Re: [SI-LIST] : ESR and bypass caps

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From: Doug Brooks (doug@eskimo.com)
Date: Mon Feb 07 2000 - 12:02:51 PST


At 10:21 AM 2/7/00 -0800, you wrote:
>Doug - you have an interesting and useful little calculator there.

Thanks

>We must not forget the power plane capacitance. The parameters for the
>power planes vary greatly (depending on the pcb stackup) but try c=1nF
>r=.01 L=.1nH. You end up with a major impedance peak at a frequency
>where all decaps have gone inductive and the capacitance of the power
>planes is still there. True, you must do a distributed plane analysis
>to really understand this. But even with your calculator, you should
>be able to see the dangerous effects of this resonance.

Note that the (admittedly arbitrary) data in the example in Appendix 3 does
simulate this and it does show the dangerous peak.

Doug

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Doug Brooks, President doug@eskimo.com
UltraCAD Design, Inc. http://www.ultracad.com

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