Subject: RE: SPICE Convergence Tricks - Consequences?

From: "Mellitz, Richard" <[email-masked]>
Date: Tue, 3 Jun 1997 07:44:14 -0400

FWIW: The following HSpice options is where I start from.

.options interp reltol=0.0001 post=2 probe ingold=2 vntol=0.1u
+ lvltim=1 chgtol=0.01f brief nomod notop noelck nolist

As colleague of say "Its sort of like 'sour dough starter'"

Nothing seems to work "every time" for me. I usually have to twiddle
around based on the what was done at the transistor level models.  The
toughest ones are the "sanitized spice" models.  Many just do not work
accurately at DC.

... Rich Mellitz, NCR Corp
>----------
>From: 	Roland James Chang[SMTP:[email-masked]]
>Sent: 	Tuesday, May 20, 1997 4:02 PM
>To: 	[email-masked]
>Subject: 	SPICE Convergence Tricks - Consequences?
>
>
>Once again, a big thanks to all who replied to my last question. :-)
>I've been using several tricks to try to solve SPICE convergence
>problems:
>
>-adding a 0.001ohm resistor in seris with the stimulating source
>-increasing the value of the ITL1 to 300-500. (more iterations allowed)
>-relaxing ABSTOL
>-decreasing the sweep of the stimulus (I couldn't quite get this one to
>work)
>
>Many people mentioned that convergence problems are quite common, I would
>like to know how common are they?
>
>Furthermore, I am curious if anyone has a convergence fix that works
>everytime, as it seems tedious to try to get things to converge everytime
>just by trial and error fixes.
>
>Also, what kinds of side-effects, or problems (in terms of IBIS
>modelling) have people encountered by forcing the analysis to converge via
>fancy SPICE tricks?
>
>One last question regards clarification about typ, min, and max
>curves.  When one is generating curves for the typical case,
>suppose the typical case passes but both the min and max fail, the columns
>should read NA for min and max right? Now should I go back and try to
>tweak the min and max to converge? OR are some curves meant to only work
>for the typical case? 
>
>
>Many thanks in advance,
>Regards,
>
>roland
>
>*************************************************************************
>*Roland Chang                          | email: [email-masked]           *
>*Simon Fraser University               |        OR                      *
>*School of Engineering Science         |        [email-masked]  *
>*3rd year Computer Engineering Option  |                                *
>*************************************************************************
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