RE: [IBIS-Users] WARNING Endpoint

From: Tom Dagostino <tom_at_.....>
Date: Fri Jan 20 2006 - 09:44:20 PST
Fabino

The check that is giving you a problem is a consistency check.  It is
determining if the VT waveforms and the IV curves are consistent in both the
load resistance present and termination voltage used to simulate the VT
waveforms.

You can look at the problem this way.  The output impedance of the buffer at
a given voltage is a resistance Ro.  This resistance is non linear and is
described by the IV curve.  When a load Rl is placed on the output there is
a voltage divider generated.  This output voltage is checked against the VT
curves endpoints.

There are several different things that can cause there to be endpoint
mismatch.  First, the load used to extract the VT curves is not the same as
the one in the check.  Remember the load has two part, Resistance and
termination voltage.  Second there may be issues with the IV extractions.
Third, there may be double counting of the clamp IV curves.  If there is
some kind of resistive  termination or pullup or pulldown in the buffer this
may not have been correctly accounted for.  Etc.

Shot gunning the solution by changing the termination resistance may or may
not fix the problem. You need to understand the cause of the problem is fix
that.

Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
tom@teraspeed.com
www.teraspeed.com

Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Fabio BRINA
Sent: Friday, January 20, 2006 6:56 AM
To: ibis-users; ibis
Subject: [IBIS-Users] WARNING Endpoint


Hi  IBIS experts,

when I check  my  IBIS  model  I  optain  these warning:

WARNING - Model 'mod_out': TYP AC Rising Endpoints ( 0.00V,  4.97V) not
within
          0.099V (2%) of ( 3.11V,  3.94V) on VI curves for 1000 Ohms to 0V
WARNING - Model 'mod_out': TYP AC Falling Endpoints ( 0.02V,  5.00V) not
within
          0.100V (2%) of ( 3.14V,  3.96V) on VI curves for 1000 Ohms to 5V

I  know  what it means,  but  I  don't know if  I  have  to modify
the  R_fixture to  eliminate it ( I fix R_fix=1k from the datasheet ).
morever in some IBIS editor this  Warning became an Error !
so  I  don't know if is an acceptable Warning.
( I use s2ibis2 v.2.1 )

What  do you think about?

many  thanks


Another type of question:
About IBIS Summit ( DATE 06 ), there is an expiry date to register on them?

thanks again.

Fabio.





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Received on Fri Jan 20 09:44:33 2006

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