This part is a kind of semiconductor called APL1084.

Function of this product has 5A Low Dropout Fast Response Positive Adjustable Regulator and Fixed 3.3V.

Manufacturers : Anpec Electronics

Image and pinout :

Some of the text within the PDF file :

The APL1084 is a low dropout three-terminal adjustable regulator with 5A output current capability. In order to obtain lower dropout voltage and speed up transient response, which is critical for low voltage applications, the APL1084 has been optimized. The output available voltage range of adjustable version is from 1.25 to 5.75V with an input supply below 7V, and the fixed 3.3V output voltage device is also available. Current limit is trimmed to ensure specified output current and controlled shortcircuit current. On-chip thermal limiting provides protection against any combination of overload that would create excessive junction temperatures. The APL1084 is available in both the through-hole and surface mount versions of the industry standard 3-pin TO-220, TO-252, and TO-263 power packages.

Features: 

l Fast Transient Response l Guaranteed Dropout Voltage at Multiple Currents l Load Regulation: 0.05% Typ. l Line Regulation: 0.03% Typ. l Low Dropout Voltage: 1.3V Typ. at IOUT = 5A l Trimmed Current Limit: 5A Typ. at TJ =125 °C l On-Chip Thermal Limiting: 150°C Typ. l Standard 3-pin TO-220, TO-252, and TO-263 Power Packages l Lead Free and Green Devices Available (RoHS Compliant)
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APL1084 PDF Datasheet Download