19-1465; Rev 2; 12/03
Advanced Lithium-Ion
Battery-Pack Protector
The MAX1666 protects the battery pack in an overcurrent
condition by disconnecting the pack from the load at a programmable limit. On-chip power MOSFET drivers control
external P-channel MOSFETs to disconnect the cells from
external terminals when faults occur.
The MAX1666 employs a unique timing scheme that
allows three modes of operation for optimal performance
and battery power conservation. The MAX1666 can operate in a stand-alone configuration or in conjunction with a
microcontroller. It is available in four versions: the S version monitors two Li+ cells, the A and V versions monitor
three cells, and the X version monitors four cells. When
the charge path is disabled by the charge control pin, the
MAX1666A reduces current consumption compared to
the MAX1666S/V/X.
Features
♦ Overvoltage Protection
Programmable Limits from +4.0V to +4.4V
Accurate to ±0.5%
♦ Undervoltage Protection
Programmable Limits from +2.0V to +3.0V
Accurate to ±2.5%
♦ Cell Mismatch Protection
Programmable Limits from 0 to 500mV
Accurate to ±10%
♦ Overcharge Current Protection
♦ Overdischarge Current Protection
♦ Low 30µA (typ) Operating Supply Current
♦ Low 1µA (max) Standby Current
♦ +28V (max) Input Voltage
♦ Available in Small 16-Pin QSOP (MAX1666S) and
20-Pin QSOP (MAX1666A/V/X) Packages
Applications
2/3/4-Cell Lithium-Ion Battery Pack
Selector Guide
PART
NUMBER OF Li+ CELLS
MAX1666S
2
MAX1666A/V
MAX1666X
3
4
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX1666SEEE
-40°C to +85°C
16 QSOP
MAX1666AEEP
-40°C to +85°C
20 QSOP
MAX1666VEEP
MAX1666XEEP
-40°C to +85°C
-40°C to +85°C
20 QSOP
20 QSOP
Typical Operating Circuits appear at end of data sheet.
Pin Configurations
TOP VIEW
SRC 1
16 VCC
SRC 1
20 UVO
SRC 1
20 UVO
DSO 2
15 REF
DSO 2
19 VCC
DSO 2
19 VCC
TKO 3
14 OVA
TKO 3
18 REF
TKO 3
18 REF
13 UVA
CGO 4
17 OVA
CGO 4
17 OVA
12 MMA
B3P 5
16 UVA
B4P 5
BIP 6
11 PKF
B3P 6
15 MMA
B3P 6
15 MMA
GND 7
10 CGI
B2P 7
14 WRN
B2P 7
14 WRN
PKN 8
9
B1P 8
13 PKF
B1P 8
13 PKF
GND 9
12 CGI
GND 9
12 CGI
PKN 10
11 DSI
PKN 10
11 DSI
CGO 4
MAX1666S
B2P 5
QSOP
DSI
MAX1666A/V
QSOP
MAX1666X
16 UVA
QSOP
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX1666A/S/V/X
General Description
The MAX1666 provides complete protection against overvoltage, undervoltage, overcharge current, overdischarge
current, and cell mismatch for 2-cell to 4-cell lithium-ion
(Li+) battery packs. The voltage of each cell in the battery
pack is checked and compared to the programmable
threshold and to the other cells in the pack.
MAX1666A/S/V/X
Advanced Lithium-Ion
Battery-Pack Protector
ABSOLUTE MAXIMUM RATINGS
SRC, DSO, TKO, CGO, UVO, PKF, WRN to GND ...-0.3V to +28V
VCC, REF, OVA, UVA, MMA to GND ........................-0.3V to +6V
B4P to B3P ...............................................................-0.3V to +6V
B3P to B2P ...............................................................-0.3V to +6V
B2P to B1P ...............................................................-0.3V to +6V
B1P to GND ..............................................................-0.3V to +6V
PKN to GND...........................................................................±2V
VCC, CGI, DSI to PKN...............................................-0.3V to +6V
Continuous Power Dissipation (TA = +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW
20-Pin QSOP (derate 9.1mW/°C above +70°C)...........727mW
Operating Temperature Range ...........................-40°C to +85°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.)
