Is it possible that AP3400 is AO3401 ?
according to this description:
The AO3400 combines advanced trench MOSFET technology with a low resistance package to provide extremely low RDS(ON). This device is suitable for use as a load switch or in PWM applications. The opposite P channel Mosfet is AO3401.
DATASHEET: http://www.aosmd.com/pdfs/datasheet/AO3400.pdf