RE: [IBIS-Users] V/T Window adjustment

Shiv,

I have modeled similarly fast switching buffers by removing leading
"dead" time from the V-t waveforms.  I treat min, typ, and max corners
as independent sets of V-t curves.  Make sure to remove the same amount
of time from all 4 min curves, typ curves, or max curves to maintain the
correct timing between the curves to different termination voltages.  I
also document in the Notes section of the model the amount of time I
shift the typ relative to the max and the min relative to the max (in
case someone wants to match up the spice model to the IBIS model).

You only show one set of V-t waveforms in the attached JPEG, but
assuming that these curves represent the earliest switch times, I would
trim off approximately the following delay times from the three corners:

Max: 90ps
Nom: 175ps
Min: 350ps

I suggest you submit your model to the IBIS Model Review Committee when
you are done and ready for a final check.

Regards,
Randy

Randy Wolff 
SI Modeling Manager 
Signal Integrity R&D Group 
Micron Technology, Inc. 


-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Shiv Harit MATHUR
Sent: Tuesday, May 29, 2007 4:14 AM
To: ibis-users@eda.org; ibis-users@eda.org
Cc: Shiv Harit MATHUR
Subject: [IBIS-Users] V/T Window adjustment

Hello Experts,

I am trying to model a buffer whose freq of operation is 1.5Ghz (time
period = 666ps).
While extracting the V/T curve for the buffer we need to take up a
window of not less than 800ps to cover all the three waveforms. The
buffer delay in MAX,NOM and MIN CORNERS is 130.31ps, 228.44ps and
424.08ps respectively.

Please find the snapshot view of the rising output waveform "TXP" of the
buffer in three corners, "SB" is the Input data given to the buffer (the
  delay values are almost same for the falling stimuli also)

Now the problem is that if I extract and dump these values in the IBIS
model, the model will certainly fail in the worst and typical cases as
the bit time is 333ps (< V/T window size). Although it will give a good
match only if MAX corner is considered.

Can anybody please suggest, what could be done for this case in order to
model the behaviour of the buffer correctly in all three corners ?

Regards
Shiv Harit Mathur
STMICROELECTRONICS PVT LTD
INDIA

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