PARAMETER
SYMBOL
Charge-Mode Detection
Threshold
VSRC - VB_P
SRC Supply Current
Supply Current
Shutdown Supply Current
VCC Output Voltage
CONDITIONS
ISUP
Overvoltage Threshold
VREF
2
10
MAX1666A only, VSRC - VB3P = 1V, VCGI =
3V, VDSI = GND
2
5
MAX1666A only, VSRC - VB3P = 1V, VDSI =
3V, VCGI = GND
2
5
No faults, long-time average current from
the top battery terminal B_P
30
45
µA
1
µA
RLOAD ≥ 665Ω, 2V < VCELL < 4.4V
3.25
3.41
V
2.7
2.85
3.0
V
3.980
4.000
4.378
4.400
Pulse on
Cell voltage
rising
1.221
OVA = GND
VOVA = VREF / 2
UVA = GND
V
4.2
1.950
VUVA = VREF / 2
UVA = REF
2
V
4.020
4.422
200
Cell voltage
falling
µA
3.09
Overvoltage-Threshold
Hysteresis
Undervoltage-Threshold
Hysteresis
UNITS
V
ISHDN
VCC
MAX
VSRC - VB_P = 1V, VCGI = VDSI = GND
OVA = REF
Undervoltage Threshold
TYP
1
VCC Undervoltage-Lockout
Threshold
Reference Output Voltage
MIN
2.000
mV
2.050
V
2.500
2.925
3.000
100
_______________________________________________________________________________________
3.075
mV
Advanced Lithium-Ion
Battery-Pack Protector
(VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = 0°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
Above undervoltage threshold, cell voltage
falling
WRN Early-Warning Threshold
WRN Early-Warning-Threshold
Hysteresis
OVA, UVA, MMA Input Current
OVA, UVA, MMA = REF
All cells > 2V
MAX
UNITS
100
mV
200
mV
0.1
20
nA
±0
MMA = GND
Cell Mismatch Threshold
TYP
±250
VMMA = VREF / 2
mV
±450
±500
±550
PKN to GND OverdischargeCurrent Threshold
270
300
330
mV
PKN to GND Overcharge-Current
Threshold
-220
-200
-180
mV
MMA = REF
Overcurrent Fault-Timer Delay
tP-DELAY
330
550
770
ms
Overdischarge/OverchargeCurrent Fault-Blanking Time
tI-DELAY
1.6
2.4
3.2
ms
40
µA
DSO, CGO, UVO Output Sink
Current
No faults, V DSO = V CGO = VUVO = 1V to
27V
20
30
DSO, CGO Output Source
Current
V DSO = VSRC - 4V and V CGO = VSRC - 4V,
fault condition
2
10
DSO, CGO, UVO Leakage
Current
V DSO = V CGO = VUVO = 27V, fault condition
TKO Pulldown Resistance,
MAX1666S/V/X
0.2
200
kΩ
1
2.5
mA
V TKO = 16V
TKO Leakage Current,
MAX1666A Only
V TKO = 16V, VCGI = 3V
Minimum B3P Voltage for TKO
Low, MAX1666A Only
VSRC = VB3P + 1V, ITKO = 0.5mA
TKO Source Current
TKO = GND
1
DSI, CGI Input High Voltage
Referenced to PKN
2
DSI, CGI Input Low Voltage
Referenced to PKN
2.4
µA
3.6
V
mA
V
0.45
VDSI, VCGI = 5V
WRN Sink Current
Fault condition, V WRN = 0.4V
2
4
PKF Sink Current
Fault condition, V PKF = 0.4V
4
8
PKF, WRN Leakage Current
V PKF = V WRN = 27V
Fault persistent for four consecutive sample
periods
1
8
DSI, CGI Input Current
tF-DELAY
µA
100
TKO Sink Current, MAX1666A
Only
Undervoltage, Overvoltage, or
Mismatch Fault, to DSO, CGO,
TKO Transition Delay
mA
1
180
320
V
µA
mA
mA
0.2
µA
460
ms
_______________________________________________________________________________________
3
MAX1666A/S/V/X
ELECTRICAL CHARACTERISTICS (continued)
MAX1666A/S/V/X
Advanced Lithium-Ion
Battery-Pack Protector
ELECTRICAL CHARACTERISTICS
(VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
Charge-Mode Detection
Threshold
VSRC - VB_P
SRC Supply Current
Supply Current
Shutdown Supply Current
VCC Output Voltage
CONDITIONS
ISUP
MIN
TYP
1
V
10
MAX1666A only, VSRC - VB3P = 1V, VCGI =
3V, VDSI = GND
