[SI-LIST] Re: We ought to address mutual SI-EMI issues in thi s forum
- From: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>
- To: "'Michael_Greim@xxxxxxxx'" <Michael_Greim@xxxxxxxx>,Roy.Leventhal@xxxxxxxx, Ken.Cantrell@xxxxxxxxxxx,vishrampandit@xxxxxxxxxxx, cpad@xxxxxxxxx
- Date: Fri, 13 Sep 2002 10:18:14 -0700
No doubt this thread will generate the inevitable list of crude instruments
we all had to work with in the dark ages. My favorite ending goes something
like:
Engineer 1: "We had to write our 1's and 0's on the cave wall with
charcoal."
Engineer 2: "WHAT, you had 0's?!?!"
:-)
Jeff Loyer
-----Original Message-----
From: Michael_Greim@xxxxxxxx [mailto:Michael_Greim@xxxxxxxx]
Sent: Friday, September 13, 2002 10:12 AM
To: Roy.Leventhal@xxxxxxxx; Ken.Cantrell@xxxxxxxxxxx;
vishrampandit@xxxxxxxxxxx; cpad@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: We ought to address mutual SI-EMI issues in thi s
forum
I thought that the slide rule was what
Pete Rose used going into bases......
Ooops, there I go showing my age again.
Damn those vintage engineers and their romantic
glory days talk of old times and the slide rule.
I'm sure that this will soon be followed up with
a scintilating discussion on how circuit boards=20
were designed without a cad system and gerber data.
Yes, kiddos, it really happened.
Design before there was MTV, in the dark ages,
in the golden age of disco....
Blanket 8-) ;-P
-----Original Message-----
From: Roy Leventhal [mailto:Roy.Leventhal@xxxxxxxx]
Sent: Friday, September 13, 2002 10:35 AM
To: Ken.Cantrell@xxxxxxxxxxx; vishrampandit@xxxxxxxxxxx; cpad@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: We ought to address mutual SI-EMI issues in this
forum
Aaargh! I've been stabbed! I knew it would happen. Touch=E9.
A slide rule is an ancient weapon sometimes employed to beat on =
recaltriant
problems.
Best Regards,
Roy
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Ken Cantrell
Sent: Friday, September 13, 2002 9:08 AM
To: Roy.Leventhal@xxxxxxxx; vishrampandit@xxxxxxxxxxx; cpad@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: We ought to address mutual SI-EMI issues in this
forum
Roy,
Excellent summary and opinion, I'm sure all agree. I've got just one
question:
what is a slide rule?
Ken
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Roy Leventhal
Sent: Thursday, September 12, 2002 5:26 PM
To: vishrampandit@xxxxxxxxxxx; cpad@xxxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: We ought to address mutual SI-EMI issues in this
forum
Vishram and Chris,
You both make excellent points. Simulators need to be reliable, easy to =
use
and their complexity/detail needs to match (or be adjustable to a =
matching
level) the complexity/detail of the problem. You pay a premium in time,
money and missed schedules if they are too complex and detailed. You =
can be
seriously mislead if they oversimplify the issues involved. The same is =
true
of the models used in the simulator and your choice of what is =
important or
not.
The same is true whether you are talking SI, EMI, analog, logic or =
anything
else. The same was true when I was using a slide rule to analyze single
stage amplifiers, 3-stage IFs, etc.
I recently listened to a good friend's technical presentation on =
simulating
an EMI problem at our local IEEE chapter meeting. He is a VERY =
experienced
and senior engineer in this area. He delivered a strong message on the =
need
to make the right simplifications. At which point an experienced person =
can
"almost" see the solution.
For me one of the marks of a good engineer is that he or she knows the =
what,
when, etc., of both measurements and simulation/and analysis. That, and =
the
engineering judgment to know how to simplify a problem are some of the =
chief
value-added contributions they can make to a project's success.
So far I hope that I have reflected and reinforced your ideas.
