BQ77904, BQ77905
SLUSCM3K – JUNE 2016 – REVISED JULY 2020
BQ77904, BQ77905 3-Series to 20-Series Ultra Low-Power Voltage, Current,
Temperature, and Open-Wire Stackable Lithium-Ion Battery Protector
1 Features
•
•
•
•
•
•
•
•
•
•
NORMAL mode: 6 µA (BQ77904 and BQ77905)
Full suite of voltage, current, and temperature
protections
Scalable cell count from 3 series to 20 series or
more
Voltage protection (accuracy ±10 mV)
– Overvoltage: 3 V to 4.575 V
– Undervoltage: 1.2 V to 3 V
Open cell and open-wire detection (OW)
Current Protection
– Overcurrent discharge 1: –10 mV to –85 mV
– Overcurrent discharge 2: –20 mV to +170 mV
– Short circuit discharge: –40 mV to +340 mV
– Accuracy ±20% for ≤ 20 mV, ±30% for > 20 mV
across full temperature
Temperature protection
– Overtemperature charge: 45°C or 50°C
– Overtemperature discharge: 65°C or 70°C
– Undertemperature charge: –5°C or 0°C
– Undertemperature discharge: –20°C or –10°C
Additional Features
– Independent charge (CHG) and discharge
(DSG) FET drivers
– 36-V absolute maximum rating per cell input
– Built-in-self-test functions for high reliability
SHUTDOWN mode: 0.5-µA maximum
Functional Safety-Capable
– Documentation available to aid functional safety
system design
of configurations. Separate overtemperature and
undertemperature thresholds for discharge (OTD and
UTD) and charge (OTC and UTC) are provided for
added flexibility.
The device achieves pack protection through the
integrated independent CHG and DSG low-side
NMOS FET drivers, which may be disabled through
two control pins. These control pins may also be used
to achieve cell protection solutions for higher series
(6 series and beyond) in a simple and economical
manner. To do this, simply cascade a higher device
CHG and DSG outputs to the immediate lower device
control pins. For a reduced component count, all
protection faults use internal delay timers.
Device Information
PART NUMBER(1)
PACKAGE
BQ77904
TSSOP (20)
BQ77905
(1)
6.50 mm × 4.40 mm
For all available packages, see the orderable addendum at
the end of the data sheet.
PACK+
VDD
VTB
VC5
TS
bq77094/5
LD
Vss
SRP
SRN
DSG
CTRD
CHGU
CTRC
VDD
2 Applications
•
•
•
•
•
•
Power tools, garden tools
Start-stop battery packs
Lead-acid (PbA) replacement batteries
Light electric vehicles
Energy storage systems, uninterruptible power
supplies (UPS)
10.8-V to 72-V packs
BODY SIZE (NOM)
VTB
VC5
TS
bq77094/5
LD
Vss
SRP
SRN
DSG
CHG
PACK-
Copyright
Copyright©
©2017,
2017,Texas
TexasInstruments
InstrumentsIncorporated
Incorporated
Simplified Schematic
3 Description
The BQ77904 and BQ77905 devices are low-power
battery pack protectors that implement a suite
of voltage, current, and temperature protections
without microcontroller (MCU) control. The device's
stackable interface provides simple scaling to support
battery cell applications from 3 series to 20
series or more. Protection thresholds and delays
are factory-programmed and available in a variety
An IMPORTANT NOTICE at the end of this data sheet addresses availability, warranty, changes, use in safety-critical applications,
intellectual property matters and other important disclaimers. PRODUCTION DATA.
BQ77904, BQ77905
www.ti.com
SLUSCM3K – JUNE 2016 – REVISED JULY 2020
Table of Contents
1 Features............................................................................1
2 Applications..................................................................... 1
3 Description.......................................................................1
4 Revision History.............................................................. 2
5 Device Comparison......................................................... 4
6 Pin Configuration and Functions...................................5
Pin Functions.................................................................... 5
7 Specifications.................................................................. 6
7.1 Absolute Maximum Ratings........................................ 6
7.2 ESD Ratings............................................................... 6
7.3 Recommended Operating Conditions.........................6
7.4 Thermal Information....................................................7
7.5 Electrical Characteristics.............................................7
7.6 Timing Requirements................................................ 10
7.7 Typical Characteristics.............................................. 11
8 Detailed Description......................................................13
8.1 Overview................................................................... 13
8.2 Functional Block Diagram......................................... 14
8.3 Feature Description...................................................14
8.4 Device Functional Modes..........................................26
9 Application and Implementation.................................. 27
9.1 Application Information............................................. 27
9.2 Typical Application.................................................... 32
9.3 System Examples..................................................... 36
10 Power Supply Recommendations..............................36
11 Layout........................................................................... 37
11.1 Layout Guidelines................................................... 37
11.2 Layout Example...................................................... 37
12 Device and Documentation Support..........................38
12.1 Documentation Support.......................................... 38
12.2 Receiving Notification of Documentation Updates..38
12.3 Support Resources................................................. 38
12.4 Trademarks............................................................. 38
12.5 Electrostatic Discharge Caution..............................38
12.6 Glossary..................................................................38
13 Mechanical, Packaging, and Orderable
Information.................................................................... 38
4 Revision History
NOTE: Page numbers for previous revisions may differ from page numbers in the current version.
Changes from Revision J (April 2020) to Revision K (July 2020)
Page
• Added the BQ7790521 evice in the Device Comparison table...........................................................................4
Changes from Revision I (December 2019) to Revision J (February 2020)
Page
• Changed the BQ7790518 device to a catalog device in the Device Comparison table......................................4
Changes from Revision H (September 2018) to Revision I (December 2019)
Page
• Added the BQ7790522 device to the Device Comparison table.........................................................................4
Changes from Revision G (September 2017) to Revision H (September 2018)
Page
• Changed some wording throughout the data sheet for clarity and conciseness ............................................... 1
• Added the BQ7790518 device to the BQ77905 Device Comparison table........................................................ 4
Changes from Revision F (May 2017) to Revision G (September 2017)
Page
• Added BQ7790511 and BQ7790512 to the Device Comparison table............................................................... 4
Changes from Revision E (March 2017) to Revision F (May 2017)
Page
• Changed the BQ7790400 setting: OV delay from 1 s to 2 s. UV from 2800 mV to 2200 mV, UV delay from 1 s
to 2 s, UV Hyst from 200 to 400 mV, UV load recovery from N to Y. OCD2 from 80 mV to 60 mV, OCD2 delay
from 700 to 350 ms. SCD from 160 mV to 100 mV.............................................................................................4
• Added BQ7790508 and BQ7790509 to the Device Comparison table...............................................................4
Changes from Revision D (March 2017) to Revision E (March 2017)
Page
• Added BQ7790505 to the Device Comparison table.......................................................................................... 4
• Changed UTC(REC) at 5°C typ from 68.8 to 69.73 %VTB. Changed UTC(REC) at 10°C typ from 64.23 to
65.52 %VTB........................................................................................................................................................7
2
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SLUSCM3K – JUNE 2016 – REVISED JULY 2020
Changes from Revision C (February 2017) to Revision D (March 2017)
Page
• Changed VOTD, VOTD(REC), VOTC, VOTC(REC), VUTD, VUTD(REC), VUTC, VUTC(REC) MIN and MAX
specification values.............................................................................................................................................7
Changes from Revision B (November 2016) to Revision C (February 2017)
Page
• Added values in the Thermal Information table to align with JEDEC standards.................................................7
Changes from Revision A (June 2016) to Revision B (November 2016)
Page
• Changed order of listed items in Features .........................................................................................................1
• Table 5-1 and Table 5-2, Changed OTC To: UTC in last column under Temperature. Changed BQ7790400
and BQ7790503 to Production Data. Updated the BQ7790503 configuration .................................................. 4
• Changed pin number from 16-pin to 20-pin ....................................................................................................... 5
• Corrected max value on the UTD at –20°C spec................................................................................................7
• Changed comparator flowcharts with new flowcharts.......................................................................................14
• Corrected CTRC and CTRD delay time entries................................................................................................18
Changes from Revision * (June 2016) to Revision A (June 2016)
Page
• Changed the device From: Product Preview To: Production.............................................................................. 1
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SLUSCM3K – JUNE 2016 – REVISED JULY 2020
5 Device Comparison
NUMBER OF
CELLS
DEVICE
BQ77904
3, 4
BQ77905
3, 4, 5
PROTECTIONS
TYPICAL NORMAL
MODE CURRENT (µA)
PACKAGE
6
20-TSSOP
OV, UV, OW, OTD, OTC, UTD, UTC, OCD1,
OCD2, SCD, CTRC, CTRD
Unless otherwise specified, the devices in Table 5-1 and Table 5-2 come, by default, with the state comparator
enabled with a 2-mV threshold. Filtered fault detection is used by default. Contact Texas Instruments for new
configuration options or devices in preview.
Table 5-1. BQ77904 Device Comparison
OV
Part Number
Threshold (mV)
Delay(s)
Hyst (mV)
4225
2
100
2200
BQ7790400
Part Number
(Cont.)
BQ7790400
(1)
UV
Thresh
(mV)
Delay(s)
2
OW
Hyst (mV)
Load Removal
Recovery (Y/N)
400
Y
OCD1
Current (nA)
Threshold
(mV)
Delay (ms)
0 (disable)
40
1420
Temperature (°C)(1)
OCD2
SCD
Current Fault Recovery
Delay (ms)
Threshold (mV)
Delay (s)
Method
OTD
OTC
UTD
UTC
350
100
0
Load Removal
70
50
–20
–5
These thresholds are target based on temperature, but they are dependent on external components that could vary based on customer
selection. The circuit is based on the 103AT NTC thermistor connected to TS and VSS, and a 10-kΩ resistor connected to VTB and
TS. Actual thresholds must be determined in mV. Refers to the overtemperature and undertemperature mV threshold in the Electrical
Characteristics table.
Table 5-2. BQ77905 Device Comparison
OV
UV
OCD1
Threshold
(mV)
Delay(s)
Hyst (mV)
Thresh
(mV)
Delay(s)
Hyst (mV)
BQ7790500
4200
0.5
100
2600
1
400
Y
100
30
BQ7790502
4250
1
200
2700
1
200
Y
100
85
700
BQ7790503
4200
1
100
2700
2
400
Y
100
80
1420
BQ7790505
4250
1
200
2700
1
200
N
0
60
10
BQ7790508
3900
1
200
2000
1
400
Y
100
50
700
BQ7790509
4250
1
100
2500
1
400
Y
100
50
700
BQ7790511
4250
1
200
2700
1
200
Y
100
50
350
BQ7790512
4175
1
100
2800
1
400
Y
100
75
1420
BQ7790518
4250
1
100
2750
1
200
Y
100
70
180
BQ7790521
3700
1
200
2500
1
200
Y
100
70
180
BQ7790522
4250
1
100
2800
1
200
Y
100
80
700
Part Number
OCD2
Part Number (Cont.)
