 and t4 are the low and high
times of the SCK input, each with a specified minimum of 200ns.
Serial Interface Overview
There are two types of serial ports on the LTC6804, a
standard 4-wire serial peripheral interface (SPI) and a
2-wire isolated interface (isoSPI). Pins 41 through 44 are
configurable as 2-wire or 4-wire serial port, based on the
state of the ISOMD pin.
There are two versions of the LTC6804: the LTC6804-1
and the LTC6804-2. The LTC6804-1 is used in a daisy
chain configuration, and the LTC6804-2 is used in an
addressable bus configuration. The LTC6804-1 provides
a second isoSPI interface using pins 45 through 48. The
LTC6804-2 uses pins 45 through 48 to set the address of
the device, by tying these pins to V– or VREG.
Table 20. SPI Master Timing
TIMING RELATIONSHIP
TIMING
TO PRIMARY SPI
SPECIFICATIONS
SPI MASTER PARAMETER
INTERFACE
AT tCLK = 1µs
Min 200ns
SDIOM Valid to SCKM
t3
Rising Setup
Min 1.03µs
SDIOM Valid from SCKM
tCLK + t4*
Rising Hold
Min 1µs
SCKM Low
tCLK
Min 1µs
SCKM High
tCLK
Min 2µs
SCKM Period (SCKM_Low
2 • tCLK
+ SCKM_High)
Min 3µs
CSBM Pulse Width
3 • tCLK
Min 5.03µs
SCKM Rising to CSBM
5 • tCLK + t4*
Rising
Min 200ns
CSBM Falling to SCKM
t3
Falling
Min 1.2µs
CSBM Falling to SCKM
tCLK + t3
Rising
SCKM Falling to SDIOM
Master requires < tCLK
Valid
*Note: When using isoSPI, t4 is generated internally and is a minimum of
30ns. Also, t3 = tCLK – t4. When using SPI, t3 and t4 are the low and high
times of the SCK input, each with a specified minimum of 200ns.
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35
LTC6804-1/LTC6804-2
Operation
4-Wire Serial Peripheral Interface (SPI)
Physical Layer
2-Wire Isolated Interface (isoSPI) Physical
Layer
External Connections
The 2-wire interface provides a means to interconnect
LTC6804 devices using simple twisted pair cabling. The
interface is designed for low packet error rates when the
cabling is subjected to high RF fields. Isolation is achieved
through an external transformer.
Connecting ISOMD to V– configures serial Port A for
4-wire SPI. The SDO pin is an open drain output which
requires a pull-up resistor tied to the appropriate supply
voltage (Figure 14).
Timing
The 4-wire serial port is configured to operate in a SPI
system using CPHA = 1 and CPOL = 1. Consequently, data
on SDI must be stable during the rising edge of SCK. The
timing is depicted in Figure 15. The maximum data rate
is 1Mbps.
V+
C12
S12
LTC6804-1
Standard SPI signals are encoded into differential pulses.
The strength of the transmission pulse and the threshold
level of the receiver are set by two external resistors, RB1
and RB2. The values of the resistors allow the user to trade
off power dissipation for noise immunity.
V+
IPB
IMB
DAISY-CHAIN SUPPORT
ICMP
5k
C12
LTC6804-2
A3
A2
A1
S12
C11
IBIAS
S11
SDO (NC)
MISO
C10
SDI (NC)
S10
SCK (IPA)
C9
CSB (IMA)
CS
S9
ISOMD
C8
WDT
C8
WDT
S8
DRIVE
S8
DRIVE
C7
VREG
C7
VREG
S7
SWTEN
S7
SWTEN
C6
VREF1
C6
VREF1
S6
VREF2
S6
VREF2
C5
GPIO5
C5
GPIO5
S5
GPIO4
S5
GPIO4
C4
V–
C4
V–
S4
V–
S4
V–
C3
GPIO3
C3
GPIO3
S3
GPIO2
S3
GPIO2
C2
GPIO1
C2
GPIO1
S2
C0
S2
C0
C1
S1
C1
ADDRESS PINS
5k
C11
A0
S11
SDO (IBIAS)
MISO
MOSI
C10
SDI (ICMP)
MOSI
CLK
S10
SCK (IPA)
CLK
C9
CSB (IMA)
CS
S9
ISOMD
VDD
MPU
VDD
MPU
S1
680412 F14
Figure 14. 4-Wire SPI Configuration
36
680412fc
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LTC6804-1/LTC6804-2
Operation
t1
t4
t2
t3
t6
t7
SCK
SDI
D3
D2
D1
D0
D7…D4
D3
t5
CSB
t8
SDO
D4
D3
D2
D1
D0
D7…D4
PREVIOUS COMMAND
D3
680412 F15
CURRENT COMMAND
Figure 15. Timing Diagram of 4-Wire Serial Peripheral Interface
LTC6804
VREG
WAKEUP
CIRCUIT
(ON PORT A)
35k
Tx = +1
LOGIC
AND
MEMORY
SCK
CSB
IDLE
VICMP/3 + 167mV
IDLE
Tx • 20 • IB
IPA OR IPB
Tx = 0
SDO
SDI
+
–
35k
Tx = –1
PULSE
ENCODER/
DECODER
IMA OR IMB
Rx = +1
Rx = 0
Rx = –1
1
COMPARATOR THRESHOLD = • VICMP
2
RM
•
•
+
IB
–
+
–
IBIAS
2V
ICMP
RB1
0.5x
RB2
Figure 16. isoSPI Interface
Figure 16 illustrates how the isoSPI circuit operates. A
2V reference drives the IBIAS pin. External resistors RB1
and RB2 create the reference current IB. This current sets
the drive strength of the transmitter. RB1 and RB2 also
form a voltage divider of the 2V reference at the ICMP
pin. This sets the threshold voltage of the receiver circuit.
Transmitted current pulses are converted into voltage by
termination resistor RM (in parallel with the characteristic
impedance of the cable).
680412 F16
External Connections
The LTC6804-1 has 2 serial ports which are called Port B
and Port A. Port B is always configured as a 2-wire interface
(master). The final device in the daisy chain does not use
this port, and it should be terminated into RM. Port A is
either a 2-wire or 4-wire interface (slave), depending on
the connection of the ISOMD pin.
680412fc
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37
LTC6804-1/LTC6804-2
Operation
Figure 17a is an example of a robust interconnection of
multiple identical PCBs, each containing one LTC6804‑1.
Note the termination in the final device in the daisy chain.
The microprocessor is located on a separate PCB. To
achieve 2-wire isolation between the microprocessor PCB
and the 1st LTC6804-1 PCB, use the LTC6820 support IC.
The LTC6820 is functionally equivalent to the diagram in
Figure 16.
As an example, if divider resistor RB1 is 2.8k and resistor
RB2 is 1.21k (so that RBIAS = 4k), then:
The LTC6804-2 has a single serial port (Port A) which can
be 2-wire or 4-wire, depending on the state of the ISOMD
pin. When configured for 2-wire communications, several
devices can be connected in a multi-drop configuration, as
shown in Figure 17b. The LTC6820 IC is used to interface
the MPU (master) to the LTC6804-2’s (slaves).
VTCMP = 0.5 • VICMP = 302mV
Using a Single LTC6804
When only one LTC6804 is needed, the LTC6804-2 is recommended. It does not have isoSPI Port B, so it requires
fewer external components and consumes less power,
especially when Port A is configured as a 4-wire interface.
However, the LTC6804-1 can be used as a single (non
daisy-chained) device if the second isoSPI port (Port B) is
properly biased and terminated, as shown in Figure 18c.
ICMP should not be tied to GND, but can be tied directly
to IBIAS. A bias resistance (2k to 20k) is required for
IBIAS. Do not tie IBIAS directly to VREG or V–. Finally, IPB
and IMB should be terminated into a 100Ω resistor (not
tied to VREG or V–).
Selecting Bias Resistors
The adjustable signal amplitude allows the system to trade
power consumption for communication robustness, and
the adjustable comparator threshold allows the system to
account for signal losses.
The isoSPI transmitter drive current and comparator voltage threshold are set by a resistor divider (RBIAS = RB1
+ RB2) between the IBIAS and V–. The divided voltage is
connected to the ICMP pin which sets the comparator
threshold to 1/2 of this voltage (VICMP). When either
isoSPI interface is enabled (not IDLE) IBIAS is held at 2V,
causing a current IB to flow out of the IBIAS pin. The IP
and IM pin drive currents are 20 • IB.
38
IB =
2V
= 0.5mA
RB1 +RB2
IDRV =IIP =IIM = 20 •IB = 10mA
VICMP = 2V •
RB2
=I •R = 603mV
RB1 +RB2 B B2
In this example, the pulse drive current IDRV will be 10mA,
and the receiver comparators will detect pulses with IP-IM
amplitudes greater than ±302mV.
If the isolation barrier uses 1:1 transformers connected
by a twisted pair and terminated with 120Ω resistors on
each end, then the transmitted differential signal amplitude
(±) will be:
VA =IDRV •
RM
= 0.6V
2
(This result ignores transformer and cable losses, which
may reduce the amplitude).
isoSPI Pulse Detail
Two LTC6804 devices can communicate by transmitting
and receiving differential pulses back and forth through an
isolation barrier. The transmitter can output three voltage
levels: +VA, 0V, and –VA. A positive output results from
IP sourcing current and IM sinking current across load
resistor RM. A negative voltage is developed by IP sinking and IM sourcing. When both outputs are off, the load
resistance forces the differential output to 0V.
To eliminate the DC signal component and enhance reliability, the isoSPI uses two different pulse lengths. This
allows for four types of pulses to be transmitted, as shown
in Table 21. A +1 pulse will be transmitted as a positive
pulse followed by a negative pulse. A –1 pulse will be
transmitted as a negative pulse followed by a positive
pulse. The duration of each pulse is defined as t1/2PW,
since each is half of the required symmetric pair. (The
total isoSPI pulse duration is 2 • t1/2PW).
