This part is a kind of semiconductor called AX3113A.

Function of this product has PWM Control 2A Step-Down Converter.

Manufacturers : AXElite

Image and pinout :

Some of the text within the PDF file :

AX3113A PWM Control 2A Step-Down Converter  GENERAL DESCRIPTION AX3113A consists of step-down switching regulator with PWM control. These devise include a reference voltage source, oscillation circuit, error amplifier, internal PMOS and etc. AX3113A provides low-ripple power, high efficiency, and excellent transient characteristics. The PWM control circuit is able to the duty ratio linearly form 0 up to 100%. An enable function, an over current protect function and short circuit protect function are built inside, and when OCP or SCP happens, the operation frequency will be reduced. Also, an internal compensation block is built in to minimum external component count. With the addition of an internal P-channel Power MOS, a coil, capacitors, and a diode connected externally, these ICs can [ ... ]

AX3113A PDF Datasheet Download