[IBIS-Users] RE: [IBIS] Re: hspice vs IBIS model correlation at different capacitive loads

From: Helliwell, Kim <Kim.Helliwell_at_.....>
Date: Wed Jan 04 2006 - 09:11:01 PST
I'd like to add a bit to Andy's response, where he says:

-----Original Message-----
SPICE is known to occasionally have numeric oscillations when it should
be
steady-state, which can be fixed by changing to Method=Gear.

------------------------==

The numeric oscillations that can be cured by METHOD=GEAR are
very distinctive: they look like a sawtooth wave in which the
timepoints oscillate between two values (this behavior sometimes
will damp out over time, but usually will continue between exactly
the same two values). The key characteristic is the
sawtooth wave pattern with only two timepoints per period. If
you have an oscillation that looks like a sawtooth (or just a
high frequency ringing) but with more than two timepoints defining
one period of the ringing, this won't be helped by changing the
integration method.

By the way, this sawtooth pattern is called "Trap ringing" because
it's a characteristic of the trapezoidal integration method SPICE
uses by default.


Kim



|------------------------------------------------------------------
|For help or to subscribe/unsubscribe, email majordomo@eda.org
|with just the appropriate command message(s) in the body:
|
|  help
|  subscribe   ibis       <optional e-mail address, if different>
|  subscribe   ibis-users <optional e-mail address, if different>
|  unsubscribe ibis       <optional e-mail address, if different>
|  unsubscribe ibis-users <optional e-mail address, if different>
|
|or email a written request to ibis-request@eda.org.
|
|IBIS reflector archives exist under:
|
|  http://www.eda.org/pub/ibis/email_archive/  Recent
|  http://www.eda.org/pub/ibis/users_archive/  Recent
|  http://www.eda.org/pub/ibis/email/          E-mail since 1993
Received on Wed Jan 4 09:11:05 2006

This archive was generated by hypermail 2.1.8 : Wed Jan 04 2006 - 09:12:08 PST