oscillation at the embed analog front end circuits of SAADC in nRF52832

[Kiyoshi Iwai]

Hello,

I found the strange phenomena on nRF52832.

By using the SAADC, I have some noise on ADC Data only at a certain temperature range.

Temperature range is depend on individual IC.

I might be the circuit oscillation at analog front end of SAADC, I think.

(internal reference voltage or op amp etc,)

I tried to switch DCDC on/off, but there's no difference on phenomena.

Anyone can resolve it?

I attach the files of real data and measurement condition.

Best regards,

Kiyoshi Iwai

3426.SAADC_noise_devzone.zip

[Kenneth]

Hi, I am not sure how we best should proceed here. It is strange that STATE is not running. I think my recommendation is:

1. Try to use the ADC without softdevice enabled, to check if you can observe the same.

2. Check if you can see the same on more than 1 chip.

3. Make sure you don't have any other peripheral running that may interfere here.

4. What LFCLK source are using when enable softdevice? Try to use an external 32kHz crystal.

5. Measure current consumption when the issue occurs, to see if there is any variations in current consumption that could affect voltage levels somehow.

If you can't find any specific issue, maybe you can send us your hardware so I may repeat the measurements here?