SCD
Threshold
(mV)
Delay (ms)
Threshold (mV)
BQ7790500
50
700
BQ7790502
120
350
BQ7790503
160
BQ7790505
80
BQ7790508
Current (nA)
Threshold
(mV)
Delay (ms)
1420
Temperature (°C)(1)
Current Fault Recovery
Delay (s)
Method
OTD
OTC
UTD
120
1
Load Removal + Delay
70
50
–20
0
240
—
Load Removal
70
50
–20
–5
350
320
—
Load Removal
70
50
–20
–5
5
100
9
Load Removal + Delay
65
45
–20
0
100
90
200
1
Load Removal + Delay
70
50
–20
–5
BQ7790509
100
90
200
1
Load Removal + Delay
70
50
–20
–5
BQ7790511
120
90
280
—
Load Removal
65
45
–20
0
BQ7790512
150
350
300
1
Load Removal + Delay
65
45
–20
0
BQ7790518
140
20
300
1
Load Removal
70
50
–20
0
BQ7790521
140
20
320
1
Load Removal
70
50
–20
0
BQ7790522
100
350
300
1
Load Removal
70
50
–20
–5
(1)
4
OW
Load
Removal
Recovery
(Y/N)
UTC
These thresholds are target based on temperature, but they are dependent on external components that could vary based on customer
selection. Circuit is based on 103AT NTC thermistor connected to TS and VSS, and a 10-kΩ resistor connected to VTB and TS.
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SLUSCM3K – JUNE 2016 – REVISED JULY 2020
Actual thresholds must be determined in mV. Refers to the overtemperature and undertemperature mV threshold in the Electrical
Characteristics table.
6 Pin Configuration and Functions
VDD
1
20
DVSS
AVDD
2
19
CTRD
VC5
3
18
CTRC
VC4
4
17
CCFG
VC3
5
16
VTB
VC2
6
15
TS
VC1
7
14
LD
AVSS
8
13
CHG
SRP
9
12
CHGU
SRN
10
11
DSG
Not to scale
Figure 6-1. PW Package 20-Pin TSSOP Top View
Pin Functions
PIN
(1)
NAME
NO.
I/O
DESCRIPTION
AVDD
2
O
Analog supply (only connect to a capacitor)
AVSS
8
P
Analog ground
CCFG
17
I
Cell in series-configuration input
CHG
13
O
CHG FET driver. Use on a single device or on the bottom device of a stack
configuration.
CHGU
12
O
CHG FET signal. Use for the upper device of a stack configuration to feed the CHG
signal to the CTRC pin of the lower device.
CTRC
18
I
CTRD
19
I
DSG
11
O
DSG FET driver
DVSS
20
P
Digital ground
LD
14
I
PACK– load removal detection
SRN
10
I
Current sense input connecting to the PACK– side of sense resistor
SRP
9
I
Current sense input connecting to the battery side of sense resistor
TS
15
I
Thermistor measurement input. Connect a 10-kΩ resistor to AVSS pin if the function is
not used.
VC1
7
I
VC2
6
I
VC3
5
I
VC4
4
I
VC5
3
I
Cell voltage sense inputs (Pin 3 must be connected to Pin 4 on the BQ77904 device.)
VDD
1
P
Supply voltage
VTB
16
O
Thermistor bias output
(1)
CHG and DSG override inputs
Cell voltage sense inputs
I = Input, O = Output, P = Power
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7 Specifications
7.1 Absolute Maximum Ratings
Over operating free-air temperature range (unless otherwise noted). All values are referenced to VSS unless otherwise
noted.(1)
VI
Input voltage
VO
Output voltage range
MIN
MAX
UNIT
VDD, VC5, VC4, VC3, VC2, VC1, CCFG, CTRD, CTRC
–0.3
36
V
LD
–30
20
V
SRN, SRP, TS, AVDD, CCFG
–0.3
3.6
V
DSG, CHGU
–0.3
20
V
CHG
–30
20
V
VTB
–0.3
3.6
V
II
Input current
LD, CHG
500
µA
II
Input current
CHGU, DSG
1
mA
IO
Output current
CHG
1
mA
IO
Output current
CHGU, DSG
1
mA
150
°C
Storage temperature, Tstg
(1)
–65
Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device. These are stress
ratings only, which do not imply functional operation of the device at these or any other conditions beyond those indicated under
Recommended Operating Conditions. Exposure to absolute-maximum-rated conditions for extended periods may affect device
reliability.
7.2 ESD Ratings
VALUE
V(ESD)
(1)
(2)
Electrostatic discharge
Human-body model (HBM), per ANSI/ESDA/JEDEC
JS-001(1)
±1000
Charged-device model (CDM), per JEDEC specification JESD22-C101(2)
±250
UNIT
V
JEDEC document JEP155 states that 500-V HBM allows safe manufacturing with a standard ESD control process.
JEDEC document JEP157 states that 250-V CDM allows safe manufacturing with a standard ESD control process.
7.3 Recommended Operating Conditions
Over operating free-air temperature range (unless otherwise noted)
VBAT
VI
Supply voltage
Input voltage
MIN
MAX
UNIT
VDD
3
25
V
VC5-VC4, VC4-VC3, VC3-VC2, VC2-VC1,
VC1-VSS
0
5
CTRD, CTRC
0
(VDD + 5)
CCFG
0
AVDD
–0.2
0.8
LD
0
16
TS
0
VTB
CHG, CHGU, DSG
0
16
VTB, AVDD
0
3
–40
85
SRN, SRP
6
VO
Output voltage
TA
Operating free-range temperature
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V
V
°C
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SLUSCM3K – JUNE 2016 – REVISED JULY 2020
7.4 Thermal Information
bq77904
bq77905
THERMAL METRIC(1)
UNITS
PW (TSSOP)
20 PINS
RθJA
Junction-to-ambient thermal resistance
RθJC(top)
Junction-to-case (top) thermal resistance
RθJB
Junction-to-board thermal resistance
ψJT
ψJB
(1)
98.4
°C/W
37
°C/W
49.3
°C/W
Junction-to-top characterization parameter
2.9
°C/W
Junction-to-board characterization parameter
48.7
°C/W
For more information about traditional and new thermal metrics, see the Semiconductor and IC Package Thermal Metrics application
report.
7.5 Electrical Characteristics
Typical values stated at TA = 25°C and VDD = 16 V (bq77904) or 20 V (bq77905). MIN and MAX values stated with TA =
–40°C to +85°C and VDD = 3 to 20 V (bq77904) or VDD = 3 to 25 V (bq77905) unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
SUPPLY VOLTAGE
V(POR)
POR threshold
VDD rising, 0 to 6 V
V(SHUT)
Shutdown threshold
VDD falling, 6 to 0 V
V(AVDD)
AVDD voltage
C(VDD) = 1 µF
2
2.1
4
V
3.25
V
2.5
3.25
V
SUPPLY AND LEAKAGE CURRENT
ICC
NORMAL mode current
(bq77904/bq77905)
Cell1 through Cell5 = 4 V,
VDD = 20 V (bq77905)
6
9
µA
I(CFAULT)
Fault condition current
State comparator on
8
12
µA
IOFF
SHUTDOWN mode current
VDD < VSHUT
0.5
µA
ILKG(OW_DIS)
Input leakage current at VCx All cell voltages = 4 V,
pins
Open-wire disable configuration
ILKG(100nA)
Open-wire sink current at
VCx pins
ILKG(200nA)
ILKG(400nA)
–100
0
100
nA
All cell voltages = 4 V,
100-nA configuration
30
110
175
nA
Open-wire sink current at
VCx pins
All cell voltages = 4 V,
200-nA configuration
95
210
315
nA
Open-wire sink current at
VCx pins
All cell voltages = 4 V,
400-nA configuration
220
425
640
nA
PROTECTION ACCURACIES
VOV
Overvoltage programmable
threshold range
3000
4575
mV
VUV
Undervoltage programmable
threshold range
1200
3000
mV
TA = 25°C, OV detection accuracy
–10
10
mV
TA = 25°C, UV detection accuracy
–18
18
mV
TA = 0 to 60°C
–28
26
mV
TA = –40 to 85°C
–40
40
mV
0
400
mV
200
800
mV
V(VA)
OV, UV, detection accuracy
VHYS(OV)
OV hysteresis
programmable threshold
range
VHYS(UV)
UV hysteresis programmable
threshold range
VOTD
Overtemperature in
discharge programmable
threshold (ratio of VTB)
Threshold for 65°C(1)
19.71%
20.56%
21.86%
V
Threshold for 70°C (1)
17.36%
18.22%
19.51%
VTB
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Typical values stated at TA = 25°C and VDD = 16 V (bq77904) or 20 V (bq77905). MIN and MAX values stated with TA =
–40°C to +85°C and VDD = 3 to 20 V (bq77904) or VDD = 3 to 25 V (bq77905) unless otherwise noted.
PARAMETER
VOTD(REC)
TEST CONDITIONS
Overtemperature in
discharge recovery (ratio of
VTB)
VOTC
Overtemperature in charge
programmable threshold
(ratio of VTB)
VOTC(REC)
Overtemperature in charge
recovery (ratio of VTB)
VUTD
Undertemperature in
discharge programmable
threshold (ratio of VTB)
VUTD(REC)
Undertemperature in
discharge recovery (ratio of
VTB)
MIN
TYP
MAX
UNIT
Recovery threshold at 55°C for
when VOTD is at 65°C(1)
25.24%
26.12%
27.44%
VTB
Recovery threshold at 60°C for
when VOTD is at 70°C(1)
22.12%
23.2%
24.24%
VTB
Threshold for 45°C(1)
32.14%
32.94%
34.54%
VTB
50°C(1)
29.15%
29.38%
31.45%
VTB
Recovery threshold at 35°C when
VOTD is at 45°C(1)
38.63%
40.97%
40.99%
VTB
Recovery threshold at 40°C when
VOTD is at 50°C(1)
36.18%
36.82%
38.47%
VTB
Threshold for –20°C(1)
86.41%
87.14%
89.72%
VTB
–10°C(1)
80.04%
80.94%
83.10%
VTB
Recovery threshold at –10°C when
VUTD is at –20°C(1)
80.04%
80.94%
83.10%
VTB
Recovery threshold at 0°C when
VUTD is at –10°C(1)
71.70%
73.18%
74.86%
VTB
75.06%
77.22%
78.32%
VTB
71.70%
73.18%
74.86%
VTB
68.80%
69.73%
71.71%
VTB
64.67%
65.52%
67.46%
VTB
Threshold for
Threshold for
VUTC
Undertemperature in charge Threshold for –5°C(1)
programmable threshold
Threshold for 0°C(1)
(ratio of VTB)
VUTC(REC)
Recovery threshold at 5°C when
(1)
Undertemperature in Charge VUTC is at –5°C
Recovery (ratio of VTB)
Recovery threshold at 10°C when
VUTC is at 0°C(1)
VOCD1
Overcurrent discharge 1
programmable threshold
range,
(VSRP – VSRN)
–85
–10
mV
VOCD2
Overcurrent discharge 2
programmable threshold
range,
(VSRP – VSRN)
–20
–170
mV
VSCD
Short circuit discharge programmable threshold range, (VSRP –
VSRN)
–40
–340
mV
VCCAL
OCD1 detection accuracy at
VOCD1 > –20 mV
lower thresholds
–30%
30%
VCCAH
OCD1, OCD2, SCD
detection accuracy
VOCD1 ≤ –20 mV; all OCD2 and
SCD threshold ranges
–20%
20%
VOW
Open-wire fault voltage
threshold at VCx per cell
with respect to VCx-1
Voltage falling on VCx, 3.6 V to
0V
450
VOW(HYS)
Hysteresis for open wire fault
Voltage rising on VCx, 0 V to
3.6 V
500
550
100
mV
mV
CHARGE AND DISCHARGE FET DRIVERS
8
VDD ≥ 12 V, CL = 10 nF
11
VDD < 12 V, CL = 10 nF
VDD – 1
12
V(FETON)
CHG/CHGU/DSG on
V(FETOFF)
CHG/CHGU/DSG off
R(CHGOFF)
CHG off resistance
CHG off for > tCHGPDN and pin held
at 2 V
0.5
R(DSGOFF)
CHGU/DSG off resistance
CHGU/DSG off and pin held at 2 V
10
ICHG(CLAMP)
CHG clamp current
CHG off and pin held at 18 V
No load when CHG/CHGU/DSG is
off.
