Subject: Modeling method and Intel non-monotonic model

From: Kellee Crisafulli <[email-masked]>
Date: 05 Apr 94 23:52:30 EDT

From: Kellee Crisafulli, HyperLynx
Re: Which modeling method does HyperLynx use, and Does the Intel 
non-monotonic model work.

  How do you use the POWER/GND clamp and pullup/down curves in your simulations?

   a) summing method, or
   b) exclusive method

1) HyperLynx uses the summing method (per your definition).

  a) By the summing method I mean that the VI curve in the clamp section is added 
     to the VI curve in the pullup/down section for the ON condition.  For the OFF 
     (3-stated) condition, only the clamp curves are used.

   b) By the exclusive method I mean that the clamp curves are strictly used for 
      the 3-state condition, and the pullup/down curves are strictly used for the ON 
      condition without adding in the currents from the clamp sections.

2) I have tested the Intel model using a falling edge driving a long transmission
   line resulting in a very large reflection below ground (> -1V).  I examined
   numerous examples using the most current version of the LineSim Pro simulator
   version 3.2.  I found that the model at appeared to work fine.

I am still against allowing non-monotonic data in IBIS models, however our simulator was
modified several months ago to allow non-monotonic data.

In conclusion we see no problem with the Intel model that would prevent it from being
released.  On that other hand we also support requiring that all V/I tables be monotonic.

Have a great week... Kellee

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From: [email-masked] (C. Kumar)
Date: Thu, 7 Apr 94 09:50:09 -0400

Reflecting more on this issue..

   Even though the data from Intel contained non monotonicity, the model 
   itself worked out nicely because of the "addition" effect of the clamps. 
   But there may arise cases where we may have
   non monotonocity in the operating region which may real or may be an 
   artifact of the modelling method and software. Worse still , if the 
   simulations do not converge, it is almost impossible to tell whether
   it is an artifact of the simulator or the real device itself is 
   unstable. In such cases , which Jon and Kellee may be alluding to ,
   we may consider issuing general warning about the presence of
   non monotonic data.

- Kumar