Re: [SI-LIST] : Parallel Plate Capacitance for Bypass

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From: Gerald Johnson (jjohnson@minn.teradyne.com)
Date: Mon Mar 27 2000 - 11:01:33 PST


Ron,

Capacitance of planes is NOT a function of inverse square of distance.
See thread in this list about a week ago. Well covered there.

Valid to use inverse square distance for point source, not for planes.

Result, capacitance would be about (5/2.2)*200 = 454.6 pF if the
100 pF per in^2 at 5 mils is correct.

Jerry Johnson
Teradyne Inc.

>Date: Mon, 27 Mar 2000 10:39:10 -0800
>From: Ron Miller <rmiller@Brocade.COM>
>To: si-list@silab.eng.sun.com
>Subject: Re: [SI-LIST] : Parallel Plate Capacitance for Bypass
>
>Thanks Steve, I knew it was somewhere around there.
>
>So, by extension, 2.2 mil dielectric, available at very little if any
>extra cost should be about 1000pf/in sq for FR4
>and eliminatee the need for discrete capacitors below 1000 pf.
>
>ron
>
>"S. Weir" wrote:
>
>> Ron,
>>
>> 5 mils should yield about 200pF / in sq, before taking away for vias.
>>
>> Regards,
>>
>>
>> Steve.
>> At 02:30 PM 3/24/2000 -0800, you wrote:
>>

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