This part is a kind of semiconductor called CN5611.

Function of this product has Low-Dropout High-Power LED Driver.

Manufacturers : CONSONANCE

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Some of the text within the PDF file :

CONSONANCE Low-Dropout High-Power LED Driver CN5611 General Description: The CN5611 current regulator operates from a 2.7V to 6V input voltage range and delivers a constant current that is up to 800mA to high-brightness LEDs, including high-brightness white LED. The LED current of CN5611 can be adjusted from 30mA to 800mA by using an external resistor. An on-chip pass element minimizes external components while providing ±8% output current accuracy. Additional features include over temperature protection, LED short and open protection. The CN5611 is available in a thermally enhanced 5-pin SOT89 package. Features:           Operating Supply Voltage Range: 2.7V to 6V On-chip Pass Element Low-Dropout Voltage Adjustable Output Current up to [ ... ]

CN5611 PDF Datasheet Download