5
MAX1666A only, VSRC - VB3P = 1V, VDSI =
3V, VCGI = GND
5
No faults, long-time average current from
the top battery terminal B_P
45
µA
µA
1
µA
3.09
3.41
V
2.7
3.0
V
OVA = GND
3.975
4.025
OVA = REF
4.373
4.427
RLOAD ≥ 665Ω, 2V < VCELL < 4.4V
VCC Undervoltage-Lockout
Threshold
Overvoltage Threshold
UNITS
VSRC - VB_P = 1V, VCGI = VDSI = GND
ISHDN
VCC
MAX
V
UVA = GND
1.950
2.050
UVA = REF
2.925
3.075
20
nA
±450
±550
mV
PKN to GND OverdischargeCurrent Threshold
270
330
mV
PKN to GND Overcharge-Current
Threshold
-220
-180
mV
Undervoltage Threshold
OVA, UVA, MMA Leakage
OVA, UVA, MMA = REF
Cell Mismatch Threshold
All cells > 2V, MMA = REF
V
Overcurrent Fault-Timer Delay
tP-DELAY
330
770
ms
Overdischarge/OverchargeCurrent Fault-Blanking Time
tI-DELAY
1.6
3.2
ms
40
µA
DSO, CGO, UVO Output Sink
Current
No faults; V DSO, V CGO, VUVO = 1V to 27V
20
DSO, CGO Output Source
Current
V DSO = VSRC - 4V and V CGO = VSRC - 4V,
fault condition
2
DSO, CGO, UVO Leakage
Current
V DSO = V CGO = VUVO = 27V, fault condition
4
_______________________________________________________________________________________
mA
0.2
µA
Advanced Lithium-Ion
Battery-Pack Protector
(VSRC = 16V, each cell voltage VCELL = 3.6V, 330kΩ load at REF, TA = -40°C to +85°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
TKO Pulldown Resistance,
MAX1666S/V/X
MIN
TYP
MAX
UNITS
100
kΩ
1
mA
TKO Sink Current,
MAX1666A Only
V TKO = 16V
Minimum B3P Voltage for
TKO Low
VSRC = VB3P + 1V, ITKO = 0.5mA
TKO Source Current
TKO = GND
1
DSI, CGI Input High Voltage
Referenced to PKN
2
DSI, CGI Input Low Voltage
Referenced to PKN
3.6
V
mA
V
0.45
V
DSI, CGI Input Current
VDSI = VCGI = 5V
WRN Sink Current
Fault condition, V WRN = 0.4V
2
mA
PKF Sink Current
Fault condition, V PKF = 0.4V
4
mA
PKF, WRN Leakage Current
V PKF = V WRN = 27V
Undervoltage, Overvoltage, or
Mismatch Fault, to DSO, CGO,
TKO Transition Delay
tF-DELAY
Fault persistent for four consecutive sample
periods
1
180
µA
0.2
µA
460
ms
Note 1: Specifications to -40°C are guaranteed by design, not production tested.
_______________________________________________________________________________________
5
MAX1666A/S/V/X
ELECTRICAL CHARACTERISTICS
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
VCELL = 3.6V
750
33
740
730
720
31
29
27
3.0015
MAX1666toc03
35
SUPPLY CURRENT (µA)
SUPPLY CURRENT (nA)
760
UNDERVOLTAGE THRESHOLD
vs. TEMPERATURE
UVA = REF
UNDERVOLTAGE THRESHOLD (V)
VCELL = 3.6V
MAX1666toc01
770
SUPPLY CURRENT
vs. TEMPERATURE
MAX1666toc02
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
3.0010
3.0005
710
700
25
40
60
80
100
3.0000
-40
-20
0
TEMPERATURE (°C)
MISMATCH VOLTAGE THRESHOLD (mV)
4.395
4.390
4.385
20
40
80
-40
100
-20
0
60
80
MMA = REF
500
499
498
497
496
-20
0
20
40
301
300
201
200
60
80
100
-40
-20
0
20
40
OVERDISCHARGE RECOVERY TIME
PKN
(0.5V/div)
tI-DELAY
tP
DSO
(10V/div)
DSO
(10V/div)
296
295
-40
-20
0
20
40
60
80
100
1ms/div
100ms/div
TEMPERATURE (°C)
6
80
OVERDISCHARGE PROTECTION
299
297
60
TEMPERATURE (°C)
PKN
(0.5V/div)
298
100
202
TEMPERATURE (°C)
MAX1666toc07
302
80
203
MAX1666toc08
OVERDISCHARGE THRESHOLD
vs. TEMPERATURE
60
199
-40
TEMPERATURE (°C)
40
OVERCHARGE THRESHOLD
vs. TEMPERATURE
495
100
20
TEMPERATURE (°C)
501
