19-2278; Rev 0; 4/02
Advanced Li+ Battery-Pack Protectors
General Description
The MAX1894/MAX1924 are lithium-ion/lithium-polymer
(Li+) battery-pack protector ICs for 3- or 4-series Li+ bat-
tery packs. The MAX1894/MAX1924 enhance the useful
operating life of Li+ batteries by monitoring individual cell
voltages and preventing over/undervoltage conditions.
The MAX1894/MAX1924 also protect the battery pack
against charge current, discharge current, and pack-
short fault conditions.
In case of a fault condition, on-board drivers control
external P-channel MOSFETs, which disconnect the cells
from the pack external terminals. The external protection
MOSFETs are connected in a common-source configura-
tion that does not require external pullup resistors. The
MAX1894/MAX1924 use only one current-sense resistor
to achieve the protection features. All protection thresh-
olds and delays do not require any external components
and are trimmed at the factory.
If any cell voltage drops below the undervoltage thresh-
old, the MAX1894/MAX1924 disconnect the pack from
the load and power down to prevent deep discharge of
the pack. The MAX1894/MAX1924 offer a trickle-charge
feature, which provides a low-current path to safely
charge a deeply discharged pack. The MAX1894/
MAX1924 also have two logic-level inputs, which can be
used by a microcontroller to disable the protection
MOSFETs and to put the device in shutdown. The
MAX1894/MAX1924 have low quiescent current (30µA
typ) and ultra-low shutdown current (0.8µA typ) to pre-
vent deep-cell discharge.
The MAX1894X is designed for 4-series battery packs,
without hysteresis on the protection thresholds. The
MAX1924V and MAX1924X include hysteresis for the 3-
and 4-series packs, respectively.
Features
o
Protect Against Cell Overvoltage
Factory Programmable Limits from 4V to 4.4V
Accurate to ±0.5%
o
Protect Against Cell Undervoltage
Factory Programmable Limits from 2V to 3.2V
Accurate to ±2.0%
o
Protect Against Charge, Discharge, and Pack-
Short Current Faults
o
Automatically Trickle Charges Deeply Discharged
Cells
o
Fully Integrated MOSFET Drivers Do Not Require
Pullup Resistors
o
0.8µA (typ) Shutdown Supply Current Prevents
Deep Discharge of Cells
o
30µA (typ) Operating Supply Current
o
28V (max) Input Voltage
o
Available in Small 16-Pin QSOP Package
MAX1894/MAX1924
Pin Configuration
TOP VIEW
B4P 1
V
CC
2
B3P 3
IC3 4
B2P 5
IC2 6
B1P 7
IC1 8
16 SRC
15 DSO
14 CGO
13 TKO
MAX1894
MAX1924
12 SHDN
11 CTL
10 PKN
9
BN
Applications
3- or 4-Series Li+ Battery Packs
QSOP
Ordering Information
PART
MAX1894XEEE
MAX1924VEEE
MAX1924XEEE
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
16 QSOP
CELLS
4
3
4
OVERVOLTAGE
4.25V*
4.35V*
4.35V*
OVERVOLTAGE
THRESHOLD HYSTERESIS
No
Yes
Yes
*Contact
factory for alternative threshold voltages.
Typical Applications Circuits appear at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
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.
