The RT8010B is a high-efficiency Pulse-Width-Modulated (PWM) step-down DC-DC converter. Capable of delivering 800mA output current over a wide input voltage range from 2.5V to 4V, the RT8010B is ideally suited for portable electronic devices that are powered from 1-cell Li-ion battery or from other power sources such as cellular phones, PDAs and hand-held devices. Two operating modes are available including PWM/LowDropout autoswitch and shut-down modes. The internal synchronous rectifier with low RDS(ON) dramatically reduces conduction loss at PWM mode. No external Schottky diode is required in practical application. The RT8010B enters Low-Dropout mode when normal PWM can not provide regulated output voltage by continuously turning on the upper PMOS. The RT8010B enters shut-down mode and consumes less than 0.1A when EN pin is pulled low.