MAX1666toc04
UNDERVOLTAGE THRESHOLD (V)
OVA = REF
0
60
MISMATCH VOLTAGE THRESHOLD
vs. TEMPERATURE
4.400
-20
40
TEMPERATURE (°C)
OVERVOLTAGE THRESHOLD
vs. TEMPERATURE
-40
20
MAX1666toc06
20
100
MAX1666toc09
0
OVERCHARGE THRESHOLD (mV)
-20
MAX1666toc05
-40
OVERDISCHARGE THRESHOLD (mV)
MAX1666A/S/V/X
Advanced Lithium-Ion
Battery-Pack Protector
_______________________________________________________________________________________
Advanced Lithium-Ion
Battery-Pack Protector
OVERCHARGE
MAX1666toc11
MAX1666toc10
OVERVOLTAGE FAULT
B1P
4.5V
PKN
(0.5V/div)
1 2 3
4.1V
4
REF
(1V/div)
CGO
(10V/div)
tP-DELAY
tF-DELAY
1 2 3
4
tF-DELAY
CGO
(10V/div)
100ms/div
100ms/div
VCELL2 = VCELL3 = VCELL4 = 4.15V,
OVERVOLTAGE THRESHOLD = 4.4V
1
2 3
4
1 2 3
4
B1P
3.4V
2.9V
1
REF
(1V/div)
REF
(1V/div)
WRN
(10V/div)
PKF
(10V/div)
tF-DELAY
tF-DELAY
1
2
3
4
tF-DELAY
DSO
(10V/div)
tF-DELAY
100ms/div
VCELL2 = VCELL3 = VCELL4 = 3.35V,
UNDERVOLTAGE THRESHOLD = 3.0V,
UVA = REF
100ms/div
VCELL2 = VCELL3 = VCELL4 = 3.6V,
CELL MISMATCH THRESHOLD = 0.5V,
MMA = REF
MAX1666toc14
UNDERVOLTAGE FAULT WITHOUT
CHARGE SOURCE (VSRC < VB4P + 1V)
B1P
DSO
(10V/div)
2 3 4
MAX1666toc13
CELL MISMATCH FAULT
MAX1666toc12
B1P
UNDERVOLTAGE FAULT
3.4V
2.9V
3.4V
2.9V
REF
(1V/div)
VCC
(2V/div)
DSO
(10V/div)
100ms/div
VCELL2 = VCELL3 = VCELL4 = 3.35V,
UNDERVOLTAGE THRESHOLD = 3.0V,
UVA = REF
_______________________________________________________________________________________
7
MAX1666A/S/V/X
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
Advanced Lithium-Ion
Battery-Pack Protector
MAX1666A/S/V/X
Pin Description
PIN
NAME
8
FUNCTION
MAX1666X
MAX1666A/V
MAX1666S
1
1
1
SRC
Charge Source Input. Provides current for gate drivers DSO, TKO,
CGO, and UVO.
2
2
2
DSO
Discharge Driver Output. Drives external P-channel MOSFET to control discharge.
3
3
3
TKO
Trickle-Charge Driver Output. Drives external P-channel MOSFET to
control trickle-charge current. MAX1666A requires an external pullup
resistor of 470kΩ
4
4
4
CGO
Fast-Charge Driver Output. Drives external P-channel MOSFET to
control fast charge.
5
—
—
B4P
Cell 4 Positive Input. Power supply input for MAX1666X.
6
5, 6
—
B3P
Cell 3 Positive Input. Power supply input for MAX1666A/V.
7
7
5
B2P
Cell 2 Positive Input. Power supply input for MAX1666S.
8
8
6
B1P
Cell 1 Positive Input
9
9
7
GND
Ground
10
10
8
PKN
Battery Pack Negative Terminal. Connect to bottom of current-sense
resistor. Ground reference for logic inputs DSI and CGI.
11
11
9
DSI
Discharge Control Input
12
12
10
CGI
Charge Control Input
13
13
11
PKF
Pack Fail Output. PKF goes low when any cell voltage exceeds the
mismatch threshold or when a shorted cell is detected.
14
14
—
WRN
Undervoltage/Overvoltage Warning Output
15
15
12
MMA
Mismatch Adjust Input. Set the mismatch threshold by a resistordivider from REF to GND.
16
16
13
UVA
Undervoltage Adjust Input. Set the undervoltage threshold with a
resistor-divider from REF to GND.
17
17
14
OVA
Overvoltage Adjust Input. Set the overvoltage threshold with a
resistor-divider from REF to GND.
18
18
15
REF
Reference Voltage Output. Minimize PC board stray capacitance on
this node.
19
19
16
VCC
3.3V Linear Regulator Output. Bypass with a 0.47µF min capacitor
to GND.
