[SI-LIST] Re: Regarding rising waveforms in the IBIS models

  • From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
  • To: <njy@xxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
  • Date: Thu, 12 Aug 2004 17:41:54 -0700

Historically, they are very likely to be different.  The peak to peak
amplitude depends on the output impedance of the buffer.  In one case, the R
to ground the pullup device is active controlling the amplitude of the
swing.  In the case of R to Vcc the pulldown device is controlling the
amplitude.  In most cases the pullup and pulldown devices do not have the
same DC output impedance so the amplitudes will differ.  I have noticed in
more modern processes the IV characteristics of the pullup and pulldown
better match each other.  This gives a more consistent output impedance,
independent of state, which makes serial termination easier to do.

Tom Dagostino
Teraspeed Consulting Group LLC
503-430-1065
tom@xxxxxxxxxxxxx
www.teraspeed.com

-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Jayasree Nayar
Sent: Thursday, August 12, 2004 5:37 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Regarding rising waveforms in the IBIS models


Hi all,
        Would like to get your inputs regarding the following questions
I have regarding the rising waveforms in an IBIS model:
In an IBIS model, for the two rising waveforms , one with V_fixture= 0
and the other with V_fixture =Vcc, should the total swing (difference
between the maximum and minimum voltage values) be the same.

If so, what could be the reason that there is a difference in the voltge
swing between the two rising waveforms.

Please advise. Thank you.

regards
Jayasree


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