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

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From: Aubrey_Sparkman@Dell.com
Date: Thu Jan 20 2000 - 13:04:33 PST


 -----Original Message-----
> From: Zabinski, Patrick [mailto:zabinski.patrick@mayo.edu]
> Sent: Thursday, January 20, 2000 2:47 PM
> To: 'si-list@silab.eng.sun.com'
> Subject: RE: [SI-LIST] : **error**: internal timestep too small
>
>
> snip
>
> I cannot claim to know why this works, but if RELV, RELI, IC,
> or NODESET helps convergence or if there are problems
> with any form of transmission line (T, U, or W), I
> simply insert 500K ohm resistors from various nodes to
> node 0 (ground). Generally, the value is high enough
> to not effect the results, but I've found it not only helps SPICE
> find its way, but it can shave off 50-80% off run-time
> as well (depending upon the circuit).

I think the answer has to do with loss. Many of our models have no loss and
therefore RING or Oscillate more than real circuits. This causes many more
calculations than needed for a more realistic, smoother waveform that you
will get with a dampened circuit.

Aubrey Sparkman
Signal Integrity
Aubrey_Sparkman@Dell.com
(512) 723-3592



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