RE: [SI-LIST] : Power Plane Inductance

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From: Doug Brooks (doug@eskimo.com)
Date: Thu Jul 13 2000 - 14:59:31 PDT


At 04:42 PM 7/13/00 -0500, you wrote:
>Doug,
>Do you really believe the inductance of a connection that is 0.5'(feet?) to
>1.0"(inch) from via to cap is negligable in all cases? Don't you think the
>connection method makes a difference? IE, thin trace VS unbroken planes.
>
>Aubrey Sparkman
>Signal Integrity
>Aubrey_Sparkman@Dell.com
>(512) 723-3592

Well two things.
(1) I read the question as .5" to 1" across a plane, not a trace (if I read
the question wrong, I apologize.) My reaction is that under that condition,
the inductance of the plane is indeed pretty small (compared to the
inductance of the cap, itself, and its connections to the pad, and the pad
and the via.)
But (2) Larry Smith raises an interesting issue that even under that
condition, there may be more inductance across the plane than people recognize.

Doug Brooks
.
************************************************************
Doug Brooks' book "Electrical Engineering for the Non-Degreed
Engineer" is now available. See our web site for details.
.
Doug Brooks, President doug@eskimo.com
UltraCAD Design, Inc. http://www.ultracad.com

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