680412fc
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IPB
GPIO5
GPIO4
V–
V–
GPIO3
GPIO2
GPIO1
C0
S1
A3
C5
S5
C4
S4
C3
S3
C2
S2
C1
V+
V–
V–
GPIO3
GPIO2
GPIO1
C0
S1
C4
S4
C3
S3
C2
S2
C1
GPIO4
V–
V–
GPIO3
GPIO2
GPIO1
C0
S1
S5
C4
S4
C3
S3
C2
S2
C1
•
•
•
•
•
IPB
VREF1
VREF2
GPIO5
GPIO4
V–
V–
GPIO3
GPIO2
GPIO1
C0
S1
C5
S5
C4
S4
C3
S3
C2
S2
C1
SWTEN
S7
S6
VREG
C7
C6
WDT
DRIVE
S9
S8
ISOMD
C9
C8
SDI (NC)
CSB (IMA)
S10
SDO (NC)
SCK (IPA)
S11
C10
ICMP
IBIAS
IMB
C11
LTC6804-1
S12
C12
V+
S12
C11
S11
A0
SDO (IBIAS)
S11
For more information www.linear.com/LTC6804-1
C10
C6
S6
C5
S5
C4
GPIO5
GPIO4
V–
C5
S5
C4
C3
S3
C2
S2
C1
V
GPIO3
GPIO2
GPIO1
C0
S1
S4
C3
S3
C2
S2
C1
S4
S7
VREF1
VREF2
S6
S7
C6
C7
SWTEN
VREG
S8
C7
C8
WDT
S9
ISOMD
S9
DRIVE
C9
S8
S10
SCK (IPA)
CSB (IMA)
C9
C8
C10
SDI (ICMP)
S10
S1
C0
GPIO1
GPIO2
GPIO3
V
–
V–
GPIO4
GPIO5
VREF2
VREF1
SWTEN
VREG
DRIVE
WDT
ISOMD
CSB (IMA)
SCK (IPA)
SDI (ICMP)
SDO (IBIAS)
A0
A1
S1
C0
GPIO1
GPIO2
GPIO3
V
–
V–
GPIO4
GPIO5
VREF2
VREF1
SWTEN
VREG
DRIVE
WDT
ISOMD
CSB (IMA)
SCK (IPA)
SDI (ICMP)
SDO (IBIAS)
A0
A1
ADDRESS = 0x1
C1
S2
C2
S3
C3
S4
C4
S5
C5
S6
C6
S7
C7
S8
C8
S9
C9
S10
C10
S11
C11
S12
C12
V+
A0
A1
A2
A3
S1
C0
GPIO1
GPIO2
GPIO3
V
–
V–
GPIO4
GPIO5
VREF2
VREF1
SWTEN
VREG
DRIVE
WDT
ISOMD
CSB (IMA)
SCK (IPA)
SDI (ICMP)
SDO (IBIAS)
LTC6804-2
Figure 17b. Multi-Drop Configuration Using LTC6804-2
C1
S2
C2
S3
C3
S4
C4
S5
C5
S6
C6
S7
C7
S8
C8
S9
C9
S10
C10
S11
C11
S12
A2
A3
ADDRESS = 0x0
•
A1
LTC6804-2
•
C12
V+
•
C11
ADDRESS = 0x2
•
A2
A3
•
S12
LTC6804-2
•
–
GPIO5
C5
•
V+
GPIO4
S5
VREF1
VREF2
SWTEN
S7
S6
VREG
C7
C6
WDT
S9
DRIVE
ISOMD
C9
S8
CSB (IMA)
S10
C8
SDI (NC)
SDO (NC)
SCK (IPA)
S11
C10
ICMP
IBIAS
C11
•
•
C12
ADDRESS = 0x3
GPIO5
C5
IPB
IMB
S12
LTC6804-1
•
Figure 17a. Transformer-Isolated Daisy-Chain Configuration Using LTC6804-1
VREF1
VREF2
SWTEN
S7
S6
VREG
C7
C6
WDT
S9
DRIVE
ISOMD
C9
S8
CSB (IMA)
S10
C8
SDI (NC)
SDO (NC)
SCK (IPA)
S11
C10
ICMP
IBIAS
C12
V+
•
•
C12
IPB
IMB
C11
LTC6804-1
S12
C12
V+
•
A2
LTC6804-2
VREF1
VREF2
SWTEN
S7
S6
VREG
C7
C6
WDT
S9
DRIVE
ISOMD
C9
S8
CSB (IMA)
S10
C8
SDI (NC)
SDO (NC)
S11
SCK (IPA)
C11
C10
ICMP
IBIAS
S12
•
IMB
•
LTC6804-1
•
C12
•
V+
POL
MISO
IP
GND
CS
IM
IP
SLOW
IBIAS
ICMP
MSTR
SCK
MOSI
MISO
POL
PHA
VDD
LTC6820
EN
MPU
VDD
IM
VDDS
CS
CLK
MOSI
GND
CS
SLOW
ICMP
IBIAS
SCK
MSTR
MOSI
MISO
PHA
VDD
LTC6820
EN
MPU
VDD
VDDS
CS
CLK
MOSI
MISO
•
•
•
•
680412 F18
680412 F17
LTC6804-1/LTC6804-2
Operation
680412fc
39
LTC6804-1/LTC6804-2
Operation
TERMINATED UNUSED PORT
RM
•
MISO
MOSI
CLK
CS MPU
LTC6820
VDD
VDDS
POL
EN
PHA
MSTR
ICMP
IBIAS
MISO
GND
MOSI
SLOW
SCK
CS
IP
IM
•
•
VDD
MISO
MOSI
CLK
CS MPU
•
ADDRESS = 0×0
LTC6804-2
V+
A3
C12
A2
S12
A1
C11
A0
S11 SDO(IBIAS)
C10 SDI(ICMP)
S10
SCK(IPA)
C9
CSB(IMA)
S9
ISOMD
C8
WDT
S8
DRIVE
C7
VREG
S7
SWTEN
C6
VREF1
S6
VREF2
C5
GPIO5
S5
GPIO4
C4
V–
S4
V–
C3
GPIO3
S3
GPIO2
C2
GPIO1
S2
C0
C1
S1
VDD
•
•
LTC6804-1
V+
IPB
C12
IMB
S12
ICMP
C11
IBIAS
S11
SDO(NC)
C10
SDI(NC)
S10
SCK(IPA)
C9
CSB(IMA)
S9
ISOMD
C8
WDT
S8
DRIVE
C7
VREG
S7
SWTEN
C6
VREF1
S6
VREF2
C5
GPIO5
S5
GPIO4
C4
V–
S4
V–
C3
GPIO3
S3
GPIO2
C2
GPIO1
S2
C0
C1
S1
LTC6820
VDD
VDDS
POL
EN
PHA
MSTR
ICMP
IBIAS
MISO
GND
MOSI
SLOW
SCK
CS
IP
IM
680412 F18a
Figure 18a. Single-Device LTC6804-1 Using 2-Wire Port A
•
•
680412 F18b
Figure 18b. Single-Device LTC6804-2 Using 2-Wire Port A
TERMINATED UNUSED PORT
LTC6804-1
V+
IPB
C12
IMB
S12
ICMP
C11
IBIAS
S11
SDO(NC)
C10
SDI(NC)
S10
SCK(IPA)
C9
CSB(IMA)
S9
ISOMD
C8
WDT
S8
DRIVE
C7
VREG
S7
SWTEN
C6
VREF1
S6
VREF2
C5
GPIO5
S5
GPIO4
C4
V–
S4
V–
C3
GPIO3
S3
GPIO2
C2
GPIO1
S2
C0
C1
S1
100Ω
20k
ADDRESS = 0×0
LTC6804-2
V+
A3
C12
A2
S12
A1
C11
A0
S11 SDO(IBIAS)
C10 SDI(ICMP)
S10
SCK(IPA)
C9
CSB(IMA)
S9
ISOMD
C8
WDT
S8
DRIVE
C7
VREG
S7
SWTEN
C6
VREF1
S6
VREF2
C5
GPIO5
S5
GPIO4
C4
V–
S4
V–
C3
GPIO3
S3
GPIO2
C2
GPIO1
S2
C0
C1
S1
REQUIRED BIAS
5k
VDD
MISO
MOSI
CLK
CS MPU
680412 F18c
Figure 18c. Single-Device LTC6804-1 Using 4-Wire Port A
40
5k
VDD
MISO
MOSI
CLK
CS MPU
680412 F18d
Figure 18d. Single-Device LTC6804-2 Using 4-Wire Port A
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Operation
Table 21. isoSPI Pulse Types
Table 22. LTC6804-1 Port B (Master) isoSPI Port Function
COMMUNICATION EVENT
(PORT A SPI)
TRANSMITTED PULSE
(PORT B isoSPI)
0V
CSB Rising
Long +1
+VA (150ns)
0V
CSB Falling
Long –1
+VA (50ns)
–VA (50ns)
0V
SCK Rising Edge, SDI = 1
Short +1
–VA (50ns)
+VA (50ns)
0V
SCK Rising Edge, SDI = 0
Short –1
PULSE TYPE
FIRST LEVEL
(t1/2PW)
SECOND LEVEL
(t1/2PW)
ENDING LEVEL
Long +1
+VA (150ns)
–VA (150ns)
Long –1
–VA (150ns)
Short +1
Short –1
A host microcontroller does not have to generate isoSPI
pulses to use this 2-wire interface. The first LTC6804 in
the system can communicate to the microcontroller using
the 4-wire SPI interface on its Port A, then daisy-chain to
other LTC6804s using the 2-wire isoSPI interface on its
Port B. Alternatively, an LTC6820 can be used to translate
the SPI signals into isoSPI pulses.
On the other side of the isolation barrier (i.e. at the other
end of the cable), the 2nd LTC6804 will have ISOMD =
VREG. Its Port A operates as a slave isoSPI interface. It
receives each transmitted pulse and reconstructs the
SPI signals internally, as shown in Table 23. In addition,
during a READ command this port may transmit return
data pulses.
LTC6804-1 Operation with Port A Configured for SPI
Table 23. LTC6804-1 Port A (Slave) isoSPI Port Function
When the LTC6804-1 is operating with port A as an SPI
(ISOMD = V–), the SPI detects one of four communication
events: CSB falling, CSB rising, SCK rising with SDI = 0,
and SCK rising with SDI = 1. Each event is converted into
one of the four pulse types for transmission through the
LTC6804-1 daisy chain. Long pulses are used to transmit
CSB changes and short pulses are used to transmit data,
as explained in Table 22.
RECEIVED PULSE
(PORT A isoSPI)
INTERNAL SPI
PORT ACTION
RETURN PULSE
Long +1
Drive CSB High
None
Long –1
Drive CSB Low
Short +1
1. Set SDI = 1
2. Pulse SCK
Short –1 Pulse if Reading a 0 bit
Short –1
1. Set SDI = 0
2. Pulse SCK
(No Return Pulse if Not in READ
Mode or if Reading a 1 bit)
+1 PULSE
+VA
+VTCMP
t1/2PW
VIP – VIM
t1/2PW
–VTCMP
tINV
–VA
–1 PULSE
+VA
+VTCMP
tINV
t1/2PW
VIP – VIM
–VTCMP
t1/2PW
–VA
680412 F19
Figure 19. isoSPI Pulse Detail
680412fc
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41
LTC6804-1/LTC6804-2
Operation
The lower isoSPI port (Port A) never transmits long
(CSB) pulses. Furthermore, a slave isoSPI port will only
transmit short –1 pulses, never a +1 pulse. The master
port recognizes a null response as a logic 1. This allows
for multiple slave devices on a single cable without risk
of collisions (Multidrop).
Bits Wn-W0 refers to the 16-bit command code and the
16-bit PEC of a READ command. At the end of bit W0 the
3 parts decode the READ command and begin shifting out
data which is valid on the next rising edge of clock SCK.
Bits Xn-X0 refer to the data shifted out by Part 1. Bits Yn-Y0
refer to the data shifted out by Part 2 and bits Zn-Z0 refer
to the data shifted out by Part 3. All this data is read back
from the SDO port on Part 1 in a daisy-chained fashion.
Figure 20 shows the isoSPI timing diagram for a READ
command to daisy-chained LTC6804-1 parts. The ISOMD
pin is tied to V– on the bottom part so its Port A is configured as a SPI port (CSB, SCK, SDI and SDO). The isoSPI
signals of three stacked devices are shown, labeled with
the port (A or B) and part number. Note that ISO B1 and
ISO A2 is actually the same signal, but shown on each
end of the transmission cable that connects parts 1 and 2.
Likewise, ISO B2 and ISO A3 is the same signal, but with
the cable delay shown between parts 2 and 3.
Waking Up the Serial Interface
The serial ports (SPI or isoSPI) will enter the low power
IDLE state if there is no activity on Port A for a time of tIDLE.
The WAKEUP circuit monitors activity on pins 41 and 42.
If ISOMD = V–, Port A is in SPI mode. Activity on the CSB
or SCK pin will wake up the SPI interface. If ISOMD = VREG,
COMMAND
CSB
READ DATA
t7
t6
t1
SDI
t5
t2
tCLK
t4
SCK
t3
t8
tRISE
SDO
t11
Xn
t10
Xn-1
Z0
t9
t10
Wn
ISO B1
W0
Wn
ISO A2
Yn
W0
Yn-1
Yn
Yn-1
tRTN
tDSY(CS)
Wn
ISO B2
tDSY(CS)
tDSY(D)
W0
Wn
ISO A3
0
1000
W0
2000
Zn
Zn
3000
Zn-1
Zn-1
4000
5000
6000
680412 F20
Figure 20. isoSPI Timing Diagram
42
680412fc
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LTC6804-1/LTC6804-2
Operation
Port A is in isoSPI mode. Differential activity on IPA-IMB
wakes up the isoSPI interface. The LTC6804 will be ready
to communicate when the isoSPI state changes to READY
within tWAKE or tREADY, depending on the Core state (see
Figure 1 and state descriptions for details.)
Figure 21 illustrates the timing and the functionally
equivalent circuit. Common mode signals will not wake
up the serial interface. The interface is designed to wake
up after receiving a large signal single-ended pulse, or a
low-amplitude symmetric pulse. The differential signal
|SCK(IPA) – CSB(IMA)|, must be at least VWAKE = 200mV
for a minimum duration of tDWELL = 240ns to qualify as a
wake up signal that powers up the serial interface.
Waking a Daisy Chain — Method 1
The LTC6804-1 sends a Long +1 pulse on Port B after it is
ready to communicate. In a daisy-chained configuration,
this pulse wakes up the next device in the stack which will,
in turn, wake up the next device. If there are ‘N’ devices in
the stack, all the devices are powered up within the time
N • tWAKE or N • tREADY, depending on the Core State. For
large stacks, the time N • tWAKE may be equal to or larger
than tIDLE. In this case, after waiting longer than the time
of N • tWAKE, the host may send another dummy byte and
wait for the time N • tREADY, in order to ensure that all
devices are in the READY state.
Method 1 can be used when all devices on the daisy chain
are in the IDLE state. This guarantees that they propagate
the wake-up signal up the daisy chain. However, this
method will fail to wake up all devices when a device in
the middle of the chain is in the READY state instead of
IDLE. When this happens, the device in READY state will
not propagate the wake-up pulse, so the devices above it
will remain IDLE. This situation can occur when attempting to wake up the daisy chain after only tIDLE of idle time
(some devices may be IDLE, some may not).
Waking a Daisy Chain — Method 2
A more robust wake-up method does not rely on the built-in
wake-up pulse, but manually sends isoSPI traffic for enough
time to wake the entire daisy chain. At minimum, a pair of
long isoSPI pulses (–1 and +1) is needed for each device,
separated by more than tREADY or tWAKE (if the core state is
STANDBY or SLEEP, respectively), but less than tIDLE. This
allows each device to wake up and propagate the next pulse
to the following device. This method works even if some
devices in the chain are not in the IDLE state. In practice,
implementing method 2 requires toggling the CSB pin
(of the LTC6820, or bottom LTC6804-1 with ISOMD = 0)
to generate the long isoSPI pulses. Alternatively, dummy
commands (such as RDCFG) can be executed to generate
the long isoSPI pulses.
REJECTS COMMON
MODE NOISE
CSB OR IMA
SCK OR IPA
VWAKE = 200mV
|SCK(IPA) - CSB(IMA)|
tDWELL= 240ns
WAKE-UP
STATE
LOW POWER MODE
tIDLE > 4.5ms
tREADY < 10µs
CSB OR IMA
SCK OR IPA
LOW POWER MODE
OK TO COMMUNICATE
tDWELL = 240ns
DELAY
RETRIGGERABLE
tIDLE = 5.5ms
ONE-SHOT
WAKE-UP
680412 F21
Figure 21. Wake-Up Detection and IDLE Timer
680412fc
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43
LTC6804-1/LTC6804-2
Operation
Data Link Layer
3. Update the 15-bit PEC as follows
All Data transfers on LTC6804 occur in byte groups.
