The MAX1737 is a switch-mode lithium-ion (Li+) batterycharger that charges one to four cells. It provides areregulated charging current and a regulated voltagewith only a ±0.8% total voltage error at the battery terminals.The external N-channel switch and synchronousrectifier provide high efficiency over a wide input voltagerange. A built-in safety timer automatically terminatescharging once the adjustable time limit has beenreached.
The MAX1737 regulates the voltage set point and chargingcurrent using two loops that work together to transitionsmoothly between voltage and current regulation. Anadditional 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 tofour 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-pinQSOP package. Use the evaluation kit (MAX1737EVKIT) to help reduce design time.

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