--- In LTspice@..., "Al Williams" <alw@a...> wrote:
I was playing with pierce.asc -- as far as I can remember, this was
a sample provided with the program (I think).
Doing a transient analysis on it shows that it oscillates at 21.114
MHz. Why is that? The quasi-crystal has L=.1, Rs=600, Cs=1.75fF,
Cp=5pF.
The series resonance should be 1/(2pi*sqrt(L*Cs))
Parallel resonance should be 1/2pi*sqrt(L*Cx))
where Cx=(Cs*Cp)/(Cs+Cp)
So Cx=1.749fF (almost no difference from Cs) and
Fs=12.031MHz
Fp=12.033MHz
External components might pull the crystal, but not to that extent.
So is this a spice problem where other components are moving the
resonant frequency even though in real life it would not? Or am I
missing something obvious?
Hello Al,
please post your circuit *.asc file and the subcircuit models if any
used. I have simulated crystal oscillators in the past and they did
run at the crystal frequency. Be aware of very long startup times.
Best Regards
Helmut