Every byte consists of 8 bits. Bytes are transferred with
the most significant bit (MSB) first. CSB must remain low
for the entire duration of a command sequence, including
between a command byte and subsequent data. On a write
command, data is latched in on the rising edge of CSB.
PEC [14] = IN14,
Network Layer
PEC [9] = PEC [8],
PEC [13] = PEC [12],
PEC [12] = PEC [11],
PEC [11] = PEC [10],
PEC [10] = IN10,
PEC [8] = IN8,
Packet Error Code
The packet error code (PEC) is a 15-bit cyclic redundancy
check (CRC) value calculated for all of the bits in a register group in the order they are passed, using the initial
PEC seed value of 000000000010000 and the following
characteristic polynomial: x15 + x14 + x10 + x8 + x7 +
x4 + x3 + 1. To calculate the 15-bit PEC value, a simple
procedure can be established:
1. Initialize the PEC to 000000000010000 (PEC is a 15-bit
register group)
2. For each bit DIN coming into the PEC register group,
set
IN0 = DIN XOR PEC [14]
IN3 = IN0 XOR PEC [2]
PEC [7] = IN7,
PEC [6] = PEC [5],
PEC [5] = PEC [4],
PEC [4] = IN4,
PEC [3] = IN3,
PEC [2] = PEC [1],
PEC [1] = PEC [0],
PEC [0] = IN0
4. Go back to step 2 until all the data is shifted. The final
PEC (16 bits) is the 15-bit value in the PEC register with
a 0 bit appended to its LSB
Figure 22 illustrates the algorithm described above. An
example to calculate the PEC for a 16-bit word (0x0001)
is listed in Table 24. The PEC for 0x0001 is computed as
0x3D6E after stuffing a 0 bit at the LSB. For longer data
streams, the PEC is valid at the end of the last bit of data
sent to the PEC register.
IN4 = IN0 XOR PEC [3]
IN7 = IN0 XOR PEC [6]
IN8 = IN0 XOR PEC [7]
IN10 = IN0 XOR PEC [9]
IN14 = IN0 XOR PEC [13]
O/P
I/P XOR GATE
I/P
X
PEC REGISTER BIT X
DIN
14
13 12 11 10
9 8
7
6 5 4
3
2 1 0
680412 F22
Figure 22. 15-Bit PEC Computation Circuit
44
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LTC6804-1/LTC6804-2
Operation
LTC6804 calculates PEC for any command or data received
and compares it with the PEC following the command or
data. The command or data is regarded as valid only if
the PEC matches. LTC6804 also attaches the calculated
PEC at the end of the data it shifts out. Table 25 shows the
format of PEC while writing to or reading from LTC6804.
register group to two daisy-chained devices (primary device
P, stacked device S), the data will be sent to the primary
device on Port A in the following order:
CFGR0(S), … , CFGR5(S), PEC0(S), PEC1(S), CFGR0(P),
…, CFGR5(P), PEC0(P), PEC1(P)
After a read command for daisy-chained devices, each
device shifts out its data and the PEC that it computed for
its data on Port A followed by the data received on Port B.
For example, when reading status register group B from
two daisy-chained devices (primary device P, stacked
device S), the primary device sends out data on port A in
the following order:
While writing any command to LTC6804, the command
bytes CMD0 and CMD1 (See Table 32 and Table 33) and
the PEC bytes PEC0 and PEC1 are sent on Port A in the
following order:
CMD0, CMD1, PEC0, PEC1
After a broadcast write command to daisy-chained
LTC6804-1 devices, data is sent to each device followed
by the PEC. For example, when writing the configuration
STBR0(P), …, STBR5(P), PEC0(P), PEC1(P), STBR0(S),
… , STBR5(S), PEC0(S), PEC1(S)
Table 24. PEC Calculation for 0x0001
PEC[14]
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
0
0
0
PEC[13]
0
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
0
0
PEC[12]
0
0
0
0
0
0
0
0
1
0
0
0
0
1
1
0
1
1
PEC[11]
0
0
0
0
0
0
0
1
0
0
0
0
1
1
0
1
1
1
PEC[10]
0
0
0
0
0
0
1
0
0
0
0
1
1
0
1
1
1
1
PEC[9]
0
0
0
0
0
1
0
0
0
0
0
0
1
0
0
0
1
1
PEC[8]
PEC[7]
PEC[6]
PEC[5]
PEC[4]
PEC[3]
PEC[2]
PEC[1]
PEC[0]
IN14
IN10
IN8
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
1
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
0
0
1
1
0
0
1
1
1
0
0
1
0
1
0
1
0
1
1
1
0
0
0
1
1
0
0
1
1
1
1
1
1
0
0
0
0
0
0
0
1
1
1
0
1
1
1
1
0
0
1
0
1
1
1
0
1
0
0
1
0
1
1
0
1
1
1
0
1
0
1
1
0
1
1
1
0
PEC Word
IN7
IN4
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
0
1
0
0
0
1
1
1
1
IN3
IN0
DIN
Clock Cycle
0
0
0
0
0
0
0
1
0
0
0
2
0
0
0
3
0
0
0
4
0
0
0
5
0
0
0
6
0
0
0
7
0
0
0
8
0
0
0
9
1
1
0
10
1
1
0
11
1
1
0
12
0
1
0
13
0
1
0
14
0
1
1
15
16
680412fc
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45
LTC6804-1/LTC6804-2
Operation
Table 25. Write/Read PEC Format
NAME
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
PEC0
RD/WR
PEC[14]
PEC[13]
PEC[12]
PEC[11]
PEC[10]
PEC[9]
PEC[8]
PEC[7]
PEC1
RD/WR
PEC[6]
PEC[5]
PEC[4]
PEC[3]
PEC[2]
PEC[1]
PEC[0]
0
Broadcast vs Address Commands
CONFIGURATION
TYPE OF COMMAND
DEVICE
INTERFACE
READ
WRITE
POLL
LTC6804-2
SPI
AddressOnly
Address
or
Broadcast
Address
or
Broadcast
(Address/Parallel)
isoSPI
LTC6804-1
(Daisy-Chain)
SPI or
isoSPI
AddressOnly†
Broadcast-Only
N/A
†The LTC6804-2 will not return data pulses when using broadcast
commands in isoSPI mode. Therefore, ADC commands will execute, but
polling will not work.
Address Commands (LTC6804-2 Only)
An address command is one in which only the addressed
device on the bus responds. Address commands are used
only with LTC6804-2 parts. All commands are compatible
with addressing. See Bus Protocols for Address command
format.
Broadcast Commands (LTC6804-1 or LTC6804-2)
A broadcast command is one to which all devices on the
bus will respond, regardless of device address. This command format can be used with LTC6804-1 and LTC6804-2
parts. See Bus Protocols for Broadcast command format.
With broadcast commands all devices can be sent commands simultaneously.
In parallel (LTC6804-2) configurations, broadcast commands are useful for initiating ADC conversions or for
sending write commands when all parts are being written
with the same data. The polling function (automatic at the
end of ADC commands, or manual using the PLADC command) can also be used with broadcast commands, but
only with parallel SPI interfaces. Polling is not compatible
with parallel isoSPI. Likewise, broadcast read commands
should not be used in a parallel configuration (either SPI
or isoSPI).
46
Daisy-chained (LTC6804-1) configurations support broadcast commands only, because they have no addressing.
All devices in the chain receive the command bytes simultaneously. For example, to initiate ADC conversions in a
stack of devices, a single ADCV command is sent, and all
devices will start conversions at the same time. For read
and write commands, a single command is sent, and then
the stacked devices effectively turn into a cascaded shift
register, in which data is shifted through each device to
the next device in the stack. See the Serial Programming
Examples section.
Polling Methods
The simplest method to determine ADC completion is
for the controller to start an ADC conversion and wait for
the specified conversion time to pass before reading the
results. Polling is not supported with daisy-chain communication (LTC6804-1).
In parallel configurations that communicate in SPI mode
(ISOMD pin tied low), there are two methods of polling. The first method is to hold CSB low after an ADC
conversion command is sent. After entering a conversion
command, the SDO line is driven low when the device is
busy performing conversions (Figure 23). SDO is pulled
high when the device completes conversions. However, the
SDO will also go back high when CSB goes high even if the
device has not completed the conversion. An addressed
device drives the SDO line based on its status alone. A
problem with this method is that the controller is not free
to do other serial communication while waiting for ADC
conversions to complete.
The next method overcomes this limitation. The controller
can send an ADC start command, perform other tasks, and
then send a poll ADC converter status (PLADC) command
to determine the status of the ADC conversions (Figure 24).
After entering the PLADC command, SDO will go low if
the device is busy performing conversions. SDO is pulled
high at the end of conversions. However, the SDO will also
680412fc
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LTC6804-1/LTC6804-2
Operation
go high when CSB goes high even if the device has not
completed the conversion. See Programming Examples on
how to use the PLADC command with devices in parallel
configuration.
In parallel configurations that communicate in isoSPI
mode, the low side port transmits a data pulse only in
response to a master isoSPI pulse received by it. So,
after entering an address command in either method of
polling described above, isoSPI data pulses are sent to
the part to update the conversion status. These pulses
can be sent using LTC6820 by simply clocking its SCK
pin. In response to this pulse, the LTC6804-2 returns an
isoSPI pulse if it is still busy performing conversions and
does not return a pulse if it has completed conversions. If
a CSB high isoSPI pulse is sent to the LTC6804-2, it exits
the polling command. Note that broadcast poll commands
are not compatible with parallel isoSPI.
Bus Protocols
Protocol Format: The protocol formats for both broadcast
and address commands are depicted in Table 27 through
Table 31. Table 26 is the key for reading the protocol
diagrams.
Table 26. Protocol Key
CMD0
First Command Byte (See Tables 32 and 33)
CMD1
Second Command Byte (See Tables 32 and 33)
PEC0
First PEC Byte (See Table 25)
PEC1
Second PEC Byte (See Table 25)
n
Number of Bytes
…
Continuation of Protocol
Master to Slave
Slave to Master
tCYCLE
CSB
SCK
SDI
MSB(CMD)
BIT 14(CMD)
LSB(PEC)
SDO
680412 F23
Figure 23. SDO Polling After an ADC Conversion Command
CSB
SCK
SDI
MSB(CMD)
BIT 14(CMD)
LSB(PEC)
SDO
CONVERSION DONE
680412 F24
Figure 24. SDO Polling Using PLADC Command
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LTC6804-1/LTC6804-2
Operation
Command Format: The formats for the broadcast and
address commands are shown in Table 32 and Table 33
respectively. The 11-bit command code CC[10:0] is the
same for a broadcast or an address command. A list of
all the command codes is shown in Table 34. A broadcast
command has a value 0 for CMD0[7] through CMD0[3].
An address command has a value 1 for CMD0[7] followed
by the 4-bit address of the device (a3, a2, a1, a0) in bits
CMD0[6:3]. An addressed device will respond to an address
command only if the physical address of the device on
pins A3 to A0 match the address specified in the address
command. The PEC for broadcast and address commands
must be computed on the entire 16-bit command (CMD0
and CMD1).
