This part is a kind of semiconductor called 3843AN.

Function of this product has UC3843AN.

Manufacturers : Fairchild Semiconductor

Image and pinout :

Some of the text within the PDF file :

www.fairchildsemi.com UC3842A/UC3843A SMPS Controller Features • • • • • • • Low Start Current 0.2mA (typ) Operating Range Up To 500KHz Cycle by Cycle Current Limiting Under Voltage Lock Out With Hysteresis Short Shutdown Delay Time: typ.100ns High Current Totem-pole Output Output Swing Limiting: 22V Description The UC3842A/UC3843A are fixed PWM controller for OffLine and DC to DC converter applications. The internal circuits include UVLO, low start up current circuit, temperature compensated reference, high gain error amplifier, current sensing comparator, and high current totem-pole output for driving a POWER MOSFET. Also UC3842A/ UC3843A provide low start up current below 0.3mA and short shutdown delay time typ. 100ns. The UC3842A has UVLO threshold [ ... ]

3843AN PDF Datasheet Download