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Typical shunt capacitance of xtals

F

frank

Jan 1, 1970
0
Hello,

I am looking for a SMD 50MHz-60MHz crystal with low shunt capacitance.
On several online datasheets, I often encounter a 5pF max. shunt
capacitance value.
5pF for my design deteriorates too much the phase shift of my pierce
oscillator ( I was led to believe that a typical value was 3.1pF for a
3rd overtone 50-60MHz xtal, and designed the pierce oscillator to
accomodate such).

But since 5pF is the MAXIMUM shunt capacitance of the xtal, I was
wondering if anyone has an idea to what is the TYPICAL shunt
capacitance of a 50-60 MHz SMD crystal? (Perphaps the design can be
salvaged). Since the question is rather quite specific, I don't expect
anyone to kmow this information off the top of their head. However, if
anyone has an idea by how much does the maximum and minimum values of
the shunt capacitance of any HF xtal vary with respect to the typical
value, it will be much appreciated. Also, I would be also interested
with the max. and min. variance w.r.t to typ. of the ESR resistance of
a HF xtal, as it obviously will affect the pierce's oscillator
performance.

B.T.W, Does the shunt capacitance vary when passing from the
fundamental operationnal mode to the 3rd overtone operationnal mode? I
have noticed that the ESR resistance significally increases when
passing from fundamental to 3rd overtone.

Thx.
-Frank
 
C

Christian Rausch

Jan 1, 1970
0
There was an interesting article on spice quartz models some years ago in
electronic design:
http://www.elecdesign.com/Articles/ArticleID/6248/6248.html

I hope this helps.

Unfortunately, Telequarz, was taken over by Corning and I could not find the
QSLIB software on their web site any more, which put out the capacitances
and inductances and other model parameters of the Telequarz products.
Maybe they send you QSLIB if you ask them kindly...

Christian
 
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