Unable to recover nRF5340 flashed with invalid DCDC configuration

[timonsku]

I have a nRF5340 module from Fanstel that was flashed with a firmware where the DCDC weren't disabled.
The board does not have the necessary inductors for the DCDC to work (nor does it expose the pins) and the nRF53 is now in a constant power on reset loop.

There are several related issues like
Unable to recover a nrf5340 MCU after first flash on a custom board using nrf5340 DK
and
Unable to recover nrf5340 after flashing nrf9160 code on it. 

Unfortunately the tip with running nrfjprog --recover -f nrf53 in a loop did not work so far after having it do a few hundred tries.
Is there any lower level way that can be used to recover an device from an invalid power configuration or do I generally risk soft bricking a board with those settings?

The brute force solution is of course to transplant the module to a board with the DCDC setup but I would really like to avoid rework on this particular board if not absolutely necessary.

[Susheel Nuguru]

You can still directly power Dec4 with 1.3V. When you have wrong setting for DCDC, then the failing DCDC regulator fails to output 1.3V to DEC4 which is the main supply to the nRF chip. If you supply 1.3V directly to DEC4 then it should bring the chip out of reset mode and you can reflash the firmware with DCDC disabled. 

This ofcourse needs the Dec4 to be exposed externally. Not sure if that is the case in Fanstel module? If it is not exposed, then it is difficult to bring the chip out of that reset loop.

[timonsku]

The docs give no reference to a DEC4. There is DECA/D/N/R. Some of which are exposed on the module but not the PCB in this case. Though for the future it would be good to know which DECx supplies this so that it can be broken out as a testpoint on R&D PCBs.

[Susheel Nuguru]

timonsku said:

Though for the future it would be good to know which DECx supplies this so that it can be broken out as a testpoint on R&D PCBs.

You are right, searching for more info on DEC4 on public docs does not give any hits. I will take this input and pass to the engineers. Some external blog mentions this but they found by probing the DEC4 and not from our docs. Feedback taken.

[timonsku]

Ah yea that blog mentions the nRF52840 there is a DEC4 but on nRF53 that I'm working with has different naming for the power related pins.

[timonsku]

I think there is just a mixup here?

Terminologies seem to just have changed between the nRF52 and nRF53?

In any case if one of the engineers could give a pointer as to how to best recover the nRF53 from this situation or which power pin would be needed as a minimum to briefly keep it alive for a reflash that would be helpful for the future and probably also helpful as an app note.