RE: [SI-LIST] : App note assumptions

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From: Chris Cheng (chris.cheng@3pardata.com)
Date: Fri Apr 14 2000 - 13:29:17 PDT


not trying to be controversial but over the years, i
have tried so many tricks on caps combination but in the
end i still found using the lowest possible esl
capacitor with the largest possible capacitance seems
to provide the best noise suppression vs. any combo
type of mixes. i still need to throw in a few "high
speed caps" to keep the emi people happy but they
don't seem to matter at all. you can remove or replace
them with the large caps and the system noise remains
the same.
chris

-----Original Message-----
From: Ray Anderson [mailto:Raymond.Anderson@Eng.Sun.COM]
Sent: Friday, April 14, 2000 1:05 PM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : App note assumptions

I don't know well how their systems function, but I do
know ours work well and we have an entirely different
decoupling methodology.

I'm not going to tell anyone how to use decoupling caps
in their system today, but I'm not going to follow the
recommendations in the app-note either :)

-Ray Anderson
Sun Microsystems

> From: Mark Geddes <mark@AudeSi.com>
> To: "SI-List (E-mail)" <si-list@silab.eng.sun.com>
> Subject: [SI-LIST] : App note assumptions
> Date: Fri, 14 Apr 2000 13:31:34 -0600
> MIME-Version: 1.0
>
> 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

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