16MHz Crystal Oscillator and external capacitor value

[Bbrotherone]

Hi.

I am trying to choose the crystal and external capacitor for nRF51822-QFAA-LDO. I found the crystal with load capacitance 10pF. As mentioned in reference paper, 

C1 = C2 = 2Cl - C_pcb - C_pin

Cl: Load capacitance of the crystal (found in the crystal datasheet)

C_pcb + C_pin is approximately 4~6 pF.

so, C1 = (2*10)-6 = 14pF or 16pF

Would it be any problem to use the crystal with 10pF load capacitance and two external capacitor with 14pF capacitance?

Thanks.

[Kaja]

Hi,

C_pcb + C_pin is approximately 4pF, see our design guidelines  or the PS, page 41. 

So optimal load capacitors value would be 16 pF, but this is a value that you also can tune, to get good enough crystal accuracy. 
Using 14 pF, will probably be fine, you just have to check the frequency offsets. 

For more information on crystal design considerations and how to measure crystal accuracy, see our white paper: Crystal Oscillator

Best regards,
Kaja