Jinx wrote...

>What I don't understand is that these are parallel cut crystals,
>the type I use all the time with micros (which require parallel
>cut), yet the series circuit seems to work so much better

I'm no expert on crystal oscillators; so I could be wrong here.  But
AFAIK there isn't anything structurally different between "parallel"
resonant and "series" resonant crystals; all crystals have parallel and
series resonant frequencies, as I understand it, and a particular unit
is defined as parallel or series simply because that's the resonant mode
that'll give you the frequency that's marked on the can. =20

Either mode will "work" but only the mode specified will give the right
frequency.  The series mode resonance and parallel mode resonant
frequencies may be very close together.  I think.

In any case, there's a good application note at Fairchild, "HCMOS
Crystal Oscillators", at=20

   http://www.fairchildsemi.com/an/AN/AN-340.pdf

which might be worth a read.

Need more coffee...

Cheers,

Dave

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