Re: Rising Waveform Loading Effects

Dileep,

There are a few "dimensions" of knowledge not explicity present in the
.ibs model which may be useful to a simulator:

   - Nearly all digital drivers can be catagorized into one
     of a few unique output stages groups whose behavior
     can been studied in depth.

   - Transistors are well defined devices whose behavior
     has been studied for decades.

*** Simulator modeling algorithms are not trivial.

Given DC vi curves for high/low states and predetermined resistively
loaded waveforms as required by simulator, waveform prediction into
arbitrary loads is possible, proven and extremely reliable for
board-level analysis.

-Chris Rokusek
Quad Deisgn Technology

Dileep Divekar wrote:
>
> Arpad Muranyi, Intel Corporation wrote:
>
> > What I mean by this is, that if the simulator is smart enough, it can take the
> > data and modify it, derive new curves, etc. So, if you have an I-V curve and a
> > V-t curve which was generated with 50 Ohm resistive load in the model, a good
> > simulator should derive a new V-t curve that matches the different load
> > resistance in that particular simulation. Taking this further, the simulator
> > could make V-t curves with reactive loads also. In general, then, the simulator
> > can simulate at each iteration with a different set of curves that matches any
> > loading condition, even if the "load" is another non-linear I-V curve. The
> > point here is that the data in the IBIS model is not supposed to be a limiting
> > factor to what the simulator does with it.
>
> This is not quite true. Simulator cannot CREATE additional information.
> If V-t data is given only for one resistive load, how can the simulator
> create V-t data for arbitrary loading conditions? To illustrate the point,
> let us assume that the so called "load" can be described by only one
> independent variable. (In real life, it is an n-dimensional problem.)
> Let us assume that the dependent entity is the V-t curve. Thus, in this
> hypothetical two dimension space, the ibis specification gives one data
> point. From this single data point, there is no way to produce a straight
> line, or at least there is no UNIQUE way. If the ibis specification were
> to give two data points, then one can say that the simulator should be
> smart enough to fit a straight line thru these two points and then
> interpolate and extrapolate(although extrapolation is dangerous in many
> situations).
> [In practice, ibis specification has room to provide V-t curves for
> multiple loads, but the simulator is still limited by the information
> provided in the ibis model. It cannot CREATE V-t curves for the
> general n-dimensional case. The simulator may be able to do this if it
> makes certain assumptions, but since these assumptions are not specified
> in the ibis model, the simulation results will be unpredictable (and even
> unreliable).]
>
> ------------------------------------------------------------
> Dileep Divekar
> Applied Simulation Technology, Inc.
> 2188 Bering Drive
> San Jose, CA 95131
>
> Phone - (408)-434-0967 x 100
> Fax - (408)-434-1003
> Email - dileep@apsimtech.com
> ------------------------------------------------------------
Received on Tue Oct 29 15:51:01 1996