But, beyond that I think there is something else. What happens when =
theory
don't match? Does the engineer understand theory well enough to know =
what to
expect from a simulation? Can they apply that understanding as soon as =
they
see the simulation results and give a rational explanation for those
results? Can they move ahead with imperfect models and simulation =
engines?
Do they have a feeling of when they are way beyond the capabilities of =
a
tool or model to provide reliable results? These are the challenges I =
set
myself. I don't always meet them. But, to do otherwise - well I might =
as
well shrug my shoulders and say "It's what the simulator gives me." and =
let
it go at that. Sometimes it takes quite a while to track down an =
answer. I'm
never happy until I do. Because, I believe one of the marks of a good
engineer is to contribute understanding. And, that is chiefly gained =
through
modeling (expaining with a story that can be expressed mathematically) =
and
simulation.
So, I proceed. I believe in my simulation and I build my product. And, =
it
doesn't behave as expected.
What have I missed? What is simply missing from or wrong in the model? =
Am I
using it beyond its specified range? Do I understand process variation =
and
have I modeled it?
The earliest (BJT) transistor models included basically 2 elements: an =
input
resistance and dependent (controlled) output generator. When the first
narrow-base planar process transistors were measured they didn't match =
the
model. Two elements - an output impedance and a dependent/controlled
(feedback from output to input) generator on the input were added. =
I.e., the
4-element, 2-Port, black box (y, z, h, abcd, etc.) transistor model. =
From
that the device physicists went to work trying to explain what was =
going on
and the SPICE program, it's a computer program not a model, =
incorporated
their improved modeling.
So, models and simulation must always proceed from trying to explain =
and
predict reality, i.e. measurements. As technology changes we've got to
expect to have to fix and extend the models and the calculation engines =
that
use them. We should be working on that in EMI/EMC.
When engineers who rely primarily on EMI measurements get a product =
that
doesn't behave as desired well, I doubt they shrug their shoulders and =
say
"Well it's what the measurements say." and let it go at that.
Modeling, measurement, a desire to understand and a willingness to push =
into
uncharted territory all belong in an engineer's tool bag.
Best Regards,
Roy
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Vishram Pandit
Sent: Thursday, September 12, 2002 12:42 PM
To: cpad@xxxxxxxxx; Roy.Leventhal@xxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: We ought to address mutual SI-EMI issues in this
forum
Hello,
I would like to express my views on this thread. I work for Hughes in =
EMC/SI
department. I had been looking for an EMC simulation tool for a long =
time.
We finally acquired a Signal and Power Integrity simulation tool that =
is
very helpful for EMC.
As discussed earlier, EMC phenominon is very complex to simulate as the
following factors contribute to it:
1] Originating sources
2] Coupling elements
3] Final Radiating elements.
Ideally, you need a simulator that includes all these, and still it =
will be
inadequate for certain situations (e.g., dynamic load, cable =
arrangements,
etc.).
SI analysis and EMC analysis go hand in hand. With the SI simulation =
you can
predict signal quality fairly accurately (in absolute gauge), while =
with the
EMC simulation you can only perform a relative analysis. You cannot =
directly
compare it to the FCC/EN limits. Of course, the simulation is only =
board
level, and coupling elements and radiating element are not considered. =
The
approach I use is attack the originating sources. Using my simulation =
tool I
try to improve the signal and power integrity on the board. Power
Distribution System plays a vital role in EMC. For signal analysis, =
only
certain nets are considered at a time, and the radiation effect of =
those
nets can be simulated (without the enclosure).
Of course, when the board comes out, I have to tweak the decaps and
ferrites, etc. But the debug time is considerably less for a board =
which has
been simulated for signal and power integrity earlier.
Comments are welcome if anyone has some other methods!
For a true EMC simulator, it may be a good idea to have a board level
analysis (including transmission line, circuits and field simulation) =
and
ability to apply the factors for external coupling elements and =
shielding
effectiveness for the enclosure. AS Chris mentioned, it needs to be =
simple
and reliable. May be we can take the corner cases and worst case =
coupling
and worst case shielding effectiveness. Again, it will be valid only =
for
those nets for which analysis is done. It needs to be performed =
separately
on different sets of nets.
