RE: [SI-LIST] : Copper pour beneath oscillators,

About this list Date view Thread view Subject view Author view

From: Ken Cantrell (Ken.Cantrell@srccomp.com)
Date: Wed Jun 06 2001 - 07:24:57 PDT


David and Shoaib,
Well, I do it differently. I do a local pour under the oscillator, then
aspect ratio stitch the pour to the nearest ground plane, which I make sure
is a very small vertical distance from the pour during the stack up
determination. I look at it as a little bucket to big bucket set up. The
little bucket provides a low inductance path, provided by the stitching, to
the big bucket, decreasing the turbulent flow during impulsive events.
Ken

-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of David Bengtson
Sent: Wednesday, June 06, 2001 4:19 AM
To: Shoaib
Cc: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : Copper pour beneath oscillators,

Putting on my RF engineering hat, I will say that copper pours over
the entire board are evil tools of the devil. You are increasing your
parasitic capacitance in an "uncontrolled" fashion.

Speaking for the oscillator, putting copper under it will increase the
parasitic capicitance, potentially coupling noise into and out of the
oscillator.

Dave

On Tue, 5 Jun 2001 10:23:39 +0500, you wrote:

>Hi,
> I'm a novice and my question might sound stupid but nontheless its a
question to me. I'm desiging a board with 20 Mhz clock oscillators on it, i
have put copper pour on the vacant areas of the board and connected the
copper to the ground (common to all components), this copper also extends
beneath the oscillators. The designer of the circuit is not happy with it
and says that it will inflict all the noise generated by other components
onto the oscillators output and rather he suggests that copper beneath the
oscillators should remain unconnected this way any noise inflicted on or by
the oscillator will remain isolated and not cause any problems. Can anyone
please explain as it is a little confusing for me.
> Thanx in advance,
> Shoaib

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Thu Jun 21 2001 - 10:12:16 PDT