EVALUATION KIT AVAILABLE
Stand-Alone, Switch-Mode
Li+ Battery Charger with
Internal 14V Switch
MAX1757
General Description
Benefits and Features
The MAX1757 is a switch-mode lithium-ion (Li+) battery
charger that charges one to three cells. It provides a
regulated charging current accurate to ±10% and a
regulated voltage with only a ±0.8% total voltage error
at the battery terminals. The internal high-side switch
delivers a programmable current of up to 1.5A to
charge the battery. The built-in safety timer automatically terminates charging once the adjustable time limit
has been reached.
The MAX1757 regulates the voltage set point and
charging current using two loops that work together to
transition smoothly between voltage and current regulation. An additional control loop monitors the total current drawn from the input source (charging + system)
and by automatically reducing battery-charging current
prevents overload of the input supply, allowing the use
of a low-cost wall adapter.
The per-cell battery regulation voltage is set between
4.0V and 4.4V using standard 1% resistors. The number
of cells is set from 1 to 3 by pin strapping. Battery temperature is monitored by an external thermistor to prevent
charging outside the acceptable temperature range.
The MAX1757 is available in a space-saving 28-pin
SSOP package. Use the MAX1757EVKIT to help
reduce design time. For a stand-alone charger with a
28V switch, refer to the MAX1758 data sheet. For a
charger controller capable of up to 4A charging current, refer to the MAX1737 data sheet.
• Stand-Alone Charger Safely Charges Up to Three Li+
Applications
•
•
•
•
Batteries
• Continuous Voltage and Temperature Monitoring
• Input Current Limiting
• ±0.8% Battery Regulation Voltage Accuracy
• Up to 1.5A Programmable Charge Current
Low Power Consumption Extends Battery Life
• 0.1μA Shutdown Battery Current
• Low-Dropout 98% Duty Cycle
Flexible Input Voltage Range Enables the Use of Low
Cost Wall Adapters
• Input Voltage Up to 14V
• Precharges Near-Dead Cells
Fixed 300kHz PWM Oscillator Allows Effective Noise
Filtering
28-Pin SSOP Package Saves Board Space
Ordering Information
PART
TEMP. RANGE
-40°C to +85°C
MAX1757EAI
PIN-PACKAGE
28 SSOP
Typical Operating Circuit
VIN
6V to 14V
Li+ Battery Packs
Notebook Computers
Hand-Held Instruments
PDAs
Desktop Cradle Chargers
DCIN
CSSP
CSSN
REF
HSD
MAX1757
ISETOUT
Pin Configuration
SYSTEM
LOAD
LX
BST
VL
TOP VIEW
ISETIN
PGND
VL 1
28 DCIN
ISETTIN 2
27 CSSP
CELL
CS
VADJ
26 CSSN
ISETOUT 3
BATT
25 CCV
THM 4
THM
24 CCI
REF 5
GND 6
MAX1757
CCS
23 CCS
VADJ 7
22 BST
BATT 8
21 CS
HSD 9
20 LX
HSD 10
THERM
19 LX
CCI
16 FULLCHG
FAULT 14
15 FASTCHG
SSOP
19-1754; Rev 2; 5/15
FULLCHG
FAULT
17 SHDN
TIMER2 13
TIMER1
18 PGND
FASTCHG
TIMER2
CELL 11
TIMER1 12
CCV
ON
OFF
SHDN
GND
Li+ BATTERY
1 TO 3 CELLS
