RE: [IBIS-Users] on-die termination

Ramiro,

Another approach to use for ODT is the submodel in the form of [Add
Submodel]. Since you're indicating you want to use this for an input
structure you should use the Non-Driving mode. You would then use the
Dynamic_clamp form of Submodel_type.

This approach is more complex and, therefore, probably only worthwhile
when the termination scheme warrants it. For example, an active form of
termination with a non-linear V/I characteristic. A simple, linear form
is easiest to handle in the clamp tables. The submodel form makes it
very clear to the user (who reads the .ibs file - poor, sad soul) that
it's there, whereas 'hiding' it in the clamps will make it less evident.
That said, I certainly wouldn't use the submodel for this reason;
something in the Notes section of the .ibs file can readily let users
know it's there in the clamps.

The IBIS spec. provides the answer to your question about when you can
(in fact, must) use Model_type Terminator. It also has a bearing on your
question about you having to use the [Rgnd] and [Rpower] keywords:-

"If one or more of [Rgnd], [Rpower], [Rac], and [Cac] keywords are used,
then the Model_type must be Terminator."

Be aware that your IBIS simulator tool will probably treat this type of
pin completely different than it treats an Input type. For example, this
type of pin may well be disregarded for timing measurements,
understandably, and it may be disregarded for signal integrity
measurements.

Note that these are not the only keywords that can be used in a
Terminator Model_type. A resistor model that uses [Series Pin Mapping]
and [R Series] could be of type Terminator.

Regards,
Tony

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of RODRIGUEZ_LECONA_RAMIRO
Sent: Monday, February 14, 2005 4:12 PM
To: ibis-users@eda.org; ibis-info@eda.org
Subject: [IBIS-Users] on-die termination


    Hi all, 

      How can I include on-die termination for an input structure in an
IBIS model? 

      Some people say that one way to include on-die termination is to
use superposition and add the termination currents to the diode currents
in the clamp sections. However this action is going to avoid that the
clamp curves reach the zero value so the IBIS parser will report a error
message. 

     Do I have to use the keywords Rgnd and/or Rpower?
     When can I use "terminator" as my [model type]? 

                                  Thanks.
      Ramiro
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