Commands
Table 34 lists all the commands and its options for both
LTC6804-1 and LTC6804-2
Table 27. Broadcast/Address Poll Command
8
8
8
8
CMD0
CMD1
PEC0
PEC1
Poll Data
Table 28. Broadcast Write Command (LTC6804-1)
8
8
8
8
8
CMD0
CMD1
PEC0
PEC1
Data Byte Low
8
8
8
8
…
Data Byte High
PEC0
PEC1
Shift Byte 1
8
8
8
…
Data Byte High
PEC0
PEC1
8
8
8
8
…
Data Byte High
PEC0
PEC1
Shift Byte 1
8
8
8
…
Data Byte High
PEC0
PEC1
8
…
Shift Byte n
Table 29.Broadcast/Address Write Command (LTC6804-2)
8
8
8
8
8
CMD0
CMD1
PEC0
PEC1
Data Byte Low
Table 30. Broadcast Read Command (LTC6804-1)
8
8
8
8
8
CMD0
CMD1
PEC0
PEC1
Data Byte Low
8
…
Shift Byte n
Table 31. Address Read Command (LTC6804-2)
8
8
8
8
8
CMD0
CMD1
PEC0
PEC1
Data Byte Low
Table 32. Broadcast Command Format
NAME
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CMD0
WR
0
0
0
0
0
CC[10]
CC[9]
CC[8]
CMD1
WR
CC[7]
CC[6]
CC[5]
CC[4]
CC[3]
CC[2]
CC[1]
CC[0]
Table 33. Address Command Format
NAME
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CMD0
WR
1
a3*
a2*
a1*
a0*
CC[10]
CC[9]
CC[8]
CMD1
WR
CC[7]
CC[6]
CC[5]
CC[4]
CC[3]
CC[2]
CC[1]
CC[0]
*ax is Address Bit x
48
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LTC6804-1/LTC6804-2
Operation
Table 34. Command Codes
COMMAND DESCRIPTION
NAME
CC[10:0] - COMMAND CODE
10
9
8
7
6
5
4
3
2
1
0
Write Configuration
Register Group
WRCFG
0
0
0
0
0
0
0
0
0
0
1
Read Configuration
Register Group
RDCFG
0
0
0
0
0
0
0
0
0
1
0
Read Cell Voltage
Register Group A
RDCVA
0
0
0
0
0
0
0
0
1
0
0
Read Cell Voltage
Register Group B
RDCVB
0
0
0
0
0
0
0
0
1
1
0
Read Cell Voltage
Register Group C
RDCVC
0
0
0
0
0
0
0
1
0
0
0
Read Cell Voltage
Register Group D
RDCVD
0
0
0
0
0
0
0
1
0
1
0
Read Auxiliary
Register Group A
RDAUXA
0
0
0
0
0
0
0
1
1
0
0
Read Auxiliary
Register Group B
RDAUXB
0
0
0
0
0
0
0
1
1
1
0
Read Status Register Group A
RDSTATA
0
0
0
0
0
0
1
0
0
0
0
Read Status Register Group B
RDSTATB
0
0
0
0
0
0
1
0
0
1
0
Start Cell Voltage ADC
Conversion and Poll Status
ADCV
0
1
MD[1]
MD[0]
1
1
DCP
0
CH[2]
CH[1]
CH[0]
Start Open Wire ADC Conversion and Poll Status
ADOW
0
1
MD[1]
MD[0]
PUP
1
DCP
1
CH[2]
CH[1]
CH[0]
Start Self-Test Cell Voltage
Conversion and Poll Status
CVST
0
1
MD[1]
MD[0]
ST[1]
ST[0]
0
0
1
1
1
Start GPIOs ADC Conversion
and Poll Status
ADAX
1
0
MD[1]
MD[0]
1
1
0
0
CHG [2]
CHG [1]
CHG [0]
Start Self-Test GPIOs
Conversion and Poll Status
AXST
1
0
MD[1]
MD[0]
ST[1]
ST[0]
0
0
1
1
1
Start Status group ADC
Conversion and Poll Status
ADSTAT
1
0
MD[1]
MD[0]
1
1
0
1
Start Self-Test Status group
Conversion and Poll Status
STATST
1
0
MD[1]
MD[0]
ST[1]
ST[0]
0
1
1
1
1
Start Combined Cell
Voltage and GPIO1, GPIO2
Conversion and Poll Status
ADCVAX
1
0
MD[1]
MD[0]
1
1
DCP
1
1
1
1
Clear Cell Voltage
Register Group
CLRCELL
1
1
1
0
0
0
1
0
0
0
1
Clear Auxiliary
Register Group
CLRAUX
1
1
1
0
0
0
1
0
0
1
0
Clear Status Register Group
CLRSTAT
1
1
1
0
0
0
1
0
0
1
1
Poll ADC Conversion Status
PLADC
1
1
1
0
0
0
1
0
1
0
0
Diagnose MUX and Poll
Status
DIAGN
1
1
1
0
0
0
1
0
1
0
1
Write COMM Register Group
WRCOMM
1
1
1
0
0
1
0
0
0
0
1
Read COMM Register Group
RDCOMM
1
1
1
0
0
1
0
0
0
1
0
Start I2C/SPI Communication
STCOMM
1
1
1
0
0
1
0
0
0
1
1
CHST [2] CHST [1] CHST [0]
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Operation
Table 35. Command Bit Descriptions
NAME
MD[1:0]
DESCRIPTION
ADC Mode
VALUES
MD
ADCOPT(CFGR0[0]) = 0
ADCOPT (CFGR0[0]) = 1
01
27kHz Mode (Fast)
14kHz Mode
10
7kHz Mode (Normal)
3kHz Mode
11
26Hz Mode (Filtered)
2kHz Mode
DCP
DCP
Discharge Permitted
0
Discharge Not Permitted
1
Discharge Permitted
Total Conversion Time in the 6 ADC Modes
CH
CH[2:0]
PUP
Cell Selection for ADC Conversion
Pull-Up/Pull-Down Current for
Open-Wire Conversions
000
All Cells
001
Cell 1 and Cell 7
010
Cell 2 and Cell 8
011
Cell 3 and Cell 9
100
Cell 4 and Cell 10
101
Cell 5 and Cell 11
110
Cell 6 and Cell 12
27kHz
14kHz
7kHz
3kHz
2kHz
26Hz
1.1ms
1.3ms
2.3ms
3.0ms
4.4ms
201ms
201µs
230µs
405µs
501µs
754µs
34ms
27kHz
14kHz
2kHz
26Hz
PUP
0
Pull-Down Current
1
Pull-Up Current
Self-Test Conversion Result
ST[1:0]
Self-Test Mode Selection
ST
7kHz
3kHz
01
Self Test 1
0x9565
0x9553
0x9555
0x9555
0x9555
0x9555
10
Self test 2
0x6A9A
0x6AAC
0x6AAA
0x6AAA
0x6AAA
0x6AAA
Total Conversion Time in the 6 ADC Modes
CHG
CHG[2:0]
GPIO Selection for ADC Conversion
000
GPIO 1-5, 2nd Ref
001
GPIO 1
010
GPIO 2
011
GPIO 3
100
GPIO 4
101
GPIO 5
110
2nd Reference
27kHz
14kHz
7kHz
3kHz
2kHz
26Hz
1.1ms
1.3ms
2.3ms
3.0ms
4.4ms
201ms
201µs
230µs
405µs
501µs
754µs
34ms
Total Conversion Time in the 6 ADC Modes
CHST
CHST[2:0]* Status Group Selection
000
SOC, ITMP, VA, VD
001
SOC
010
ITMP
011
VA
100
VD**
27kHz
14kHz
7kHz
3kHz
2kHz
26Hz
748µs
865µs
1.6ms
2.0ms
3.0ms
134ms
201µs
230µs
405µs
501µs
754µs
34ms
*Note: Valid options for CHST in ADSTAT command are 0-4. If CHST is set to 5/6 in ADSTAT command, the LTC6804 treats it like ADAX command with
CHG = 5/6.
**The use of the ADSTAT command with CHST = 100 is not recommended unless special care is taken. See the Data Acquisition System Diagnostics
section for more details.
50
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LTC6804-1/LTC6804-2
Operation
Table 36. Configuration Register Group
REGISTER
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
CFGR0
RD/WR
GPIO5
GPIO4
GPIO3
GPIO2
CFGR1
RD/WR
VUV[7]
VUV[6]
VUV[5]
VUV[4]
CFGR2
RD/WR
VOV[3]
VOV[2]
VOV[1]
VOV[0]
CFGR3
RD/WR
VOV[11]
VOV[10]
VOV[9]
CFGR4
RD/WR
DCC8
DCC7
DCC6
CFGR5
RD/WR
DCTO[3]
DCTO[2]
BIT 6
BIT 3
BIT 2
BIT 1
BIT 0
GPIO1
REFON
SWTRD
ADCOPT
VUV[3]
VUV[2]
VUV[1]
VUV[0]
VUV[11]
VUV[10]
VUV[9]
VUV[8]
VOV[8]
VOV[7]
VOV[6]
VOV[5]
VOV[4]
DCC5
DCC4
DCC3
DCC2
DCC1
DCTO[1]
DCTO[0]
DCC12
DCC11
DCC10
DCC9
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Table 37. Cell Voltage Register Group A
REGISTER
RD/WR
BIT 7
CVAR0
RD
C1V[7]
C1V[6]
C1V[5]
C1V[4]
C1V[3]
C1V[2]
C1V[1]
C1V[0]
CVAR1
RD
C1V[15]
C1V[14]
C1V[13]
C1V[12]
C1V[11]
C1V[10]
C1V[9]
C1V[8]
CVAR2
RD
C2V[7]
C2V[6]
C2V[5]
C2V[4]
C2V[3]
C2V[2]
C2V[1]
C2V[0]
CVAR3
RD
C2V[15]
C2V[14]
C2V[13]
C2V[12]
C2V[11]
C2V[10]
C2V[9]
C2V[8]
CVAR4
RD
C3V[7]
C3V[6]
C3V[5]
C3V[4]
C3V[3]
C3V[2]
C3V[1]
C3V[0]
CVAR5
RD
C3V[15]
C3V[14]
C3V[13]
C3V[12]
C3V[11]
C3V[10]
C3V[9]
C3V[8]
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Table 38. Cell Voltage Register Group B
REGISTER
RD/WR
BIT 7
CVBR0
RD
C4V[7]
C4V[6]
C4V[5]
C4V[4]
C4V[3]
C4V[2]
C4V[1]
C4V[0]
CVBR1
RD
C4V[15]
C4V[14]
C4V[13]
C4V[12]
C4V[11]
C4V[10]
C4V[9]
C4V[8]
CVBR2
RD
C5V[7]
C5V[6]
C5V[5]
C5V[4]
C5V[3]
C5V[2]
C5V[1]
C5V[0]
CVBR3
RD
C5V[15]
C5V[14]
C5V[13]
C5V[12]
C5V[11]
C5V[10]
C5V[9]
C5V[8]
CVBR4
RD
C6V[7]
C6V[6]
C6V[5]
C6V[4]
C6V[3]
C6V[2]
C6V[1]
C6V[0]
CVBR5
RD
C6V[15]
C6V[14]
C6V[13]
C6V[12]
C6V[11]
C6V[10]
C6V[9]
C6V[8]
Table 39. Cell Voltage Register Group C
REGISTER
CVCR0
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RD
C7V[7]
C7V[6]
C7V[5]
C7V[4]
C7V[3]
C7V[2]
C7V[1]
C7V[0]
CVCR1
RD
C7V[15]
C7V[14]
C7V[13]
C7V[12]
C7V[11]
C7V[10]
C7V[9]
C7V[8]
CVCR2
RD
C8V[7]
C8V[6]
C8V[5]
C8V[4]
C8V[3]
C8V[2]
C8V[1]
C8V[0]
CVCR3
RD
C8V[15]
C8V[14]
C8V[13]
C8V[12]
C8V[11]
C8V[10]
C8V[9]
C8V[8]
CVCR4
RD
C9V[7]
C9V[6]
C9V[5]
C9V[4]
C9V[3]
C9V[2]
C9V[1]
C9V[0]
CVCR5
RD
C9V[15]
C9V[14]
C9V[13]
C9V[12]
C9V[11]
C9V[10]
C9V[9]
C9V[8]
Table 40. Cell Voltage Register Group D
REGISTER
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
CVDR0
RD
C10V[7]
C10V[6]
C10V[5]
C10V[4]
C10V[3]
C10V[2]
C10V[1]
C10V[0]
CVDR1
RD
C10V[15]
C10V[14]
C10V[13]
C10V[12]
C10V[11]
C10V[10]
C10V[9]
C10V[8]
CVDR2
RD
C11V[7]
C11V[6]
C11V[5]
C11V[4]
C11V[3]
C11V[2]
C11V[1]
C11V[0]
CVDR3
RD
C11V[15]
C11V[14]
C11V[13]
C11V[12]
C11V[11]
C11V[10]
C11V[9]
C11V[8]
CVDR4
RD
C12V[7]
C12V[6]
C12V[5]
C12V[4]
C12V[3]
C12V[2]
C12V[1]
C12V[0]
CVDR5
RD
C12V[15]
C12V[14]
C12V[13]
C12V[12]
C12V[11]
C12V[10]
C12V[9]
C12V[8]
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Operation
Table 41. Auxiliary Register Group A
REGISTER
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
AVAR0
RD
G1V[7]
G1V[6]
G1V[5]
G1V[4]
G1V[3]
G1V[2]
G1V[1]
G1V[0]
AVAR1
RD
G1V[15]
G1V[14]
G1V[13]
G1V[12]
G1V[11]
G1V[10]
G1V[9]
G1V[8]
AVAR2
RD
G2V[7]
G2V[6]
G2V[5]
G2V[4]
G2V[3]
G2V[2]
G2V[1]
G2V[0]
AVAR3
RD
G2V[15]
G2V[14]
G2V[13]
G2V[12]
G2V[11]
G2V[10]
G2V[9]
G2V[8]
AVAR4
RD
G3V[7]
G3V[6]
G3V[5]
G3V[4]
G3V[3]
G3V[2]
G3V[1]
G3V[0]
AVAR5
RD
G3V[15]
G3V[14]
G3V[13]
G3V[12]
G3V[11]
G3V[10]
G3V[9]
G3V[8]
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Table 42. Auxiliary Register Group B
REGISTER
RD/WR
BIT 7
AVBR0
RD
G4V[7]
G4V[6]
G4V[5]
G4V[4]
G4V[3]
G4V[2]
G4V[1]
G4V[0]
AVBR1
RD
G4V[15]
G4V[14]
G4V[13]
G4V[12]
G4V[11]
G4V[10]
G4V[9]
G4V[8]
AVBR2
RD
G5V[7]
G5V[6]
G5V[5]
G5V[4]
G5V[3]
G5V[2]
G5V[1]
G5V[0]
AVBR3
RD
G5V[15]
G5V[14]
G5V[13]
G5V[12]
G5V[11]
G5V[10]
G5V[9]
G5V[8]
AVBR4
RD
REF[7]
REF[6]
REF[5]
REF[4]
REF[3]
REF[2]
REF[1]
REF[0]
AVBR5
RD
REF[15]
REF[14]
REF[13]
REF[12]
REF[11]
REF[10]
REF[9]
REF[8]
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
Table 43. Status Register Group A
REGISTER
RD/WR
BIT 7
STAR0
RD
SOC[7]
SOC[6]
SOC[5]
SOC[4]
SOC[3]
SOC[2]
SOC[1]
SOC[0]
STAR1
RD
SOC[15]
SOC[14]
SOC[13]
SOC[12]
SOC[11]
SOC[10]
SOC[9]
SOC[8]
STAR2
RD
ITMP[7]
ITMP[6]
ITMP[5]
ITMP[4]
ITMP[3]
ITMP[2]
ITMP[1]
ITMP[0]
STAR3
RD
ITMP[15]
ITMP[14]
ITMP[13]
