Re: [IBIS-Users] ibischk4: ramp<->static curves

Katja and Andy:

Comments below.

Bob

Andrew Ingraham wrote:

>>... Do you have physical or mathematical
>>basis for the cosine wave?
>
>
> Not really. Just from observations of simulated and measured waves. A
> cosine wave is easy to simulate and has the right kind of rounded corners on
> both leading and trailing parts of the edge, and overall shape.
>
> I always was a little uncomfortable about the sharp corners in a Pulse or
> PWL waveform which never happen in real life.
>

The mathematical basis for a quadradic polynomial is that you
can produce smoothing that matches the start and end points AND
their slopes exactly at 0% and 100% and arbitrary percentages
(e.g., 20-80% , 10-90%, etc.) for a continuously smooth, but slightly
delayed "ramp". Other functions might also work.

>
>>And what about the signals into resistive loads?
>
>
> That's what I was talking about. Resistive load. Or light capacitive load
> (for on-chip signals).
>
> Heavy capacitive loads cause edges that aren't symmetrical, and are better
> modeled with the traditional RC exponential decay shape.
>
> Regards,
> Andy
>

-- 
Bob Ross
Teraspeed Consulting Group LLC     Teraspeed Labs
121 North River Drive              13610 SW Harness Lane
Narragansett, RI 02882             Beaverton, OR 97008
503-750-6481                       503-430-1065
http://www.teraspeed.com           503-246-8048 Direct
bob@teraspeed.com
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