[SI-LIST] Re: Do you ever measure any of the things you model?
- From: "Haller, Robert" <rhaller@xxxxxxxxxxxxx>
- To: "Scott McMorrow" <scott@xxxxxxxxxxxxx>, "Joel Brown" <joel@xxxxxxxxxx>
- Date: Tue, 1 Apr 2008 13:09:26 -0400
Bravo Scott
I was reminded by a good friend and Co-Author that we insisted the same
point at Designcon98 - Constructing Accurate Behavioral Models of I/O
buffers) From the Final slide
"Do it yourself or Put it in the PO!"
Summary
In order to insure sufficient noise and timing margins for error-free
system operation, it is absolutely critical to analyze a system design
using accurate, lab-verified circuit models. We have documented a
technique to verify models in the lab. We have demonstrated a method for
developing accurate behavioral I/O buffer models. We have shown that
their development involves a significant investment, and we have counted
the costs of making that investment. If you don't wish to spend your
time making and verifying models, write a specification for accurate
models and make it a condition of purchase.
Regards,
Bob=20
Robert Haller
Architect Engineer, Switching
Enterasys Networks
Phone: +1 978 684 1340
Fax: +1 978 684 1499
E-mail: rhaller@xxxxxxxxxxxxx
Web: www.enterasys.com=20
=20
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Scott McMorrow
Sent: Monday, March 31, 2008 7:50 PM
To: Joel Brown
Cc: 'Alfred P. Neves'; 'Tom Dagostino'; 'Schumacher, Richard (HSTD
Signal Integrity)'; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Do you ever measure any of the things you model?
Joel
Unless modeling compliance is directly tied to revenue, this situation=20
will not change. I encourage all of my clients to tie device models to=20
their purchasing requirements for components. A few companies do this.
Scott
Scott McMorrow
Teraspeed Consulting Group LLC
121 North River Drive
Narragansett, RI 02882
(401) 284-1827 Business
(401) 284-1840 Fax
http://www.teraspeed.com
Teraspeed(r) is the registered service mark of
Teraspeed Consulting Group LLC
Joel Brown wrote:
> It seems that the voluntary system of IBIS compliance is broken.
> Actually compliance is not the right word because we don't hold
anybody
> accountable for distributing bad models.
> Not only that, some companies don't offer models on parts they should
and
> sometimes it requires signing NDAs and waiting three months to get a
model
> (that actually happened to me).
> There is no counterpart to IBIS in the PDN world and there should be
because
> we can't guess at any accuracy what the on chip PDN and power spectrum
are
> which really makes it difficult to "design" the board PDN.
> When we all have to comply with and pass regular ISO audits in our
work
> environments, it seems that the equally important discipline of SI and
PI
> have no such standards to live up to. While a completely voluntary
system is
> desirable, it clearly is not working well. When will the industry wake
up
> and do something about this?
> End of rant.
>
> Joel
> =20
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Alfred P. Neves
> Sent: Monday, March 31, 2008 3:47 PM
> To: 'Tom Dagostino'; 'Schumacher, Richard (HSTD Signal Integrity)';
> si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Do you ever measure any of the things you
model?
>
> Adding to what Tom already said... My personal experience working at
> numerous semiconductor companies marketing high speed products (both =
=3D
> digital and analog oriented, including PHY's, SERDES, etc.,) is that
they =3D
> typically select a design engineer that generates the IV and VT
curves,
> along with dynamic characteristics with only simulations, no
measurements..
> =3D20
>
> Unfortunately, since design engineering time is expensive and the good
=3D
> ones are VERY busy designing new products, to my experience (not a
rule, and
> =3D not meant to insult any engineers who pride themselves in this
effort) it
> =3D was not always the most experienced or talented engineer that was
> designated =3D for this activity. =3D20
>
> This all of course assumes the design represents the process
variations, =3D
> the package model was included in the full simulation suite and the =
=3D
> simulation was set up and performed correctly.
>
> Anyhow, I recall a significant number of customers complaining that
the
> models either would not work at all (a test parser was not run) or
they
> poorly matched measurements. =3D20
>
> Maybe it is the geek in me, but it sends tingles up my spine when my
> simulations match almost perfectly to measure-based results.
>
>
>
>
> Alfred P. Neves=3DA0=3DA0=3DA0=3DA0=3DA0 <*)))))><{=3D20
>
> Hillsboro Office:=3D20
> 735 SE 16th Ave.=3D20
> Hillsboro, OR, 97123=3D20
> (503)=3DA0718 7172=3DA0 Business=3D20
> (503)=3DA0679 2429=3DA0=3DA0 Mobile=3DA0
> =3DA0=3D20
> Main Corporate office:=3D20
> Teraspeed Consulting Group LLC=3D20
> 121 North River Drive=3D20
> Narragansett, RI 02882=3D20
> (401) 284-1827 Business=3D20
> (401) 284-1840 Fax=3D20
> http://www.teraspeed.com=3D20
> =3DA0=3D20
> Teraspeed is the registered service mark=3D20 of Teraspeed Consulting
Group
> LLC=3D20
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] =3D
> On Behalf Of Tom Dagostino
> Sent: Monday, March 31, 2008 2:54 PM
> To: 'Schumacher, Richard (HSTD Signal Integrity)';
si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Do you ever measure any of the things you
model?
>
> Richard
>
> We measured one Quellan device for the model and used a different
device =3D
> 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 =3D
> 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 =3D
> at the hot low voltage point for a CMOS device. This would have given
a
> complete process/temperature/voltage model. =3D20
>
> But what we have seen from much experience is the IV and VT curves of
=3D 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
=3D the
> same process. We see stronger effects from temperature and voltage
than =3D 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=3D20
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] =3D
> 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 =3D
simulation
> =3D3D and measurements (a few psec correspondence for a 10Meter length
signal
> =3D pat=3D3D h, see page 36) made with our DSO. The correspondence =
was
very
> much =3D =3D3D3D du=3D3D e to the quality of the model in that it was
generated
> with very =3D carefully =3D3D acquired measure-base data using a high
signal
> integrity fixture, fast =3D TDR =3D3D head, etc.
>
> I checked the IBIS model separately and it looked exactly like
measured =3D
> dat=3D3D a in terms of not just rise/fall time in an eye diagram but
also the
> =3D pedest=3D3D al and features of the eye were captured extremely =
well.
I have
> found =3D IBIS=3D3D model accuracy to be critical, and unfortunately =
most
of
> the vendor =3D based =3D3D models are a bit disappointing in their
> representation.
>
> Check it out:
>
>
http://www.home.agilent.com/upload/cmc_upload/All/SI3_Teraspeed_Equaliza
t=3D
> io=3D3D
> n06.pdf "
>
>
> To be precise, this uses an IBIS model of a specific instance of the =
=3D
> Qualla=3D3D n RX, true? In other words parameters such as silicon
> characteristics, =3D ope=3D3D rating temperature, supply voltages, =
channel
> impedances etc. were =3D identical=3D3D in both the system and in the
> measurement-based model of that system. =3D How=3D3D good is the
agreement
> when that same IBIS model is used to simulate =3D anothe=3D3D r =
instance
of the
> same device type, or when that same device instance is =3D op=3D3D =
erated
at
> different but within-spec values for temperature or voltage?
>
> Could an IBIS model of the TX be used?
>
>
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