ITMP[12]
ITMP[11]
ITMP[10]
ITMP[9]
ITMP[8]
STAR4
RD
VA[7]
VA[6]
VA[5]
VA[4]
VA[3]
VA[2]
VA[1]
VA[0]
STAR5
RD
VA[15]
VA[14]
VA[13]
VA[12]
VA[11]
VA[10]
VA[9]
VA[8]
Table 44. Status Register Group B
REGISTER
STBR0
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
RD
VD[7]
VD[6]
VD[5]
VD[4]
VD[3]
VD[2]
VD[1]
VD[0]
STBR1
RD
VD[15]
VD[14]
VD[13]
VD[12]
VD[11]
VD[10]
VD[9]
VD[8]
STBR2
RD
C4OV
C4UV
C3OV
C3UV
C2OV
C2UV
C1OV
C1UV
STBR3
RD
C8OV
C8UV
C7OV
C7UV
C6OV
C6UV
C5OV
C5UV
STBR4
RD
C12OV
C12UV
C11OV
C11UV
C10OV
C10UV
C9OV
C9UV
STBR5
RD
REV[3]
REV[2]
REV[1]
REV[0]
RSVD
RSVD
MUXFAIL
THSD
Table 45. COMM Register Group
REGISTER
RD/WR
BIT 7
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1
BIT 0
COMM0
RD/WR
ICOM0[3]
ICOM0[2]
ICOM0[1]
ICOM0[0]
D0[7]
D0[6]
D0[5]
D0[4]
COMM1
RD/WR
D0[3]
D0[2]
D0[1]
D0[0]
FCOM0[3]
FCOM0[2]
FCOM0[1]
FCOM0[0]
COMM2
RD/WR
ICOM1[3]
ICOM1[2]
ICOM1[1]
ICOM1[0]
D1[7]
D1[6]
D1[5]
D1[4]
COMM3
RD/WR
D1[3]
D1[2]
D1[1]
D1[0]
FCOM1[3]
FCOM1[2]
FCOM1[1]
FCOM1[0]
COMM4
RD/WR
ICOM2[3]
ICOM2[2]
ICOM2[1]
ICOM2[0]
D2[7]
D2[6]
D2[5]
D2[4]
COMM5
RD/WR
D2[3]
D2[2]
D2[1]
D2[0]
FCOM2[3]
FCOM2[2]
FCOM2[1]
FCOM2[0]
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Operation
Table 46. Memory Bit Descriptions
NAME
GPIOx
REFON
SWTRD
ADCOPT
VUV
VOV
DCC[x]
DCTO
CxV
GxV
REF
SOC
ITMP
VA
VD
CxOV
CxUV
REV
RSVD
DESCRIPTION
VALUES
GPIOx Pin Control Write: 0 -> GPIOx Pin Pull-Down ON; 1-> GPIOx Pin Pull-Down OFF (Default)
Read: 0 -> GPIOx Pin at Logic 0; 1 -> GPIOx Pin at Logic 1
Reference
1 -> Reference Remains Powered Up Until Watchdog Timeout
0 -> Reference Shuts Down after Conversions (Default)
Powered Up
SWTEN Pin Status 1 -> SWTEN Pin at Logic 1
(Read Only)
0 -> SWTEN Pin at Logic 0
ADC Mode Option ADCOPT: 0 -> Selects Modes 27kHz, 7kHz or 26Hz with MD[1:0] Bits in ADC Conversion Commands (Default).
1 -> Selects Modes 14kHz, 3kHz or 2kHz with MD[1:0] Bits in ADC Conversion Commands.
Bit
Undervoltage
Comparison voltage = (VUV + 1) • 16 • 100µV
Comparison
Default: VUV = 0x000
Voltage*
Comparison voltage = VOV • 16 • 100µV
Overvoltage
Default: VOV = 0x000
Comparison
Voltage*
Discharge Cell x
x = 1 to 12 1 -> Turn ON Shorting Switch for Cell x
0 -> Turn OFF Shorting Switch for Cell x (Default)
Discharge Time
DCTO
0
1
2
3
4
5
6
7
8
9
A
B
C
D
Out Value
(Write)
Time Disabled 0.5
1
2
3
4
5
10
15
20
30
40
60
75
(Min)
DCTO
0
1
2
3
4
5
6
7
8
9
A
B
C
D
(Read)
0.5
1
2
3
4
5
10
15
20
30
40
60
Time Disabled
0
to
to
to
to
to
to
to
to
to
to
to
to
to
Left
or
1
2
3
4
5
10
15
20
30
40
60
75
(Min) Timeout 0.5
E
F
90
120
E
F
75
to
90
90
to
120
Cell x Voltage*
x = 1 to 12 16-Bit ADC Measurement Value for Cell x
Cell Voltage for Cell x = CxV • 100µV
CxV Is Reset to 0xFFFF on Power-Up and After Clear Command
GPIO x Voltage* x = 1 to 5 16-Bit ADC Measurement Value for GPIOx
Voltage for GPIOx = GxV • 100µV
GxV Is Reset to 0xFFFF on Power-Up and After Clear Command
2nd Reference
16-Bit ADC Measurement Value for 2nd Reference
Voltage for 2nd Reference = REF • 100µV
Voltage*
Normal Range Is within 2.985V to 3.015V
Sum of Cells
16-Bit ADC Measurement Value of the Sum of All Cell Voltages
Sum of All Cells Voltage = SOC • 100µV • 20
Measurement*
Internal Die
16-Bit ADC Measurement Value of Internal Die Temperature
Temperature Measurement (°C) = ITMP • 100µV/7.5mV/°C – 273°C
Temperature*
Analog Power
16-Bit ADC Measurement Value of Analog Power Supply Voltage
Analog Power Supply Voltage = VA • 100µV
Supply Voltage*
Normal Range Is within 4.5V to 5.5V
Digital Power
16-Bit ADC Measurement Value of Digital Power Supply Voltage
Digital Power Supply Voltage = VA • 100µV
Supply Voltage*
Normal Range Is within 2.7V to 3.6V
Cell x Overvoltage x = 1 to 12 Cell Voltage Compared to VOV Comparison Voltage
0 -> Cell x Not Flagged for Overvoltage Condition. 1 -> Cell x Flagged
Flag
Cell x
x = 1 to 12 Cell Voltage Compared to VUV Comparison Voltage
0 -> Cell x Not Flagged for Undervoltage Condition. 1 -> Cell x Flagged
Undervoltage Flag
Revision Code
Device Revision Code. See Revision Code and Reserved Bits in Operation Section.
Reserved Bits
See Revision Code and Reserved Bits in Operation Section.
680412fc
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53
LTC6804-1/LTC6804-2
Operation
Table 46. Memory Bit Descriptions
NAME
DESCRIPTION
MUXFAIL Multiplexer SelfTest Result
THSD
Thermal
Shutdown Status
ICOMn
Initial
Communication
Control Bits
Dn
FCOMn
I2C/SPI
Communication
Data Byte
Final
Communication
Control Bits
VALUES
Read: 0 -> Multiplexer Passed Self Test 1 -> Multiplexer Failed Self Test
Read: 0 -> Thermal Shutdown Has Not Occurred 1 -> Thermal Shutdown Has Occurred
THSD Bit Cleared to 0 on Read of Status RegIster Group B
Write
I2C
0110
0001
0000
0111
STOP
BLANK
NO TRANSMIT
START
SPI
1000
1001
1111
CSB Low
CSB High
NO TRANSMIT
Read
I2C
0110
0001
0000
0111
START from Master
STOP from Master
SDA Low Between Bytes
SDA High Between
Bytes
SPI
0111
Data Transmitted (Received) to (From) I2C/SPI Slave Device
Write
I2C
SPI
Read
I2C
0000
Master ACK
1000
Master NACK
X000
CSB Low
0000
0111
ACK from Master
ACK from Slave
1111
NACK from Slave
1001
Master NACK + STOP
1001
CSB High
0001
1001
ACK from Slave + NACK from Slave
STOP from Master
+ STOP from
Master
SPI
1111
*Voltage equations use the decimal value of registers, 0 to 4095 for 12 bits and 0 to 65535 for 16 bits.
Programming Examples
4. Wait for the amount of time 3 • tREADY
The following examples use a configuration of 3 stacked
LTC6804-1 devices: S1, S2, S3. Port A on device S1 is
configured in SPI mode (ISOMD pin low). Port A on devices S2 and S3 is configured in isoSPI mode (ISOMD pin
high). Port B on S1 is connected to Port A on S2. Port B
on S2 is connected to Port A on S3. The microcontroller
communicates to the stack through Port A on S1.
5. Send commands
Write Configuration Registers
1. Pull CSB low
2. Send WRCFG command (0x00 0x01) and its PEC (0x3D
0x6E)
Waking Up Serial Interface
3. Send CFGR0 byte of device S3, then CFGR1(S3), …
CFGR5(S3), PEC of CFGR0(S3) to CFGR5(S3)
1. Send a dummy byte. The activity on CSB and SCK will
wake up the serial interface on device S1.
4. Send CFGR0 byte of device S2, then CFGR1(S2), …
CFGR5(S2), PEC of CFGR0(S2) to CFGR5(S2)
2. Wait for the amount of time 3 • tWAKE in order to power
up all devices S1, S2 and S3.
5. Send CFGR0 byte of device S1, then CFGR1(S1), …
CFGR5(S1), PEC of CFGR0(S1) to CFGR5(S1)
For large stacks where some devices may go to the IDLE
state after waking, apply steps 3 and 4:
6. Pull CSB high, data latched into all devices on rising
edge of CSB
3. Send a second dummy byte.
54
680412fc
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LTC6804-1/LTC6804-2
Operation
Calculation of serial interface time for sequence above:
Clear Cell Voltage Registers
Number of LTC6804-1s in daisy chain stack = n
1. Pull CSB low
Number of bytes in sequence (B):
2. Send CLRCELL command (0x07 0x11) and its PEC
(0xC9 0xC0)
Command: 2 (command byte) + 2 (command PEC) = 4
Data: 6 (Data bytes) + 2 (Data PEC) per LTC6804 = 8
bytes per device
B=4+8•n
3. Pull CSB high
Poll ADC Status
(Parallel configuration and ISOMD = 0)
Serial port frequency per bit = F
Time = (1/F) • B • 8 bits/byte = (1/F) • [4 + 8 • n] • 8
Time for 3 LTC6804 example above, with 1MHz serial
port = (1/1e6) • (4 + 8 • 3) • 8 = 224µs
Note: This time will remain the same for all write and read
commands.
Read Cell Voltage Register Group A
1. Pull CSB low
2. Send RDCVA command (0x00 0x04) and its PEC (0x07
0xC2)
3. Read CVAR0 byte of device S1, then CVAR1(S1), …
CVAR5(S1), PEC of CVAR0(S1) to CVAR5(S1)
4. Read CVAR0 byte of device S2, then CVAR1(S2), …
CVAR5(S2), PEC of CVAR0(S2) to CVAR0(S2)
5. Read CVAR0 byte of device S3, then CVAR1(S3), …
CVAR5(S3), PEC of CVAR0(S3) to CVAR5(S3)
6. Pull CSB high
This example uses an addressed LTC6804-2 with address
A [3:0] = 0011 and ISOMD = 0
1. Pull CSB low
2. Send PLADC command (0x9F 0x14) and its PEC (0x1C
0x48 )
3. SDO output is pulled low if the LTC6804-2 is busy. The
host needs to send clocks on SCK in order for the polling status to be updated from the addressed device.
4. SDO output is high when the LTC6804-2 has completed
conversions
5. Pull CSB high to exit polling
Talk to an I2C Slave Connected to LTC6804
The LTC6804 supports I2C slave devices by connection to
GPIO4(SDA) and GPIO5(SCL). One valuable use for this
capability is to store production calibration constants or
other information in a small serial EEPROM using a connection like shown in Figure 25.
Start Cell Voltage ADC Conversion
(All cells, normal mode with discharge permitted) and
poll status
1. Pull CSB low
4.7k
WP
VCC
1µF
10V
VREG
LTC6804
SCL
GPIO5(SCL)
24AA01 VSS
GPIO4(SDA)
SDA
V–
2. Send ADCV command with MD[1:0] = 10 and DCP = 1
i.e. 0x03 0x70 and its PEC (0xAF 0x42)
3. Pull CSB high
4.7k
680412 F25
Figure 25. Connecting I2C EEPROM to LTC6804 GPIO Pins
680412fc
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55
LTC6804-1/LTC6804-2
Operation
This example uses a single LTC6804-1 to write a byte
of data to an I2C EEPROM. The LTC6804 will send three
bytes of data to the I2C slave device. The data sent will be
B0 = 0xA0 (EEPROM address), B1 = 0x01 (write command), and B2 = 0xAA (data to be stored in EEPROM).
