Choosing the right crystal capacitors

Other Hardware 3rd Party Boards
1

Hi :slight_smile:

I want to use these two crystals with two chips:

Googling the subject I know that crystal caps should be 2 x Cl - Cs with Cl = Crystal Load capacitance and Cs = stray capacitance.

I am assuming 3pF stray capacitance because this will be on a pcb and I will keep the crystals as close to the chips as possible.

My questions are:

  • Can you confirm the load capacitance of the crystals (the datasheet is really unclear about it so I am just looking at the value in the "description" on the website):

  • 16Mhz crystal: 9pF

  • 25Mhz crystal: 12pF

  • If these values are correct, are these a good value for crystal capacitors:

  • 16Mhz crystal: 15pF

  • 25Mhz crystal: 22pF (would 20 make a significant difference or is 22 ok?

Thank you!

2

(deleted)

3

Ok thanks I will not worry too much about it then. I only did because the previous crystal I was using was 20pF, now changing to 9pF I thought it was a big change I should take into account.

4

The "9pF" spec would most likely be for the series combination of the two caps (plus stray), so 2x18pF, ignoring trace capacitance.