# [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator

*From*: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>*To*: si-list@xxxxxxxxxxxxx, "Mike Mayer" <mwmayer@xxxxxxx>*Date*: Mon, 11 Aug 2003 08:26:49 -0700

If the location of decoupling capacitors matters, perhaps some technical demonstration would prove that. Short of such a demonstration, this is speculation and not the sort of thing that should be used to make design choices. It's time to do some good engineering on this subject and do away with opinion. The UMR paper is good engineering. Anyone who chooses to disagree with it has the burden of showing where it is wrong by using some good science. Lee Lee Ritchey leeritchey@xxxxxxxxxxxxx Why Wait? Move to EarthLink. > [Original Message] > From: Mike Mayer <mwmayer@xxxxxxx> > To: <si-list@xxxxxxxxxxxxx> > Date: 8/3/2003 12:02:48 PM > Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator > > On Fri, 2003-08-01 at 14:50, Ray Anderson wrote: > > With all due respect to the UMR authors, I think the location > > of a decap on a set of power planes DOES matter. > > [...] > > And the UMR authors agree. From the Summary of their paper*: > > "A lumped element model has been developed for decoupling on a > multilayer PCB. The model is valid for frequencies below the distributed > resonances of the power bus, which for PCBs on the order of 6-10" is > approximately 200-300MHz." > > and > > "Experimental results show that the location of the decoupling capacitor > is not critical to performance in the frequency range below several > hundred megahertz (where a lumped element model is valid)." > > *Drewniak, J.L., Hubing, T.H. et al, Modeling Power Bus Decoupling on > Multilayer Printed Circuit Boards, 1994. > > > -- > ============================================================================ = > Mike Mayer > mwmayer@xxxxxxx > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > http://www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List archives are viewable at: > http://www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: http://www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: http://www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu

**Follow-Ups**:**[SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator***From:*Ray Anderson

**[SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator***From:*Kim Flint

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