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

From: Shiv Harit MATHUR <shiv.mathur_at_.....>
Date: Wed May 30 2007 - 04:38:35 PDT
Hello Cary,

Thanks alot for guiding me. I have read those mails.

Regards
Shiv

Mandel, Cary wrote:

>Hello Shiv,
>
>A related question - regarding trimming V/T curve dead-times AND
>correlating simulations with Spice - was raised by a colleague of yours
>on the IBIS reflector on May 14, 2007. His name was 
>    Akhilesh Chandra - akhilesh.chandra@st.com
>
>I think the dialog - on the IBIS reflector - with Akhilesh should
>contain enough information to answer your question. I suggest you check
>the IBIS reflector archives - starting 14 May, which will contain a
>record of the dialog with Akilesh. You might want to contact Akilesh
>directly.
>
>Regards,
>Cary Mandel
>
>-----Original Message-----
>From: Shiv Harit MATHUR [mailto:shiv.mathur@st.com] 
>Sent: 30 May 2007 05:39
>To: rrwolff@micron.com; twesterh@sisoft.com; Mandel, Cary
>Cc: ibis-users@eda.org
>Subject: 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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Received on Wed May 30 04:39:43 2007

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