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V
VDD
V
0.5
V
kΩ
16
Ω
450
µA
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Typical values stated at TA = 25°C and VDD = 16 V (bq77904) or 20 V (bq77905). MIN and MAX values stated with TA =
–40°C to +85°C and VDD = 3 to 20 V (bq77904) or VDD = 3 to 25 V (bq77905) unless otherwise noted.
PARAMETER
TEST CONDITIONS
MIN
TYP
MAX
UNIT
16
18
20.5
V
50
150
µs
VCHG(CLAMP)
CHG clamp voltage
ICHG(CLAMP) = 300 µA
tCHGON
CHG on rise time
CL = 10 nF, 10% to 90%
tDSGON
CHGU/DSG on rise time
CL = 10 nF, 10% to 90%
2
75
µs
tCHGOFF
CHG off fall time
CL = 10 nF, 90% to 10%
15
30
µs
tDSGOFF
CHGU/DSG off fall time
CL = 10 nF, 90% to 10%
5
15
µs
0.6
V
CTRC AND CTRD CONTROL
With respect to VSS. Enabled <
MAX
VCTR1
Enable FET driver (VSS)
VCTR2
Enable FET driver (Stacked) Enabled > MIN
VCTR(DIS)
Disable FET driver
Disabled between MIN and MAX
VCTR(MAXV)
CTRC and CTRD clamp
voltage
ICTR = 600 nA
tCTRDEG_ON) (2)
CTRC and CTRD deglitch
for ON signal
7
ms
tCTRDEG_OFF (2)
CTRC and CTRD deglitch
for OFF signal
7
ms
VDD + 2.2
V
2.04
VDD + 2.8
VDD + 4
VDD + 0.7
V
VDD + 5
V
CURRENT STATE COMPARATOR
V(STATE_D1)
Discharge qualification
threshold1
Measured at SRP-SRN
–3
–2
–1
mV
V(STATE_C1)
Charge qualification
threshold1
Measured at SRP-SRN
1
2
3
mV
tSTATE (2)
State detection qualification
time
1.2
ms
LOAD REMOVAL DETECTION
VLD(CLAMP)
LD clamp voltage
I(LDCLAMP) = 300 µA
ILD(CLAMP)
LD clamp current
V(LDCLAMP) = 18 V
16
VLDT
LD threshold
Load removed < when VLDT
1.25
RLD(INT)
LD input resistance when
enabled
Measured to VSS
tLD_DEG
LD detection deglitch
18
20.5
V
450
µA
1.3
1.35
V
160
250
375
kΩ
1
1.5
2.3
ms
CCFG PIN
V(CCFGL)
CCFG threshold low (ratio of
3-cell configuration
VAVDD)
V(CCFGH)
CCFG threshold high (ratio
of VAVDD)
4-cell configuration
65%
V(CCFGHZ)
CFG threshold high-Z (ratio
of VAVDD)
5-cell configuration, CCFG floating,
internally biased
25%
tCCFG_DEG (2)
CCFG deglitch
33%
10%
V
100%
V
45%
V
6
ms
CUSTOMER TEST MODE (CTM)
V(CTM)
Customer test mode entry
voltage at VDD
VDD > VC5 + V(CTM), TA = 25°C
8.5
tCTM_ENTRY (3)
Delay time to enter and exit
Customer Test Mode
VDD > VC5 + V(CTM), TA = 25°C
50
tCTM_DELAY (3)
Delay time of faults while in
Customer Test Mode
TA = 25°C
tCTM_OC_REC
(1)
(3)
Fault recovery time of
OCD1, OCD2, and SCD
1 s and 8 s options, TA = 25°C
faults while in Customer Test
Mode
10
V
ms
200
ms
100
ms
Based on a 10-KΩ pull-up and 103AT thermistor
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(2)
(3)
Not production tested parameters. Specified by design
The device is in a no fault state prior to entering Customer Test Mode.
7.6 Timing Requirements
PROTECTION DELAYS
tOVn_DELAY
MIN
TYP
MAX
0.5-s delay option
0.4
0.5
0.8
1-s delay option
0.8
1
1.4
2-s delay option
1.8
2
2.7
UNIT
(2)
Overvoltage detection delay time
4.5-s delay option
4
4.5
5.2
1-s delay option
0.8
1
1.5
2-s delay option
1.8
2
2.7
4
4.5
5.5
s
tUVn_DELAY
Undervoltage detection delay time
8
9
10.2
tOWn_DELAY
Open-wire detection delay time
3.6
4.5
5.3
s
tOTC_DELAY
Overtemperature charge detection
delay time
3.6
4.5
5.3
s
tUTC_DELAY
Undertemperature charge detection
delay time
3.6
4.5
5.3
s
tOTD_DELAY
Overtemperature discharge
detection delay time
3.6
4.5
5.3
s
tUTD_DELAY
Undertemperature discharge
detection delay time
3.6
4.5
5.3
s
10-ms delay option
8
10
15
20-ms delay option
17
20
26
45-ms delay option
36
45
52
4.5-s delay option
9-s delay option
tOCD1_DELAY
Overcurrent 1 detection delay time
90-ms delay option
78
90
105
180-ms delay option
155
180
205
350-ms delay option
320
350
405
700-ms delay option
640
700
825
1420-ms delay option
1290
1420
1620
4
5
8
10-ms delay option
8
10
15
20-ms delay option
17
20
26
45-ms delay option
36
45
52
90-ms delay option
78
90
105
180-ms delay option
155
180
205
350-ms delay option
320
350
405
5-ms delay option
tOCD2_DELAY
tSCD_RELAY
tCD_REC
10
Overcurrent 2 detection delay time
700-ms delay option
640
700
825
Short-circuit detection delay time
360-µs delay option
220
400
610
Overcurrent 1, Overcurrent 2, and
Short-circuit recovery delay time
1-s option
0.8
1
1.4
9-s option
8
9
10.2
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s
ms
ms
µs
s
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7.7 Typical Characteristics
7.5
0.25
0.2
Shutdown Current (PA)
Normal Mode Current (PA)
7
6.5
6
5.5
5
0.15
0.1
0.05
4.5
4
-40
-15
10
35
Temperature (qC)
60
0
-40
85
D001
15
10
10
5
60
85
D002
0
UV Error (mV)
-5
-10
-10
-15
-15
-20
-40
-15
10
35
Temperature (qC)
60
-20
-40
85
-15
10
35
Temperature (qC)
D003
85
D004
Figure 7-4. UV Error at 2.8-V Threshold
Figure 7-3. OV Error at 4.25-V Threshold
0.2
0.1
60
4.0
2.5
0.05
3.5
0.0
2
±0.2
-0.1
±0.4
-0.15
-0.2
±0.6
-0.25
Error (in mV)
Error (in %)
-0.3
-0.35
±40
±20
0
20
40
60
3.0
2.5
1.5
2.0
1
1.5
1.0
0.5
±0.8
Error (in mV)
Error (in %)
0
±1.0
80
Temperature (ºC)
OCD2 Error (mV)
-0.05
OCD1 Error (%)
OCD1 Error (mV)
0
±40
±20
0
20
40
60
0.5
0.0
80
Temperature (ºC)
C001
Figure 7-5. OCD1 Error at 40-mV Threshold
OCD2 Error (%)
OV Error (mV)
5
-5
10
35
Temperature (qC)
Figure 7-2. Shutdown Current
Figure 7-1. NORMAL Mode Current
0
-15
C002
Figure 7-6. OCD2 Error at 60-mV Threshold
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1.6
2.5
1.4
1.2
1.0
1.5
0.8
1
0.6
SCD Error(%)
SCD Error (mV)
2
0.4
0.5
Error (in mV)
Error (in %)
0
±40
±20
0
20
40
60
0.2
0.0
80
Temperature (ºC)
C003
Figure 7-7. SCD Error at 160-mV Threshold
12
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8 Detailed Description
8.1 Overview
The BQ77904 and BQ77905 families are full-feature stackable primary protectors for Li-ion/Li-Polymer batteries.
The devices implement a suite of protections, including:
• Cell voltage: overvoltage, undervoltage
• Current: Overcurrent discharge 1 and 2, short circuit discharge
• Temperature: overtemperature and undertemperature in charge and discharge
• PCB: cell open-wire connection
• FET body diode protection
Protection thresholds and delays are factory-programmed and available in a variety of configurations.
The BQ77904 supports 3-series-to–4-series cell configuration and BQ77905 supports 3-series-to–5-series cell
configuration. Up to four devices can be stacked to support ≥6-series cell configurations, providing protections
up to 20-series cell configurations.
The device has built-in CHG and DSG drivers for low-side N-channel FET protection, which automatically open
up the CHG and/or DSG FETs after protection delay time when a fault is detected. A set of CHG/DSG overrides
is provided to allow disabling of CHG and/or DSG driver externally. Although the host system can use this
function to disable the FETs' control, the main use of these pins is to channel down the FET control signal from
the upper device to the lower device in a cascading configuration in ≥6-series battery packs.
8.1.1 Device Functionality Summary
In this and subsequent sections, a number of abbreviations are used to identify specific fault conditions. The fault
descriptor abbreviations and their meanings are defined in Table 8-1.
