AVR-Chat

A crystal is only a part of a crystal oscillator circuit.. therefore
crystals are specified to work in circuit in either a series or parallel
mode, for a given load capacitance.

Here's a bit of info on series vs parallel resonance.
http://www.circuitcellar.com/library/print/0298/bujanos91/8.htm
http://drt.com.au/Technotes.htm

your spec for your crystal means that the particular crystal needs to be in
a series resonant circuit with 18pf of load on the crystal, for the crystal
to run at its specified frequency.

Running the crystal in a parallel resonant configuration, or with different
load capacitance might still make the crystal work - but it won't be at the
specified frequency.



Julian Higginson
Bruttour International P/L
http://www.bruttour.com.au
Ph: +612 9987 1581

-----Original Message-----
From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of Brian
Sent: Thursday, 23 October 2008 10:45 AM
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] crystals

I was looking at Jameco for crystals. Under impedance is says 18pf and 
series. What is the difference on how they are hooked up to a uC?

Brian