Re: [SI-LIST] : EMC techniques on 2-layer board

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From: polus@lexmark.com
Date: Fri Feb 04 2000 - 08:06:51 PST


We are quite successful using two layer boards for certain designs at speeds
much higher that yours.

1) Be sure your grounds are connected or 'stitched' continuously across the
card. A lot of times the grounds will only travel a certain portion of the card,
then suddenly stop with no connection to the other logic ground on the card,
which should really be at the same reference level.

2) Have good, solid grounding points to the frame of whatever the PCB goes into.

3) The ground stitching should also be done to minimize ground loops. It will
take some time to do this once the majority of the circuit layout is complete.

4) Run clocks at 90 degrees with relation to buses wherever possible.

5) Run Ground -Signal- Ground on any signals you might deem as critical,
particularly clock signals.

6) Use a spread Spectrum Clock Source if you still have problems.

Good Luck.

Harold Polus
Lexmark International, Inc.
High Speed design, SI, and EMC Evaluation

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