[IBIS] Re: [IBIS-Users] Question regarding V-T data of IBIS model

From: Chris Reid <chris.reid_at_.....>
Date: Wed May 03 2006 - 08:52:44 PDT
Kiran,

The V(t) tables under different load conditions are all supposed to be used to generate a single model, so no choice is required.  The nominal model is a pullup transistor, a pulldown transistor, a power clamp, a ground clamp, and capacitance to ground.  The V(t) curves make it possible for the simulation tool to estimate the switching characteristics of the two transistors.  Two V(t) curves at different loading conditions are required to compute the two transistor characteristics.  If only one curve is supplied then the tool must assume that the switching of the two transistors is complimentary.

If more than two V(t) curves are supplied the system is over determined.  Most tools ignore the additional curves.  Ideally a least-squares fitting should be used to generate a model that best matches all supplied V(t) values.  I don't think any tools do that today.

Christopher E. Reid
Chief Scientist and Founder
Pressando SI
9315 SW Lake Street
Tigard, OR 97223-6034
503-869-6703 (cell)
503-624-8159 (home)

  ----- Original Message ----- 
  From: seshadri.kirankumar@wipro.com 
  To: ibis-users@server.eda.org ; ibis@server.eda.org 
  Sent: Wednesday, May 03, 2006 6:46 AM
  Subject: [IBIS-Users] Question regarding V-T data of IBIS model


  Hi Experts,

        

          I have a doubt on IBIS modeling regarding to V-T data using a Signal Integrity tool. 

  Suppose if IBIS model contains V-T data generated for different R_fixtures . how SI engineer is able to make the tool to use required R_fixture data  from all  V-T tables?

   

   As an example if I am generating V-T data(2 Risings and 2 Fallings) against 2 Rloads i.e RLOAD1 and RLOAD2  both are less than 100 Ohms, then s2ibis3 will put V-T will be in the below following order based on assumption  RLOAD1 > RLOAD2 

   

  Rising  connected VSS  using RLOAD1 

  Rising  connected VDDS  using RLOAD1 

  Rising  connected VSS  using RLOAD2 

  Rising  connected VDSS  using RLOAD2 

   

  Falling  connected VSS  using RLOAD1 

  Falling  connected VDDS  using RLOAD1 

  Falling  connected VSS  using RLOAD2 

  Falling  connected VDSS  using RLOAD2 

   

   So how a person using SI tool will chose the required V-T table data based on RLOAD1 and RLOAD2 ? or will these be taken care automatically by the tool?

   

  Thanks for providing information on this 

   

  Best Regards

  Kiran Kumar

   

   

   


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Received on Wed May 3 08:53:03 2006

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