RE: [IBIS-Users] IBIS DIFF input buffers

Hi Eric,
If I understand you correctly you are using single-ended buffers to model
the inverting and non-inverting pins of a differential input buffer and you
are using the Series R keyword in IBIS to represent the on-die termination.

If so, then in general, your approach will be valid. Basically you will want
to generate the ground and power clamp IV curve on one differential input
pin. Depending on the differential buffer design and technology
(LVDS,CML,etc) you can leave the other differential input pin floating or
you may have to put some type of load on it as a feedback loop. Other
assumptions are that there is not differential current flowing as in a true
differential buffer and that you can essentially treat your differential
design as pseudo differential. If your differential design is unbalanced
then you should create separate buffer models for each differential input
pin.

Unfortunately there are still a lot of EDA tool issues with using Series pin
mapping and keywords so be aware of your end customers target environment.
You could also always try and include the on-die termination current in the
clamp IV curves to avoid using the Series keywords.

Hope this helps.

Best,

Tim

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of Eric Monteiro
Sent: Thursday, May 27, 2010 4:45 PM
To: ibis-users@eda.org
Subject: [IBIS-Users] IBIS DIFF input buffers

Hello Everyone

I need a little validation/clarification.

I have a differential input IBIS model, however my IBIS simulator is so out
of date that it does not recognize the Series Keywords. So instead what I
did was remove the series maping, and placed 2 single ended buffers with a
resitor whos value equalled that in the Series R definition: i.e.

------------|BUFFER|
        |
        Z
        Z
        |
------------|BUFFER|

My understanding is that the Diff buffer in IBIS DC tables should be the
COMMON mode current into ONE of the diffential pins (i.e. I assume its not
the sum of the current into the 2 pins, or 2 times the current I think it
is). Based on that, the above should be valid. Can anyone confirm?

Cheers,
Eric

This communication contains confidential information intended only for the
addressee(s). If you have received this communication in error, please
notify us immediately and delete this communication from your mail box.

-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
--------------------------------------------------------------------
|For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org
|with 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 e-mail a request to ibis-request@eda-stds.org.
|
|IBIS reflector archives exist under:
|
|  http://www.eda-stds.org/pub/ibis/email_archive/ Recent
|  http://www.eda-stds.org/pub/ibis/users_archive/ Recent
|  http://www.eda-stds.org/pub/ibis/email/         E-mail since 1993
-- 
This message has been scanned for viruses and
dangerous content by MailScanner, and is
believed to be clean.
--------------------------------------------------------------------
|For help or to subscribe/unsubscribe, e-mail majordomo@eda-stds.org
|with 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 e-mail a request to ibis-request@eda-stds.org.
|
|IBIS reflector archives exist under:
|
|  http://www.eda-stds.org/pub/ibis/email_archive/ Recent
|  http://www.eda-stds.org/pub/ibis/users_archive/ Recent
|  http://www.eda-stds.org/pub/ibis/email/         E-mail since 1993