20
20
—
UVO
Undervoltage Fault Output
_______________________________________________________________________________________
Advanced Lithium-Ion
Battery-Pack Protector
SRC
SRC
"1"
D
Q
D
Q
RB
CK
"1"
RB
DSO
CK
N
CGI
MAX1666A/S/V/X
DSI
CGO
N
OV_FAULT
CM_FAULT
UV_FAULT
CQI_FAULT
UV_FAULT
CM_FAULT
DQY_FAULT
N
N
30µA
30µA
GND
MAX1666
LATCH_WRN
REG
EARLY
WARNING
50kHz
OSC
WARNING
GND
OSC
B4P
LATCH_OV
B3P
CELL
VOLTAGE
SELECTOR
B2P
BIP
STATE
MACHINE
LATCH_UV
REG
OVERVOLTAGE
OV-FAULT
CMP
REG
UNDERVOLTAGE
UV-FAULT
CMP_P
GND
OVA
THRESHOLD
VOLTAGE
SELECTOR
UVA
MMA
CMP_N
LATCH_CM
REF
REG
CELL
MISMATCH
1.221V
CM-FAULT
PKF
N
GND
200mV
CQI_HI
CQI_FAULT
550ms
TIMER
SET/RESET
PKN
DQI_HI
WRN
OV_FAULT
WARNING
UV_FAULT
N
DQI_FAULT
300mV
B4P
GND
SRC
CHARGE
SHUTDOWN
1V
3.3V
LINEAR
REG.
VCC
UV_FAULT
B4P
BIAS
TKO
UVO
CM_FAULT
UV_FAULT
N
CGI
30µA
OV_FAULT
CM_FAULT
GND
Figure 1. Functional Diagram
_______________________________________________________________________________________
9
MAX1666A/S/V/X
Advanced Lithium-Ion
Battery-Pack Protector
YES
BATTERY
CONNECTED
VSRC < VB4P + 1V
SHUTDOWN
VSRC > VB4P + 1V
VCC > 2.85V
NO
YES
(DISCHARGE CURRENT · RCS)
300mV
(>2.4ms)
OVERDISCHARGE
DSO = H
CHARGE
CURRENT
MONITOR
RESET RESET
DS0 = L CGO = L
(CHARGE CURRENT · RCS)
200mV
(>2.4ms)
OVERCHARGE
CGO = H
550ms DELAY
STANDBY
80ms
VCELL <
UNDERVOLTAGE
THRESHOLD
SAMPLE
2.5ms
YES
CHECK VREF
NO
NO
VREF > 1.1V
YES
VCELL <
UNDERVOLTAGE
WARNING
THRESHOLD
CELL MISMATCH
YES
NO
LATCH UVF = ‘1’
LATCH MMF = ‘1’
VCELL >
OVERVOLTAGE
THRESHOLD
UVF = ‘1’
AND
VSRC < VB4P + 1V
YES
NO
NO
LATCH OVF = ‘1’
GO TO
TABLE 2
YES
NO
LATCH UVW = ‘1’
Figure 2. Cell Fault Monitor
10
______________________________________________________________________________________
YES
Advanced Lithium-Ion
Battery-Pack Protector
MAX1666
R1
R3
R5
R2
R4
R6
OVA
UVA
MMA
Normal Mode
The standby state activates the bias circuitry, overcurrent
comparator, and timer. The standby state lasts 80ms,
then the MAX1666 goes into the sample state for 2.5ms.
GND
Figure 3. Using an External Resistor-Divider to Adjust
Overvoltage Threshold
Detailed Description
The MAX1666 battery-pack protectors supervise the
charging and discharging processes of Li+ battery
cells. Designed for 2-, 3-, and 4-cell applications, these
devices monitor the voltage across each cell to provide
protection against undervoltage, overvoltage, and overcurrent damage.
Control pins CGO, TKO, and DSO allow control of
external MOSFET gates. This allows fast charging, trickle charging, and discharging processes (see the
Typical Operating Circuits). The voltage of each cell is
measured individually. Also, each cell is measured differentially between every other cell of the pack.
The MAX1666 contains a state machine, a voltage regulator, an oscillator, and other logic functions to selectively drive CGO, UVO, TKO, DSO, WRN, and PKF
(Figure 1).
Modes of Operation
Within the 2.5ms, the MAX1666 checks for overvoltage,
undervoltage, and mismatch between cells sequentially, and it stores the results in internal latches. The
MAX1666 drives the outputs according to the faults (if
any) detected by reading the latches (Figure 2) at the
end of the sample state. Then the MAX1666 returns to
the standby state.
Overvoltage Protection
The MAX1666 provides overvoltage protection to avoid
overcharging of any cell. When any cell is at overvoltage, CGO and TKO go high, turning off the external
MOSFETs and stopping the charging process (see the
Typical Operating Circuits). WRN goes low. Overvoltage
is set when any cell voltage exceeds the overvoltage
threshold.
Overvoltage threshold is linearly adjustable through an
external 1% resistor-divider (Figure 3) from REF.
Determine the overvoltage threshold (VOVT) required.
