RE: [SI-LIST] : Comments from your SI seminar (SendII)`

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From: Denomme, Paul S. ([email protected])
Date: Thu Oct 28 1999 - 05:37:03 PDT

First of All,

        I do not and would not advocate running signals over a split plane
and multipoint grounding is an area where there are many opinions. I was
just explaining what was stated in the High speed course.

But a comment on our industry in general,

        I went to several courses at the PCB Design East, and each course
instructor had their own opinion on what they believe is the correct way of
doing things.
It is sad that our industry cannot take a concensus and come up with the
CORRECT way of doing things. Instead of using testing and empirical data to
determine what is accurate, they bicker about why ones methods will or won't


Paul Denomme

> -----Original Message-----
> From: Ron Miller [SMTP:[email protected]]
> Sent: Wednesday, October 27, 1999 4:52 PM
> To: [email protected]
> Subject: Re: [SI-LIST] : Comments from your SI seminar (SendII)`
> I hope everyone goes to the seminar, because I will be the only
> person left
> in this field that understands what is really happening.
> Ron Miller
> In regards to comment 1. In a high frequency signalling
> environment, The
> return current will flow on the nearest plane whether it is power or
> ground.
> If you have two planes coupled closely togther you create a
> capacitor which
> the high frequency return current uses to traverse the planes and
> takes the
> path of least impedance.
> If there were not two planes coupled together, it would be an EMI
> catastrophe and you would not know where the return current is
> flowing.
> Regarding comment 2, he was stating that grounding in multiple
> locations is
> a bad idea. This can create some ground loops within the chassis.
> There
> will be some type of potential difference from one chassis
> connection point
> to another and this will create some current in the chassis. This
> is very
> bad from an EMI perspective.
> He believes one Solid connection to the ground plane is sufficient.
> I
> --
> Ronald B. Miller _\\|//_ Signal Integrity Engineer
> (408)487-8017 (' 0-0 ') fax(408)487-8017
> ==========0000-(_)0000===========
> Brocade Communications Systems, 1901 Guadalupe Parkway, San Jose, CA
> 95131
> [email protected], [email protected]

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