3.3V Regulator Checks
The IC just above the audio IC (labelled ENxx), is the 3.3V regulator.
The EN chip receives the VSYS power (from the BQ24193 chip). It outputs 3.3V when working.
It has an output limit of about 150mA, so if something on the 3.3V rail is shorting out, you will not see a dead-short current draw.
Testing For Shorts
If there is a short on the 3.3V rail, the output would be 0.5V or less for example, so it may not be a faulty regulator.
To test for shorts on 3.3V rail, solder a wire to ground, and a wire to the 3.3V out capacitor or test pad and use your bench power supply to inject 1V into the rail. If it draws more than 0.1A then you likely have a short somewhere on a component connected to the rail.
Use a thermal camera or IPA fluid or a resin pen to look for the shorts.
Components connected to the 3.3V Rail
These are the current known components that are connected to the 3.3V rail and could be shorting it out.
- Bluetooth/WiFi Module
There may be more components so far unconfirmed such as eMMC and smaller regulators that are connected to this rail too. I will update this list as I confirm them.
