RE: Shielding

Peterson, James F (jfpeterson@space.honeywell.com)
Wed, 2 Jul 1997 08:00:54 -0400

I don't think you will have digital signals crosstalking into your
analog section with your configuration.
But you could have analog signals crosstalking into other analog
circuits. It would depend on the slew rates, signal swing, and how
sensitive the circuits are. The analog ground plane will reduce
crosstalk but it won't get rid of it. What kind of signal to noise ratio
can you tolerate?
Good luck,
Jim

>----------
>From: Sean Murray[SMTP:SMURRAY@SLIP.NET]
>Sent: Tuesday, July 01, 1997 10:26 AM
>To: 'Signal Integrity'
>Subject: Shielding
>
>I'm a little confused on the subject of shielding (guard traces). I'm
>currently designing a board for a customer, in which the analog & digital
>traces are on seperate layers. Both layers are shielded by their respective
>planes (i.e. Digital by Dgnd; Analog by Agnd). My question is; do the
>analog traces still need to have guard traces to protect against any noise
>that might be coming from other analog traces on that layer? (and likewise
>for Digital). The customer has stated that he wants the traces shielded,
>but when asked why he could not give me a scientific answer. I was under
>the understanding that you only needed to shield the traces if they were
>very high speed and were not utilizing proper ground shielding (planes)
>techniques.
>
>Any help?
>
>Regards,
>Sean Murray
>M&M Specialties, Inc.
>