Asymmetric load capacitors on nRF51422 32k crystal

[KariMa3]

Is it allowed to use nonsymmetric capacitors to get more accurate 32k ? With 2x10pF we run some 35ppm too fast and 2x12pF the clock is 10ppm slow. We could use non standard 11pF capacitors or use 10pF+12pF to get very accurate clock. Is there any recommendation on this ? It is recommended on reference to use symmetric but DevZone reply (15. Aug 2018/Joakim) for nRF52 to have 13pF+15pF as acceptable.

[Simonr]

Hi Kari

Yes, this should be fine. I'd suggest 11pF capacitors, as symmetrical capacitor values are the recommended option, but it should be fine using 10pf + 12pf as well if necessary. 

Best regards,

Simon

[KariMa3]

Hi Simon,

Thank's for quick answer. I continue testing with 10pF+12pF to get some statistical data.

Best Regards,

Kari