The MB39A119 is the N-ch MOS drive of the synchronous rectification type DC/DC converter IC using pulsewidth modulation (PWM) type that can charge Li-ion battery from 1 cell to 4 cells and suitable for down-conversion. This IC integrates built-in comparator for the voltage detection of the AC adapter and switches the power supply to the AC adapter or battery automatically, enabling supply it to system. In addition, the constant voltage control state detection function is built in, which prevents mis-detecting the full charge. The MB39A119 provides a wide range of power supply voltage and low standby current, high efficiency, making it ideal for use as a built-in charge device in products such as notebook PC.