Table 8-1. Device Functionality Summary
FAULT DESCRIPTOR
OV
FAULT DETECTION THRESHOLD and DELAY OPTIONS
FAULT RECOVERY METHOD and SETTING OPTIONS
Overvoltage
3 V to 4.575 V (25-mV step)
0.5, 1, 2, 4.5 s
Hysteresis
0, 100, 200, 400 mV
UV
Undervoltage
1.2 V to 3 V
(100-mV step for < 2.5 V,
50-mV step for ≥ 2.5 V)
1, 2, 4.5, 9 s
Hysteresis OR
Hysteresis + Load Removal
200, 400 mV
OW
Open wire (cell to pcb
disconnection)
0 (disabled), 100, 200, or 400
nA
4.5 s
Restore bad VCx to pcb connection
VCx > VOW
OTD(1)
Overtemperature during
discharge
65°C or 70°C
4.5 s
Hysteresis
10°C
OTC(1)
Overtemperature during
charge
45°C or 50°C
4.5 s
Hysteresis
10°C
UTD(1)
Undertemperature during
discharge
–20°C or –10°C
4.5 s
Hysteresis
10°C
UTC (1)
Undertemperature during
charge
–5°C or 0°C
4.5s
Hysteresis
10°C
OCD1
Overcurrent1 during
discharge
10 mV to 85 mV (5-mV step)
10, 20, 45, 90, 180, 350, 700,
1420 ms
OCD2
Overcurrent1 during
discharge
20 mV to 170 mV (10-mV step)
5, 10, 20, 45, 90, 180, 350, 700
ms
Delay OR
Delay + Load Removal OR
Load Removal
1 s or 9 s
SCD
Short circuit discharge
40 mV to 340 mV (20-mV step)
360 µs
tCTRDEG_ON
Enable via external control or via CHGU
signal from the upper device in the stack
configuration.
tCTRDEG_OFF
tCTRDEG_ON
Enable via external control or via DSG
signal from the upper device in the stack
configuration.
tCTRDEG_OFF
CTRC
CHG signal override control
Disable via external control
or via CHGU signal from the
upper device in the stack
configuration.
CTRD
DSG signal override control
Disable via external control
or via DSG signal from the
upper device in the stack
configuration.
(1)
These thresholds are target based on temperature, but they are dependent on external components that could vary based on customer
selection. The circuit is based on a 103AT NTC thermistor connected to TS and VSS, and a 10-kΩ resistor connected to VTB and
TS. Actual thresholds must be determined in mV. Refers to the overtemperature and undertemperature mV threshold in the Electrical
Characteristics table.
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8.2 Functional Block Diagram
VDD
CCFG
CONFIG
LOGIC
BG
REFERENCE
BIAS
AVDD
VDIG
REGULATOR
AND
SHUTDOWN
VTB
POR
TS
VC5
VC4
EEPROM
MUX
VC3
COMPARE
1
CTRC
VC2
STACK
INTERFACE
CTRD
VC1
CONTROL
LOGIC
OPEN
WIRE
CHG
CHG
DRIVER
CHGU
MUX
COMPARE
2
DSG
DRIVER
DSG
LOAD
DETECTION
LD
SRP
STATE
COMPARE
SRN
CLOCK
and
WDT
AVSS
DVSS
Copyright © 2018, Texas Instruments Incorporated
8.3 Feature Description
8.3.1 Protection Summary
The BQ77904 and BQ77905 have two comparators. Both are time multiplexed to detect all protection fault
conditions. Each of the comparators runs on a time-multiplexed schedule and cycles through the assigned
14
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protection-fault checks. Comparator 1 checks for OV, UV, and OW protection faults. Comparator 2 checks for
OCD1, OCD2, SCD, OTC, OTD, UTC, and UTD protection faults. For OV, UV, and OW protection faults, every
cell is checked individually in round-robin fashion, starting with cell 1 and ending with the highest-selected cell.
The number of the highest cell is configured using the CCFG pin.
Devices can be ordered with various timing and hysteresis settings. See the Section 5 section for a summary of
options available per device type.
Check OV VCELL1
Check OV VCELL2
n = the highest call
configured by CCFG pin
Check OV VCELLn
NO
Time to check
UV?
Time to check
OW?
YES
NO
YES
Check OW VCELLx,
x = x +1
Check UV VCELL1
Check UV VCELL2
x starts
from 1
at POR
Reset x = 1, if x >
the highest cell
configured via
CCFG pin
Check UV VCELLn
Turn off Comp1 until
next cycle start
Figure 8-1. Comparator 1 Flowchart
Check SCD
Time to check
OCD1?
NO
YES
Check
OCD1
Time to check
OCD2?
NO
Time to check
OT?
YES
Check
OCD2
YES
Check OT
NO
Time to check
UT?
NO
YES
Check UT
Figure 8-2. Comparator 2 Flowchart
8.3.2 Fault Operation
8.3.2.1 Operation in OV
An OV fault detection is when at least one of the cell voltages is measured above the OV threshold, VOV. The
CHG pin is turned off if the fault condition lasts for a duration of OV Delay, tOVn_DELAY. The OV fault recovers
when the voltage of the cell in fault is below the (OV threshold – OV hysteresis, VHYS_OV) for a time of OV Delay.
The BQ77904 and BQ77905 assume OV fault after device reset.
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8.3.2.2 Operation in UV
An UV fault detection is when at least one of the cell voltages is measured below the UV threshold, VUV. The
DSG is turned off if the fault condition lasts for a duration of UV Delay, tUVn_DELAY. The UV fault recovers when:
•
•
The cell voltage in fault is above the (UV threshold + UV hysteresis, VHYS_UV) for a time of UV Delay only OR
The cell voltage in fault is above the (UV threshold + UV hysteresis) for a time of UV Delay AND load removal
is detected.
If load removal is enabled as part of the UV recovery requirement, the CHG FET RGS value should change to
around 3 MΩ. Refer to the Section 9.1.1.4 section of this document for more detail. This requirement applies to
load removal enabled for UV recovery only. Therefore, if load removal is selected for current fault recovery, but
not for the UV recovery, a lower CHG FET RGS value (typical of 1MΩ) can be used to reduce the CHG FET turn
off time.
To minimize supply current, the device disables all overcurrent detection blocks any time the DSG FET is turned
off (due to a fault or CTRD being driven to the DISABLED state). Upon recovery from a fault or when CTRD is no
longer externally driven, all overcurrent detection blocks reactivate before the DSG FET turns back on.
8.3.2.3 Operation in OW
An OW fault detection is when at least one of the cell voltages is measured below the OW threshold, VOW. Both
CHG and DSG are turned off if the fault condition lasts for a duration of OW Delay, tOWn_DELAY. The OW fault
recovers when the cell voltage in fault is above the OW threshold + OW hysteresis, VOW_HYS for a time of OW
Delay.
The tOWn_DELAY time starts when voltage at a given cell is detected below the VOW threshold and is not from
the time that the actual event of open wire occurs. During an open-wire event, it is common that the device
detects an undervoltage and/or overvoltage fault before detecting an open-wire fault. This may happen due to
the differences in fault thresholds, fault delays, and the VCx pin filter capacitor values. To ensure both CHG and
DSG return to normal operation mode, the OW, OV, and UV faults recovery conditions must be met.
8.3.2.4 Operation in OCD1
An OCD1 fault is when the discharge load is high enough that the voltage across the RSNS resistor, (VSRP-VSRN),
is measured below the OCD1 voltage threshold, VOCD1. Both CHG and DSG are turned off if the fault condition
lasts for a duration of OCD1 Delay, tOCD1_DELAY.
The OCD1 fault recovers when:
•
•
•
Load removal is detected only, VLD < VLDT OR
Overcurrent Recovery Timer, tCD_REC, expiration only OR
Overcurrent Recovery Timer expiration and load removal are detected.
8.3.2.5 Operation in OCD2
An OCD2 fault is when the discharge load is high enough that the voltage across the RSNS resistor, (VSRP-VSRN),
is measured below the OCD2 voltage threshold, VOCD2. Both CHG and DSG are turned off if the fault condition
lasts for a duration of OCD2 Delay, tOCD2_DELAY.
The OCD2 fault recovers when:
•
•
•
Load removal detected only, VLD < VLDT OR
Overcurrent Recovery Timer, tCD_REC, expiration only OR
Overcurrent Recovery Timer expiration and load removal are detected.
8.3.2.6 Operation in SCD
An SCD fault is when the discharge load is high enough that the voltage across the RSNS resistor, (VSRP-VSRN),
is measured below the SCD voltage threshold, VSCD. Both CHG and DSG are turned off if the fault condition
lasts for a duration of SCD Delay, tSCD_DELAY.
The SCD fault recovers when:
16
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•
•
•
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Load removal detected only, VLD < VLDT OR
Overcurrent Recovery Timer, tCD_REC, expiration only OR
Overcurrent Recovery Timer expiration and load removal are detected.
8.3.2.7 Overcurrent Recovery Timer
The timer expiration method activates an internal recovery timer as soon as the initial fault condition exceeds the
OCD1/OCD2/SCD time. When the recovery timer reaches its limit, both CHG and DSG drivers are turned back
on. If the combination option of timer expiration AND load removal is used, then the load removal condition is
only evaluated upon expiration of the recovery timer, which can have an expiration period of tCD_REC.
8.3.2.8 Load Removal Detection
The load removal detection feature is implemented with the LD pin (see Table 8-2). When no undervoltage fault
and current fault conditions are present, the LD pin is held in an open-drain state. Once any UV, OCD1, OCD2,
or SCD fault occurs and load removal is selected as part of the recovery conditions, a high impedance pull-down
path to VSS is enabled on the LD pin. With an external load still present, the LD pin will be externally pulled
high: It is internally clamped to VLDCLAMP and should also be resistor-limited through RLD externally to avoid
conducting excessive current. If the LD pin exceeds VLDT, this is interpreted as a load present condition. When
the load is eventually removed, the internal high-impedance path to VSS should be sufficient to pull the LD pin
below VLDT for tLD_DEG. This is interpreted as a load removed condition and is one of the recovery mechanisms
selectable for undervoltage and overcurrent faults.
PACK+
bq77094/5
Load Detect
block
When load detect is
enabled, the LD pin is
connected to Vss via the
RLD_INT.
VLDT
LD
pin
RLD_INT
RLD
The load, RLD and RLD_INT
create a resister divider,
which the load detect
circuit is used to detect
when the load is removed.
LOAD
PACKFigure 8-3. Load Detection Circuit for Current Faults Recovery
Table 8-2. Load State
LD PIN
LOAD STATE
≥ VLDT
Load present
< VLOT for tLD_DEG
Load removed
8.3.2.9 Load Removal Detection in UV
During a UV fault, only the DSG FET driver is turned off while the CHG FET driver remains on. When load
removal is selected as part of the UV recovery condition, the active CHG FET driver would alter the resistor
divider ratio of the load detection circuit. To ensure the load status can still be detected properly, it is required to
increase the CHG FET external RGS value to about 3 MΩ. Refer to the Section 9.1.1.4 section for more detail.
Note that if load removal is only selected for the current fault recovery (and is not used for UV recovery), it is not
required to use a larger CHG FET RGS value.
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8.3.2.10 Operation in OTC
An OTC Fault occurs when the temperature increases such that the voltage across an NTC thermistor goes
below the OTC voltage threshold, VOTC. CHG is turned off if the fault condition lasts for an OTC delay time,
tOTC_DELAY. The state comparator is turned on when CHG is turned off. If a discharge current is detected, the
device immediately switches the CHG back on. The response time of the state comparator is typically in 700 µs
and should not pose any disturbance in the discharge event. The OTC fault recovers when the voltage across
thermistor gets above OTC recovery threshold, VOTC_REC, for OTC delay time.
