[SI-LIST] Algorithm to interpolate ramp data in IBIS
- From: "BHAGWATH,NITIN (HP-Roseville,ex1)" <nitin.bhagwath@xxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Thu, 20 Nov 2003 18:54:40 -0500
Hello all,
I am trying to convert a spice buffer model to ibis, and am having an issue
with the rampup/down portion. If I have a hundred (or fewer) points in a
rise or fall section with each point being sampled at a regular interval,
then the resolution of the curve seems to be inadequate for my purposes.
I have been reading articles about selectively removing points in the ramp
up/down curves to reduce the number of points required for a given accuracy.
Unfortunately, I have been unable to definitevely find an algorithm used by
IBIS simulators to interpolate data points at timepoints not in the IBIS
file given two data points in the IBIS file at timepoints on both sides of
the desired timepoint.
My understanding so far is that to extrapolate any values at times either
before or after the endpoints of the curve, the last two points are linearly
extended. More critically (for getting a good algorithm for points
removal), is it valid to assume that a voltage can be obtained for any
arbitrary time by taking the voltages at the two closest timepoints, and
linearly interpolating at the desired time using these two given points? If
so, then certain points can be removed if they can be obtained by two more
extreme points. Would there be any issues if the resulting ramp up/down
curves no longer have points at regular intervals of time?
Any help is much appreciated.
Thanks
-Nitin Bhagwath
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