[SI-LIST] : Capacitor, Parameter, Calculator

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From: Peter Baxter (peter.baxter@tantau.com.au)
Date: Wed Nov 01 2000 - 14:46:25 PST


Hi,

Another Capacitor Parameter Calaculator is on the Murata web site.

It looks very slick, but..

Set up a capacitor type and value, say 08010nf, 0805, and get it's
parameters.
Then change the cap value to 4n7 and re-plot. The parameters now are all
over the place.

FYI. I priced AVX's 0508 Interdigitated capacitors (47n) at less than 50
cents each.

Peter Baxter

Here are three capacitor vendor sites offering tools to help obtain
estimated parasitics (ESR, ESL, etc.) and performance (impedance
magnitude)
for their caps.

http://www.avxcorp.com/SpiApps/default.asp

http://www.kemet.com/kemet/web/homepage/kechome.nsf/vabypagename/spicesoft

http://www.atceramics.com/designsupport/index.html

I've used all three, and it appears AVX SpiCap assumes a single, common
ESL
for
a given package style (e.g., 0805 = 1.0 nH) regardless of capacitance.
However,
to obtain different capacitance values, the physical structure must
change
(thinner
dielectrics, additional layers, etc.), so the inductance much change
accordingly.

Kemet's ESL values do change with different capacitance values (which
leads
me to believe they've done a bit more work on their part), but as they
clearly state (Kemet: thanks for being clear on this) that their
inductance
is obtained slightly different than others; thus their published values
will
be slightly higher than those from other companies (by about 600 pH).
If
I am reading between the lines of their explanation correctly, the ~600
pH
they add is related to return-path inductance.

I haven't tried the ATC software in quite some time, but if I recall
correctly,
it did not have useful information on multilayer chip caps (e.g., 0805).
They
might have updated their tools/database since I last use it.

Anyone know of other/additional tools? Does anyone have a different
opinion of
or experience with these three tools? Are there similar tools for
resistors
and inductors?

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