Thanks,
Vishram Pandit
Hughes Network Systems
(301)212-7932
>From: Chris Padilla <cpad@xxxxxxxxx>
>Reply-To: cpad@xxxxxxxxx
>To: Roy.Leventhal@xxxxxxxx
>CC: <si-list@xxxxxxxxxxxxx>
>Subject: [SI-LIST] Re: FW: We ought to address mutual SI-EMI issues in
>this forum
>Date: Wed, 11 Sep 2002 17:04:56 -0700
>
>
>Gentlemen,
>
>A thought provoking discussion.... As an EMC/EMI engineer, I think I =
can
>add some thought to the thread below.
>
>First, I am a YOUNG EMC engineer...I have 4 short years under my belt =
at
>Cisco Systems and have a master's degree in EE focusing on, what else,
>EM. Cisco is my first job out of grad school.
>
>The reason I mention my youth and degree is to point out that I came =
from
>graduate school heavily involved in EM simulation software and
>research--most of it was for microwave frequency work. My job is in =
EMC
>Design for Cisco and I am passionately involved at every step of the =
PC
>design process. I do use simulation software to assist me with my
>job. Granted, I do not get to use it as much as I'd like to (the =
"job"
>tends to get in the way some times!) and I do end up spending most of =
time
>in semi-anechoic chambers scanning systems, using copper tape, =
changing out
>cap values, adding ferrites/cm-chokes, and playing with all sorts of =
filter
>designs. I mostly work in the 30 - 10000 MHz region but have lately =
been
>fighting switching frequencies of power supplies as a source of noise. =
It
>was interesting to be able to use circuit theory in its most basic =
form
>again without worrying about the inductance of my traces causing =
problem
>but I digress....
>
>There is one company out there that I am aware of that is focusing on =
the
>needs of EMC engineers and that is a firm called Flomerics. They have =
an
>EMC tool called FloEMC. It is based on the TLM method (akin to the =
FDTD
>method, time based....) and works very well for us. The main =
difficulty,
>pointed out clearly already, is the EMC simulation is a system level
>phemomenon whereas SI is more of a board level phenomenon. This =
doesn't
>mean one is more complex than the other but from a computer simulation
>point of view, system level modeling is significantly more difficult =
and
>consumes vast amounts of computer innards. The main trick with EMC
>simulations is to know when to include stuff from a system and to =
equally
>know when to leave it out to save resources. THAT is the most =
difficult
>part. One wants it complex enough to get meaningful, useful data but =
not
>so complex that it bogs your poor computer down to the point where the =
data
>is meaningless or simply never converges. I am quite happy with my
>simulation tool and it does help me but we are FAR from being able to =
put
>in a whole computer's motherboard and pushing a button to tell us if =
we are
>going to meet FCC Class B. How does one deal with the "variable load" =
that
>48 Cat5 UTP cables provide when running a Gigabit Ethernet board for
>compliance testing in a simulation package? Now THAT is a complex =
problem.
>
>Yes, EMC engineers are a skeptical bunch that is hard to please! If I =
run
>a scan of a system and the results are too good, I am suspicious and =
if the
>results are too bad, I am equally suspicious! It is a fine line =
before we
>are no longer suspicious.... With that, I am not too suspicious of my
>simulation software as it has proven itself a valuable tools several =
times
>already.
>
>
>Thanks,
>
>Chris Padilla
>EMC Engineer
>Cisco Systems
>San Jose, CA
>
> >-----Original Message-----
> >From: Roy Leventhal [mailto:Roy.Leventhal@xxxxxxxx]
> >Sent: Wednesday, September 11, 2002 4:56 PM
> >To: Fred Balistreri; si-list@xxxxxxxxxxxx
> >Subject: RE: [SI-LIST] We ought to address mutual SI-EMI issues in =
this
> >forum
> >
> >
> >Fred,
> >
> >Thank you for your reply. It is well informed , correct and thought
> >provoking in every respect. My "Yes, but(s):" do not take exception =
with
> >your reply. But, they are my questions and thoughts to you and the
>SI-LIST
> >as to where we are going in the future.
