Subject: Re: [IBIS-Users] IBIS Info.
From: Al Davis (aldavis@ieee.org)
Date: Thu Mar 14 2002 - 09:26:00 PST
On Thursday 14 March 2002 09:39, Peters, Stephen wrote:
> That is one way of doing it. An easier method (easier in that
> you don't have to edit the actual netlist) would be to:
>
> a) set the output in the logical low then do the I-V sweep
> b) tri-state the output then do another I-V sweep
> c) subtract the two curves,
d) manually adjust the values in the difference curve to remove
numerical and measurement noise.
Remember, you are subtracting two large numbers to get a small one.
Based on the precision of the measurements, you really get an
interval in which the result lies. In the clamp region, this region
is large compared to the data, so you would be just as accurate just
calling it 0.
I have an idea:
c) Compute the derivatives of the two curves you want to subtract.
d) Check to see that they are reasonable. Correct if necessary.
e) Back-annotate the corrections to the original curves.
f) Subtract the derivatives.
g) Check to see that it is reasonable. Correct if necessary.
h) Integrate the result, using some known point in the non-clamp
region as a reference.
The state of the art in instrumentation and simulators is not
accurate enough for you to just subtract.
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