[SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx, "Ray Anderson" <raymond.anderson@xxxxxxx>
- Date: Tue, 12 Aug 2003 09:02:24 -0700
Ray,
Good point. Some of the science I and others draw from was done by
engineers at Sun. Some was from UMR. Some was actual lab measurements
that I and my partners have made. I accept opinion that has as its basis
some actual experiment or analysis. That is valid opinion, or better
observation based on experiment. That is the stuff of engineering.
Hunches and rules of thumb are not. We have a great deal of the latter in
circulation that mislead. All of us should work at reducing this kind of
rule making.
Several engineers at Sun have done quite a bit of this and shared it with
the engineering community. Among them, Larry Smith.
This very forum is a major contributor to this cause and I applaud Sun for
doing it. The rest of us are in its debt for doing so.
Lee Ritchey
leeritchey@xxxxxxxxxxxxx
Why Wait? Move to EarthLink.
> [Original Message]
> From: Ray Anderson <raymond.anderson@xxxxxxx>
> To: <si-list@xxxxxxxxxxxxx>
> Date: 8/11/2003 9:36:25 AM
> Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
>
>
>
> Lee Ritchey wrote:
> > 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.
>
>
> Or conversely, show that it doesn't matter.
>
> Take a large system board (say about 24" square) put a bunch of high
current
> processors and ASICS on the left side of the board. Put all your decaps
> on the right side of the board (since you maintain position doesn't
matter).
>
> In this hypothetical case I can just about guarantee the board won't
function
> properly or pass EMI. Admittedly, it is a contrived case, but I think it
> illustrates the point.
>
> As far as the technical demonstration goes, we have indeed demonstrated to
> ourselves that position does matter.
>
> I'm not attempting to further an argument, but I do feel those who have
> responded with viewpoints other than yours shouldn't be chastised and
accused
> of spreading unfounded opinion. Don't discount the chance that an opinion
that
> differs from yours just might be correct.
>
> -Ray Anderson
> Sun Microsystems Inc.
>
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