VOVT must be between 4V and 4.4V. Set RTOTAL = R1
+ R2 = 1MΩ. Calculate R1 and R2 as follows:
Shutdown Mode
The MAX1666 goes into shutdown mode when a battery pack is first connected. The quiescent current is
less than 1µA. All circuitry is inactive except the com-
R2 = [(VOVT - 4V) / (4.4V- 4V)] · RTOTAL
R1 = RTOTAL - R2
Table 1. Operating Modes
MODE
STATE
TIME
(ms)
TYPICAL
QUIESCENT
CURRENT (µA)
Standby
80
24
Only bias circuitry, overcurrent comparator, and timer are active.
Sample
2.5
250
All circuitry active.
—
—
0.7
All circuitry inactive. Device enters shutdown when it detects an undervoltage fault and VSRC < VTOP-CELL + 1V (no charge source).
CONDITION
Normal
Shutdown
______________________________________________________________________________________
11
MAX1666A/S/V/X
parator monitoring VSRC and the top-cell voltage. The
MAX1666 remains in shutdown mode as long as VSRC
is less than the top-cell voltage. When SRC is connected to an external charger and VSRC is 1V above the
top-cell voltage, the device goes into standby mode.
The MAX1666 returns to shutdown mode under two
conditions: the battery is disconnected and then reconnected, or the device detects an undervoltage fault
and no charge source.
REF
MAX1666A/S/V/X
Advanced Lithium-Ion
Battery-Pack Protector
threshold (VUVT) accuracy including the internal undervoltage-threshold accuracy (±2.5%) is ±3.2%.
B4P
I4
+
V4
-
ICB = V4
R
Undervoltage Warning
When any cell drops to 100mV above the undervoltage
threshold, WRN goes low. WRN returns high when all
cells are 300mV above the undervoltage threshold.
B3P
I3P
+
V3
-
ICB = V4
R
I3
Cell-Mismatch Protection
B2P
I2P
+
V2
-
I2
+
V1
-
I1
ICB = V4
R
B1P
I1P
+
V1
-
+
V2
-
R
V1
R
+
V3
-
R
V2
R
+
V4
-
R
V3
R
R
V4
R
R6 = (VCMT / 500mV) RTOTAL
R5 = RTOTAL - R6
Figure 4. Cell Voltage Sampling
Maximum mismatch of 1% external resistor-dividers is
±2%. The external adjusted overvoltage-threshold accuracy includes the internal overvoltage-threshold accuracy
(±0.5%) and the error due to the external resistor-divider
multiplied by maximum adjustment:
±2%
4.4V − 4.0V
4.4V
Maximum mismatch of a 1% external resistor-divider is
±2%. The total external adjusted cell-mismatch threshold accuracy, including the internal cell-mismatch
threshold accuracy (±10%), is ±12%.
Cell Voltage Sampling
= ± 0.2%
The total external adjusted overvoltage-threshold (VOVT)
accuracy is ±0.7%.
Undervoltage Protection
The MAX1666 provides undervoltage protection to
avoid overdischarging the cells. When any cell is under
voltage, UVO, DSO, and CGO go high, turning off the
external charging and discharging MOSFETs. TKO
remains low to keep the trickle-charge current on.
Undervoltage threshold is linearly adjustable through
an external resistor-divider (Figure 3) from REF.
Determine the undervoltage threshold (VUVT) required.
VUVT must be between 2V and 3V. Set RTOTAL = R3 +
R4 = 1MΩ. Calculate R3 and R4 as follows:
R4 = [(VUVT - 2V) / (3V - 2V)] RTOTAL
R3 = RTOTAL - R4
Maximum mismatch of 1% external resistor-dividers is
±2.0%, and the error due to the external resistor-divider
multiplied by maximum adjustment is ±2% (3V - 2V) / 3V
= ±0.7%. The total external adjusted undervoltage-
12
The MAX1666 disables charging or discharging when
mismatch occurs. When any two cells are mismatched,
TKO, CGO, UVO, and DSO go high, turning off the
external MOSFETs. PKF goes low. PKF has a strong
pulldown current (>4mA), and can be used to control
an external thermal fuse. The cell-mismatch threshold is
linearly adjustable through an external resistor-divider
(Figure 3) from REF. Determine the cell-mismatch
threshold (VCMT) required. VCMT has to be between 0
and 500mV. Set RTOTAL = R5 + R6 = 1MΩ. Calculate
R5 and R6:
The MAX1666 does not introduce cell mismatch. When
the battery cells are matched, the MAX1666 draws
close to zero current from the intermediate cells.