The three bytes will be transmitted to the I2C slave device
in the following format:
START – B0 – NACK – B1 – NACK – B2 – NACK – STOP
1. Write data to COMM register using WRCOMM command
a. Pull CSB low
b. Send WRCOMM command (0x07 0x21) and its PEC
(0x24 0xB2)
c. Send
COMM0 = 0x6A, COMM1 = 0x08 ([START] [B0]
[NACK]),
COMM2 = 0x00, COMM3 = 0x18 ([BLANK] [B1]
[NACK]),
COMM4 = 0x0A, COMM5 = 0xA9 ([BLANK] [B2]
[NACK+STOP])
3. Data transmitted to slave during the STCOMM command is stored in the COMM register. Use the RDCOMM
command to retrieve the data
a. Pull CSB low
b. Send RDCOMM command (0x07 0x22) and its PEC
(0x32 0xD6)
c. Read COMM0-COMM5 and the PEC for the 6 bytes
of data.
Assuming the slave acknowledged all 3 bytes of data,
the read back data in this example would look like:
COMM0 = 0x6A, COMM1 = 0x07, COMM2 = 0x70,
COMM3 = 0x17, COMM4 = 0x7A, COMM5 = 0xA1,
PEC = 0xD0 0xDE
d. Pull CSB high
Note: If the slave returns data, this data will be placed in
COMM0-COMM5.
Figure 26 shows the activity on GPIO5 (SCL) and GPIO4
(SDA) ports of the I2C master for 72 clock cycles during
the STCOMM command in the above example.
and PEC = 0x6D 0xFB for the above data
d. Pull CSB high
2. Send the 3 bytes of data to I2C slave device using
STCOMM command
a. Pull CSB low
b. Send STCOMM command (0x07 0x23) and its PEC
(0xB9 0xE4)
c. Send 72 clock cycles on SCK
d. Pull CSB high
SCK
SCL (GPIO5)
SDA (GPIO4)
START
LAST CLOCK OF
STCOMM COMMAND
0xA0
0x01
ACK FROM SLAVE
0xAA
ACK FROM SLAVE
STOP
ACK FROM SLAVE
680412 F26
Figure 26. LTC6804 I2C Communication Example
56
680412fc
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LTC6804-1/LTC6804-2
Operation
Talk to a SPI Slave Connected to LTC6804
This example uses a single LTC6804-1 device which has a
SPI device connected to it through GPIO3 (CSBM), GPIO4
(SDOM) and GPIO5 (SCKM). In this example, the LTC6804
device sends out 3 bytes of data B0 = 0x55, B1 = 0xAA
and B2 = 0xCC to the SPI slave device in the following
format: CSB low – B0 – B1 – B2 – CSB high
1. Write data to COMM register using WRCOMM command
a. Pull CSBM low
b. Send WRCOMM command (0x07 0x21) and its PEC
(0x24 0xB2)
c. Send
COMM0 = 0x85, COMM1 = 0x50 ([CSBM low]
[B0] [CSBM low]),
COMM2 = 0x8A, COMM3 = 0xA0 ([CSBM low]
[B1] [CSBM low]),
COMM4 = 0x8C, COMM5 = 0xC9 ([CSBM low]
[B2] [CSBM high])
3. Data transmitted to slave during the STCOMM command is stored in the COMM register. Use the RDCOMM
command to retrieve the data.
a. Pull CSB low
b. Send RDCOMM command (0x07 0x22) and its PEC
(0x32 0xD6)
c. Read COMM0-COMM5 and the PEC for the 6 bytes
of data. The read back data in this example would
look like:
COMM0 = 0x755F, COMM1 = 0x7AAF, COMM2 =
7CCF, PEC = 0xF2BA
d. Pull CSB high
Note: If the slave returns data, this data will be placed in
COMM0-COMM5.
Figure 27 shows the activity on GPIO3 (CSBM), GPIO5
(SCKM) and GPIO4 (SDOM) ports of SPI master for 72
clock cycles during the STCOMM command in the above
example.
and PEC = 0x89 0xA4 for the above data.
d. Pull CSB high
2. Send the 3 bytes of data to SPI slave device using
STCOMM command
a. Pull CSB low
b. Send STCOMM command (0x07 0x23) and its PEC
(0xB9 0xE4)
c. Send 72 clock cycles on SCK
d. Pull CSB high
SCK
CSBM (GPIO3)
SCKM (GPIO5)
SDOM (GPIO4)
CSBM LOW
0x55
0xAA
LAST CLOCK OF
STCOMM COMMAND
0xCC
CSBM HIGH
680412 F27
Figure 27. LTC6804 SPI Communication Example
680412fc
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57
LTC6804-1/LTC6804-2
Applications Information
Simple Linear Regulator
Improved Regulator Power Efficiency
The LTC6804 draws most of its power from the VREG input
pin. 5V ±0.5V should be applied to VREG. A regulated DC/
DC converter can power VREG directly, or the DRIVE pin
may be used to form a discrete regulator with the addition
of a few external components. When active, the DRIVE
output pin provides a low current 5.6V output that can
be buffered using a discrete NPN transistor, as shown in
Figure 28. The collector power for the NPN can come from
any potential of 6V or more above V–, including the cells
being monitored or an unregulated converter supply. A
100Ω/100nF RC decoupling network is recommended for
the collector power connection to protect the NPN from
transients. The emitter of the NPN should be bypassed
with a 1µF capacitor. Larger capacitor values should be
avoided because they increase the wake-up time of the
LTC6804. Some attention to the thermal characteristic
of the NPN is needed, as there can be significant heating
with a high collector voltage.
To minimize power consumption within the LTC6804, the
current drawn on the V+ pin has been designed to be very
small (500µA). The voltage on the V+ pin must be at least
as high as the top cell to provide accurate measurement.
The V+ and VREG pins can be unpowered to provide an
exceptionally low battery drain shutdown mode. In many
applications, the V+ will be permanently connected to
the top cell potential through a decoupling RC to protect
against transients (100Ω/100nF is recommended).
100Ω
LTC6804
WDT
DRIVE
VREG
SWTEN
VREF1
VREF2
GPIO5
GPIO4
V–
V–
GPIO3
NSV1C201MZ4
0.1µF
For better running efficiency when powering from the cell
stack, the VREG may be powered from a buck converter
rather than the NPN pass transistor. An ideal circuit for
this is based on the LT3990 as shown in Figure 29. A 1k
resistor should be used in series with the input to prevent
inrush current when connecting to the stack and to reduce
conducted EMI. The EN/UVLO pin should be connected to
DRIVE so that the converter sleeps along with the LTC6804.
The LTC6804 watchdog timer requires VREG power to
timeout. Therefore, if the EN/UVLO pin is not connected
to DRIVE, care must be taken to allow the LTC6804 to
timeout first before removing VREG power; otherwise the
LTC6804 will not enter sleep mode.
VIN
28V TO
62V
1µF
1k
VIN
1µF
BOOST
LT3990
1µF
OFF ON
EN/UVLO
PG
33µH
BD
22pF
RT
374k
Figure 28. Simple VREG Power Source Using
NPN Pass Transistor
f = 400kHz
GND
VREG
5V
40mA
SW
2.2µF
680412 F28
0.22µF
1M
FB
22µF
316k
680412 F29
Figure 29. VREG Powered from Cell Stack with High Efficiency
58
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LTC6804-1/LTC6804-2
Applications Information
Fully Isolated Power
current from conducting through internal parasitic paths
inside the IC when the isolated power is removed.
A simple DC/DC flyback converter can provide isolated
power for an LTC6804 from a remote 12V power source
as shown in Figure 30. This circuit, along with the isoSPI
transformer isolation, results in LTC6804 circuitry that is
completely floating and uses almost no power from the
batteries. Aside from reducing the amount of circuitry
that operates at battery potential, such an arrangement
prevents battery load imbalance. The LTC6804 watchdog
timer requires VREG power to timeout. Therefore, care
must be taken to allow the LTC6804 to timeout first before
removing VREG power; otherwise the LTC6804 will not
enter sleep mode. A diode should be added between the
V+ and the top cell being monitored. This will prevent any
Reading External Temperature Probes
Figure 31 shows the typical biasing circuit for a negativetemperature-coefficient (NTC) thermistor. The 10kΩ at 25°C
is the most popular sensor value and the VREF2 output stage
is designed to provide the current required to directly bias
several of these probes. The biasing resistor is selected
to correspond to the NTC value so the circuit will provide
1.5V at 25°C (VREF2 is 3V nominal). The overall circuit
response is approximately –1%/°C in the range of typical
cell temperatures, as shown in the chart of Figure 31 .
CONNECT TO TOP CELL
CMHD459A
130k
12VRETURN
8
22.1k
RFB
GND
EN/UVLO
SW
VIN
5
•1
4•
CMMSH1-40
52V
13V
4.7µF
25V
7
•2
V+
CMHZ5265B
62V
1µF
100V
NSV1C201MZ4
1µF
10V
PA0648NL
12V
100nF
100V
LTC6804
DRIVE
VREG
V–
680412 F30
Figure 30. Powering LTC6804 from a Remote 12V Source
100
90
80
VREF2
10k
VTEMP
NTC
10k AT 25°C
V–
VTEMPx (% VREF2)
100k
4.7µF
25V
LT8300
100Ω
70
60
50
40
30
20
10
0
–40
–20
0
20
40
60
TEMPERATURE (°C)
80
680412 F31
Figure 31. Typical Temperature Probe Circuit and Relative Output
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59
LTC6804-1/LTC6804-2
Applications Information
Expanding the Number of Auxiliary
Measurements
Filtering of Cell and GPIO Inputs
The LTC6804 uses a delta-sigma ADC, which has deltasigma modulator followed by a SINC3 finite impulse
response (FIR) digital filter. This greatly reduces input
filtering requirements. Furthermore, the programmable
oversampling ratio allows the user to determine the best
trade-off between measurement speed and filter cutoff
frequency. Even with this high order lowpass filter, fast
transient noise can still induce some residual noise in measurements, especially in the faster conversion modes. This
can be minimized by adding an RC lowpass decoupling to
each ADC input, which also helps reject potentially damaging high energy transients. Adding more than about 100Ω
to the ADC inputs begins to introduce a systematic error
in the measurement, which can be improved by raising
the filter capacitance or mathematically compensating in
software with a calibration procedure. For situations that
demand the highest level of battery voltage ripple rejection, grounded capacitor filtering is recommended. This
configuration has a series resistance and capacitors that
decouple HF noise to V–. In systems where noise is less
The LTC6804 provides five GPIO pins, each of which is
capable of performing as an ADC input. In some applications there is need to measure more signals than this, so
one means of supporting higher signal count is to add
a MUX circuit such as shown in Figure 32. This circuit
digitizes up to sixteen source signals using the GPIO1
ADC input and MUX control is provided by two other
GPIO lines configured as an I2C port. The buffer amplifier
provides for fast settling of the selected signal to increase
the usable conversion rate.
Internal Protection Features
The LTC6804 incorporates various ESD safeguards to ensure a robust performance. An equivalent circuit showing
the specific protection structures is shown in Figure 33.
While pins 43 to 48 have different functionality for the
-1 and -2 variants, the protection structure is the same.
Zener-like suppressors are shown with their nominal clamp
voltage, other diodes exhibit standard PN junction behavior.
ANALOG1
ANALOG2
ANALOG3
ANALOG4
ANALOG5
ANALOG6
ANALOG7
ANALOG8
ANALOG9
ANALOG10
ANALOG11
ANALOG12
ANALOG13
ANALOG14
ANALOG15
ANALOG16
1
2
3
4
5
6
7
8
1
2
3
4
5
6
7
8
16
S0
VCC
15
SCL
S1
14
SDA
S2
13
A0
S3
LTC1380
12
A1
S4
11
GND
S5
10
VEE
S6
9
DO
S7
16
S0
VCC
15
SCL
S1
14
SDA
S2
13
A0
S3
LTC1380
12
A1
S4
11
GND
S5
10
VEE
S6
9
DO
S7
4.7k
4.7k
1µF
37
LTC6804
VREG
33
GPIO5(SCL)
32
GPIO4(SDA)
31 –
V
3
4
+
5
LTC6255
–
1
100Ω
2
27
GPIO1
10nF
680412 F32
ANALOG INPUTS: 0.04V TO 4.5V
Figure 32. MUX Circuit Supports Sixteen Additional Analog Measurements
60
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LTC6804-1/LTC6804-2
Applications Information
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
31
30
C12
S12
C11
S11
C10
S10
C9
S9
C8
S8
C7
S7
C6
S6
C5
S5
C4
S4
C3
S3
C2
S2
C1
S1
C0
12V
1
30V
10k
30V
12V
30V
12V
10k
12V
12V
30V
10k
12V
12V
12V
12V
12V
10k
12V
12V
12V
12V
10k
12V
12V
12V
10k
12V
12V
12V
30V
10k
12V
12V
12V
12V
12V
10k
12V
12V
12V
12V
10k
12V
12V
12V
10k
12V
12V
12V
12V
30V
10k
12V
12V
12V
12V
10k
12V
12V
12V
12V
V–
V–
V+
LTC6804
IPB/A3
IMB/A2
ICMP/A1
IBIAS/A0
SDO
SDI
SCK
CSB
ISOMD
WDT
DRIVE
VREG
SWTEN
VREF1
VREF2
GPIO5
48
47
46
45
44
43
periodic or higher oversample rates are in use, a differential
capacitor filter structure is adequate. In this configuration
there are series resistors to each input, but the capacitors
connect between the adjacent C pins. However, the differential capacitor sections interact. As a result, the filter
response is less consistent and results in less attenuation
than predicted by the RC, by approximately a decade. Note
that the capacitors only see one cell of applied voltage (thus
smaller and lower cost) and tend to distribute transient
energy uniformly across the IC (reducing stress events on
the internal protection structure). Figure 34 shows the two
methods schematically. Basic ADC accuracy varies with R,
C as shown in the Typical Performance curves, but error is
minimized if R = 100Ω and C = 10nF. The GPIO pins will
always use a grounded capacitor configuration because
the measurements are all with respect to V–.
