RE: [SI-LIST] : **error**: internal timestep too small

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From: Muranyi, Arpad (arpad.muranyi@intel.com)
Date: Thu Jan 20 2000 - 12:18:42 PST


Kim,

I meant the series version:

  U-element---------R-------|---------R---------U-element
                            |
U-element---------R-------node---------R---------U-element
                            |
  U-element---------R-------|---------R---------U-element

I used resistors much less than 1 Ohm, something like 1e-4 or so.
I also reported this to Avant! and since it was around the time
when the W-element came out I was told that I should not expect
any research and fixes to this.

Arpad Muranyi
Intel Corporation
====================================================================

-----Original Message-----
From: Kim Helliwell [mailto:khelliwe@acuson.com]
Sent: Thursday, January 20, 2000 10:16 AM
To: si-list@silab.eng.sun.com
Subject: Re: [SI-LIST] : **error**: internal timestep too small

> 3) I observed this with the U-element in HSPICE (anyone still using
> it?). If you connect more than two of them to the same node it
> will blow up (with kVolt differences on the two ends of the same
> element). However, a small resistor (yes, resistor) between the
> U-elements and the common joint will allow it to converge. Anyone
> knows why?

Hmmm, I don't know specifically. So you "float" the common joint
on a small resistor? Or is the resistor in series with and between
the two U's?

1 ohm resistors put 1s (or -1s) on the diagonal of the matrix, and
the more 1s on the diagonal, the better, in general. That's
why "cheater" resistors usually help in SPICE. But I doubt
that's the explanation here. At least, not the whole story.

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