Quote Originally Posted by Darrel Taylor
... The PLL's VCO always runs at 96mhz. And the crystals frequency is always divided down to 4mhz for the PLL reference. So in effect, the frequency of the crystal doesn't matter, only it's tolerance....

DT
I noticed the division part, that makes a lot of sense. I just didn't know if there were other factors that would make a performance difference. So now I know that the tolerance is really what I'm concerned with when I'm selecting crystals.

I'll probably stick to 20 MHz components 'cause I've got lots in stock and I use them in other projects. But it is good to know that a 4 MHz crystal can be just as good for a 18F USB application.

Thanks guys!

Robert