Unable to recover nRF5340 flashed with invalid DCDC configuration

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

Simonr — Thu, 14 Mar 2024 12:23:00 GMT

Hi Timon

Thank you for your feedback, but I don't think this will be changed in the SDK. The DCDC is enabled by default to showcase optimized power consumption in our sample projects by default. And since our samples generally are for the Development Kits, where the DCDC components are mounted, that will be what we're testing for. I think this will stay as an opt-out thing.

Best regards,

Simon

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

timonsku — Wed, 13 Mar 2024 17:31:27 GMT

Oh, one thing that would help is if the DCDC is not enabled by default in nRF Connect. It seems the Nordic DK's work with any configuration.
My issue was that I only provided my own overlay for a sample code but did not add the KConfig options to disable the DCDC. My assumption would typically be that optional internal regulators are opt-in options and not opt-out.

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

timonsku — Wed, 13 Mar 2024 15:23:06 GMT

Thanks for that info Susheel! That helps with future designs.

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

Susheel Nuguru — Tue, 12 Mar 2024 07:46:27 GMT

Sorry for the mixup Timon, I continued to give you info for the nRF52.

Now coming back to the details on nRF5340,

The idea is that the DCDC inductor is missing, so it can not power the corresponding DEC pin (supply output pin), similar to your case.

On the 53 series you have DCDC inductors for DECD which is on the application core side, and you also have DCDC inductors for DECR which is on the network core side. Since it is the application it self that enables the DCDC, I assume it is enough to power the application supply externally (DECD) in order to flash a new application firmware that does not enable DCDC, One think we are not entirely sure is that maybe both DECD and DECN has to be powered if DCDC is enabled on both domains, and inductors are missing on both domains

It's a good idea to have a current limiter on the external supply at 20 mA ish, to protect the regulator

So in short try powering both DECD (and DECN just to be sure to power modem aswell) to bring the chip out of the non responsive state that occurred by enabling DCDC in firmware without necessary inductors for DCDC to work.

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

timonsku — Fri, 08 Mar 2024 15:00:33 GMT

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.

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

Susheel Nuguru — Fri, 08 Mar 2024 10:09:20 GMT

[deleted]

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

timonsku — Tue, 05 Mar 2024 18:55:21 GMT

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.

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

Susheel Nuguru — Tue, 05 Mar 2024 07:57:24 GMT

[quote user="DiodesDelight"] 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.[/quote]

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.

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

timonsku — Mon, 04 Mar 2024 18:01:01 GMT

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.

RE: Unable to recover nRF5340 flashed with invalid DCDC configuration

Susheel Nuguru — Mon, 04 Mar 2024 12:44:07 GMT

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.