Re: [SI-LIST] : App note assumptions

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From: S. Weir (weirsp@a.crl.com)
Date: Sat Apr 15 2000 - 00:55:13 PDT


Is this a question or a rant?

Regards,

Steve.
At 01:31 PM 4/14/2000 -0600, you wrote:
>Has anyone else noticed in this "app note" (see below) that Cypress has a
>very good
>scientific explanation about why using several values of decoupling
>capacitors can cause problems, and then they go on to recommend a bunch of
>general routing rules that they haven't substantiated?
>
>This is how false information is spread.
>
>1+1=2, because if I have one cow in a field, & then put another cow in that
>field, I will have two cows in the field. Therefore use one cap per power
>pin, 1+1=2, place caps close to the IC & on the same side, and keep leads
>below 6mm. Can anyone pick out the assumptions I made after giving an
>example why 1+1=2?
>
>Thanks Lee Ritchey, for making me skeptical of app notes!
>
>Mark Geddes
>
> >
> > What worries me about using bulk capacitors with different capacitance
> > in parallel as in the picture you sent is well described in
> > the following
> > article:
> > http://www.cypress.com/pub/appnotes/decouple.pdf
> > (look especially picture 5 on page 3)
> >
>
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