The AP2008 integrates Pulse-Width-Modulation (PWM) control circuit into a single chip, mainly designs for power-supply regulator. All the functions included an on-chip 0.77V reference output, an error amplifier, an adjusted oscillator, a soft-start, UVLO, SCP circuitry, and a push-pull output circuit. Switching frequency can be adjustable by trimming CT. During low VCC situation, the UVLO makes sure that the outputs are off until the internal circuit is operational normally.