[SI-LIST] Re: Do you ever measure any of the things you model?
- From: Scott McMorrow <scott@xxxxxxxxxxxxx>
- To: Joel Brown <joel@xxxxxxxxxx>
- Date: Mon, 31 Mar 2008 19:49:32 -0400
Joel
Unless modeling compliance is directly tied to revenue, this situation
will not change. I encourage all of my clients to tie device models to
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® 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
>
>
> -----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 =
> digital and analog oriented, including PHY's, SERDES, etc.,) is that they =
> typically select a design engineer that generates the IV and VT curves,
> along with dynamic characteristics with only simulations, no measurements..
> =20
>
> Unfortunately, since design engineering time is expensive and the good =
> ones are VERY busy designing new products, to my experience (not a rule, and
> = not meant to insult any engineers who pride themselves in this effort) it
> = was not always the most experienced or talented engineer that was
> designated = for this activity. =20
>
> This all of course assumes the design represents the process variations, =
> the package model was included in the full simulation suite and the =
> 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. =20
>
> 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=A0=A0=A0=A0=A0 <*)))))><{=20
>
> Hillsboro Office:=20
> 735 SE 16th Ave.=20
> Hillsboro, OR, 97123=20
> (503)=A0718 7172=A0 Business=20
> (503)=A0679 2429=A0=A0 Mobile=A0
> =A0=20
> Main Corporate office:=20
> Teraspeed Consulting Group LLC=20
> 121 North River Drive=20
> Narragansett, RI 02882=20
> (401) 284-1827 Business=20
> (401) 284-1840 Fax=20
> http://www.teraspeed.com=20
> =A0=20
> Teraspeed is the registered service mark=20 of Teraspeed Consulting Group
> LLC=20
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] =
> 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 =
> 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. =20
>
> 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=20
>
>
> -----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
> =3D and measurements (a few psec correspondence for a 10Meter length signal
> = pat=3D h, see page 36) made with our DSO. The correspondence was very
> much = =3D3D du=3D e to the quality of the model in that it was generated
> with very = carefully =3D acquired measure-base data using a high signal
> integrity fixture, fast = TDR =3D head, etc.
>
> I checked the IBIS model separately and it looked exactly like measured =
> dat=3D a in terms of not just rise/fall time in an eye diagram but also the
> = pedest=3D al and features of the eye were captured extremely well. I have
> found = IBIS=3D model accuracy to be critical, and unfortunately most of
> the vendor = based =3D models are a bit disappointing in their
> representation.
>
> Check it out:
>
> http://www.home.agilent.com/upload/cmc_upload/All/SI3_Teraspeed_Equalizat=
> io=3D
> n06.pdf "
>
>
> To be precise, this uses an IBIS model of a specific instance of the =
> Qualla=3D n RX, true? In other words parameters such as silicon
> characteristics, = ope=3D rating temperature, supply voltages, channel
> impedances etc. were = identical=3D in both the system and in the
> measurement-based model of that system. = How=3D good is the agreement
> when that same IBIS model is used to simulate = anothe=3D r instance of the
> same device type, or when that same device instance is = op=3D erated at
> different but within-spec values for temperature or voltage?
>
> Could an IBIS model of the TX be used?
>
>
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