This part is a kind of semiconductor called 2SK3891-01R.

Function of this product has Power MOSFET.

Manufacturers : Fuji Semiconductors

Image and pinout :

Some of the text within the PDF file :

2SK3891-01R N-CHANNEL SILICON POWER MOSFET Outline Drawings (mm) 200407 FUJI POWER MOSFET Super FAP-G Series Features High speed switching, Low on-resistance Low driving power, Avalanche-proof No secondary breakdown Applications Switching regulators UPS (Uninterruptible Power Supply) DC-DC converters Maximum ratings and characteristic Absolute maximum ratings (Tc=25°C unless otherwise specified) Item Drain-source voltage Continuous Drain Current Pulsed Drain Current Gate-Source Voltage Non-Repetitive Maximum Avalanche current Repetitive Maximum Avalanche current Non-Repetitive Maximum Avalanche Energy Repetitive Maximum Avalanche Energy Maximum Drain-Source dV/dt Peak Diode Recovery dV/dt Max. Power Dissipation Operating and Storage Temperature range Isolation Voltage Symbol V DS VDSX [ ... ]

2SK3891-01R PDF Datasheet Download