This part is a kind of semiconductor called AP1533.

Function of this product has PWM CONTROL 1.8A STEP-DOWN CONVERTER.

Manufacturers : Diodes Incorporated

Image and pinout :

Some of the text within the PDF file :

AP1533 PWM CONTROL 1.8A STEP-DOWN CONVERTER Features • • • • • • • • • • Input voltage: 4V to 23V Output voltage: 0.8V to VCC Output current: 1.8A up to peak 2A Duty ratio: 0% to 99% PWM control Oscillation frequency: 300KHz typ. Soft-start like, Current limit and Enable function Thermal Shutdown function Built-in internal SW P-channel MOS SOP-8L: Available in “Green” Molding Compound (No Br, Sb) Lead Free Finish / RoHS Compliant (Note 1) General Description AP1533 consists of step-down switching regulator with PWM control. These devices include a reference voltage source, oscillation circuit, error amplifier, internal PMOS. AP1533 provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is a [ ... ]

AP1533 PDF Datasheet Download