RE: [IBIS-Users] Vinl and Vinh For Differential Input Model

From: Tom Dagostino <tom_at_.....> Date: Fri Mar 04 2005 - 16:12:14 PST · This archive was generated by hypermail 2.1.8 : Fri Mar 04 2005 - 16:15:54 PST

For completeness and to avoid having to explain to a customer why there are
warnings in an IBIS file it is easy to place a Vinl/Vinh into input buffers
that are used as differential only.  In the case of an LVDS buffer I would
start with the common mode voltage, about 1.25V to that I would add the 1/2
of the threshold voltage.  That would become Vinh.  I'd subtract 1/2 of the
threshold voltage and that would become Vinl.  As Arpad and the IBIS
specification say, the values in vdiff over ride Vinl/Vinh so the simulator
will use vdiff and ignore the Vinl/Vinh values.

Tom Dagostino
Teraspeed Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
http://www.teraspeed.com
tom@teraspeed.com

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

Teraspeed is the registered service mark of
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-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Muranyi, Arpad
Sent: Friday, March 04, 2005 1:58 PM
To: ibis-users@eda.org
Subject: RE: [IBIS-Users] Vinl and Vinh For Differential Input Model

This look like that the parser doesn't check that the [Model]
is used as a differential pair, and issues a warning regardless.
Keep in mind that the same [Model] can be referenced as a single
ended buffer as well as part of a differential pair.

However, this is only a warning, and if you are aware of the
rules that the vdiff value overrides the Vinh and Vinl parameters
you can rest in piece that there is nothing wrong with your model.

Arpad Muranyi
================================================================

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of lee yang
Sent: Friday, March 04, 2005 6:40 AM
To: ibis-users@eda.org
Subject: [IBIS-Users] Vinl and Vinh For Differential Input Model

Hi IBIS experts,

As far i as concern, the differential input does not base on the Vinl and
Vinh to determine the voltage level but based on the difference between
posite and negative pins.
I am wondering that I got the warning if i did not put the vinl and vinh
values for diffrentil LVDS input model in an IBIS file. Why should we put
the values? And how can we determine the Vinl and Vinh values for LVDS or
any other differential input standards (since we only talking about Vid and
Vicm most of the time)?
Thanks a lot.

-Lee

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