> >
> >First, there are traditions and history to consider. Simulation does =
not
> >seem to carry much weight or have much of a following in the EMI
>community.
> >This, perhaps, is one reason the SI community went its own way from =
the
>EMI
> >community because people saw that progress could be made. As you =
point
>out,
> >there is work to be done in producing usable data (package data
> >particularly) and software programs that do something with it. =
However,
>in
> >any died-in-the-wool attitudes against innovation there are always
> >individual exceptions and early adopters. I wish they would make
>themselves
> >known and join in the discussion. Because, I see simulation =
technology
> >positioned for a new period of some progress on EMI simulation.
> >
> >What I perceive EMI engineers would like to see in the way of =
simulation
> >would be a virtual test/EMI scan instrument that they can compare
>directly
> >with their instrument data no matter how large the board or how =
complex
>its
> >data patterns. I don't think that will happen anytime soon.
> >
> >But, I'm sure that SI engineers can learn to use the tools that are
> >available to do near field simulations, and think in terms of =
current
> >magnitudes and frequency spectrum content on a trace and radiation =
from
>it.
> >Then, based on the principle that you're money ahead if you knock =
down
>hot
> >spots on a board, do some intelligent EMI design, re-simulate, etc., =
to
>get
> >there. If this encroaches on some traditional EMI engineering turf, =
so be
> >it.
> >
> >I would welcome it if EMI engineers want to step up and start =
driving
> >progress on simulating EMI. That doesn't seem to be happening. But, =
I
>know
> >they're interested, smart and educated enough to be able to provide
> >leadership. Ten years ago I didn't much believe in any simulation
>software
> >either. But, an inquiring attitude informed by practical experience =
and
> >striving for improvement changed my outlook.
> >
> >The progress I do see happening in simulation packages includes =
dealing
>with
> >non-ideal reference planes, additional high frequency effects such =
as
> >dielectric losses and simulation of both near and far field =
radiation.
>I'm
> >sure there are other improvements that can be pointed out and yet to =
be
>made
> >if simulator companies believed that the ROI is there.
> >
> >Package data is missing as you and I have pointed out. Probably, the
> >majority of package engineers don't see it of any consequence to =
SI-EMI
> >problems on the board/system or their responsibility to provide it. =
But,
>I
> >believe speeds have been high enough for their assumptions and rules =
of
> >thumb to no longer be valid on leading edge technologies. If they =
opt out
>of
> >the issue of EMI contribution (and simulation of same) from the =
package,
> >there will exist an unbridgeable gap between board/system level
>simulation
> >and measurements. Leading edge companies are realizing this and =
driving
>to
> >see that gap filled.
> >
> >As I've stated, it's not intelligence, experience or anything else =
that
>is
> >holding back progress. It is assumptions. It's clear that progress =
is
>needed
> >when you consider the usual way products get qualified for
>EMI-regulatory
> >requirements. It's after the fact and back to the bench. Often with
>repeated
> >product dooming failures to pass regulatory.
> >
> >I believe we can do better. I've seen it done better, and in a small =
way
> >helped make that happen.
> >
> >Best Regards,
> >
> >Roy
> >
> >
> >-----Original Message-----
> >From: fred@xxxxxxxxxxxxxxxxxxxxxx [mailto:fred@xxxxxxxxxxxxxxxxxxxxxx=
]On
> >Behalf Of Fred Balistreri
> >Sent: Tuesday, September 10, 2002 6:00 PM
> >To: Roy.Leventhal@xxxxxxxx
> >Subject: Re: [SI-LIST] We ought to address mutual SI-EMI issues in =
this
> >forum
> >
> >
> >Roy, I agree with much of what you say. From an EDA vendor point of =
view
> >here
> >are some of the issues.
> >
> >1. Methodology; the traditional role of the EMI engineer would be to
> >pass compliance.
