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PDF MAX1894 Data sheet ( Hoja de datos )
| Número de pieza | MAX1894 | |
| Descripción | Advanced Li+ Battery-Pack Protectors | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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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.
Applications
3- or 4-Series Li+ Battery Packs
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
Pin Configuration
TOP VIEW
B4P 1
VCC 2
B3P 3
IC3 4
B2P 5
IC2 6
B1P 7
IC1 8
MAX1894
MAX1924
16 SRC
15 DSO
14 CGO
13 TKO
12 SHDN
11 CTL
10 PKN
9 BN
QSOP
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX1894XEEE
-40°C to +85°C 16 QSOP
MAX1924VEEE
-40°C to +85°C 16 QSOP
MAX1924XEEE
-40°C to +85°C 16 QSOP
*Contact factory for alternative threshold voltages.
Typical Applications Circuits appear at end of data sheet.
CELLS
4
3
4
OVERVOLTAGE
4.25V*
4.35V*
4.35V*
OVERVOLTAGE
THRESHOLD HYSTERESIS
No
Yes
Yes
________________________________________________________________ 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.
1 page  
Advanced Li+ Battery-Pack Protectors
(TA = +25°C, unless otherwise noted.)
SHUTDOWN SUPPLY CURRENT
vs. TEMPERATURE
1.2
1.1
1.0
4-SERIES BATTERY PACK
0.9
0.8
0.7
0.6
0.5
0.4
-40
-15 10 35 60
TEMPERATURE (°C)
85
Typical Operating Characteristics
SUPPLY CURRENT
vs. TEMPERATURE
50
4-SERIES BATTERY PACK
40
30
20
10
0
-40
-15 10 35 60
TEMPERATURE (°C)
85
UNDERVOLTAGE THRESHOLD
vs. TEMPERATURE
2.310
2.305
2.300
2.295
B1P
B3P
B4P
B2P
2.290
-40
-15 10 35 60
TEMPERATURE (°C)
85
OVERVOLTAGE THRESHOLD
vs. TEMPERATURE
4.360
MAX1924X
4.355
B1P
4.350
4.345
B3P
B4P
B2P
4.340
-40
-15 10 35 60
TEMPERATURE (°C)
85
CHARGE-CURRENT FAULT
THRESHOLD vs. TEMPERATURE
130
120
110
100
90
80
70
-40
-15 10 35 60
TEMPERATURE (°C)
85
CHARGE-CURRENT FAULT RECOVERY
THRESHOLD vs. TEMPERATURE
100
90
80
70
60
50
40
30
20
-40
-15 10 35 60
TEMPERATURE (°C)
85
DISCHARGE-CURRENT FAULT THRESHOLD
vs. TEMPERATURE
155
150
145
140
135
-40
-15 10 35 60
TEMPERATURE (°C)
85
DISCHARGE-CURRENT FAULT RECOVERY
THRESHOLD vs. TEMPERATURE
100
90
80
70
60
50
40
30
20
-40
-15 10 35 60
TEMPERATURE (°C)
85
PACK-SHORT CURRENT FAULT
THRESHOLD vs. TEMPERATURE
415
410
405
400
395
-40
-15 10 35 60
TEMPERATURE (°C)
85
_______________________________________________________________________________________ 5
5 Page 
Advanced Li+ Battery-Pack Protectors
NORMAL OPERATION
OC FAULT
NO VRSENSE < VOC_TH
FOR 3ms
YES
TKO, CGO = H
NORMAL OPERATION
OD FAULT
NO VRSENSE > VOD_TH
FOR 3ms
YES
DSO, TKO, CGO = H
NO
VB4P > VSRC + 0.1V
YES
NO
VSRC > VB4P + 0.1V
YES
Figure 5. Charge-Current Fault
Set the nominal values of the trickle charge current by
selecting resistor RTKO based on the following equation:
RTKO = (VCHRG - VPACK)/ITKO
where VCHRG is the charger output voltage, VPACK is
the battery-pack voltage, and ITKO is the trickle-charge
current.
When the trickle-charge option is not used, float CGO
and connect TKO to the gate of the overcharge protec-
tion MOSFET (see Figure 9). When a charger is applied
and the voltage on one or more cells is less than
VUV_TH, the MAX1894/MAX1924 modulate the TKO out-
put until all cells exceed VUV_TH.
Protection FET Drivers
All three external MOSFETs have their source pins con-
nected to the SRC pin. When a MOSFET is turned off, FET
drivers pull the gate to the SRC voltage. Additional exter-
nal pullup resistors are not needed. When the MOSFET is
turned on, the VGS is limited to -14V by a clamp circuit
built in the drivers. This allows use of MOSFETs with maxi-
mum VGS of -20V. All three drivers have the same circuit-
ry and drive capability. The quiescent current in normal
operation is less than 3µA per driver.
Figure 6. Discharge-Current Fault
RSENSE Selection
All current faults are detected using a current-sense
resistor connected between BN and PKN. The value of
this resistor sets the fault current levels. Charge-current
fault is given by:
IOC_ TH
=
VOC_ TH
RSENSE
=
100mV
RSENSE
Discharge-current fault is given by:
IOD_ TH
=
VOC_ TH
RSENSE
=
145mV
RSENSE
Pack-short current fault is given by:
IPS_ TH
=
VPS_ TH
RSENSE
=
405mV
RSENSE
Select RSENSE to obtain the desired fault current levels.
For example, a 20mΩ RSENSE sets the charge current
fault at 5A. Choose an RSENSE that can withstand the
dissipation during normal operation and current fault
conditions. For example, pack-short current is given by:
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet MAX1894.PDF ] | |
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