[SI-LIST] : RE: bypass caps

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From: Jay Marano (jay_marano@adaptec.com)
Date: Mon Jun 05 2000 - 11:59:45 PDT


I'm looking for any feedback from those who have
read the white paper on the Ultracad web site
regarding ESR and Bypass self resonant behavior.
One of the things it demonstrates is that for a
given number of capacitors, better system impedance
results are obtained from using more cap values,
with moderate but not super low ESR, spread over a
range than with a smaller set of cap values, with
very low ESR, at well chosen self-resonant frequecies.
I understand the theory behind his analysis, but it
raises an interesting question: In the frequency range
between the bulk capacitors and the knee frequency of your
system, is it better to purposely use wider tolerance caps
and use a smaller number of values, or buy more tighter tolerence
values and rely on the nominal values to smooth out the system
impedance? Any feedback on this analysis would be appreciated.

Jay Marano
Sr. Hardware Design Engineer
Adaptec
Maitland, FL 32751
321-207-1387
jay_marano@adaptec.com <mailto:jay_marano@adaptec.com>

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