[SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
- From: "Brent DeWitt" <bdewitt@xxxxxxxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Mon, 11 Aug 2003 20:26:00 -0600
Hi there!
I'm afraid you're agreeing with something that Ray says is actually an
opinion on an extreme case. The assumption that all power consumers are
distributed evenly across the board is not unreasonable in many designs, in
which case the S11/S21 data still has validity. In spite of my past
experiences I'd have to believe that with new technologies that the UMR
paper is pretty much spot on. Of course, they're always exceptions.
See you in Boston?
bd
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Grasso, Charles
Sent: Monday, August 11, 2003 10:54 AM
To: 'si-list@xxxxxxxxxxxxx'
Subject: [SI-LIST] Re: UltraCAD ESR and Bypass Capacitor Caculator
Agreed wholeheartedly Ray. One should not
discount experience .. In the UMR experiments
-taking S11/S21 data - I would not expect
location to be that important. However,
that was only a measure of the performance
of the board and makes no judgement of location
of Ics.
Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx
-----Original Message-----
From: Ray Anderson [mailto:raymond.anderson@xxxxxxx]
Sent: Monday, August 11, 2003 10:36 AM
To: si-list@xxxxxxxxxxxxx
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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