This part is a kind of semiconductor called AT1312B.

Function of this product has High Efficiency Constant Current White-LEDs Driver.

Manufacturers : Aimtron Technology

Image and pinout :

Some of the text within the PDF file :

AT1312A/B/C Preliminary Product Information High Efficiency, Constant Current White-LEDs Driver Feature Description The AT1312A/B/C step-up converter drives white •Operating Voltage:2.5V to 6.0V. LEDs with a constant current to provide backlight in •High Operating Frequency: 1MHz cell phones, PDAs, and other hand-held devices. It •High Output Voltage: Up to 16V/23V/28V features allowing series connection of the white LEDs so that the LED currents are identical for •Shutdown Current <1µA uniform brightness. An enable input can be pulsed •16V/23V/28V Output Over-Voltage Protection repeatedly to adjust LED’s brightness. The fast 1.0 •Digital Dimming Control. MHz current-mode PWM control allows for smaller capacitor and inductor. Fault condition protection [ ... ]

AT1312B PDF Datasheet Download