The NCP1511 step-down PWM DC-DC converter is optimized for portable applications powered from 1-cell Li-ion or 3-cell Alkaline/NiCd/NiMH batteries. This DC-DC converter utilizes a current-mode control architecture for easy compensation and better line regulation. It also uses synchronous rectification to increase efficiency and reduce external part count. The NCP1511 optimizes efficiency in light load conditions when switched from a normal PWM mode to a "pulsed switching" mode. The device also has a built-in oscillator for the PWM circuitry, or it can be synchronized to an external 500 kHz to 1000 kHz clock signal. Finally, it includes an integrated soft-start, cycle-by-cycle current limiting, and thermal shutdown protection. The NCP1511 is available in a chip scale package.