8.3.2.11 Operation in OTD
An OTD fault is when the temperature increases such that the voltage across an NTC thermistor goes below
the OTD voltage threshold, VOTD. Both CHG and DSG are turned off if the fault condition lasts for an OTD
delay time, tOTD_DELAY. The OTD fault recovers when the voltage across thermistor gets above OTD recovery
threshold, VOTD_REC, a time of an OTD delay.
8.3.2.12 Operation in UTC
A UTC fault occurs when the temperature decreases such that the voltage across an NTC thermistor gets
above the UTC voltage threshold, VUTC. CHG is turned off if the fault condition lasts for a time of a UTC delay,
tUTC_DELAY. The state comparator is turned on when CHG is turned off. If a discharge current is detected, the
device will immediately switch CHG back on. The response time of the state comparator is typically in 700 µs
and should not pose any disturbance in the discharge event. The UTC fault recovers when the voltage across
thermistor gets below UTC recovery threshold, VUTC_REC, a time of a UTC delay.
8.3.2.13 Operation in UTD
A UTD fault occurs when the temperature decreases such that the voltage across an NTC thermistor goes
above the UTD voltage threshold, VUTD. Both CHG and DSG are turned off if the fault condition lasts for a
UTD delay time. The UTD fault recovers when the voltage across the thermistor gets below the UTD recovery
threshold, VUTD_REC, a time of the UTD delay.
8.3.3 Protection Response and Recovery Summary
Table 8-3 summarizes how each fault condition affects the state of the DSG and CHG output signals, as well
as the recovery conditions required to resume charging and/or discharging. As a rule, the CHG and DSG output
drivers are enabled only when no respective fault conditions are present. When multiple simultaneous faults
(such as an OV and OTD) are present, all faults must be cleared before the FET can resume operation.
18
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Table 8-3. Fault Condition, State, and Recovery Methods
FAULT
RECOVERY
DELAY
tCTRDEG_ON
tCTRDEG_OFF
CHG
DSG
CTRC disabled
CTRC disabled for deglitch
delay time
OFF
—
CTRC must be enabled for deglitch delay time
CTRD disabled
CTRD disabled for deglitch
delay time
—
OFF
CTRD must be enabled for deglitch delay time
OV
V(Cell) rises above VOV for
delay time
OFF
—
V(Cell) drops below VOV – VHYS_OV for delay
tOVn_DELAY
UV
V(Cell) drops below VUV for
delay time
—
OFF
V(Cell) rises above VUV + VHYS_UV for delay
tUVn_DELAY
OW
VCX – VCX–1 < VOW for delay
time
OFF
OFF
Bad VCX recovers such that VCX – VCX–1 > VOW
+ VOW_HYS for delay
tOWn_DELAY
OCD1, OCD2,
SCD
(VSRP - VSRN) < VOCD1,
VOCD2, or VSCD for delay
time
OFF
OFF
Recovery delay expires OR
LD detects < VLDT OR
Recovery delay expires + LD detects < VLDT
OTC(1)
Temperature rises above TOTC
for delay time
OFF
—
Temp drops below TOTC – TOTC_REC for delay
tOTC_DELAY
OTD(1)
Temperature rises above TOTD
for delay time
OFF
OFF
Temp drops below TOTD – TOTD_REC for delay
tOTD_DELAY
UTC(1)
Temperature drops below TUTC
for delay time
OFF
—
Temperature rises above TUTC + TUTC_REC for
delay
tUTC_DELAY
UTD(1)
Temp drops below TUTD for
delay time
OFF
OFF
Temp rises above TUTD + TUTD_REC for delay
tUTD_DELAY
(1)
RECOVERY METHOD
TRIGGER DELAY
FAULT TRIGGER CONDITION
tOCD1_DELAY,
tOCD2_DELAY,
tSCD_DELAY,
tCD_REC
TUTC, TUTD, TUTC_REC, and TUTD_REC correspond to the temperature produced by VUTC, VUTD, VUTC_REC, and VUTD_REC of the selected
thermistor resistance.
For BQ77904 and BQ77905 devices to prevent CHG FET damage, there are times when the CHG FET may be
enabled even though an OV, UTC, OTC, or CTRC low event has occurred. See the State Comparator section for
details.
8.3.4 Configuration CRC Check and Comparator Built-In-Self-Test
To improve reliability, the device has built in CRC check for all the factory-programmable configurations, such as
the thresholds and delay time setting. When the device is set up in the factory, a corresponding CRC value is
also programmed to the memory. During normal operation, the device compares the configuration setting against
the programmed CRC periodically. A CRC error will reset the digital circuitry and increment the CRC fault
counter. The digital reset forces the device to reload the configuration as an attempt to correct the configurations.
A correct CRC check reduces the CRC fault counter. Three CRC faults counts will turn off both the CHG and
DSG drivers. If FETs are opened due to a CRC error, only a POR can recover the FET state and reset the CRC
fault.
In addition to the CRC check, the device also has built-in-self-test (BIST) on the comparators. The BIST runs
in a scheduler, and each comparator is checked for a period of time. If a fault is detected for the entire check
period, the particular comparator is considered at fault, and both the CHG and DSG FETs is turned off. The BIST
continues to run by the scheduler even if a BIST fault is detected. If the next BIST result is good, the FET driver
resumes normal operation.
The CRC check and BIST check do not affect the normal operation of the device. However, there is not a
specific indication when a CRC or BIST error is detected besides turning off the CHG and DSG drivers. If there
is no voltage, current, or temperature fault condition present, but CHG and DSG drivers remain off, it is possible
that either a CRC or BIST error is detected. Users can power-on reset (POR) the device.
8.3.5 Fault Detection Method
8.3.5.1 Filtered Fault Detection
The device detects a fault once the applicable fault is triggered after accumulating sufficient trigger sample
counts. The filtering scheme is based on a simple add/subtract. Starting with the triggered sample count cleared,
the counts go up for a sample that is taken across the tested condition (for example, above the fault threshold
when looking for a fault) and the counts go down for a sample that is taken before the tested condition (that is,
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below the fault threshold). Figure 8-4 shows an example of a signal that triggers a fault when accumulating five
counts above the fault threshold. Once a fault has been triggered, the triggered sample counts reset, and counts
are incremented for every sample that is found to be below the recovery threshold.
Note
With a filtered detection, when the input signal falls below the fault threshold, the sample count does
not reset, but only counts down as shown in Figure 8-4. Therefore, it is normal to observe a longer
delay time if a signal is right at the detection threshold. The noise can push the delay count to be
counting up and down, resulting a longer time for the delay counter to reach its final accumulated
trigger target.
Based on Fault Trigger After 5 Counts
Fault Threshold
Recovery Threshold
FAULT
FAULT
Sample
Triggered Sample Count
0 1 2 3 4 3 2 1 2 3 4 5 0 0 0 0 0 0 0 0 0 0 0 0 1 2 1 2 3 4 5 0 0 0
Looking for a Fault
Looking for a Recovery
Looking for a Fault
Figure 8-4. Fault Trigger Filtering
8.3.6 State Comparator
A small, low-offset analog state comparator monitors the sense-resistor voltage (SRP-SRN) to determine when
the pack is in a DISCHARGE state less than a minimum threshold, VSTATE_D or a CHARGE state greater than
a maximum threshold, VSTATE_C. The state comparator is used to turn the CHG FET on to prevent damage or
overheating during discharge in fault states that call for having only the CHG FET off, and vice versa for the DSG
FET during charging in fault states that call for having only the DSG FET off.
Table 8-4 summarizes when the state comparator is operational. The state comparator is only on during faults
detected that call for only one FET driver to be turned off.
Table 8-4. State Comparator Operation Summary
20
STATE COMP
CHG
DSG
MODE
OFF
ON
ON
Normal
VSTATE_C Detection
ON
OFF
UV, CTRD
VSTATE_D Detection
OFF
ON
OV, UTC, OTC, CTRC
OFF
OFF
OFF
OCD1, OCD2, SCD, UTD, OTD, OW
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PACK IS CHARGING
PACK IS DISCHARGING
SRP - SRN
VSTATE_D
0V
VSTATE_C
Figure 8-5. State Comparator Thresholds
8.3.7 DSG FET Driver Operation
The DSG pin is driven high only when no related faults (UV, OW, OTD, UTD, OCD1, OCD2, SCD, and CTRD
are disabled) are present. It is a fast switching driver with a target on resistance of about 15–20 Ω and an off
resistance of RDSGOFF. It is designed to allow users to select the optimized RGS value to archive the desirable
FET rise and fall time per the application requirement and the choice of FET characteristics. When the DSG FET
is turned off, the DSG pin drives low and all overcurrent protections (OCD1, OCD2, SCD) are disabled to better
conserve power. These resume operation when the DSF FET is turned on. The device provides FET body diode
protection through the state comparator if one FET driver is on and the other FET driver is off.
The DSG driver may be turned on to prevent FET damage if the battery pack is charging while a discharge
inhibit fault condition is present. This is done with the state comparator. The state comparator (with the VSTATE_C
threshold) remains on for the entire duration of a DSG fault with no CHG fault event.
• If (SRP-SRN) ≤ VSTATE_C and no charge event is detected, the DSG FET output will remain OFF due to the
present of a DSG fault.
• If (SRP-SRN) > VSTATE_C and a charge event is detected, the DSG FET output will turn ON for body diode
protection.
See the Section 8.3.6 section for details.
The presence of any related faults, as shown in Figure 8-6, results in the DSGFET_OFF signal .
DSGFET_OFF_UVn
DSGFET_OFF_OCD1
DSGFET_OFF_OCD2
DSGFET_OFF_SCD
DSGFET_OFF
DSGFET_OFF_UTD
DSGFET_OFF_OTD
OWn
CTRD
Figure 8-6. Faults that Can Qualify DSGFET_OFF
8.3.8 CHG FET Driver Operation
The CHG and CHGU pins are driven high only when no related faults (OV, OW, OTC, UTC, OTD, UTD, OCD1,
OCD2, SCD, and CTRC are disabled) are present or the pack has a discharge current where (SRP-SRN) <
VSTATE_D1 . The CHG pin drives the CHG FET, which is for use on the single device configuration or by the
bottom device in a stack configuration. The CHGU pin has the same logic state as the CHG pin and is for use in
the upper device (in a multi-stack configuration) to provide the drive signal to the CTRC pin of the lower device.
The CHGU pin should never connect to the CHG FET directly.
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Turning off the CHG pin has no influence on the overcurrent protection circuitry. The CHG pin is designed to
switch on quickly and the target on resistance is about 2 kΩ. When the pin is turned off, the CHG driver pin is
actively driven low and will fall together with PACK–.
The CHG FET may be turned on to protect the FET's body diode if the pack is discharging, even if a charging
inhibit fault condition is present. This is done through the state comparator. The state comparator (with the
VSTATE_D threshold) remains on for the entire duration of a DSG fault with no CHG fault event.
• If (SRP-SRN) > VSTATE_D and no discharge event is detected, the CHG FET output will remain OFF due to
the present of a CHG fault.
• If (SRP-SRN) ≤ VSTATE_D and a charge event is detected, the CHG FET output will turn ON for body diode
protection.
