Stand-Alone, Switch-Mode Li+ Battery Charger with Internal 14V Switch

Active: In Production.

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.

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