Crystal question

Hey all,

I've just been going on good faith on this, but was curious if anyone could point me to someplace that explains why the crystal oscillator needs those 2 22uf ceramic capacitors to function. I accidentally used 2 that were out of range and it literally stopped it dead (accidentally grabbed 2 22pf caps).

As always, thanks for clearing up any of my newbie confusion.

Thanks,

Y-aji

http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1824&appnote=en011973

Thanks. I got it figured out. If anyone reads this in the future, below is what I found.

One of the capacitors are a "phase adjusting" capacitor and also appear to help kind of kick-start the crystal at initial power up (which is probably why mine didn't work with such a low capacitance, it probably never built up enough charge to calibrate itself to a proper oscillation). This particular capacitor charged through the impedance of the crystal.

The other capacitor is a "gain adjusting" capacitor which increases the stability of the overall frequency at which the crystal oscillates.

Neat.

The only mystery left is that 22pF is approximately the correct capacitance for these, while 22 uF is impossibly too large a cap. Did you reverse which ones did and didn't work?

Maybe you also want to consult

and

Udo