[SI-LIST] Re: HSPICE DC Convergence Problem
- From: "Lynne D. Green" <lgreen22@xxxxxxxxxxxxxx>
- To: <esayre@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Sun, 1 Oct 2006 22:42:56 -0700
Hi, Ed,
Here are a few convergence thoughts...
Have you looked at the minimum HSPICE transient time step compared to the
max S-param frequency? Ditto the edge rate of the signal sources? The
simulation time step is probably reported - somewhere - in the output file.
If this is the problem, you might need to set min and/or max time steps as
well as the various tolerance controls.
How do the S-param values extrapolate for low and high frequency? Do both
ends extrapolate to passive values? Sometimes adding your own
"extrapolated" end points, based on known interconnect characteristics, can
be helpful. Sometimes it helps to add 2 points at each end to set both
value and slope. One way to debug this is to do an AC simulation on the
S-param model with AC sources and your 50-ohm terminations.
Another possibility is excessive "noise" in the S-params, that might appear
to HSPICE as non-causal, non-passive behavior. Viewing the S-param data
graphically can help debug this problem, or one could try the matrix checks
for causality and passivity.
Happy hunting!
Best regards,
Lynne
"IBIS training when you need it, where you need it."
Dr. Lynne Green
Green Streak Programs
http://www.greenstreakprograms.com
425-788-0412
lgreen22@xxxxxxxxxxxxxx
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of esayre@xxxxxxxx
Sent: Sunday, October 01, 2006 12:23 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] HSPICE DC Convergence Problem
Folks:
I'm running an HSPICE S-Parameter based transient (.TRAN) and frequency
(.AC) simulations on a 16 x 16 S-Parameter Touchstone matrix (4-diff ports
in and 4-diff ports out). I have appropriately matched diff sources and 50
ohm terminations to ground. I have referenced everything to global ground
"0" and removed all pad and via capacitances. The 16 x
16 matrix elements are complex single ended and start at 200 MHz and extend
to 20 GHz.
I'm using HSPICE version 2004.x. In the .TRAN simulations, the sources start
from zero so there is no difficulty with having DC value problems at t = 0.
For some reason, I can't seem to get to first base on this, namely DC
convergence, so neither of the simulations proceeds to its purpose.
Any suggestions gratefully appreciated.
Dr. Edward P. Sayre, P. E.
North East Systems Associates, Inc.
1 South Avenue, 3rd Floor
Natick, MA 01760
[T] 508-652-0088
[F] 508-652-0083
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