This part is a kind of semiconductor called FR9808.

Function of this product has 500KHz Synchronous PWM-Buck DC/DC Converter.

Manufacturers : Fiti

Image and pinout :

Some of the text within the PDF file :

fitipower integrated technology lnc. FR9808 85T 21V, 4A, 500KHz Synchronous PWM-Buck DC/DC Converter Description FR9808 is a high-efficiency synchronous step-down DC/DC converter that employs a special process technique to obtain very low RDS(ON) for the internal metal–oxide–semiconductor field-effect transistor (MOSFET). The input operation voltage is in a wide 4.75V to 21V, and continuous load current capability is 4A. Control circuit is designed by a particular current mode which provides fast transient response and eases loop stabilization. This product has a very low standby current less than 1μA in shutdown mode. When the EN/SYNC pin voltage is less than 0.4V, FR9808 will turn off. Fault protection includes over current protection (OCP), under voltage lockout protection (UVLO) [ ... ]

FR9808 PDF Datasheet Download