42
41
100Ω
CELL2
33Ω
40
39
GPIO2
GPIO1
3.3k
33Ω
37
C0
10nF
BATTERY V–
36
S1
10nF
100Ω
V–
Differential Capacitor Filter
35
34
100Ω
CELL2
C2
3.3k
BSS308PE
33Ω
33
3.3k
C
100Ω
29
S1
*
C0
C
28
LTC6804
C1
BSS308PE
32
S2
C *
100Ω
33Ω
GPIO3
LTC6804
C1
BSS308PE
38
S2
10nF
100Ω
CELL1
CELL1
GPIO4
C2
3.3k
BSS308PE
BATTERY V–
*
V–
*6.8V ZENERS RECOMMENDED IF C > 100nF
27
25Ω
680412 F34
Grounded Capacitor Filter
680412 F33
NOTE: NOT SHOWN ARE PN DIODES TO ALL OTHER PINS FROM PIN 31
Figure 34. Input Filter Structure Configurations
Figure 33. Internal ESD Protection Structure of LTC6804
680412fc
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61
LTC6804-1/LTC6804-2
Applications Information
Cell Balancing with Internal Mosfets
LTC6804
C(n)
RFILTER
The S1 through S12 pins are used to balance battery cells.
If one cell in a series becomes overcharged, an S output
can be used to discharge the cell. Each S output has an
internal N-channel MOSFET for discharging. The NMOS
has a maximum on resistance of 20Ω. An external resistor
should be connected in series with the NMOS to dissipate
heat outside of the LTC6804 package as illustrated in
Figure 35. It is still possible to use an RC to add additional
filtering to cell voltage measurements but the filter R must
remain small, typically around 10Ω to reduce the effect
on the programmed balance current. When using the
internal MOSFETs to discharge cells, the die temperature
should be monitored. See Power Dissipation and Thermal
Shutdown section.
RDISCHARGE
+
S(n)
RFILTER
C(n – 1)
680412 F35
Figure 35. Internal Discharge Circuit
LTC6804
C(n)
+
BSS308PE
R
S(n)
3.3k
C(n – 1)
680412 F36
Figure 36. External Discharge Circuit
Cell Balancing with External MOSFETS
The S outputs include an internal pull-up PMOS transistor.
The S pins can act as digital outputs suitable for driving
the gate of an external MOSFET. For applications requiring
high battery discharge currents, connect a discrete PMOS
switch device and suitable discharge resistor to the cell,
and the gate terminal to the S output pin, as illustrated in
Figure 36. Figure 34 shows external MOSFET circuits that
include RC filtering.
Discharge Control During Cell
Measurements
If the discharge permited (DCP) command bit is high in a
cell measurement command, then the S pin discharge states
are not altered during the cell measurements. However, if
the DCP bit is low, any discharge that is turned on will be
turned off when the corresponding cell or adjacent cells
are being measured. Table 47 illustrates this during an
Table 47. Discharge Control During an ADCV Command with DCP = 0
CELL MEASUREMENT PERIODS
DISCHARGE
PIN
CELL CALIBRATION PERIODS
CELL1/7
CELL2/8
CELL3/9 CELL4/10 CELL5/11 CELL6/12 CELL1/7
t0 to t1M
t1M to t2M t2M to t3M t3M to t4M t4M to t5M t5M to t6M
OFF
ON
ON
ON
OFF
t6M to t1C
CELL2/8
CELL3/9 CELL4/10 CELL5/11 CELL6/12
t1C to t2C
t2C to t3C
t3C to t4C
t4C to t5C
t5C to t6C
S1
OFF
OFF
OFF
ON
ON
ON
OFF
S2
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
ON
ON
S3
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
ON
S4
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
S5
ON
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
S6
OFF
ON
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
S7
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
S8
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
ON
ON
S9
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
ON
S10
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
ON
S11
ON
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
OFF
S12
OFF
ON
ON
ON
OFF
OFF
OFF
ON
ON
ON
OFF
OFF
62
680412fc
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LTC6804-1/LTC6804-2
Applications Information
ADCV command with DCP = 0. In this table, OFF implies
that a discharge is forced off during that period even if
the corresponding DCC[x] bit is high in the configuration
register. ON implies that if the discharge is turned on, it
will stay on during that period. Refer to Figure 3 for the
timing of the ADCV command.
Power Dissipation and Thermal Shutdown
The internal MOSFETs connected to the pins S1 through
S12 pins can be used to discharge battery cells. An external resistor should be used to limit the power dissipated
by the MOSFETs. The maximum power dissipation in the
MOSFETs is limited by the amount of heat that can be tolerated by the LTC6804. Excessive heat results in elevated
die temperatures. Little or no degradation will be observed
in the measurement accuracy for die temperatures up to
125°C. Damage may occur above 150°C, therefore the
recommended maximum die temperature is 125°C. To
protect the LTC6804 from damage due to overheating a
thermal shutdown circuit is included. Overheating of the
device can occur when dissipating significant power in the
cell discharge switches. The thermal shutdown circuit is
enabled whenever the device is not in sleep mode (see
LTC6804 Core State Descriptions). If the temperature detected on the device goes above approximately 150°C the
configuration registers will be reset to default states turning off all discharge switches. When a thermal shutdown
has occurred, the THSD bit in the status register group
B will go high. The bit is cleared after a read operation of
the status register group B. The bit can also be set using
the CLRSTAT command. Since thermal shutdown interrupts normal operation, the internal temperature monitor
should be used to determine when the device temperature
is approaching unacceptable levels.
Method to Verify Balancing Circuitry
The functionality of the discharge circuitry is best verified
by cell measurements. Figure 37 shows an example using
the LTC6804 battery monitor IC. The resistor between the
battery and the source of the discharge MOSFET causes
cell voltage measurements to decrease. The amount of
measurement change depends on the resistor values and
the MOSFET on resistance.
The following algorithm could be used in conjunction
with Figure 37:
1. Measure all cells with no discharging (all S outputs
off) and read and store the results.
2. Turn on S1 and S7
3. Measure C1-C0, C7-C6
4. Turn off S1 and S7
5. Turn on S2 and S8
6. Measure C2-C1, C8-C7
7. Turn off S2 and S8
…
14. Turn on S6 and S12
15. Measure C6-C5, C12-C11
16. Turn off S6 and S12
17. Read the voltage register group to get the results of
steps 2 thru 16.
18. Compare new readings with old readings. Each cell
voltage reading should have decreased by a fixed
percentage set by RB1 and RB2 (Figure 37). The exact
amount of decrease depends on the resistor values
and MOSFET characteristics.
Improved PEC Calculation
The PEC allows the user to have confidence that the serial
data read from the LTC6804 is valid and has not been corrupted by any external noise source. This is a critical feature
for reliable communication and the LTC6804 requires that
a PEC be calculated for all data being read from and written
to the LTC6804. For this reason it is important to have an
efficient method for calculating the PEC. The code below
demonstrates a simple implementation of a lookup table
derived PEC calculation method. There are two functions,
the first function init_PEC15_Table() should only be called
once when the microcontroller starts and will initialize a
PEC15 table array called pec15Table[]. This table will be
used in all future PEC calculations. The pec15 table can
also be hard coded into the microcontroller rather than
running the init_PEC15_Table() function at startup. The
pec15() function calculates the PEC and will return the
correct 15 bit PEC for byte arrays of any given length.
680412fc
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LTC6804-1/LTC6804-2
Applications Information
RB1
RB2
RB1
RB2
RB1
V+
C12
RB2
LTC6804
S12
C11
RB1
S11
C10
RB2
S10
C9
RB1
S9
RB2
C8
S8
C7
RB1
S7
RB2
C6
S6
C5
RB1
S5
RB2
C4
S4
RB1
C3
S3
RB2
RB1
C2
V–
S2
C0
C1
S1
RB2
RB1
RB2
RB1
RB2
RB1
RB2
680412 F37
Figure 37. Balancing Self Test Circuit
64
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Applications Information
/************************************
Copyright 2012 Linear Technology Corp. (LTC)
Permission to freely use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies:
THIS SOFTWARE IS PROVIDED “AS IS” AND LTC DISCLAIMS ALL WARRANTIES
INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO
EVENT SHALL LTC BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM ANY USE OF SAME, INCLUDING
ANY LOSS OF USE OR DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
OR OTHER TORTUOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
PERFORMANCE OF THIS SOFTWARE.
***********************************************************/
int16 pec15Table[256];
int16 CRC15_POLY = 0x4599;
void init_PEC15_Table()
{
for (int i = 0; i < 256; i++)
{
remainder = i 0; --bit)
{
if (remainder & 0x4000)
{
remainder = ((remainder 7) ^ data[i]) & 0xff;//calculate PEC table address
remainder = (remainder 0.9μs + 2 • tCABLE(0.2m per ns)
For long links (>50m): IB = 1mA and K = 0.25
1.2
For addressable multi-drop: IB = 1mA and K = 0.4
68
1.0
DATA RATE (Mbps)
For applications with little system noise, setting IB to 0.5mA
is a good compromise between power consumption and
noise immunity. Using this IB setting with a 1:1 transformer
and RM = 100Ω, RB1 should be set to 3.01k and RB2 set
to 1k. With typical CAT5 twisted pair, these settings will
allow for communication up to 50m. For applications in
very noisy environments or that require cables longer than
50m it is recommended to increase IB to 1mA. Higher drive
current compensates for the increased insertion loss in
the cable and provides high noise immunity. When using
cables over 50m and a transformer with a 1:1 turns ratio
and RM = 100Ω, RB1 would be 1.5k and RB2 would be 499Ω.
CAT5 ASSUMED
0.8
0.6
0.4
0.2
0
1
10
CABLE LENGTH (METERS)
100
680412 F42
Figure 42. Data Rate vs Cable Length
680412fc
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LTC6804-1/LTC6804-2
Applications Information
The use of cables between battery modules, particularly
in automotive applications, can lead to increased noise
susceptibility in the communication lines. For high levels
of electromagnetic interference (EMC), additional filtering
is recommended. The circuit example in Figure 43 shows
the use of common mode chokes (CMC)to add common
mode noise rejection from transients on the battery lines.
The use of a center tapped transformer will also provide
additional noise performance. A bypass capacitor connected to the center tap creates a low impedance for
common mode noise (Figure 43b). Since transformers
without a center tap can be less expensive, they may be
preferred. In this case, the addition of a split termination
resistor and a bypass capacitor (Figure 43a) can enhance
the isoSPI performance. Large center tap capacitors
greater than 10nF should be avoided as they may prevent
the isoSPI common mode voltage from settling. Common
mode chokes similar to those used in Ethernet or CANbus
applications are recommended. Specific examples are
provided in Table 49.
100µH CMC
300Ω
62Ω
•
300Ω
•
62Ω
LTC6804-1
10nF
IM
V–
XFMR
•
•
isoSPI LINK
10nF
a)
IP
51Ω
100µH CMC
•
The hardware design of a daisy-chain isoSPI bus is identical for each device in the network due to the daisy-chain
point-to-point architecture. The simple design as shown in
Figure 41 is functional, but inadequate for most designs. The
termination resistor RM should be split and bypassed with
a capacitor as shown in Figure 43. This change provides
both a differential and a common mode termination, and
as such, increases the system noise immunity.
IP
LTC6804-1
10nF
IM
V–
51Ω
CT XFMR
•
•
isoSPI LINK
•
Implementing a Modular isoSPI Daisy Chain
10nF
680412 F43
b)
Figure 43. Daisy Chain Interface Components
An important daisy chain design consideration is the
number of devices in the isoSPI network. The length of the
chain determines the serial timing and affects data latency
and throughput. The maximum number of devices in an
isoSPI daisy chain is strictly dictated by the serial timing
requirements. However, it is important to note that the serial
read back time, and the increased current consumption,
might dictate a practical limitation.
For a daisy chain, two timing considerations for proper
operation dominate (see Figure 20):
1. t6, the time between the last clock and the rising chip
select, must be long enough.
2. t5, the time from a rising chip select to the next falling
chip select (between commands), must be long enough.
