This part is a kind of semiconductor called XL1509.
Function of this product has 2A 150KHz 40V Buck DC to DC Converter.
Manufacturers : XLSEMI
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Some of the text within the PDF file :
Datasheet 2A 150KHz 40V Buck DC to DC Converter Features n n n n n XL1509 General Description The XL1509 is a 150 KHz fixed frequency PWM buck (step-down) DC/DC converter, capable of driving a 2A load with high efficiency, low ripple and excellent line and load regulation. Requiring a minimum number of external components, the regulator is simple to use and include internal frequency compensation and a fixed-frequency oscillator. The PWM control circuit is able to adjust the duty ratio linearly from 0 to 100%. An enable function, an over current protection function is built inside. When second current limit function happens, the operation frequency will be reduced from 150KHz to 50KHz. An internal compensation block is built in to minimize external component count. Wide 4.5V to 40V Input [ ... ]