BQ24079: Design review + short circuit protection

Hi Prithvi,

For your schematic, everything looks good! You've got all the necessary capacitors that we recommend and any resistor programmable pins are configured according to what you've got on the schematic. For the layout, I believe everything looks good. You've got thick traces for power/current. The only thing that I'm taking note of is the 90 degree trace on the BACKUP trace connecting to BAT. It looks like you've got the space to make it more of an angled connection. 90 degree connections I believe generally aren't recommended as there can be arcs at high voltages or dielectric breakdowns. 

Edit: What is the reason for the P-channel MOSFET for the battery? Internally, we have a FET that connects the OUT pin and the BAT pin that is controlled by SYSOFF. This may seem a bit redundant to have in the schematic. 

As for the heat issue where does the short occur? From your connections, it sounds like it'd be at the OUT pin. If the short is causing it to pull a lot of current from the input and battery, this can cause the device to heat up. If the temperature is exceeding 150C limit we've got for the junction temperature limit, this can definitely be an issue. 

The first suggestion is to diagnose why the STM MCU is causing the short when it gets damaged. Avoiding the short is the easiest way to avoid the heat issue.

The second possibility would be to lower the currents that you've already got programmed for the charging portion. If this heat is due to high power loss causing temperature, reducing the power flowing through the device can  potentially be a path to reduce the temperature increasing. But this would not solve the problem of your STM 32H7 MCU being the problem if it is, as you say, creating the short when it gets damaged. 

From a schematic and layout point of view, everything should be working fine regarding the BQ24079. If you are seeing the proper current when the battery is being charged, the BQ24079 is working according to what you have.