[SI-LIST] Re: Do you ever measure any of the things you model?
- From: "Tom Dagostino" <tom@xxxxxxxxxxxxx>
- To: "'Schumacher, Richard \(HSTD Signal Integrity\)'" <schumach@xxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 31 Mar 2008 14:53:50 -0700
Richard
We measured one Quellan device for the model and used a different device for
the system test. When we measure a device we vary it's temperature and
supply voltage over the datasheet's operating limits. We usually do not get
process corner sample but if we did we would have used the strong fast
corner at the cold high voltage operating point and the slow weak corner at
the hot low voltage point for a CMOS device. This would have given a
complete process/temperature/voltage model.
But what we have seen from much experience is the IV and VT curves of the
random devices we get are very consistent from part to part of the same
manufacturing process. When I say part to part we are including both the
different die of the same part number and different part numbers from the
same process. We see stronger effects from temperature and voltage than we
see from process variation.
Regards
Tom Dagostino
Teraspeed(R) Labs
13610 SW Harness Lane
Beaverton, OR 97008
503-430-1065
503-430-1285 FAX
tom@xxxxxxxxxxxxx
www.teraspeed.com
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
401-284-1827
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Schumacher, Richard (HSTD Signal Integrity)
Sent: Monday, March 31, 2008 2:19 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Do you ever measure any of the things you model?
Drifting the topic a little:
"[...] developed a measure-based IBIS model of the Quallan equalizer
[...]
We were able to achieve excellent correspondence between system simulation =
and measurements (a few psec correspondence for a 10Meter length signal pat=
h, see page 36) made with our DSO. The correspondence was very much =3D du=
e to the quality of the model in that it was generated with very carefully =
acquired measure-base data using a high signal integrity fixture, fast TDR =
head, etc.
I checked the IBIS model separately and it looked exactly like measured dat=
a in terms of not just rise/fall time in an eye diagram but also the pedest=
al and features of the eye were captured extremely well. I have found IBIS=
model accuracy to be critical, and unfortunately most of the vendor based =
models are a bit disappointing in their representation.
Check it out:
http://www.home.agilent.com/upload/cmc_upload/All/SI3_Teraspeed_Equalizatio=
n06.pdf "
To be precise, this uses an IBIS model of a specific instance of the Qualla=
n RX, true? In other words parameters such as silicon characteristics, ope=
rating temperature, supply voltages, channel impedances etc. were identical=
in both the system and in the measurement-based model of that system. How=
good is the agreement when that same IBIS model is used to simulate anothe=
r instance of the same device type, or when that same device instance is op=
erated at different but within-spec values for temperature or voltage?
Could an IBIS model of the TX be used?
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