Stand-Alone Switch-Mode Lithium-Ion Battery-Charger Controller


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 terminals. The external N-channel switch and synchronous rectifier provide high efficiency over a wide input voltage range. A built-in safety timer automatically terminates charging once the adjustable time limit has been reached.

The MAX1737 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 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 battery 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.
MAX1737: Typical Operating Circuit MAX1737: Typical Operating Circuit Enlarge+

Key Features

  • Stand-Alone Charger for Up to Four Li+ Cells
  • ±0.8% Accurate Battery Regulation Voltage
  • Low Dropout: 98% Duty Cycle
  • Safely Precharges Near-Dead Cells
  • Continuous Voltage and Temperature Monitoring
  • < 1µA Shutdown Battery Current
  • Input Voltage Up to +28V
  • Safety Timer Prevents Overcharging
  • Input Current Limiting
  • Space-Saving 28-Pin QSOP
  • 300kHz PWM Oscillator Reduces Noise
  • 90% Conversion Efficiency


  • Desktop Cradle Chargers
  • Handheld Instruments (PDAs, Palmtops)
  • Li+ Battery Packs
  • Notebook Computers
Part Number Lithium Ion Cells Protected VIN
Charging VIN
Charge Rate Set by Max. ICHG
Charge Termination Charge Regulation Oper. Temp.
Package/Pins Budgetary
max max See Notes
28 28 Resistor 4 Timer Switchmode -40 to +85
$2.86 @1k
See All Battery Chargers (75)
Pricing Notes:
This pricing is BUDGETARY, for comparing similar parts. Prices are in U.S. dollars and subject to change. Quantity pricing may vary substantially and international prices may differ due to local duties, taxes, fees, and exchange rates. For volume-specific and version-specific prices and delivery, please see the price and availability page or contact an authorized distributor.

MAX1737EVKIT: Evaluation Kit for the MAX1737

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