The CHGFET_OFF signal is a result of the presence of any related faults, as shown in Figure 8-7.
CHGFET_OFF_OVn
CHGFET_OFF_UTC
CHGFET_OFF_OTC
CHGFET_OFF_OCD1
CHGFET_OFF_OCD2
CHGFET_OFF
CHGFET_OFF_SCD
CHGFET_OFF_UTD
CHGFET_OFF_OTD
OWn
CTRC
Figure 8-7. Faults That Can Qualify CHGFET OFF
8.3.9 External Override of CHG and DSG Drivers
The device allows direct disabling of the CHG and DSG drivers through the CTRC and CTRD pins, respectively.
The operation of the CTRC and CTRD pins is shown in Figure 8-8. To support the simple-stack solution for
higher-cell count packs, these pins are designed to operate above the device’s VDD level. Simply connect a
10-MΩ resistor between a lower device CTRC and CTRD input pins to an upper device CHGU and DSG output
pins (see the schematics in Section 8.3.11.
CTRC only enables or disables the CHG pin, while CTRD only enables or disables the DSG pin. When the
CTRx pin is in the DISABLED region, the respective FET pin will be off, regardless of the state of the protection
circuitry. When the CTRx pin is in either ENABLED region, the protection circuitry determines the state of the
FET driver.
Both CTRx pins apply the fault-detection filtered method to improve the robustness of the signal detection: The
counter counts up if an ENABLED signal is sampled; the counter counts down if a DISABLED signal is sampled.
When the counter counts up from 0% to > 70% of its full range, which takes about 7 ms typical of a solid signal,
the CTRx pins take the signal as ENABLED. If the counter counts down from 100% to < 30%, of its full range,
which takes about 7 ms typical of a solid signal, the CTRx pins take the signal as DISABLED. From a 0 count
counter (solid DISABLE), a solid ENABLE signal takes about tCTRDEG_ON time to deglitch. From a 100% count
(solid ENABLE), a solid DISABLE signal takes about tCTRDEG_OFF time to deglitch. Although such a filter scheme
provides a certain level of noise tolerance, it is highly recommended to shield the CTRx traces and keep the
traces as short as possible in the PCB layout design. The CTRx deglitch time will add onto the FET response
timing on the OV, UV, and OW faults in a stack configuration. The tCTRDEG_OFF time adds an additional delay to
the fault detection timing and the tCTRDEG_ON time adds an additional delay to the fault recovery timing.
22
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ENABLED
VCTR2
VCTRDIS (max)
VDD
DISABLED
(FET OFF)
VCTRDIS (min)
VCTR1
ENABLED
VSS
CHG driver set by CTRC
DSG driver set by CTRD
Figure 8-8. External Override of CHG and DSG Drivers
8.3.10 Configuring 3-S, 4-S, or 5-S Mode
The BQ77904 supports 3-S and 4-S packs, while the BQ77905 supports 3-S, 4-S, and 5-S packs. To avoid
accidentally detecting a UV fault on unused (shorted) cell inputs, the device must be configured for the specific
cell count of the pack. This is set with the configuration pin, CCFG, which is mapped as in Table 8-5. The device
periodically checks the CCFG status and takes tCCFG_DEG time to detect the pin status.
Table 8-5. CCFG Configurations
CCFG
CONFIGURATION
CONNECT TO
< VCCFGL for tCCFG_DEG
3 cells
AVSS
Within VCCFGM for tCCFG_DEG
4 cells
AVDD
> VCCFGH for tCCFG_DEG
5 cells
Floating
The CCFG pin should be tied to the recommended net from Table 8-5. The device compares the CCFG input
voltage to the AVDD voltage and should never be set above the AVDD voltage. When the device configuration is
for 5 S, leave the CCFG pin floating. The internal pin bias is approximately 30% of the AVDD voltage for the 5-S
configuration. Note that the BQ77904 should not be configured in 5-S mode, as this results in a permanent UV
fault.
8.3.11 Stacking Implementations
Higher than 5-S cell packs may be supported by daisy-chaining multiple devices. Each device ensures OV, UV,
OTC, OTD, UTC, and UTD protections of its directly monitored cells, while any fault conditions automatically
disable the global CHG and/or DSG FET driver. Note that upper devices do not provide OCD1, OCD2, or SCD
protections, as these are based on pack current. For the BQ77904 and BQ77905 devices used on the upper
stack, the SRP and SRN pins should be shorted to prevent false detection.
Table 8-6. Stacking Implementation Configurations
CONFIGURATION
CHG PIN
CHGU PIN
Bottom or single device
Connect to CHG FET
Leave unconnected
Upper stack
Leave unconnected
Connect to CTRC of the lower device
To configure higher-cell packs, follow this procedure:
•
•
Each device must have a connection on at least three lowest-cell input pins.
TI recommends to connect a higher-cell count to the upper devices (for example, for a 7-S configuration,
connect four cells on the upper device and three cells on the bottom device). This provides a stronger CRTx
signal to the bottom device.
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•
•
•
•
•
Ensure that each device’s CCFG pin is configured appropriately for its specific number of cells (three, four, or
five cells).
For the bottom device, the CHG pin should be used to drive the CHG FET and leave the CHGU pin
unconnected. For the upper device, the CHGU pin should be used to connect to lower device’s CTRC pin
with a RCTRx and leave the CHG pin unconnected.
Connect the upper DSG pins with a RCTRx to the immediate lower device CTRD pin.
All upper devices should have the SRP and SRN to its AVSS pin.
If load removal is not used for UV recovery, connect the upper device LD pin to its AVSS pin, as shown in
Figure 8-9 and Figure 8-10. Otherwise, refer to Figure 9-7 for proper LD connection.
PACK+
RVDD
CVDD
CVDD
RIN
CIN
RIN
DVSS
CTRD
VC5
CTRC
VC4
CCFG
VC3
CIN
RIN
VDD
AVDD
bq77905
VC2
RIN
CIN
RIN
RTS
TS
VC1
CIN
RTS_PU
VTB
LD
AVSS
CHG
SRP
CHGU
SRN
DSG
CIN
RVDD
CVDD
CVDD
RIN
CIN
RIN
RIN
RIN
VDD
DVSS
AVDD
CTRD
VC5
CTRC
VC4
CCFG
VC3
CIN
VC2
VC1
CIN
CIN
RIN
bq77905
RCTRD
RCTRC
RTS_PU
VTB
RTS
TS
LD
AVSS
CHG
SRP
CHGU
SRN
DSG
RCHG
RDSG
RLD
CIN
RGS_DSG
RGS_CHG
RSNS
PACK-
Figure 8-9. 10S Pack Using Two BQ77905 Devices
24
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PACK+
RVDD
CVDD
RIN
CVDD
CIN
RIN
CIN
RIN
CIN
VDD
DVSS
AVDD
CTRD
VC5
CTRC
VC4
CCFG
VC3
VTB
bq77905
VC2
CIN
RIN
CIN
RTS
TS
VC1
RIN
RTS_PU
LD
AVSS
CHG
SRP
CHGU
SRN
DSG
RVDD
CVDD
CVDD
RIN
CIN
RIN
DVSS
CTRD
VC5
CTRC
VC4
CCFG
VTB
VC3
CIN
RIN
VDD
AVDD
bq77905
VC2
CIN
RIN
RTS_PU
RTS
LD
AVSS
RIN
RCTRC
TS
VC1
CIN
RCTRD
CHG
SRP
CHGU
SRN
DSG
CIN
RVDD
CVDD
CVDD
VDD
DVSS
AVDD
CTRD
VC5
CTRC
VC4
CCFG
VTB
VC3
VC2
RIN
RIN
RIN
VC1
CIN
CIN
bq77905
RCTRD
RCTRC
RTS_PU
RTS
TS
LD
AVSS
CHG
SRP
CHGU
SRN
DSG
RCHG
RDSG
RLD
CIN
RGS
RSNS
RGS
PACK-
Figure 8-10. 13S Pack Using Three BQ77905 Devices
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8.3.12 Zero-Volt Battery Charging Inhibition
Once the device is powered up, it can pull the CHG pin up if the VDD ≥ VSHUT, which varies from about 1 V per
cell on a 3-S configuration to about 0.6 V per cell on a 5-S configuration. If the battery stack voltage falls below
VSHUT, the device is in SHUTDOWN mode and the CHG driver is no longer active and charging is not allowed
unless VDD rises above VPOR again.
8.4 Device Functional Modes
8.4.1 Power Modes
8.4.1.1 Power-On Reset (POR)
The device powers up when VDD ≥ VPOR. At POR, the following events occur:
•
•
•
A typical 5-ms hold-off delay applies to both CHG and DSG drivers, keeping both drivers in the OFF state.
This provides time for the internal LDO voltage to ramp up.
CTRC and CTRD deglitch occurs. During the deglitch time, the CHG and DSG driver remains off. Note that
deglitch time masks out the 5-ms hold-off delay.
The device assumes OV fault at POR; thus, the CHG driver is off for OV recovery time if all the cell voltages
are < (VOV – VHYS_OV). The OV recovery time starts after the 5-ms hold-off delay. If the device reset occurs
when any cell voltage is above the OV hysteresis range, the CHG driver will remain off until an OV recovery
condition is met.
8.4.1.2 FAULT Mode
If any configured protection fault is detected, the device enters the FAULT mode. In this mode, the CHG and/or
DSG driver can be turned off depending on the fault. Refer to the fault response summary, Section 8.4.1.2, for
detail. When one of the FET drivers (either CHG or DSG) is turned off, while the other FET driver is still on, the
state comparator is activated for FET body diode protection.
8.4.1.3 SHUTDOWN Mode
This is the lowest power consumption state of the device when VDD falls below VSHUT. In this mode, all fault
detections and theCHG and DSG drivers are disabled. The device will wake up and enter NORMAL mode when
VDD rises above VPOR.
8.4.1.4 Customer Fast Production Test Modes
The BQ7790x device supports the ability to greatly reduce production test time by cutting down on protection
fault delay times. To shorten fault times, place the BQ7790x device into Customer Test Mode (CTM). CTM is
triggered by raising VDD to VCTM voltage above the highest cell input pin (that is, VC5) for tCTM_ENTRY time.
The CTM is expected to be used in single-chip designs only. CTM is not supported for stacked designs. Once
the device is in CTM, all fault delay and non-current fault's recovery delay times reduce to a value of tCTM_DELAY.
The fault recovery time for overcurrent faults (OCD1, OCD2, and SCD) is reduced to tCTM_OC_REC.
Verification of protection fault functionality can be accomplished in a reduced time frame in CTM. Reducing the
VDD voltage to the same voltage applied to the highest-cell input pin for tCTM_ENTRY will exit CTM.
In CTM, with reduced time for all internal delays, qualification of all faults will be reduced to a single instance.
Thus in this mode, fault condition qualification is more susceptible to transients, so take care to have fault
conditions clearly and cleanly applied during test mode to avoid false triggering of fault conditions during CTM.
