[SI-LIST] : AGND & DGND stitching

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From: Patel, Bhavesh (bpatel@ciena.com)
Date: Tue May 15 2001 - 18:40:37 PDT


Hi! I needed some feedback regarding the concept of stitching AGND and DGND
planes.
From some reference material that I have read:
1) AGND & DGND should be stitched at one point, this way you ensure the
return point and do not create ground loops.
Now, on a board that I have the designer stitched agnd and dgnd with
shorting bars all over the place with no constraint i.e. number and location
on top layer and bottom layer. Later, when the board was being debugged some
of the chips that had both agnd and dgnd pins were seeing a huge potential
difference which made some sections of the IC not to function properly.
My take on this is that the multiple stitching points are giving rise to
weird ground loops which create this potential difference.
What is the best approach for connecting AGND and DGND and should the
highest operating frequency on the board should play a role in the number of
stitches .
Thanks in advance
Bhavesh Patel

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