This part is a kind of semiconductor called FP5138B.

Function of this product has Non-Synchronous PWM Boost Controller.

Manufacturers : Feeling Technology

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FP5138B Non-Synchronous PWM Boost Controller General Description The FP5138B is a boost switching regulator controller IC for battery-used applications. The FP5138B includes a totem-pole output stage for driving NPN transistor or N-MOS, high precision reference (0.5V) for comparing output voltage by feedback amplifier, precision maximum duty cycle control, programmable soft start with short circuit protection function and operating mode control between operation and standby mode. Features  Wide Supply Voltage Operating Range: 1.8 to 15V  Reference Voltage Precision: 2%  Low Current Consumption: 5.5mA in Operation Mode  Low Current Consumption: 1μA in Standby Mode  High Oscillator Frequency: 1MHz max.  Programmable Soft Start Function (SS)  Short Circuit Protection F [ ... ]

FP5138B PDF Datasheet Download