Advanced Li+ Battery-Pack Protectors
MAX1894/MAX1924
ABSOLUTE MAXIMUM RATINGS
SRC, IC2, IC3, V
CC
to BN.......................................-0.3V to +28V
IC1 to BN ..................................................................-0.3V to +6V
DSO, TKO, CGO
to BN.............................-0.3V to (V
SRC
+ 0.3V)
B4P to B3P ...............................................................-0.3V to +6V
B3P to B2P ...............................................................-0.3V to +6V
B2P to B1P ...............................................................-0.3V to +6V
B1P to BN .................................................................-0.3V to +6V
CTL, SHDN to PKN...................................................-0.3V to +6V
PKN to BN ...................................................................-2V to +2V
ESD Protection on All Pins ...............................................±2000V
Continuous Power Dissipation (T
A
= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°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
(V
SRC
= V
B4P
+ 0.1V, each battery cell voltage (V
CELL
) = 3.6V, V
CTL
= V
SHDN
= V
PKN
,
T
A
= 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER
SRC Input Current
Supply Current (Note 1)
Shutdown Supply Current
Top Cell Sampling Current
(Note 2)
Intermediate Cell Input Bias
Current (Note 3)
V
CC
Undervoltage Lockout
Threshold
Charge-Mode Detection
Threshold
Overvoltage Threshold (Note 4)
Overvoltage Threshold
Hysteresis
Undervoltage Threshold (Note 4)
PKN to BN Discharge Current
Fault Threshold
PKN to BN Charge Current
Fault Threshold
PKN to BN Discharge Current
Fault Threshold, Pack-Short
Condition
Discharge or Charge Current
Fault to
DSO, CGO, TKO
Transition Delay Time
Discharge Current Fault to
DSO
Transition Time Delay for Pack-
Short Condition
V
OV_TH
V
OV_HYT
V
UV_TH
V
OD_TH
V
OC_TH
V
PS_TH
SYMBOL
I
SUP
I
SHDN
CONDITIONS
V
SRC
- V
B_P
= 1V
No faults
Undervoltage without charge source
V
CELL
= 3.6V
V
CELL
= 3.6V
Rising edge, hysteresis = 1% falling edge
V
SRC
- V
B4P
MAX1894X cell voltage rising
MAX1924X, MAX1924V cell voltage rising
MAX1924X, MAX1924V cell voltage falling
Cell voltage falling
2.260
130
-120
25
4.225
4.325
4.250
4.350
200
2.300
145
-100
2.340
160
-80
MIN
TYP
20
30
0.8
60
500
4.5
100
4.275
4.375
MAX
40
45
2
UNITS
µA
µA
µA
µA
pA
V
mV
V
mV
V
mV
mV
385
405
425
mV
t
I-DELAY
2.5
3
3.5
ms
t
P-DELAY
400
450
500
µs
2
_______________________________________________________________________________________
Advanced Li+ Battery-Pack Protectors
ELECTRICAL CHARACTERISTICS (continued)
(V
SRC
= V
B4P
+ 0.1V, each battery cell voltage (V
CELL
) = 3.6V, V
CTL
= V
SHDN
= V
PKN
,
T
A
= 0°C to +85°C,
unless otherwise noted.
Typical values are at T
A
= +25°C.)
PARAMETER
Charge-Voltage Comparator
Threshold for Resetting
Discharge-Current Fault Latch
Discharge-Voltage Comparator
Threshold for Resetting Charge-
Current Fault Latch
DSO, CGO,
and
TKO
Sink
Current
DSO, CGO,
and
TKO
Source Current
Under/Overvoltage to
DSO,
CGO, TKO
Transition Delay
SHDN, CTL Input High (Note 6)
SHDN, CTL Input Low (Note 6)
SHDN, CTL Input Leakage
Current
SHDN, CTL Delay to Output
Change
DSO, CGO, TKO
Output High
(Note 7)
DSO, CGO, TKO
Output Low
(Note 7)
V
B_P
= 4V, V
CTL
= 3V
V
B_P
= 4V
t
V-DELAY
Rising edge
Falling edge
PKN = BN
50
-0.1
-14
SYMBOL
V
SRC
- V
B4P
CONDITIONS
MIN
25
TYP
MAX
100
UNITS
mV
MAX1894/MAX1924
V
B4P
- V
SRC
V
SRC
= 12V, V
PIN
= 5V (Note 5)
V
SRC
= 12V, V
PIN
= 10V
V
CTL
= 3V (Note 5)
25
100
3.5
270
2.4
200
5
320
100
mV
µA
mA
370
ms
V
1.2
1
V
µA
ns
V
V
_______________________________________________________________________________________
3
Advanced Li+ Battery-Pack Protectors
MAX1894/MAX1924
ELECTRICAL CHARACTERISTICS
(V
SRC
= V
B4P
+ 0.1V, each battery cell voltage (V
CELL
) = 3.6V, V
CTL
= V
SHDN
= V
PKN
,
T
A
= -40°C to +85°C,
unless otherwise noted.)
