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

[Kiyoshi Iwai]

Hello Kenneth,

Thank you for your advice.

1. I need to modify the software.  So it takes a little bit time to check it.

  But I should use softdevice on real product, if ADC without softdevice will work

  normally, I could not apply it.  It will be in vain,I think.

2. I already checked 5 devices and 4 in 5 have same failure.

3. I stopped all peripheral things and checked again. The result was same.

4. I already use external 32kHz crystal.   I was surprised to hear that, does the LFCLK concern ADC?

  I think ADC is operated by HFCLK only, right or not?

5. It's a little difficult to measure it, but I will try

regards,

Kiyoshi Iwai