On Sun, 08 Sep 2002 21:45:51 -0400, Brian Guralnick wrote:

>Having not placed enough power supply decoupling caps on a beta PCB, I'm looking for 
>a temporary overpriced decoupling solution
>until the next beta boards are printed.

>I'm looking for the lowest ESR possible caps.  I found this company WIMA.

>http://www.wima.de/smd2220.htm
>1.0uf, 0.1uf, 0.01uf. -> 0.07 Ohm thru ~0.15

Well who knows what your exact requirement is but putting better capacitors
in not enough places probably isn't a fix. 

Also those capacitors tan delta is specified at 1, 10, 100 kHz - not
intended for high frequency decoupling, the SMT 100n looks like it is self
resonant around 6 or 7 MHz. 

Actually it looks like you read that graph to get the ESR figures you
quoted but as I read it the line on the graph shows impedance at resonance
not ESR. 

Is it high speed logic? Do you *know* you have a problem? Boards tend to be
way over decoupled anyway especially if you have decently coupled power
planes. 

I would wait till you know you have a problem and strap some extra
capacitors across chip leads if you really need to. 

Cheers, Terry.

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