How to validate 32k crystal capacitor?

[Sam]

I am designing with nrf52832 and experiencing some connection issues at 0C. The system gets disconnected every few seconds with 32k crystal, but no issue with RC oscillator, so the issue should be related to the crystal. I confirmed the crystal meets the datasheet specs and changing the caps help. What's the best way or tool to validate the capacitor value? Right now I just changed the cap and put the system at different temp to check the connections for 30+ minutes (including soak time). Any other less time-consuming methods, e.g. toggling GPIO and measuring the frequency drift?

[Dave_couling]

For custom hardware its often best to get the parasitic capacitance of your PCB measure to verify that you have the correct loading capacitors (tuned to the expected value for that crystal)

[bjorn-spockeli]

Hi Sam,

I suggest that you take a look at the answer to this post.

Best regards

Bjørn

[Sam]

thanks. I found a cap that works across temperature with 500ppm setting on one device. Any actual validation I can do to confirm the crystal and its caps are correctly chosen besides checking the datasheet specs?

[bjorn-spockeli]

You will have to probe the XL1 and XL2 pins with an oscilloscope to verify that the crystal is oscilating at 32768kHz.