RE: [IBIS-Users] Confused about clamp data in pull-up/down

Bob

I think the following should be modified:

(4.3.14) Any IBIS models with on-die termination should be labeled as
such using comment lines. On die termination should be modeled in [Power
Clamp] and/or [GND Clamp] tables. Document the method used to embed the
termination into the clamps.

It is proper to model on die terminations as series elements if appropriate.
Trying to put a differential termination into the power and ground clamps is
not possible.

Regards

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 Robert Haller
Sent: Tuesday, June 21, 2005 9:55 AM
To: De Paepe, Kristiaan
Cc: 'ibis-users@eda.org'
Subject: Re: [IBIS-Users] Confused about clamp data in pull-up/down


Kriistiaan
    Different model creators construct models differently, and different
CAD tools may implement IBIS features differently. A good model creator
will construct a model so that it will behave properly (and correlate to
reality) in all simulators. But at a  minimum a model creator should
construct, validate and document the methods and correlation achieved.
The IBIS quality committee recommeds the following  regarding IV curves
(subset);

(4.3.4,4.3.5) The sweep for [Pulldown], (Pullup) should be made between
-vcc to 2*vcc. The Pulldown,(pullup) table combined with the power and
ground clamp should be monotonic. Non-monotonic combined I-V tables must
be documented.
(4.3.6)[GND Clamp] should turn on approximately one Diode drop below 0.0
(i.e. 0.7 volts). The sweep for [GND Clamp] should be made at least
between -vccmax and +vccmax (it is permitted to extend the range).
Non-monotonic I-V tables must be documented.
(4.3.14) Any IBIS models with on-die termination should be labeled as
such using comment lines. On die termination should be modeled in [Power
Clamp] and/or [GND Clamp] tables. Document the method used to embed the
termination into the clamps.


Regards,
Bob Haller
Chair IBIS Quality Committee

De Paepe, Kristiaan wrote:

> Dear experts,
>
> I'm a little confused. While going through some papers, I got confused
> about data I found in a particular LVTTL IBIS model of a normally
> trusted source.
>
> At least one source of knowledge tells me that nor the pullup nor the
> pulldown curves should contain clamping information (3-stated input
> static clamping).
>
> Although, when viewing the curves, I can clearly observe a typical
> diode behaviour (for pulldown, gnd relative this appears above vcc,
> for the pullup, this appears below 0V)
>
> This made me lose my marbles, with only a few to spare...
>
> I tried finding any supporting information, but all sources I found,
> state the same conditions.
>
> Can somebody pls explain why these curves are (in)correct?
>
> Many thanks,
>
> Kind regards,
>
> Kristiaan
>
>
>
> *BarcoView*
> Command & Control - TDT
> Pr. Kennedypark 35
> B-8500 Kortrijk
> Belgium
> Tel: +32-56-233408
> Fax:+32-56-233462
> _<mailto:kristiaan.depaepe@barco.com>_
> _<http://www.barcoview.com <http://www.barcoview.com/>>_
>
>
>
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