PARAMETER
SRC Input Current
Supply Current (Note 1)
Shutdown Supply Current
Charge-Mode Detection
Threshold
Overvoltage Threshold (Note 4)
Undervoltage Threshold (Note 4)
PKN to BN Discharge-Current
Fault Threshold
PKN to BN Charge-Current
Fault Threshold
PKN to BN Discharge-Current
Fault Threshold, Pack Short
Condition
Discharge- or Charge-Current
Fault to
DSO, CGO, TKO
Transition Delay Time
Discharge-Current Fault to
DSO
Transition Time Delay for Pack
Short Condition
Charge-Voltage Comparator
Threshold for Resetting
Discharge-Current Fault Latch
Discharge-Voltage Comparator
Threshold for Resetting Charge-
Current Fault Latch
DSO, CGO,
and
TKO
Sink
Current
DSO, CGO,
and
TKO
Source Current
Under/Overvoltage to
DSO,
CGO, TKO
Transition Delay
SHDN, CTL Input High (Note 6)
SHDN, CTL Input Low (Note 6)
t
V-DELAY
Rising edge
Falling edge
V
OV_TH
V
UV_TH
V
OD_TH
V
OC_TH
V
PS_TH
I
SUP
I
SHDN
SYMBOL
No faults
Undervoltage without charge source
V
SRC
- V
B4P
MAX1894X cell voltage rising
MAX1924X, MAX1924V cell voltage rising
Cell voltage falling
25
4.21
4.32
2.24
120
-130
CONDITIONS
V
SRC
- V
B_P
= 1V
MIN
TYP
MAX
40
50
2
100
4.29
4.38
2.36
170
-70
UNITS
µA
µA
µA
mV
V
V
mV
mV
345
465
mV
t
I-DELAY
2
4
ms
t
P-DELAY
370
480
µs
V
SRC
- V
B4P
25
100
mV
V
B4P
- V
SRC
V
SRC
= 12V, V
PIN
= 5V (Note 5)
V
SRC
= 12V, V
PIN
= 10V
V
CTL
= 3V (Note 5)
25
100
mV
100
3.5
270
2.4
1.2
370
µA
mA
ms
V
V
Note 1:
Average current from the top of the battery pack. Measured at V
CC
.
Note 2:
Typical supply current for the top cell during the 0.5ms sampling period.
Note 3:
Input bias current for this measurement is valid when all cell voltages are equal and the measurement is made over a time
greater than 3 seconds.
Note 4:
Each cell voltage is sampled individually and a differential measurement is made (V
B4P
- V
B3P
, V
B3P
- V
B2P
, V
B2P
- V
B1P
,
and V
B1P
- BN).
Note 5:
V
PIN
represents V
DSO
, V
CGO
, or V
TKO
.
Note 6:
Inputs to SHDN and CTL pins are referred to PKN.
Note 7:
Measurements are with respect to V
SRC
.
4
_______________________________________________________________________________________
Advanced Li+ Battery-Pack Protectors
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
MAX1894 toc01
MAX1894/MAX1924
SUPPLY CURRENT
vs. TEMPERATURE
MAX1894 toc02
UNDERVOLTAGE THRESHOLD
vs. TEMPERATURE
MAX1894 toc03
1.2
1.1
SUPPLY CURRENT (µA)
1.0
4-SERIES BATTERY PACK
0.9
0.8
0.7
0.6
0.5
0.4
-40
-15
10
35
60
50
4-SERIES BATTERY PACK
40
SUPPLY CURRENT (µA)
2.310
2.305
CELL VOLTAGE (V)
B1P
B3P
2.300
B4P
B2P
2.295
30
20
10
0
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
2.290
-40
-15
10
35
60
85
TEMPERATURE (°C)
OVERVOLTAGE THRESHOLD
vs. TEMPERATURE
MAX1924X
4.355
CELL VOLTAGE (V)
MAX1894 toc04
CHARGE-CURRENT FAULT
THRESHOLD vs. TEMPERATURE
MAX1894 toc05
CHARGE-CURRENT FAULT RECOVERY
THRESHOLD vs. TEMPERATURE
90
80
MAX1894 toc06
4.360
130
120
V
BN
- V
PKN
(mV)
110
100
90
80
100
V
B4P
- V
SRC
(mV)
-15
10
35
60
B1P
B3P
70
60
50
40
30
20
4.350
B4P
B2P
4.345
4.340
-40
-15
10
35
60
85
TEMPERATURE (°C)
70
-40
85
TEMPERATURE (°C)
-40
-15
10
35
60
85
TEMPERATURE (°C)
DISCHARGE-CURRENT FAULT THRESHOLD
vs. TEMPERATURE
MAX1894 toc07
DISCHARGE-CURRENT FAULT RECOVERY
THRESHOLD vs. TEMPERATURE
MAX1894 toc08
PACK-SHORT CURRENT FAULT
THRESHOLD vs. TEMPERATURE
MAX1894 toc09
155
100
90
80
V
B4P
- V
SRC
(mV)
70
60
50
40
30
415
150
V
PKN
- V
BN
(mV)
410
V
PKN
- V
BN
(mV)
-40
-15
10
35
60
85
145
405
140
400
135
-40
-15
10
35
60
85
TEMPERATURE (°C)
20
TEMPERATURE (°C)
395
-40
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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