Re: [SI-LIST] : 20-H Rule for Power Planes

Mike Mayer (Mike.Mayer@cp.artesyn.com)
Thu, 27 May 1999 16:39:08 -0500 (CDT)

I have no experience one way or the other with this, but I get
suspicious of rules that have no solid data to back them up. A similar
EMC type issue that affects alot of boards is whether to create an
isolated chassis ground at I/O connectors or connect the logic ground
directly to chassis ground. Some references say do it, some say
don't. The only study I have seen was done by or with Sun and tried to
compare two boards that only differed in the way the ground plane was
handled at the I/O interface. As I recall, connecting the plane to
chassis ground was much better than having an isolated I/O ground.

The people advocating the isolated ground approach may never have
looked closely and really compared to boards that differed *only* in
the connection. THerefore they are really just saying "it has always
worked for me".

I would be very interested in simulation results.

-- 
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Mike Mayer                               Artesyn Communication Products, Inc
                                         Madison, WI
                                         http://www.artesyn.com/cp
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