General Description

AP1538 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS. AP1538 provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is able to vary the duty ratio linearly from 0 up to 99. This converter also contains an error amplifier circuit as well as a soft-start circuit that

prevents overshoot at startup. An enable function, an over current protect function and a short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced from 300KHz to 50KHz. Also, an internal compensation block is built in to minimum external component count.

Features

• Input voltage : 3.6V to 18V

• Output voltage : 0.8V to VCC

• Output current : up to 3A

• Duty ratio: 0 to 99 PWM control

• Oscillation frequency: 300KHz typical

• Soft-start like, Current limit and Enable function

• Thermal Shutdown function

• Built-in internal SW P-channel MOS

• SOP-8L and SOP-8L-DEP: Available in “Green” Molding Compound (No Br, Sb)

• Lead Free Finish / RoHS Compliant

Applications

• PC Motherboard

• LCD Monitor

• Graphic Card

• DVD-Video Player

• Telecom Equipment

• ADSL Modem

• Printer and other Peripheral Equipment

• Microprocessor core supply