RE: [IBIS-Users] Extract IBIS data from lab measurement

Yuancheng

It is easy to extract good VT data from a measurement if you have the proper
equipment. We've done this for 1000s of models.

Hopefully you are not trying to measure at -3.3V. If you are I can
understand that there would be a large difference between what is measured
and what the manufacture's model shows. I've not seen an IC's ground clamp
that could handle that much forward bias. You need to keep the forward bias
to a volt or less in most cases and extrapolate to -Vdd. But without
knowing what difference you are seeing it is hard to tell why you are seeing
it.

Regards,

Tom Dagostino

Teraspeed Labs

13610 SW Harness Lane

Beaverton, OR 97008

503-430-1065

tom@teraspeed.com

www.teraspeed.com

Teraspeed Consulting Group LLC

121 North River Drive
Narragansett, RI 02882

401-284-1827

www.teraspeed.com

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf
Of ji xiao
Sent: Tuesday, November 23, 2010 1:15 AM
To: ibis-users
Subject: [IBIS-Users] Extract IBIS data from lab measurement

Dear all,

I want to extract the IV and Vt data from the chip measurement results, but
there are two problems.

1. For the Vt data, IBIS cookbook Version 4.0 and 5.0 only mention the
procedure of extract ramp rate. If I want to extract the detail Vt curve
table from the measurement results of a packaged chip, is it possible?

2. For the IV data, I successfully extract it from the measurement but the
extracted result only show agreement with original IBIS model (provided by
manufacturer) for operation region. When out of the operation region, i.e.,
in diode model, the IV characteristics I got is quite different from the
original one.

For example, the voltage operation region of my chip is [-0.5, 3.8], in this
range, the measurement value of current is reasonable. However, for the
current measured beyond this voltage range, such as [-3.3, -0.5], the
measurement result will distort severely from the original IBIS value. Could
anyone help me analyze the possible reason for the disagreement? Or is there
something wrong I may make in measurement setting? (I made the measurement
setup according to cookbook version4.0)

Thanks and regards,

Yuancheng

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