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9 Application and Implementation
Note
Information in the following applications sections is not part of the TI component specification, and
TI does not warrant its accuracy or completeness. TI’s customers are responsible for determining
suitability of components for their purposes. Customers should validate and test their design
implementation to confirm system functionality.
9.1 Application Information
The BQ77904 and BQ77905 devices are low-power stackable battery pack protectors with an integrated
low-side NMOS FET driver. The BQ77904 and BQ77905 devices provide voltage, current, temperature, and
open-wire protections. All the devices protect and recover without MCU control. The following section highlights
several recommended implementation when using these devices.
9.1.1 Recommended System Implementation
9.1.1.1 CHG and DSG FET Rise and Fall Time
The CHG and DSG FET drivers are designed to have fast switching time. Users should select a proper gate
resistor (RCHG and RDSG in the reference schematic) to set to the desired rise/fall time.
CHG
DSG
Select proper gate
resistor to adjust
the desired rise/fall
time
RDSG
RCHG
RGS_DSG
RGS_CHG
Q2 Q1
RSNS
PACK-
Figure 9-1. Select Proper Gate Resistor for FET Rise and Fall Time
The CHG FET fall time is generally slower, because it is connected to the PACK– terminal. The CHG driver will
pull to VSS quickly when the driver is signaled to turn off. Once the gate of the CHG FET reaches ground or
Vgsth, the PACK– will start to fall below ground and the CHG signal will follow suit in order to turn off the CHG
FET. This portion of the fall time is strongly dependent on the FET characteristic, the number of FETs in parallel,
and the value of gate-source resistor (RGS_CHG).
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Strong pull down by the CHG driver
when the device is initially signaled to
turn off CHG.
Once the CFET gate voltage reach PACK-, PACKvoltage starts to fall below ground. The gate
voltage is then relying on RGS_CHG to fall with
PACK- to keep the CHG FET off.
Figure 9-2. CHG FET Fall Time
9.1.1.2 Protecting CHG and LD
Because both CHG and LD are connected to the PACK– terminal, these pins are specially designed to sustain
an absolute max of –30 V. However, the device can be used in a wide variety of applications, and it is possible to
expose the pins lower than –30 V absolute max rating.
To protect the pins, TI recommends to put a PMOS FET in series of the CHG pin and a diode in series of the LD
pin as shown below.
DSG
CHG
LD
Q3 and the LD pin diode are used to
keep CHG and LD away from any
voltages below VSS. Apply these
components when CHG and LD pins can
be exposed beyond the absolute -30V.
Q3
RDSG
RCHG
RLD
RGS_DSG
RGS_CHG
Q2
Q3 will allow RGS_CHG to keeps Q1 OFF,
since all voltages below this FET can
^(}oo}Á_ W =1MŸ)
RGS_DSG
Q2
This zener clamp may be
needed to prevent the Vgs of Q1
excesses absolute max rating.
Q1
16V
RSNS
PACK-
Figure 9-4. Protect CHG FET from a High Voltage on PACK–
DSG
LD
CHG
Q3
RCHG
(1MŸ )
RDSG
RGS_DSG
Q2
Q1
RLD
RGS_CHG
(>=1MŸ)
RSNS
16V
PACK-
Figure 9-5. Optional Components Combining Protecting CHG and LD and Protecting CHG FET
Protections
9.1.1.4 Using Load Detect for UV Fault Recovery
A larger CHG FET gate-source resistor is required if load removal is enabled as part of the UV recovery criteria.
When the load removal circuit is enabled, the device is internally connected to Vss. Because in a UV fault the
CHG driver remains on, it creates a resistor divider path to the load detect circuit.
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PACK+
bq77094/5
Load Detect
block
VLDT
LD
pin
RLD_INT
FET driver
block
LOAD
CHG
pin
VFETON
RCHG
RLD
16V
RGS_CHG
CFET
PACKFigure 9-6. Load Detect Circuit During UV Fault
To ensure load removal is detected properly during a UV fault, TI recommends to use 3.3 MΩ for RGS_CHG
(instead of a typical of 1 MΩ when load removal is NOT required for UV recovery). RCHG can stay in 1 MΩ
as recommended when using CHG FET protection components. The CHG FET rise time impact is minimized
as described in the Protecting CHG FET section. On a stacked configuration, connect the LD pin, as shown in
Figure 9-7 if load removal is used for a UV fault recovery. If load detection is not required for a UV fault recovery,
a larger value of RGS_CHG can be used (that is, 10 MΩ) and the LD pin on the upper devices can be left floating.
bq77094/5
LD
pin
Upper
device
Vss
pin
Ra is used to keep the LD pin pull
down when load detect circuit is
not activated
Ra
(1M)
Must have block
diode on the upper
device.
RLD
bq77094/5
LD
pin
Bottom
device
Vss
pin
RLD
Diode for the bottom
device is optional.
Use if the LD pin will
be exposed lower
than -30V.
PACKFigure 9-7. Simplified Circuit: LD Connection on Upper Device When Using for UV Fault Recovery
30
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9.1.1.5 Temperature Protection
The device detects temperature by checking the voltage divided by RTS_PU and RTS, with the assumption of
using 10-KΩ RTS_PU and 103AT NTC for RTS. System designers should always check the thermistor resistance
characteristics and refer to the temperature protection threshold specifications in the Electrical Characteristics
table to determine if a different pullup resistor should be used. If a different temperature trip point is required, it is
possible to scale the threshold using this equation: Temperature Protection Threshold = RTS / (RTS + RTS_PU).
Example: Scale OTC trip points from 50°C to 55°C
The OTC protection can be set to 45°C or 50°C. When the device's OTC threshold is set to 50°C, it is referred
to configure the VOTC parameter to 29.38% of VTB (typical), with the assumption of RTS_PU = 10 KΩ and RTS
= 103AT or similar NTC (which the NTC resistance at 50°C = 4.16 KΩ). The VOTC specification is the resistor
divider ratio of RTS_PU and RTS.
The VOTC, VOTD, VUTC, and VUTD configuration options are fixed in the device; thus, the actual temperature trip
point can only adjust by using a different B-value NTC and/or using a different RTS_PU.
In this example, the 103AT NTC resistance at 55°C is 3.536 KΩ. By changing the RTS_PU from 10 KΩ to 8.5 KΩ,
users can scale the actual OTC temperature trip point from 50°C to 55°C. Because the RTS_PU value is smaller,
this change affects all the other temperature trip points and scales OTD, UTC, and UTD to ~5°C higher as well.
9.1.1.6 Adding Filter to Sense Resistor
Current fault is sense through voltage across a sense resistor. Optional RC filters can be added to the sense
resistor to improve stability.
SRP
0.1 µF
SRN
0.1 µF
100 Ÿ
0.1 µF
100 Ÿ
R SNS
PACK-
Figure 9-8. Optional Filters Improve Current Measurement
9.1.1.7 Using a State Comparator in an Application
The state comparator does not have built-in hysteresis. It is normal to observe the FET body diode protection
toggling on and off with the VSTATE_C1 or VSTATE_D1 accuracy range. In a typical application, the sense resistor is
selected according to the application current, which usually is not close to the state comparator threshold.
9.1.1.7.1 Examples
As an example, using a 5-Ah battery, with 1C-rate (5 A) charge and 2C-rate (10 A) discharge, the sense resistor
is 3 mΩ or less. The typical current to turn on the FET body diode protection is 667 mA using this example.
Because there is no built-in hysteresis, noise can reset the state comparator counter and toggle off the FET
body diode protection and vice versa; thus, it is normal to observe the device toggles the FET body diode
protection on or off within a 1-mV to 3-mV range. With a 3-mΩ sense resistor, it is about 330 mA to 1 A. As this
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behavior is due to noise from the system, the FET toggling behavior usually occurs right at the typical 2-mV state
comparator threshold. As current increases or decreases from the typical value, the detection is more solid and
has less frequent FET toggling. Using this example, either charge or discharge should provide a solid FET body
diode protection detection.
Look at the device behavior during an OV event (and no other fault is detected). In an OV event, CHG FET is off
and DSG FET is on. If a discharge of > –1 A occurs, the device would turn on the CHG FET immediately to allow
the full discharge current to pass through. Once the overcharged cell is discharged to the OV recovery level, the
OV fault is recovered and the CHG driver turns on (or remains on in this scenario) and the state comparator is
turned off.
If the discharge current is < 1 A when the device is still in an OV fault, the CHG FET may toggle on and off until
the overcharged cell voltage is reduced down to the OV recovery level. When the OV fault recovers, the CHG
FET is solidly turned on and the state comparator is off.
Without the FET body diode protection, if a discharge occurs during an OV fault state, the discharge current
can only pass through the CHG FET body diode until the OV fault is recovered. This increases the risk of
damaging the CHG FET if the MOSFET is not rated to sustain this amount of current through its body diode. It
also increases the FET temperature as current is now carried through the body diode.
9.2 Typical Application
PACK+
RVDD
CVDD
CVDD
VDD
DVSS
AVDD
CTRD
VC5
CTRC
RIN
VC3
CIN
VC2
RIN
RIN
RIN
CCFG
VC4
VC1
CIN
CIN
bq77905
bq77904
RTS_PU
VTB
RTS
TS
LD
AVSS
CHG
SRP
CHGU
SRN
DSG
RCHG
RDSG
RLD
CIN
RGS
RGS
RSNS
PACKCopyright © 2016, Texas Instruments Incorporated
Figure 9-9. BQ77904 and BQ77905 with Four Cells
9.2.1 Design Requirements
For this design example, use the parameters shown in Table 9-1.
Table 9-1. Design Parameters
PARAMETER
DESCRIPTION
VALUES
RIN
Cell voltage sensing (VCx pins) filter resistor
CIN
Cell voltage sensing (VCx pins) filter capacitor
RVDD
Supply voltage filter resistor
1 kΩ ±5%
CVDD
Supply voltage filter capacitor
1 µF ±20%
32
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1 kΩ ±5%
0.1 µF ±10%
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SLUSCM3K – JUNE 2016 – REVISED JULY 2020
Table 9-1. Design Parameters (continued)
PARAMETER
DESCRIPTION
VALUES
RTS
NTC thermistor
103AT, 10 kΩ ±3%
RTS_PU
Thermistor pullup resistor to VTB pin, assuming using 103AT NTC or NTC with similar
resistance-temperature characteristics
RGS_CHG
CHG FET gate-source Load removal is enabled for UV recovery.
resistor
Load removal is disabled for UV recovery.
RGS_DSG
DSG FET gate-source resistor
RCHG
CHG gate resistor
10 kΩ ±1%
3.3 MΩ ±5%
1 MΩ ±5%
1 MΩ ±5%
System designers should adjust this parameter to meet the
desired FET rise/fall time.
1 kΩ ±5%
If additional components are used to protect the CHG FET
and/or to enable load removal detection for UV recovery.
1 MΩ ±5%
RDSG
DSG gate resistor, system designers should adjust this parameter to meet the desired
FET rise/fall time.
RCRTC and RCTRD
CTRC and CTRD current limit resistor
10 MΩ ±5%
RLD
LD resistor for load removal detection
450 KΩ ±5%
RSNS
Current sense resistor for current protection. System designers should change this
parameter according to the application current protection requirements.
