This part is a kind of semiconductor called 78D09.

Function of this product has 3-TERMINALS 0.5A POSITIVE VOLTAGE REGULATOR.

Manufacturers : Unisonic Technologies

Image and pinout :

Some of the text within the PDF file :

UNISONIC TECHNOLOGIES CO., LTD 78DXX LINEAR INTEGRATED CIRCUIT 3-TERMINALS 0.5A POSITIVE VOLTAGE REGULATOR  DESCRIPTION The UTC 78DXX family is monolithic fixed voltage regulator integrated circuit. They are suitable for applications that required supply current up to 0.5 A.  FEATURE * Output Current Up To 0.5 A * Fixed Output Voltage Of 5V, 6V, 8V, 9V, 12V, 15V, 18V and 24V Available * Thermal Overload Shutdown Protection * Short Circuit Current Limiting * Output Transistor SOA Protection 11 SOT-223 TO-251 1 TO-252 1 TO-252-3  ORDERING INFORMATION Ordering Number Lead Free Halogen Free - 78DXXG-AA3-R 78DXXL-TM3-T 78DXXG-TM3-T 78DXXL-TN3-R 78DXXG-TN3-R 78DXXL-TNA-R 78DXXG-TNA-R Note: 1. XX: Output Voltage, refer to Marking Information 2. Pin Code: I: Input G: [ ... ]

78D09 PDF Datasheet Download