Subject: RE: [IBIS-Users] RE: model issue for input receiver
From: Muranyi, Arpad (arpad.muranyi@intel.com)
Date: Thu May 01 2003 - 12:30:14 PDT
This is also a good way of doing it.
Arpad
=====================================
-----Original Message-----
From: Tom Dagostino [mailto:tom@teraspeed.com]
Sent: Thursday, May 01, 2003 9:02 AM
To: 'Todd Westerhoff'; 'Ibis-Users (E-mail)'
Subject: RE: [IBIS-Users] RE: model issue for input receiver
The approach I use is very simple to perform. Assume you have a pulldown
termination. I'd normally include the termination along with the ground
clamp. I start with the IV sweep that covers the full -Vcc to +2*Vcc range.
I create a second curve that is identical to the first except the current in
the range from Vcc to 2*Vcc is replaced by the linear extrapolation of the
current in the region between ground and Vcc. I then subtract the two. The
second curve will be the ground clamp curve and the subtraction becomes the
power clamp curve once the proper formatting is applied to it to make if Vcc
relative.
If the termination was a pullup I'd place the termination in the powerclamp
via the same method. The same procedure works for any arbitrary termination
voltage but in those cases you have to decide which clamp to put the
termination in.
Tom Dagostino
Teraspeed Consulting Group LLC Teraspeed Consulting Group LLC
2926 SE Yamhill St. Device Modeling Division
Portland, OR 97214 13610 SW Harness Lane
Beaverton, OR 97008
http://www.teraspeed.com 503-430-1065
tom@teraspeed.com
-----Original Message-----
From: owner-ibis-users@server.eda.org
[mailto:owner-ibis-users@server.eda.org]On Behalf Of Todd Westerhoff
Sent: Wednesday, April 30, 2003 9:34 PM
To: Ibis-Users (E-mail)
Subject: RE: [IBIS-Users] RE: model issue for input receiver
Funny you should say that - we were just puzzling over this yesterday!
Arpad - I agree with the statement that the terminator characteristics
should be in one clamp curve or the other - the question is - how?
If the input buffer truly uses on-die termination, then the DC sweeps you
perform for BOTH the ground clamp and the power clamp will include the
termination characteristics, correct? If you put those clamp curves in the
IBIS file as-is, won't you get twice the current (and therefore twice the
termination strength) you bargained for?
We were trying to figure out the right approach to de-embedding the
termination effect from either one of the clamp curves - can you shed any
light on this?
Thanks,
Todd.
Todd Westerhoff
High Speed Design Specialist
Cisco Systems
1414 Massachusetts Ave - Boxboro, MA - 01719
email:twesterh@cisco.com
ph: 978-936-2149
============================================
"When did the choices get so hard, with so much more at stake?
Life gets mighty precious when there's less of it to waste"
- Bonnie Raitt, "Nick of Time"
-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Muranyi, Arpad
Sent: Wednesday, April 30, 2003 6:41 PM
To: Eric Hsu; Ibis-Users (E-mail)
Cc: Frank Dunlap
Subject: [IBIS-Users] RE: model issue for input receiver
Eric,
No. The reason is because the difference between a terminator and an input
is
that the first one just terminates, and doesn't have Vinh and Vinl. If you
want to make an input model that also has an on-die terminator, you have to
put the terminator's characteristics into one or the other clamp IV curves.
Arpad
============================================================================
==
> -----Original Message-----
> From: Eric Hsu [mailto:ehsu@netlogicmicro.com]
> Sent: Wednesday, April 30, 2003 3:33 PM
> To: Ibis-Users (E-mail)
> Cc: Frank Dunlap
> Subject: model issue for input receiver
>
> Hi
>
> Can I choose "terminator" as my [model type] if I have an input receiver
with on die terminator? If true, can I also use subparameters [Vinh] and
[Vinl] to define input threshold voltage? If true, then what is the meaning
of "...but has no digital logic thresholds..." for terminator model in IBIS
spec. 3.2 version, page20?
>
> Best Regards,
>
> Eric Hsu
> Interface Technologies
> NetLogic Microsystems, Inc.
> 450 National Ave.
> Mountain View, CA 94043
> 650-961-6676 x198
>
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