General Description

The MAX1737 is a switch-mode lithium-ion (Li+) battery

charger that charges one to four cells. It provides a

regulated charging current and a regulated voltage

with only a ±0.8% total voltage error at the battery ter-

minals. The external N-channel switch and synchronous

rectifier provide high efficiency over a wide input volt-

age range. A built-in safety timer automatically termi-

nates charging once the adjustable time limit has been

reached.

The MAX1737 regulates the voltage set point and charg-

ing current using two loops that work together to transi-

tion smoothly between voltage and current regulation. An

additional control loop monitors the total current drawn

from the input source to prevent overload of the input

supply, allowing the use of a low-cost wall adapter.

The per-cell battery voltage regulation limit is set

between +4.0V and +4.4V and can be set from one to

four by pin strapping. Battery temperature is monitored

by an external thermistor to prevent charging if the bat-

tery temperature is outside the acceptable range.

The MAX1737 is available in a space-saving 28-pin

QSOP package. Use the evaluation kit (MAX1737EVKIT)

to help reduce design time.

Applications

Features

o Stand-Alone Charger for Up to Four Li+ Cells

o ±0.8% Accurate Battery Regulation Voltage

o Low Dropout: 98% Duty Cycle

o Safely Precharges Near-Dead Cells

o Continuous Voltage and Temperature Monitoring

o <1µA Shutdown Battery Current

o Input Voltage Up to +28V

o Safety Timer Prevents Overcharging

o Input Current Limiting

o Space-Saving 28-Pin QSOP

o 300kHz PWM Oscillator Reduces Noise

o 90% Conversion Efficiency

Stand-Alone Switch-Mode

Lithium-Ion Battery-Charger Controller

________________________________________________________________ Maxim Integrated Products

1

GND

DCIN

CSSP

CSSN

LX

BST

VLO

DLO

PGND

CS

THM

BATT

FASTCHG

FULLCHG

FAULT

SHDN

ON

OFF

TIMER2

TIMER1

Li+

BATTERY

1 TO 4

CELLS

CCI

CCV

CCS

VADJ

ISETIN

VL

REF

ISETOUT

INPUT SUPPLY

CELL

DHI

SYSTEM

LOAD

MAX1737

19-1626; Rev 1; 7/00

PART

MAX1737EEI

-40°C to +85°C

TEMP. RANGE

PIN-PACKAGE

28 QSOP

EVALUATION

KIT

AVAILABLE

Typical Operating Circuit

28

27

26

25

24

23

22

21

20

19

18

17

16

15

1

2

3

4

5

6

7

8

9

10

11

12

13

14

DCIN

CSSP

CSSN

DHI

LX

BST

FAULT

VLO

DLO

PGND

CS

SHDN

FULLCHG

FASTCHG

TIMER2

TIMER1

CELL

CCI

CCS

CCV

VADJ

BATT

GND

REF

THM

ISETOUT

ISETIN

VL

QSOP

TOP VIEW

MAX1737

Pin Configuration

Ordering Information

Notebook Computers

Hand-Held Instruments

Li+ Battery Packs

Desktop Cradle Chargers

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.