This part is a kind of semiconductor called APL431L.

Function of this product has Low Voltage Adjustable Precision Shunt Regulator.

Manufacturers : ANPEC

Image and pinout :

Some of the text within the PDF file :

APL431L Low Voltage Adjustable Precision Shunt Regulator Features General Description • Precise Reference Voltage to 1.24V • Guaranteed 0.5%, 1% or 1.5% Reference Voltage Tolerance • Sink Current Capability, 80uA to 100mA • Quick Turn-on • Adjustable Output Voltage, VO = VREF to 20V • Low Operational Cathode Current, 80µA Typical • 0.1Ω Typical Output Impedance • SOT-23-3, SOT-23-5, TO-92 and SOT-89 Packages • Lead Free and Green Devices Available (RoHS Compliant) Applications • Linear Regulators • Adjustable Power Supply • Switching Power Supply The APL431L is a 3-terminal low voltage adjustable precision reference with specified thermal stability over applicable commercial temperature ranges. Output voltage may be set to any value between VREF (1.24 V) and [ ... ]

APL431L PDF Datasheet Download