Subject: RE: [IBIS-Users] Modeling input receivers with on-die termination
From: Mike LaBonte (milabont@cisco.com)
Date: Thu May 08 2003 - 14:16:15 PDT
There is a way to deal with any uncertainty over how simulators will treat
the "missing" data in power clamp and gnd clamp curves - don't have any
missing data! If both curves extended from -VDD to 2VDD there would be no
guessing. Of course if you are going to go that far, why not just model both
clamps in one curve (Proposal 1). But even if you do Proposal 2, don't end
the curves at the zero current point. Take the zero current all the way to
the other end of the voltage range. Don't make the simulators guess what the
remaining data is.
An observation: characterizing both clamps in one V/I curve is more or less
a black-box approach, in that it does not assume any knowledge that the
buffer has separate diodes connected to power and ground. It just measures
how the buffer behaves when tristated. I like the simplicity of that. Now if
we measured the static behavior of the buffer in 2 other states and added
dynamic info on how to make the transitions from each state to the others we
would have a truly behavioral model, with no notion of structure. In our
attempt to model the behavior of buffers at 3 ports (pad, power, ground)
IBIS became complicated.
Mike
> -----Original Message-----
> From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
> Behalf Of Todd Westerhoff
> Sent: Thursday, May 08, 2003 1:44 AM
> To: Ibis-Users (E-mail)
> Subject: [IBIS-Users] Modeling input receivers with on-die termination
>
>
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