This part is a kind of semiconductor called SI2305.

Function of this product has P-Channel Enhancement Mode Field Effect Transistor.

Manufacturers : MCC

Image and pinout :

Some of the text within the PDF file :

MCC TM Micro Commercial Components
  omponents 20736 Marilla Street Chatsworth    !"# $ %    !"# SI2305 • • • • • • • • Features Halogen free available upon request by adding suffix "-HF" Epoxy meets UL 94 V-0 flammability rating Moisture Sensitivity Level 1 TrenchFET Power MOSFET Load Switch for Portable Devices DC/DC Converter SOT-23 Package Marking Code: S5 P-Channel Enhancement Mode Field Effect Transistor SOT-23 A D Maximum Ratings @ 25OC Unless Otherwise Specified Symbol VDS ID IS VGS PD RθJA TJ TSTG Parameter Drain-source Voltage Continuous Drain Current Continuous Source-Drain Diode Current Gate-source Voltage Total Power Dissipation Thermal Resistance Junction to Ambientb Operating Junction Temperature [ ... ]

SI2305 PDF Datasheet Download