This part is a kind of semiconductor called AIC1731.

Function of this product has Low Dropout Linear Regulator.

Manufacturers : Analog Intergrations Corporation

Image and pinout :

Some of the text within the PDF file :

AIC1731 300mA, Low Dropout Linear Regulator with Shutdown FEATURES Active Low Shutdown Control. Very Low Quiescent Current. Very Low Dropout Voltage of 470mV at 300mA Output Current (3.0V Output Version) 1.5V, 1.8V, 2.5V, 2.8V, 3.0V, 3.3V Output Voltage. Short Circuit and Thermal Protection. ±2% Output Tolerance. Miniature Package: SOT-23-5 DESCRIPTION AIC1731 is a 300mA low noise, low dropout linear regulator, and is housed in small SOT-23-5 package. The device is in the “ON” state when the SHDN pin is set to logic high level. An internal P-MOSFET pass transistor is used to achieve 470mV low dropout voltage at 300mA load current. It offers high precision output voltage of ±2%. The quality of low quiescent current and low dropout voltage makes this device ideal for battery power ap [ ... ]

AIC1731 PDF Datasheet Download