Re: Crystal circuits

G'day David,

Yep you just got lucky :)
18, 22 and 27pF are more the range required, any larger
and it loads up the crystal too much, probably won't even start
oscillating.
What crystal speed and spec are you using? Usually the required load
capacitance is on the crystal spec sheet, but if you can't find
anything and you're using somewhere from 2-10Mhz then 22pF should
be close enough.

Best regards,

Marc

----- Original Message -----
From: David Shoemaker
To: vectorlist@vectorlist.org
Sent: Tuesday, October 21, 2003 3:43 PM
Subject: VECTOR: Crystal circuits

While building up the two beta 9100 keyboard wedge boards I realized I didn't have any 22pf caps. So I tossed a pair of 100pf caps
onto my breadboard of the circuit and everything worked great.

Then I went to build the perfboard version and realized I only had two of the 100pf caps and as I wanted to leave the breadboard
version intact for now so I grabbed a pair of .1uf caps.

Hooked everything up and it didn't work.

So I checked everything twice more and still no go. Got to wondering if maybe the value of those caps is really important and
realized I have NO idea how to spec them nor even what they do.

So can anyone enlighten me?

I have seen circuits use 18pf, 22pf and 27pf for the crystal caps. The 100pfs do work, but I wonder now if I just got lucky.

David

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Received on Tue Oct 21 02:52:28 2003