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Date: | Wed, 23 Oct 1996 08:07:32 -0400 |
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Elroy,
I recently attended the University of Wisconsin's "System EMC
Compliance through Printed Circuit Design" seminar and was taught that
if the external planes are for shielding purposes, it is a good idea
to run a guard ring of ground around the periphery of the board on all
layers and tie the external planes and the internal ground plane
together through closely spaced (.25 inch) vias only at the guard
ring. Tying the IC and Cap ground pins to the external plane only puts
noise onto the shield. The course contained other subtle tricks. Take
it if you can get the chance.
Gary Fuller
Edwards Systems Technology
Sarasota, Florida 34243
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______________________________ Reply Separator _________________________________
Subject: Internal and external ground planes
Author: "Elroy A. Tesch; Jr." <[log in to unmask]> at Internet2
Date: 10-22-96 19:37
We design high speed line scan cameras and use internal and
external ground planes (external for shielding) on our PCB's.
My question is this-
Should the internal and external planes be tied throughout the board (at
vias, etc.) or should the external planes be tied back only at a single
soure (power connector) and leave the internal plane(s) for all component
connections? I am wondering if there are advantages of one over the other.
VIP Lab
University of Arkansas
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