This part is a kind of semiconductor called UC3842T.

Function of this product has (UC3842T - UC3845T) HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER.

Manufacturers : STMicroelectronics

Image and pinout :

Some of the text within the PDF file :

® UC3842T UC3843T UC3844T UC3845T HIGH PERFORMANCE CURRENT MODE PWM CONTROLLER . . . . . . . . . TRIMMED OSCILLATOR FOR PRECISE FREQUENCY CONTROL OSCILLATOR FREQUENCY GUARANTEED AT 250kHz CURRENT MODE OPERATION TO 500kHz AUTOMATIC FEED FORWARD COMPENSATION LATCHING PWM FOR CYCLE-BY-CYCLE CURRENT LIMITING INTERNALLY TRIMMED REFERENCE WITH UNDERVOLTAGE LOCKOUT HIGH CURRENT TOTEM POLE OUTPUT UNDERVOLTAGE LOCKOUT WITH HYSTERESIS LOW START-UP AND OPERATING CURRENT Minidip SO8 DESCRIPTION The UC384XT family of control ICs provides the necessary features to implement off-line or DC to DC fixed frequency current mode control schemes with a minimal external parts count. Internally implemented circuits include a trimmed oscillator for precise DUTY CYCLE CONTROL under vol [ ... ]

UC3842T PDF Datasheet Download