RE: [IBIS-Users] Simulation with VT tables for different load conditions

Hi All,
 Thanks for responses.
         Actually in one of the cases of modeling, I met with
over-clocking issue when I used R_fixture. Then I came to know that the
design was made only to drive capacitive load Hence I tried with
C_fixture value and modeled it. Initially I found problem with C_comp
but later by changing its value I was able to get good correlation when
compared with spice netlist simulation. Is that the way correct to model
if results are pretty good?

Regards
Surendra

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Muranyi, Arpad
Sent: Friday, September 17, 2010 10:15 AM
To: ibis-users@eda.org
Subject: RE: [IBIS-Users] Simulation with VT tables for different load
conditions

Bob,

Thanks for the note on this. This seems to be a pretty
clever way of doing the extraction, and fairly simple
too (as long as the *_fixture circuit remains simple
and can be solved like that).

But we need to be careful with our selection of words.
This presentation talks about extraction, and calculates
the I_die(t) in the presence of the known LRC *_fixture
elements during extraction. And this is the correct
answer to the original question which dealt with
*_fixture.

My presentation, on the other hand, deals with the
reactive loading problem of an I-V / V-t curve based
IBIS model during simulation. This problem cannot be
solved with the Synopsys presentation you quoted if the
basic IBIS algorithm only uses the 2EQ/2UK algorithm,
because it involves only Ohm's law and doesn't have
enough information for the EDA tool to solve the
differential equations associated with the reactive
loads.

So strictly speaking I have to admit that I didn't
answer the original question by quoting my own
presentation, but the two topics are related.

Arpad
========================================================

-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Bob Ross
Sent: Thursday, September 16, 2010 1:52 PM
Cc: ibis-users@eda.org
Subject: Re: [IBIS-Users] Simulation with VT tables for different load
conditions

Hi Sunrendra:

Even though IBIS has syntax to support reactive load elements
(L_fixture, C_fixture, and even L_dut and C_dut) we recommend
not extracting models using these elements. Some tools do not
even support these load elements, and others may support them
by vendor-specfic methods.

However, it is possible to process reactive loads by
accounting for the time-varying reactive path derivatives
within the four V-T methodology. One presentation provides
some details.

   http://www.eda.org/ibis/summits/sep07a/chen.pdf

Bob

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