Oscillator capacitor values

Ouroborus · Post by **Ouroborus** » Fri Mar 14, 2008 9:18 pm

The crystal's associated pair of capacitors are usually listed as 27p but the Atmel docs usually recommend 12-22p. I'm not really clear on how to pick values for these caps to begin with. If I had to guess, the higher values have to do with using 3.3V rather than 5V. Is that the reason for the difference in values? Is it something else?

For reference, the caps I'm talking about are C2 & C3 on the schematic at http://www.obdev.at/products/avrusb/index.html and are C1 & C2 on the schematic at http://www.obdev.at/products/avrusb/hidkeys.html.

Post by **christian** » Mon Mar 17, 2008 12:10 am

There's no particular reason for these values. This are the values I have on stock. Since I never had a problem with a wide range of capacitor values, I just use these.

Ouroborus · Post by **Ouroborus** » Fri Mar 21, 2008 4:03 pm

Ah, then I guess these values aren't particularly critical. Well, that's good to know, thank you.