Both t5 and t6 must be lengthened as the number of
LTC6804 devices in the daisy chain increases. The equations for these times are below:
t5 > (#devices • 70ns) + 900ns
t6 > (#devices • 70ns) + 950ns
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69
LTC6804-1/LTC6804-2
IPB
LTC6804-1
49.9Ω
10nF
49.9Ω
GNDD
IMB
IBIAS
ICMP
1k
1k
GNDD
IPA
49.9Ω
10nF
49.9Ω
V–
GNDD
GNDD
10nF*
•
IMA
•
GNDD
10nF*
GNDC
IPB
LTC6804-1
49.9Ω
10nF
49.9Ω
GNDC
IMB
IBIAS
ICMP
1k
1k
GNDC
IPA
49.9Ω
49.9Ω
V–
IMA
10nF
GNDC
GNDC
10nF*
•
GNDC
•
10nF*
GNDB
IPB
LTC6804-1
49.9Ω
49.9Ω
IMB
IBIAS
ICMP
1k
10nF
GNDB
1k
GNDB
IPA
49.9Ω
49.9Ω
V
–
IMA
10nF*
10nF
GNDB
GNDB
•
•
IP
LTC6820
49.9Ω
10nF*
GNDA
49.9Ω
IBIAS
ICMP
10nF
GNDA
IM
1k
1k
GNDA
V–
GNDA
GNDB
* IF TRANSFORMER BEING USED HAS A CENTER TAP, IT SHOULD BE BYPASSED WITH A 10nF CAP
680412 F44
Figure 44. Daisy Chain Interface Components on Single Board
70
680412fc
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LTC6804-1/LTC6804-2
Applications Information
Connecting Multiple LTC6804-1s on the Same PCB
On single board designs with low noise requirements, it
is possible for a simplified capacitor-isolated coupling as
shown in Figure 45 to replace the transformer. Dual Zener
diodes are used at each IC to clamp the common mode
voltage to stay within the receiver’s input range. The optional common mode choke (CMC) provides noise rejection
with symmetrically tapped termination. The 590Ω resistor
creates a resistor divider with the termination resistors and
attenuates common mode noise. The 590Ω value is chosen
to provide the most noise attenuation while maintaining
sufficient differential signal. The circuit is designed such
that IB and VICMP are the same as would be used for a
transformer based system with cables over 50m.
When connecting multiple LTC6804-1 devices on the same
PCB, only a single transformer is required between the
LTC6804‑1 isoSPI ports. The absence of the cable also
reduces the noise levels on the communication lines and
often only a split termination is required. Figure 44 shows
an example application that has multiple LTC6804-1s
on the same PCB, communicating to the bottom MCU
through an LTC6820 isoSPI driver. If a transformer with
a center tap is used, a capacitor can be added for better
noise rejection. Additional noise filtering can be provided
with discrete common mode chokes (not shown) placed
to both sides of the single transformer.
VREG
590Ω
100Ω
3.3V 10nF
100Ω
3.3V
V–
IPB
LTC6804-1
3.3V 10nF
100Ω
3.3V
IPA
V–
GNDA
IMA
CMC
•
100Ω
GNDB
VREG
590Ω
100Ω
3.3V 10nF
100Ω
3.3V
1.5k
590Ω
GNDA
IMB
IBIAS
ICMP
1nF
GNDB
VREG
IMA
GNDB
1nF
499Ω
•
IPA
1.5k
499Ω
GNDA
VREG
100Ω
3.3V 10nF
100Ω
3.3V
CMC
•
IBIAS
ICMP
1nF
590Ω
GNDB
IMB
1nF
•
IPB
LTC6804-1
GNDA
1nF
1nF
680412 F45
Figure 45. Capacitive Isolation Coupling for LTC6804-1s on the Same PCB
680412fc
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71
LTC6804-1/LTC6804-2
Applications Information
When an LTC6804-2 is not addressed, it will not transmit
data pulses. This scheme eliminates the possibility for collisions since only the addressed device returns data to the
master. Generally, multi-drop systems are best confined
to compact assemblies where they can avoid excessive
isoSPI pulse-distortion and EMC pickup.
Connecting an MCU to an LTC6804-1 with an isoSPI
Data Link
The LTC6820 will convert standard 4-wire SPI into a
2-wire isoSPI link that can communicate directly with
the LTC6804. An example is shown in Figure 46. The
LTC6820 can be used in applications to provide isolation
between the microcontroller and the stack of LTC6804s.
The LTC6820 also enables system configurations that
have the BMS controller at a remote location relative to
the LTC6804 devices and the battery pack.
Basic Connection of the LTC6804-2 in a Multi-Drop
Configuration
In a multi-drop isoSPI bus, placing the termination at the
ends of the transmission line provides the best performance
(with 100Ω typically). Each of the LTC6804 isoSPI ports
should couple to the bus with a resistor network, as shown
in Figure 48a. Here again, a center-tapped transformer offers
the best performance and a common mode choke (CMC)
increases the noise rejection further, as shown in Figure
48b. Figure 48b also shows the use of an RC snubber at
the IC connections as a means to suppress resonances
(the IC capacitance provides sufficient out-of-band rejection). When using a non-center-tapped transformer,
a virtual CT can be generated by connecting a CMC as
a voltage-splitter. Series resistors are recommended to
decouple the LTC6804 and board parasitic capacitance
from the transmission line. Reducing these parasitics on
the transmission line will minimize reflections.
Configuring the LTC6804-2 in a Multi–Drop isoSPI
Link
The addressing feature of the LTC6804-2 allows multiple
devices to be connected to a single isoSPI master by distributing them along one twisted pair, essentially creating
a large parallel SPI network. A basic multi-drop system is
shown in Figure 47; the twisted pair is terminated only at
the beginning (master) and the end of the cable. In between,
the additional LTC6804-2s are connected to short stubs
on the twisted pair. These stubs should be kept short, with
as little capacitance as possible, to avoid degrading the
termination along the isoSPI wiring.
IPB
LTC6804-1
49.9Ω
•
•
•
•
10nF*
10nF
49.9Ω
IMB
IBIAS
ICMP
1k
GNDB
GNDB
1k
IPA
49.9Ω
10nF
GNDB
IMA
GNDB
GNDB
LTC6820
49.9Ω
10nF*
49.9Ω
V–
IP
10nF*
GNDA
IBIAS
ICMP
10nF
1k
1k
GNDA
49.9Ω
GNDA
IM
* IF TRANSFORMER BEING USED HAS A CENTER TAP, IT SHOULD BE BYPASSED WITH A 10nF CAP
V–
GNDA
680412 F46
Figure 46. Interfacing an LTC6804-1 with a µC Using an LTC6820 for Isolated SPI Control
72
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Applications Information
LTC6804-2
•
•
IPA
VREGC
ISOMD
IBIAS
100Ω
1.21k
ICMP
IMA
806Ω
V–
GNDC
LTC6804-2
•
•
IPA
GNDC
VREGB
ISOMD
IBIAS
1.21k
ICMP
IMA
GNDB
LTC6804-2
5V
•
•
•
•
IPA
GNDB
VREGA
ISOMD
IBIAS
5V
100Ω
1.21k
100nF
ICMP
IMA
806Ω
V–
GNDA
GNDA
680412 F47
Figure 47. Connecting the LTC6804-2 in a Multi-Drop Configuration
IPA
LTC6804-2
15pF
IMA
V–
100µH CMC HV XFMR 22Ω
100µH CMC
•
•
402Ω
•
isoSPI
BUS
22Ω
•
POL
PHA
IBIAS
ICMP
GND
SLOW
MSTR
IP
IM
VDD
806Ω
V–
806Ω
•
5V
VDDS
EN
MOSI
MISO
SCK
CS
1.21k
•
5k
LTC6820
10nF
a)
IPA
LTC6804-2
402Ω
15pF
IMA
V–
100µH CMC
CT HV XFMR 22Ω
•
µC
SDO
SDI
SCK
CS
5V
•
•
isoSPI
BUS
22Ω
•
100nF
10nF
680412 F48
b)
Figure 48. Preferred isoSPI Bus Couplings For Use With LTC6804-2
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73
LTC6804-1/LTC6804-2
Applications Information
Table 48. Recommended Transformers
TEMPERATURE
MANUFACTURER
PART NUMBER
RANGE
VWORKING VHIPOT/60s CT CMC
H
Dual Transformers
l
6.0mm
Pulse
HX1188FNL
–40°C to 85°C
60V (est) 1.5kVrms l
l
2.1mm
Pulse
HX0068ANL
–40°C to 85°C
60V (est) 1.5kVrms l
l
3.4mm
Pulse
HM2100NL
–40°C to 105°C
1000V
4.3kVdc
–
l
l
Pulse
HM2102NL
–40°C to 125°C
1000V
4.3kVdc
4.9mm
l
Sumida
CLP178–C20114
–40°C to 125°C 1000V (est) 3.75kVrms l
9mm
–
5.7mm
Sumida
CLP0612–C20115
600Vrms 3.75kVrms l
l
l 10.9mm
Wurth Elektronik
7490140110
–40°C to 85°C
250Vrms
4kVrms
–
8.4mm
Wurth Elektronik
7490140111
0°C to 70°C
1000V (est) 4.5kVrms l
l
l
8.4mm
Wurth Elektronik
749014018
0°C to 70°C
250Vrms
4kVrms
l
6.4mm
Halo
TG110–AE050N5LF
–40°C to 85/125°C 60V (est) 1.5kVrms l
Single Transformers
Pulse
PE–68386NL
–40°C to 130°C
60V (est)
1.5kVdc
–
–
2.5mm
l
5.7mm
Pulse
HM2101NL
–40°C to 105°C
1000V
4.3kVdc
–
Wurth Elektronik
750340848
–40°C to 105°C
250V
3kVrms
–
–
2.2mm
l
–
10mm
Halo
TGR04–6506V6LF
–40°C to 125°C
300V
3kVrms
l
–
9.4mm
Halo
TGR04–A6506NA6NL
–40°C to 125°C
300V
3kVrms
l
TDK
ALT4532V–201–T001
–40°C to 105°C
60V (est)
~1kV
–
2.9mm
l
Halo
TDR04–A550ALLF
–40°C to 105°C
1000V
5kVrms
–
6.4mm
Sumida
CEEH96BNP–LTC6804/11 –40°C to 125°C
600V
2.5kVrms –
–
7mm
–
10mm
Sumida
CEP99NP–LTC6804
–40°C to 125°C
600V
2.5kVrms l
Sumida
ESMIT–4180/A
–40°C to 105°C
250Vrms
3kVrms
–
–
3.5mm
TDK
VGT10/9EE–204S2P4
–40°C to 125°C 250V (est) 2.8kVrms l
– 10.6mm
Transformer Selection Guide
As shown in Figure 41, a transformer or pair of transformers isolates the isoSPI signals between two isoSPI ports.
The isoSPI signals have programmable pulse amplitudes
up to 1.6VP-P and pulse widths of 50ns and 150ns. To be
able to transmit these pulses with the necessary fidelity
the system requires that the transformers have primary
inductances above 60µH and a 1:1 turns ratio. It is also
necessary to use a transformer with less than 2.5µH of
leakage inductance. In terms of pulse shape the primary
inductance will mostly effect the pulse droop of the 50ns
and 150ns pulses. If the primary inductance is too low,
the pulse amplitude will begin to droop and decay over
the pulse period. When the pulse droop is severe enough,
the effective pulse width seen by the receiver will drop
substantially, reducing noise margin. Some droop is acceptable as long as it is a relatively small percentage of
74
L
W
(W/LEADS)
PINS
12.7mm
12.7mm
14.7mm
14.8mm
17.5mm
12.7mm
24.6mm
17.1mm
17.1mm
12.7mm
9.7mm
9.7mm
14.9mm
14.7mm
15.1mm
9.4mm
17.0mm
15.2mm
15.2mm
9.5mm
16SMT
16SMT
10SMT
12SMT
12SMT
16SMT
16SMT
12SMT
12SMT
16SMT
6.7mm
7.6mm
4.4mm
9.5mm
8.9mm
3.2mm
8.9mm
9.2mm
9.2mm
5.2mm
10.4mm
8.6mm
9.3mm
9.1mm
12.1mm
12.1mm
4.5mm
16.6mm
12.0mm
12.0mm
9.1mm
12.7mm
6SMT
6SMT
4SMT
6SMT
6SMT
6SMT
6TH
4SMT
8SMT
4SMT
8SMT
AEC–
Q200
–
–
l
l
–
–
–
–
–
l
–
l
–
–
l
l
l
–
–
l
–
the total pulse amplitude. The leakage inductance primarily
affects the rise and fall times of the pulses. Slower rise
and fall times will effectively reduce the pulse width. Pulse
width is determined by the receiver as the time the signal
is above the threshold set at the ICMP pin. Slow rise and
fall times cut into the timing margins. Generally it is best
to keep pulse edges as fast as possible. When evaluating
transformers, it is also worth noting the parallel winding
capacitance. While transformers have very good CMRR at
low frequency, this rejection will degrade at higher frequencies, largely due to the winding to winding capacitance.
When choosing a transformer, it is best to pick one with
less parallel winding capacitance when possible.
When choosing a transformer, it is equally important to
pick a part that has an adequate isolation rating for the
application. The working voltage rating of a transformer
is a key spec when selecting a part for an application.
680412fc
For more information www.linear.com/LTC6804-1
LTC6804-1/LTC6804-2
Interconnecting daisy-chain links between LTC6804-1
devices see
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