This part is a kind of semiconductor called SI-3122V.

Function of this product has 3-Terminal/ Low Dropout Voltage Dropper Type.

Manufacturers : Sanken electric

Image and pinout :

Some of the text within the PDF file :

qSI-3000V Series SI-3000V Series 3-Terminal, Low Dropout Voltage Dropper Type sFeatures • • • • TO-3P package 3-terminal regulator Output current: 2.0A Low dropout voltage: VDIF≤1V (at IO=2.0A) Built-in foldback overcurrent protection circuit sApplications • For stabilization of the secondary stage of switching power supplies • Electronic equipment sAbsolute Maximum Ratings Parameter DC Input Voltage DC Output Current Power Dissipation Junction Temperature Ambient Operating Temperature Storage Temperature Thermal Resistance (junction to case) Symbol SI-3052V VIN IO PD1 PD2 Tj Top Tstg Rth(j-c) 25 2.0 50(TC=25°C) 1.6(Without heatsink, stand-alone operation) –30 to +125 –20 to +100 –30 to +125 2.0 Ratings SI-3122V/3152V 30 V A W W °C °C °C °C/W Unit (Ta=25°C) [ ... ]

SI-3122V PDF Datasheet Download