Re: [SI-LIST] : adjacent planes.....sort of

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From: [email protected]
Date: Thu Mar 29 2001 - 09:11:48 PST

Hi, Jim:

You asked, "My question is, do we still reap the benefits of the adjacent
plane when we have a signal layer in between them? "

Absolutely. The distributed capacitance between the two planes can be
calculated pretty much independently of the traces in between the layers
(with minor consideration for the trace copper thickness). The E-field
(volts/meter) between the two planes is set by your power plane voltage and
the trace layer is at an equipotential level throughout the area of concern.
The trace copper density/coverage is likely less than 25% and will have
little effect on the interplanar coupling. The traces are AC-referenced to
both planes and the local (and normally very small) delta-V caused in the
planes by signals traveling down the traces should have a negligible affect.

Michael L. Conn
Owner/Principal Consultant
Mikon Consulting

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