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PP3V42_G3H takes power from either the DC in or battery through a three legged SOT dual diode. It creates 3.42V from either source. It is used to power the circuits needed to create the S5 power rail. The SMC and inrush/charging circuits use PP3V42_G3H as does the one-wire circuit. Without this rail you will not get a charger light. Check this first if you have no charger light with an OEM charger.


Check for a short to ground on the output side of this power rail after the inductor. If there is a short you can inject voltage to find the component that gets hot.

If there is no short test the input and SHDN pins. The SHDN pin is fed through a resistor from VIN. After that test all the passive components around the buck converter. The voltage divider between output, feedback, and ground is used to keep the output as close to 3.42V as possible. If either resistor is out of spec, the voltage will be off.

If everything looks good, replace the chip.