High power consumption during sleep (caused by ADC probably)

RE: High power consumption during sleep (caused by ADC probably)

Golaz — Wed, 19 Feb 2025 10:01:37 GMT

This seems to be the solution.
We have tested it for a week and the glitch did not appear.
Thank you.

RE: High power consumption during sleep (caused by ADC probably)

Golaz — Tue, 04 Feb 2025 12:03:21 GMT

Thank you very much. Will do. I wil let you know in a couple of days.

RE: High power consumption during sleep (caused by ADC probably)

Kenneth — Tue, 04 Feb 2025 11:57:24 GMT

Hello,

After some discussion internally, we think this may be your problem:
https://docs.nordicsemi.com/bundle/errata_nRF52840_Rev3/page/ERR/nRF52840/Rev3/latest/anomaly_840_246.html

Can you try the workaround and see if that fixes the issue?

Kenneth

RE: High power consumption during sleep (caused by ADC probably)

Golaz — Tue, 04 Feb 2025 09:56:39 GMT

We ran some additional tests and have noticed that this issues seems to appear only when radio and ADC events are aligned. Even with the proposed fix in OP.
In the image I posted in a separate reply, radio events are those large 15mA spikes and ADC events are small 5mA spikes. Both events are normally set to occur periodically with 1 sec period.

For a test we set ADC conversion to periodically occur at 1.17 sec and radio communication at 1 sec. When this was set we did not see any power consumption glitches in the span of 4 days.
This indicates to us that the glitch happens when radio and ADC are triggered at very close (maybe exactly) time intervals relative to each other. Because of our lack ot debug capabilities we could not determine what the exact condition is, which event has to occur first and what their relative timing is.

Kenneth Do you have any ideas why this would happen and how we can further debug this issues?
Also note that we have very similar code (same ADC and RTC) running on a different product and we never noticed this issue there. The difference there is that that code does not use FreeRTOS but is baremetal.

RE: High power consumption during sleep (caused by ADC probably)

Golaz — Fri, 24 Jan 2025 07:56:44 GMT

The issue seems to still not 100% resolved (see image).
Time between two CPU wake events is 1sec.
In this particular case radio event (20mA spike) seems to have aligned perfectly with ADC conversion. Like I already mentioned in OP, there seems to be some issue with IRQ timing.
This may not be the exact case since here the static current draw is ~560uA.

With proposed fix 1 glitch occured in 16h span. So this is manageable.

RE: High power consumption during sleep (caused by ADC probably)

Kenneth — Thu, 23 Jan 2025 18:27:57 GMT

Hi,

I am glad to hear that you have found a workaround, not entirely sure what was the root cause here, but for anyone else finding this post the errata mentioned is found here:
https://docs.nordicsemi.com/bundle/errata_nRF52840_Rev3/page/ERR/nRF52840/Rev3/latest/anomaly_840_241.html#anomaly_840_241

And a link to the description of the SAADC here:
https://docs.nordicsemi.com/bundle/ps_nrf52840/page/saadc.html#ariaid-title7

Kenneth