4.5 kΩ ±5%
1 mΩ ±1%
9.2.2 Detailed Design Procedure
The following is the detailed design procedure.
1. Based on the application current, select the proper sense resistor value. The sense resistor should allow
detection of the highest current protection, short circuit current.
2. Temperature protection is set with the assumption of using a 103AT NTC (or NTC with similar specification).
If a different type of NTC is used, a different RTS_PU may be used for the application. Refer to the actual
temperature detection threshold voltage to determine the RTS_PU value.
3. Connect the CCFG pin correctly based on the number of cells in series.
4. Review the Recommended Application Implementation to determine if optional components should be added
to the schematic.
9.2.2.1 Design Example
To design the protection for a 36-V Li-ion battery pack using 4.2-V LiCoO2 cells with the following protection
requirements:
Voltage Protection
• OV at 4.3 V, recover at 4.1 V
• UV at 2.6 V, recover at 3 V and when load is removed.
Current Protection
• OCD1 at 40 A with 300-ms–400-ms delay
• OCD2 at 80 A with the shortest delay option
• SCD at 100 A with < 500-µs delay
• Requires load removal for recovery
Temperature Protection
• Charge – OTC at 50°C, UTC at –5°C
• Discharge – OTD at 70°C, UTD at –10°C
To start the design:
1. Start the schematic.
• A 36-V pack using LiCoO2 cells requires 10-S configuration; thus, two BQ77905 devices in a stackable
configuration is needed.
• Follow the 10-S reference schematic in this document. Follow the recommended design parameters
listed in the Section 9.2.1 section of this document.
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•
The power FET used in this type of application usually has an absolute of 20 V Vgs. For a 36-V pack
design, TI recommends to use the additional components to protect the CHG FET Vgs. See the Section
9.1.1.4 section for details.
• Because load removal for UV recovery is required, a 3-MΩ RGS_CHG should be used for the schematic.
2. Decide the value of the sense resistor, RSNS.
• When selecting the value of RSNS, ensure the voltage drop across SRP and SRN is within the available
current protection threshold range.
• In this example, select RSNS = 1 mΩ (any value ≤ 2 mΩ will work in this example).
3. Determine all of the BQ77905 protection configurations (see Table 9-2).
4. Review the available released or preview devices in the Section 5 section to determine if a suitable option is
available. If not, contact TI representative for further assistance.
Table 9-2. Design Example Configuration
Protection
Threshold
Hysteresis
Delay
OV
4.3 V
200 mV
1 s (default setting)
Hysteresis
Recovery Method
UV
2.6 V
400 mV
1 s (default setting)
Hysteresis + load removal
OW
100 nA
(default setting)
—
—
OCD1
40 mV
—
350 ms
Load removal only
OCD2
80 mV
—
5 ms
Load removal only
SCD
100 mV
—
Fixed at 360 µs
Load removal only
OTC
50°C
10°C
4.5 s
Hysteresis
OTD
70°C
10°C
4.5 s
Hysteresis
UTC
–5°C
10°C
4.5 s
Hysteresis
UTD
–10°C
10°C
4.5 s
Hysteresis
(VCx – VCx–1) > 600 mV (typical)
9.2.3 Application Curves
DSG remains on
DSG remains on
CHG recovers after
2nd OV fault is removed
CHG falls due to
detection of 1st OV fault
1st Fault removed
1st OV Fault
Figure 9-10. OV Fault Protection
34
2nd Fault removed
Figure 9-11. OV Fault Recovery
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State comparator detects discharge and
turns CHG back on even OV fault is present
Device is set to recovery after
current recovery delay. Both
CHG/DSG turns back on, but
device detects OCD2 fault and
turns off both FET driver again
Both CHG/DSG are
off in OCD2 fault
CHG falls due to OV fault.
State comparator is on to detect any
discharge activity
OV fault
OCD2 fault inserted
Figure 9-13. Detect OTC Fault While in 30-A
Discharge
Figure 9-12. OV and OCD2 Faults Protection
DSG falls due to
UV fault on VC2
DSG falls after ~ 1s due to
UV fault on VC2
CHG falls after ~ 1s due to
OV fault on VC3
In real application, OV and UV are usually
triggered first in an open wire event, masking out
the OW protection. This capture is to demonstrate
the OW protection by observing the CHG delay
time
CHG falls after
~5s due to OW
Relay opens ± open cell2 to pcb connection
VC2 ramped to 0V, while other cell
voltages stay in normal
In real application, an open wire event will deplete the filter
capacitor connects to the device cell voltage sensing pin. The
depleted capacitor will trigger the UV fault. It also causes the upper
cell voltage sensing pin to see a sum of 2 cell voltages, which will
trigger an OV fault.
OV and UV delays are shorter than OW delay, hence, the OV and
UV will triggered before OW protection activates.
Figure 9-14. OW Fault Protection—Open Cell2 To
PCB Connection
Figure 9-15. OW Fault Protection—Ramping Down
Cell2 Voltage
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9.3 System Examples
PACK+
RVDD
CVDD
RIN
RIN
RIN
RIN
CVDD
CIN
CIN
CIN
CIN
RIN
VDD
DVSS
AVDD
CTRD
VC5
CTRC
VC4
CCFG
VC3
VTB
bq77905
VC2
TS
VC1
LD
AVSS
CHG
SRP
CHGU
SRN
DSG
RTS_PU
RTS
RCHG
RDSG
RLD
CIN
RGS
RSNS
RGS
PACKCopyright © 2016, Texas Instruments Incorporated
Figure 9-16. BQ77905 with Five Cells
10 Power Supply Recommendations
The recommended cell voltage range is up to 5 V. If three cells in series are connecting to BQ77905, the unused
VCx pins should be shorted to the highest unused VCx pin. The recommended VDD range is from 3 V–25 V.
This implies the device is still operational when cell voltage is depleted down to approximately 1.5-V range.
36
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SLUSCM3K – JUNE 2016 – REVISED JULY 2020
11 Layout
11.1 Layout Guidelines
1. Match SRN and SRP traces.
2. RIN filters, VDD, AVDD filters, and the CVDD capacitor should be placed close to the device pins.
3. Separate the device ground plane (low current ground) from the high current path. Filter capacitors should
reference to the low current ground path or device Vss.
4. In a stack configuration, the RCTRD and RCTRC should be placed closer to the lower device CTRD and CTRC
pins.
5. RGS should be placed near the FETs.
11.2 Layout Example
High current Path
Please filters
close to IC pins VDD
DVSS
Connect AVSS and DVSS
to device ground plane
AVDD
RC
Filters
PACK+
VC5
:
:
Low current, local
ground for each device
VC1
AVSS
AVSS
CHGU
DSG
Connect the device ground at
šZ o}Á Œ oo[• oo- on each
cell group
Please filters
close to IC pins VDD
AVDD
RC
Filters
VC5
:
:
DVSS
DVSS
CTRD
Please CTRs
resistors close to
the lower device
CTRC
VC1
AVSS
AVSS
Connect the bottom
device ground at BAT-.
Using BAT- as the mutual
point to connect high
and low current path
Low current, local
device ground.
Separate from high
power path
PACK-
Figure 11-1. Layout Example
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12 Device and Documentation Support
12.1 Documentation Support
12.1.1 Related Links
The table below lists quick access links. Categories include technical documents, support and community
resources, tools and software, and quick access to order now.
Table 12-1. Related Links
PARTS
PRODUCT FOLDER
ORDER NOW
TECHNICAL
DOCUMENTS
TOOLS &
SOFTWARE
SUPPORT &
COMMUNITY
BQ77904
Click here
Click here
Click here
Click here
Click here
BQ77905
Click here
Click here
Click here
Click here
Click here
12.2 Receiving Notification of Documentation Updates
To receive notification of documentation updates, navigate to the device product folder on ti.com. In the upper
right corner, click on Alert me to register and receive a weekly digest of any product information that has
changed. For change details, review the revision history included in any revised document.
12.3 Support Resources
TI E2E™ support forums are an engineer's go-to source for fast, verified answers and design help — straight
from the experts. Search existing answers or ask your own question to get the quick design help you need.
Linked content is provided "AS IS" by the respective contributors. They do not constitute TI specifications and do
not necessarily reflect TI's views; see TI's Terms of Use.
12.4 Trademarks
TI E2E™ is a trademark of Texas Instruments.
All trademarks are the property of their respective owners.
12.5 Electrostatic Discharge Caution
This integrated circuit can be damaged by ESD. Texas Instruments recommends that all integrated circuits be handled
with appropriate precautions. Failure to observe proper handling and installation procedures can cause damage.
ESD damage can range from subtle performance degradation to complete device failure. Precision integrated circuits may
be more susceptible to damage because very small parametric changes could cause the device not to meet its published
specifications.
12.6 Glossary
TI Glossary
This glossary lists and explains terms, acronyms, and definitions.
13 Mechanical, Packaging, and Orderable Information
The following pages include mechanical, packaging, and orderable information. This information is the most
current data available for the designated devices. This data is subject to change without notice and revision of
this document. For browser-based versions of this data sheet, refer to the left-hand navigation.
38
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PACKAGE OPTION ADDENDUM
www.ti.com
10-Dec-2020
PACKAGING INFORMATION
Orderable Device
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
BQ7790400PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790400
BQ7790400PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790400
BQ7790500PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790500
BQ7790500PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790500
BQ7790502PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790502
BQ7790502PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790502
BQ7790503PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790503
BQ7790503PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790503
BQ7790505PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790505
BQ7790505PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790505
BQ7790508PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790508
BQ7790508PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790508
BQ7790509PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790509
BQ7790509PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790509
BQ7790511PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790511
BQ7790511PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790511
BQ7790512PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790512
BQ7790512PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790512
BQ7790518PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790518
BQ7790518PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790518
Addendum-Page 1
Samples
PACKAGE OPTION ADDENDUM
www.ti.com
Orderable Device
10-Dec-2020
Status
(1)
Package Type Package Pins Package
Drawing
Qty
Eco Plan
(2)
Lead finish/
Ball material
MSL Peak Temp
Op Temp (°C)
Device Marking
(3)
(4/5)
(6)
BQ7790521PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790521
BQ7790521PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790521
BQ7790522PW
ACTIVE
TSSOP
PW
20
70
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790522
BQ7790522PWR
ACTIVE
TSSOP
PW
20
2000
RoHS & Green
NIPDAU
Level-2-260C-1 YEAR
-40 to 85
B7790522
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
RoHS: TI defines "RoHS" to mean semiconductor products that are compliant with the current EU RoHS requirements for all 10 RoHS substances, including the requirement that RoHS substance
do not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered at high temperatures, "RoHS" products are suitable for use in specified lead-free processes. TI may
reference these types of products as "Pb-Free".
RoHS Exempt: TI defines "RoHS Exempt" to mean products that contain lead but are compliant with EU RoHS pursuant to a specific EU RoHS exemption.
Green: TI defines "Green" to mean the content of Chlorine (Cl) and Bromine (Br) based flame retardants meet JS709B low halogen requirements of
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