Figure 4 shows a simplified diagram of the voltage
sampling scheme:
B4P: I4 = 3ICB + V4 / R = 4V4 / R = BAT4 current
B3P: I3 = I3P + I4 = BAT3 current
I3P + ICB = V3 / R ⇒ I3P = V3 / R - V4 / R
I3 = I4 + (V3 - V4) / R = (3V4 + V3) / R
B2P: I2 = I2P + I3 = BAT2 current
I2P + ICB = V2 / R ⇒ I2P = V2 / R - V4 / R
I2 = I3 + V2 / R - V4 / R = I4 + (V3 - V4) / R +
(V2 - V4) / R = (2V4 + V3 + V2) / R
B1P: I1 = I1P + I2 = BAT1 current
I1P + ICB = V1 / R ⇒ I1P = V1 / R - V4 / R
I1 = I2 + V1 / R - V4 / R = I4 + (V3 - V4) / R +
(V2 - V4) / R + (V1 - V4) / R
= (V4 + V3 + V2 + V1) / R
when V1 = V2 = V3 = V4, I1P = I2P = I3P = 0, and
I1 = I2 = I3 = I4 = 4V4 / R
______________________________________________________________________________________
______________________________________________________________________________________
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
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
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
0
0
1
1
1
1
0
0
0
0
0
0
0
0
MMF
1
1
0
0
1
1
0
0
1
1
1
0
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
1
0
0
0
1
1
0
0
1
1
1
0
0
0
0
0
CGI
1
0
1
0
1
0
1
0
1
0
0
1
1
0
0
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
0
1
0
0
1
0
1
0
1
0
0
1
1
0
0
0
DSI
CONTROL INPUTS
OVF
0
0
0
0
0
0
0
0
0
0
0
1
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
1
0
1
0
0
OCC
0
0
0
0
0
0
0
0
0
1
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
1
0
0
0
0
0
0
1
0
0
0
0
1
0
ODC
H
H
H
H
H
H
H
H
H
PS
L
H
H
L
PS
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
PS
L
H
PS
L
H
H
H
H
H
PS
L
H
H
L
PS
L
DSO
H
H
H
H
H
H
H
H
H
H
H
PS
L
PS
L
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
PS
L
PS
L
L
H
H
H
H
H
H
H
H
H
H
H
L
L
L
L
L
H
H
H
H
H
H
H
H
H
H
L
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
L
L
L
L
L
TKO
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
H
H
H
H
WRN
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
H
H
H
H
L
L
L
L
H
H
H
H
H
H
L
L
L
L
H
H
H
H
H
H
H
H
PKF
CONTROL OUTPUTS
CGO
H
H
H
H
H
H
H
H
L
L
L
L
L
L
L
L
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
L
L
L
L
L
L
H
H
H
H
L
L
L
L
L
L
L
L
UVO
UVF: Undervoltage fault
ODC: Overdischarge current fault
UVW: Undervoltage fault early warning
OCC: Overcharge current fault
NOTES
Undervoltage fault early warning, overvoltage fault, mismatch fault, disable charge and discharge path
Undervoltage fault early warning, overvoltage fault, mismatch fault, disable charge path
Undervoltage fault early warning, overvoltage fault, mismatch fault, disable discharge path
Undervoltage fault early warning, overvoltage fault, mismatch fault
Undervoltage fault early warning, mismatch fault, disable charge and discharge path
Undervoltage fault early warning, mismatch fault, disable charge path
Undervoltage fault early warning, mismatch fault, disable discharge path
Undervoltage fault early warning, mismatch fault
Undervoltage fault early warning, disable charge and discharge path
Undervoltage fault early warning, disable charge path, overdischarge current fault
Undervoltage fault early warning, disable charge path
Undervoltage fault early warning, disable discharge path, overcharge current fault
Undervoltage fault early warning, disable discharge path
Undervoltage fault early warning, overcharge current fault
Undervoltage fault early warning, overdischarge current fault
Undervoltage fault early warning
Undervoltage fault, overvoltage fault, mismatch fault, disable charge and discharge path
Undervoltage fault, overvoltage fault, mismatch fault, disable charge path
Undervoltage fault, overvoltage fault, mismatch fault, disable discharge path
Undervoltage fault, overvoltage fault, mismatch fault
Undervoltage fault, mismatch fault, disable charge and discharge path
Undervoltage fault, mismatch fault, disable charge path
Undervoltage fault, mismatch fault, disable discharge path
Undervoltage fault, mismatch fault
Undervoltage fault, disable charge and discharge path
Undervoltage fault, disable charge path
Undervoltage fault, disable discharge path
Undervoltage fault
Overvoltage fault, mismatch fault, disable charge and discharge path
Overvoltage fault, mismatch fault, disable charge path
Overvoltage fault, mismatch fault, disable discharge path
Overvoltage fault, mismatch fault
Overvoltage fault, disable charge and discharge path
Overvoltage fault, disable charge path, overdischarge current fault
Overvoltage fault, disable charge path
Overvoltage fault, disable discharge path
Overvoltage fault, overdischarge current fault
Overvoltage fault
Mismatch fault, disable charge and discharge path
Mismatch fault, disable charge path
Mismatch fault, disable discharge path
Mismatch fault
Disable charge and discharge path
Disable charge path, overdischarge current fault
Disable charge path
Disable discharge path, overcharge current fault
Disable discharge path
Overcharge current fault
Overdischarge current fault
Normal operation
OVF: Overvoltage fault
CGI: Charge control input
MMF: Mismatch fault
DSI: Discharge control input
PS: Overcurrent fault pulse sampling. (Output goes high for 500ms then resets low to monitor charge/discharge current. Output goes high again if fault persists.)
