Atmega32u4 Crystal Question

Other Hardware 3rd Party Boards
1

I am working on a project with an embedded 32u4 and was using the Adafruit 32u4 breakout as an example. I was wonder about the crystal load capacitors. The schematic has 2 18pf capacitors and the only crystals on digi-key that are the same need 8pf. I know you have to account for other stray and pin capacitances but I wanted to make sure this was right. I also would assume it is worth the little extra for the 30\20ppm instead of the 50\50ppm?

Here is one of them from digi-key

Here is the board from Adafruit,

I plan on this being basically a embedded leonardo.

Thanks

2

I think you take the two capacitors value in series + strays to determine the actual load capacitance that the crystal sees, so 2 18pf = 9 pf, so close enough.

Lefty

3

Thanks, I feel better. I was pretty sure it was right.