Subject: Re: Clarifing example for Packaging EGG

From: J Eric Bracken <[email-masked]>
Date: Mon, 08 May 1995 12:08:08 -0400

Hi again,

  Jon Powell's comment is totally accurate:

>> A circuit that demands the simulation of all 28 pins (and therefor all
>> 28 nets connecting to these pins) at the same time is not
>> acceptable.  A mechanism that allows overlapping and redundant 
>> coupling descriptions is needed.

  But I disagree that a SPICE-like description, or, for that matter,
any RLC matrix-based description, is unusable because of this.  

  We all know that to get ULTIMATE accuracy requires very rigorous
analysis.  In principal that means all 28 pins fully coupled.  Anything
less than that is just an approximation.

  But that's fine if the approximation is a good one.  And it's even better
if the approximation makes the analysis run a lot faster.

  I would assume that the simulation vendor would do something internally
to simplify the model with lots of coupling between pins, so that they
could get results in a reasonable length of time.  How they go about 
doing it is their business (literally.)  I don't think we want to force
them to do it in any particular way.

  So, basically, I don't see why SPICE is not sufficiently "overlapping
and redundant."  It's a lot MORE information than the simulator will 
probably ever need.  The existing matrix descriptions are probably equally
expressive, since they permit "full" or "sparse" coupling as needed.

  The one thing I _do_ worry about here is how the model MAKERS will 
go about producing the coupling information...using field solver software?
Doing cut-and-try on measured data?  With a dart board?  This could 
really affect the accuracy of results, particularly when different vendors
are doing their own thing.

--Eric

__________________________________________________________________
     ________   ________   __   ________
    /\_______\ /\_______\ /\_\ /\_______\ J. Eric Bracken, Ph.D.
   / / ______// / ____  // / // / ______/ Visiting Lecturer, Dept. of ECE
  / / /__\   / / /__\/ // / // / /        Carnegie Mellon University
 / / ____/  / / ___  _// / // / /___      Pittsburgh, PA 15213
/ / /____\ / / / \/ / / / // / /____\     (412) 268-8944 FAX (412) 268-3204
\/_______/ \/_/  \/_/ \/_/ \/_______/     [email-masked]
__________________________________________________________________

---

From: [email-masked] (Jon Powell)
Date: Mon, 8 May 95 11:20:43 PDT

>>expressive, since they permit "full" or "sparse" coupling as needed.

I want to use a format that "lends" itself to easy partioning. If people believe
that a 100 element SUBCKT does this, then we should use it. If however, people
feel that a different format would be either easier to create or easier to interpret,
then we should use that.

>>  Jon Powell's comment is totally accurate:

but thanks for agreeing with me, I think.

jon