Subject: s2ibis2 problems

From: gerald_truong <[email-masked]>
Date: Tue, 30 Nov 1999 08:54:31 -0700

Hello all,

    I am currently trying to get acquainted with the s2ibis2 utility but
I am running into some problems. I am using Star-Hspice 98.2 as my
simulator. On the second example, the tristate buffer, I keep getting
errors and hspice aborting the simulation. The errors deal with
non-convergence but I do not know how to fix them, I have already added
a 1 ohm resistor on the output as advised by Alan Glaser the author of
s2ibis2. Hspice craps out when trying to gather the data for the max
pulldown output disabled curve, it then gives the following error:

**warning** both nodes of source     0:vgnds2i
            are connected together

**warning** negative-mos conductance =     0:mx24             iter=   21

vds,vgs,vbs =       24.3         0.594         -3.67
 gm,gds,gmbs,ids=     4.697E-04     3.444E-05    -4.614E-06
2.122E-04
convergence problems in dc sweep curves at -0.30000
 resimulating with dc convergence controls

**diagnostic** dc convergence failure,
resetting dcon option to 1 and retrying

**diagnostic** dc convergence failure,
resetting dcon option to 2 and retrying.

*** error ***: no convergence in dc sweep curves at -0.30000

    The first warning does not stop hspice from completing the
simulation but I would like to know what it means and how can it be
fixed.

Thank you for your time. Long live IBIS!

Gerald Truong
Motorola Computer Group
(602)438-3525.

---

From: Syed Huq <[email-masked]>
Date: Tue, 30 Nov 1999 09:05:24 -0800 (PST)

This is a very typical problem. For example, most devices will fail DC 
convergence if you are sweeping at the extreme ranges required for IBIS(ie, 
-Vdd to +2Vdd).

You need to tweak your sweep range. At -0.3V, it fails to converge. You can
do this by editing your .spi file and manually changing the sweep range.
Try a range from 0.0 to 3.3V

Regards,
Syed
Cisco Systems, Inc