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

An old saying:
"In theory, there is no difference between theory and practice;
however in practice, there is."
Dave Wyland


Grasso, Charles wrote:

>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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