[SI-LIST] Re: package SSN model accuracy requirements, now Behavioral Modeling

  • From: Larry SMITH <Larry.Smith@xxxxxxx>
  • To: lgreen22@xxxxxxxxxxxxxx
  • Date: Fri, 18 Mar 2005 13:29:01 -0800

Lynne and all - A really basic question... Do all of these macro and
behavioral models for SSN properly account for the current on Vdd and
Ground as well as the driver output?

Sometimes the word "macro model" refers to a frequency domain model that
may only have a voltage or impedance when brought to the time domain.
It may not properly account for the current on the power rail.

It was mentioned below that "'Behavioral modeling' involves creating a
model from performance characteristics rather than topology."  I was
just wondering if the model still includes the VDD portion of the
topology, or is it more of a transfer function kind of model?

regards,
Larry Smith
Sun Microsystems

lgreen wrote:
> Hi, Donald and Syed,
> 
> In academia, a distinction is made between the two modeling approaches,
> although you are correct that the distinction is often fuzzy in industry.
> 
> "Macromodeling" involves adding components to a model.  A textbook example
> is adding components to an ideal op amp to add effects like input offset
> voltage, input bias current, output impedance, poles and zeroes, etc.  A
> macromodel's added components could be passive or active, linear or
> non-linear.  In this sense, all netlist-based tools (such as SPICE) can do
> macromodeling.
> 
> "Behavioral modeling" involves creating a model from performance
> characteristics rather than topology, usually using equations or data
> tables.   IBIS 3.2 is the classic example, but there are hundreds of
> AMS-style models that have been created over the past twenty years.
> 
> There is also a "meet in the middle" approach, where equation-based V and I
> sources are added to a model.  The use of a V or I component makes it
> macromodeling (in the academic sense of the word).  SPICE 3f5 seems to be a
> common subset of programmable sources for general purpose analog simulators
> (which means it is the most limited).
> 
> There are advantages to both approaches.  Macromodeling is easier to do if
> there is an existing model (such as an ideal op amp or IBIS buffer) that is
> almost what you need.  Behavioral models can simulate faster (factors of 10
> to 200, depending on how the model is coded), since they do not add
> extraneous components or nodes to the simulation netlist.
> 
> Best regards,
> Lynne
> 
> 
> "IBIS training when you need it, where you need it."
> 
> Dr. Lynne Green
> Green Streak Programs
> http://www.greenstreakprograms.com
> 425-788-0412
> lgreen22@xxxxxxxxxxxxxx
> 
> 
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of Donald Telian
> Sent: Friday, March 18, 2005 9:49 AM
> To: Syed Huq
> Cc: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: package SSN model accuracy requirements, now
> Behavioral Modeling
> 
> Syed,
> 
> Thanks for helping us refine terminology.
> 
> Let's be careful not to mix up concepts with tools and languages.  While
> it seems you want to confine "macromodeling" to something only Cadence
> tools do, I believe that if you look around you will find that
> 
> macromodeling =3D=3D behavioral modeling
> 
> ...and the two are used interchangeably within industry and academia.
> If you reference every one of the research papers I give links to on
> slide 22 - as well as the quote from Franzon - you will note that they
> all use "macromodeling" in both the titles and paper texts to describe
> their work in "behavioral modeling".  They use the term "macromodeling"
> to refer to various implementations spanning equation-based Hspice
> models, VHDL-AMS models in ICX, SPICE models in IBM PowerSPICE, etc.
> And yes, "macromodeling" can also be done in DML/Espice, Pspice,
> Berkeley SPICE, Verilog-AMS, and a variety of other tools/languages.
> 
> Regarding your comments about Cadence tools, I'll acknowledge that it
> takes a fair amount of skill and craftsmanship to construct effective
> macromodels.  However, I've yet to find a device that can not be
> behaviorally modeled in the environment.  Kumar and others have shown
> considerable skill in adding things like time-controlled sources, nth
> derivative processing, multi-dimensional table-based controlled sources,
> and such into our tools to make this possible.  Thanks to their
> contributions, users have had a number of published successes (slide 21)
> and implementing your BIRD95 ideas would be a snap.  If your team is
> struggling with other particular implementations, Cadence can provide
> you assistance in a variety of ways and would be happy to do so.
> 
> During the years while it's simpler for IC companies to encrypt and ship
> their transistor layout-derived model, and model users continue to ask
> for faster behavioral solutions, I think it's important that we keep an
> open mind regarding the options before us.  Working together, let's
> encourage those working on the various tools and languages as new
> solutions emerge and keep the comments on the positive side.  It's a
> challenging problem to solve.
> 
> Donald
> 
> 
> 
>>-----Original Message-----
>>From: Syed Huq [mailto:shuq@xxxxxxxxx]=20
>>Sent: Wednesday, March 16, 2005 2:44 PM
>>To: Donald Telian
>>Cc: si-list@xxxxxxxxxxxxx
>>Subject: Re: [SI-LIST] Re: package SSN model accuracy=20
>>requirements, nowBehavioral Modeling
>>
>>Donald,
>>
>>Certainly our definitions are different. What you described is=20
>>what I would call behavioral modeling. There is a difference=20
>>and let me explain with an example:
>>
>>Let's pick your tool. SpecctraQuest uses this DML scheme(which=20
>>I call macromodeling), in practical applications such as ours,=20
>>we see the tool choking in many aspects in it's use of macro=20
>>modeling. Hence I would like to stay far away from such an=20
>>approach(macromodeling I mean). Maybe version 20.x would have=20
>>it all sovled. I am sure there are 10s of other application=20
>>where is excels quite well too.
>>
>>On the other side, behavioral modeling (atleast again in our
>>applications) has already proven it's capabilities many times=20
>>over and I am more than open to explore further with tools to=20
>>see how BIRD95 could be implemented thru "behavioral modeling".
>>
>>Syed
> 
> 
> 
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
> 
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
> 
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> 
> List FAQ wiki page is located at:
>                 http://si-list.org/wiki/wiki.pl?Si-List_FAQ
> 
> List technical documents are available at:
>                 http://www.si-list.org
> 
> List archives are viewable at:     
>               //www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>   
> 

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List FAQ wiki page is located at:
                http://si-list.org/wiki/wiki.pl?Si-List_FAQ

List technical documents are available at:
                http://www.si-list.org

List archives are viewable at:     
                //www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts:

  1. Home
  2. si-list
  3. Archive
  4. 03-2005