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PotatoMania / uconsole-cm3

Now you can put RPi CM3/CM4S in uConsole and run ArchLinux! Support CM3, CM4(S) in uConsole.
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CM3: Internal 5V boost circuit stays enabled after shutdown #1

Open PotatoMania opened 7 months ago

PotatoMania commented 7 months ago

Internal 5V boost circuit won't be turned off after powering off when using CM3L+ with uConsole motherboard. The noise produced by the boost circuit may be heard after opening the case.

The problem probably because CM3(CM3L+ in my case) feeds power back to SYS_3V3, which causes it having a voltage of approximately 0.9V to 1.6V, depending on the situation. Neither CM3L+ nor motherboard will consume the energy fast enough. TPS61178 needs voltage lower than 0.4V on EN to turn itself off, while 0.9V on SYS_3V3 will produce 0.9V / (10K + 68K) * 68K ~= 0.78V, which is not sufficiently low.

By shorting SYS_3V3 to GND, the capacitors drained, and SYS_5V goes to 0V. Popping out the CM3 module also reset the circuit.

Extending the active time after powering off the PMU doesn't resolve this issue.

This issue is not observed when using R01 core module.

PotatoMania commented 6 months ago

Changing R106 from 10K to 120K seems to resolve the issue. R01 core also works after the modification.