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

Hello,

Thanks allot for your prompt and very useful suggestions. 

As you said we can trim off V/T curves dead-times, maintaining corner 
correlation intact
while losing out synchronisation across corners.
Now if i do so, then how can we validate our model ??

Also, does there exist some way to add these trimmed delay values in the 
model or the tool for different corners.
I think the dead-time value should be added to the internal delay value 
to avoid overclocking.

Regards
Shiv Harit Mathur



rrwolff@micron.com wrote:

>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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>

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