Q1403 "The Mosfet"

This component is the mosfet that connects battery power and main power---this component can fail from knockoff charger usage and is part of the "full monty" repair of replacing tristar, tigris, and the mosfet after a charging system failure. There are a few other mosfets on iPhone logic boards, but this is the common one.

iPhone 5s: Q4

iPhone 6/6+: Q1403