UVF
UVW
MAX1666A/S/V/X
Table 2. Truth Table
Advanced Lithium-Ion
Battery-Pack Protector
13
MAX1666A/S/V/X
Advanced Lithium-Ion
Battery-Pack Protector
Overcharge/Overdischarge
Current Protection
The MAX1666 checks for overcharge or overdischarge
current in standby and sample states. The thresholds
are factory preset to 200mV and 300mV, respectively. A
charge current makes PKN go below GND. A discharge current makes PKN go above GND. When PKN
exceeds the threshold, a fault is acknowledged. CGO
goes high when the overcharge threshold is exceeded.
DSO goes high when the overdischarge threshold is
exceeded. An internal 550ms timer starts. At the end of
550ms, DSO or CGO goes low while the MAX1666
rechecks for an overcharge/overdischarge fault. A persistent fault causes DSO and CGO to return high and
restarts the 550ms timer again.
Truth Table
Table 3. MOSFET Selection
P-CHANNEL MOSFETs
MAXIMUM DRAIN CURRENT (A)
IRF7404
5.3
IRF7406
4.7
Si4431
4.5
Si4947 (dual)
2.5 EA
CGO controls the MOSFET for normal charging of the
battery. TKO controls the MOSFET for trickle charge of
the cells. DSO controls the discharging MOSFET. Use different MOSFETs to optimize each function depending on
the maximum charge and discharge rates. Table 3 lists
some suitable MOSFETs in a small 8-pin SO package.
The MAX1666 has a total of eight signal inputs and six
outputs. Table 2 lists all the possible states.
Layout Considerations and Bypassing
Applications Information
As with all PC board designs, a careful layout is suggested. Minimize lead lengths to reduce losses in the traces.
Choosing an External MOSFET
The external P-channel MOSFETs act as a gated switch
to enable or disable the charging/discharging process.
14
______________________________________________________________________________________
Advanced Lithium-Ion
Battery-Pack Protector
OVERDISCHARGE
PROTECTION
PACK+
P
1
470kΩ
470kΩ
SRC
2
VCC
DSO
19
P
4 CGO
P
OVERCHARGE
PROTECTION 3
TRICKLE
CHARGE
270Ω
DSI
CGI
TKO
WRN
5
6
8
9
UVO
14
20
18
B2P
499kΩ
1%
499kΩ
1%
499kΩ
1%
499kΩ
1%
499kΩ
1%
499kΩ
1%
MAX1666X
GND
PKN
10
RSENSE
0.05Ω
12
PKF
B3P
B1P
0.47µF
13
B4P
REF
7
11
+3.3V
5mA
17
OVA
16
UVA
15
MMA
PACK-
______________________________________________________________________________________
15
MAX1666A/S/V/X
Typical Operating Circuits
Advanced Lithium-Ion
Battery-Pack Protector
MAX1666A/S/V/X
Typical Operating Circuits (continued)
OVERDISCHARGE
PROTECTION
PACK+
P
470kΩ
470kΩ
1
SRC
2
VCC
DSO
19
P
1µF
4 CGO
P
TRICKLE
CHARGE
270Ω
OVERCHARGE
PROTECTION 3
DSI
CGI
TKO
WRN
5
6
8
9
100kΩ
220kΩ
VCC
OUT1
11
OUT2
14
IN1
IN2
PKF
UVO
B3P
20
IN3
18
B2P
B1P
100kΩ
12
13
B4P
REF
7
PACK
CONTROLLER
499kΩ
1%
499kΩ
1%
499kΩ
1%
MAX1666X
GND
GND
17
16
UVA
15
MMA
OVA
PKN
10
RSENSE
0.05Ω
+3.3V
5mA
499kΩ
1%
499kΩ
1%
499kΩ
1%
PACK-
___________________Chip Information
TRANSISTOR COUNT: 4835
16
______________________________________________________________________________________
Advanced Lithium-Ion
Battery-Pack Protector
QSOP.EPS
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 17
© 2003 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX1666A/S/V/X
________________________________________________________Package Information
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