[SI-LIST] Special Effects in Spice vs IBIS waveform correlation

From: Vishwanath Elechithaya <elechi@xxxxxxxxx>
To: si-list@xxxxxxxxxxxxx
Date: Mon, 13 Sep 2010 12:53:44 +0530

Hi All,
   I am seeing some unexpected behaviour of the IBIS models while comparing
with that of the Spice waveforms.
 Before I try to explain the actual problem, let me tell something about
what NOT a problem.

1. The IBIS waveforms Match well in Typical and MAX corners.and problem seen
only in Min.
2. There IS a time-shift required for the IBIS waveforms to match (as
initial dead times have been removed).
3. Double counting of C_comp is NOT a case (as I did this simulation already
and see no differences with ideal T-Line).
   Ref: http://www.semiconductorsimulation.com/dblcnt2.htm

Now to the actual probelm:

I am using a noisy 4inch microstrip model with 50Ohm termination as a
testload to a DDR IBIS model designed for datarate 1066Mbps.

The typical and max corner waveforms match well with that of Spice.
However, in the MIN corner, IBIS waveforms have higher overshoots!? (or do
Spice has under shoots?).

The C_comp values are derived with AC analysis @ 533MHz (Same freq @ which I
am running the simulations) so
I do not  suspect the C_comp values (and also as Typ & Max are running fine,
I do not suspect the method of C_comp extraction as well).

Any other pointer what other things could go wrong would be of great help.

Thanks in advance,
elechi


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[SI-LIST] Special Effects in Spice vs IBIS waveform correlation

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