> > As such the tools used by the EMI engineer are more or less lab =
or
> >field instruments
> > for measurement. It is the nature that such testing be done at =
such a
> >time that the
> > hardware to be measured already exists. In my experience the EMI =
guy
> >is the last guy
> > to have input on the project and at that it's usually in the =
area of
> >the enclosure. By
> > nature EMI engineers and CAD do not mix well. I grant you that =
this
> >is changing. In
> > larger corporations or in companies where the product is very
> >expensive to manufacture
> > (think 10's of layers) or millions of units in volume, then some
> >great efforts are spent
> > up front. Usually those companies have three meter rooms and a =
great
> >deal of time and
> > effort goes into the design before the product ever makes it to =
the 3
> >meter chamber.
> >
> >2. The EMI engineer looks at more or less system level or product
> >problems. This usually or may involve
> > cables and several grounding systems, boxes etc. The EMI =
simulators
> >today can look at a system
> > level problem but at a very rudamentary level. Once we get into =
the
> >details of the IC models,
> > packages and lands we are in trouble. Yet it is these very tiny =
lands
> >and entities that often
> > are a cause of problems. The EMI engineer then would like to see
> >better coorelation between
> > simulation and what is measured in the field. This is something =
that
> >although sounds good, in
> > real life may be impractical.
> >
> >3. There are lots of technical problems to overcome in order to =
acheive
> >the goals set in number 2
> > above. One problem is that today's CAD data does not contain the =
3d
> >information for the IC packages.
> > Although its true that models of the package exist these are =
usually
> >in the form of LCR discretes
> > or transmission lines. They do not contain the x,y, z locations =
of
> >the structures. That information
> > is usually contained in a DXF or other 3d mechanical package =
which is
> >not an integral part of the
> > CAD layout program. The CAD program usually has a footprint =
only.
> >Still another nasty problem is
> > that the LCR information given is usually for signal nets only. =
The
> >pwr and gnd information is usually
> > not avaliable. That is also for a good reason. Unless the =
package is
> >one that contains internal gnd/pwr
> > layers it's not possible to predict the capacitive and inductive
> >properties. Those are determined by
> > the proximity of a plane, sometimes the plane is on the PCB =
board and
> >the IC package guy has no idea
> > where that plane may be located in the z axis. In other words =
the
> >simulation has to be done on the fly.
> > Pre-existing models don't work. And that goes back to the first
> >premise. The data is just not avaliable
> > in CAD. Another tid bit. The data for some of these packages is =
HUGE.
> >Still another problem is the IC
> > models itself. We have a pretty good grip on the I/O's thanks to =
IBIS
> >and SPICE. However the internal
> > currents are another story. Unfortunately in large LSI designs =
the
> >internal currents are rather substantial
> > and can cause tremendous SSI noise if not designed correctly. We
> >don't have any idea what these currents
> > are and the data for such is very difficult to get. Yet it is =
this
> >switching current that is the source
> > of a lot of problems. Needless to say there are other such nasty
> >problems that I don't see addressed
> > on the grand scale of things. Consider the enclosures which are =
also
> >designed outside of the PCB CAD.
> >
> >4. So as to not seem to put the shoe on the other foot. EDA vendors =
also
> >have had their share of problems.
> > Promises, promises and more promises have been meant =
disappointment
> >by the user community. I course
> > I would never make such a promise that I can't keep. But in the =
heat
> >of the battle salesman can slightly
> > overstate the capability or functionality of the tools, or make
> >claims, promises which cannot be fulfilled.
> > EMI engineers are by nature sceptics and there is most =
definately a
> >credability gap which is greater in
> > the EMI simulation community than exist in the general EDA =
world.
> >
> >Anyway these are some issues at the top of my head at the moment.
> >
> >Best regards,
> >
> >Roy Leventhal wrote:
> > >
> > > All,
> > >
> > > I'm sending you this message because I believe we need to begin =
much
> >better
> > > communications with our co-workers who concentrate on EMI/EMC =
issues.
>You
> > > can help by sharing your views. These can be on any subject of =
mutual
> > > interest between the EMI community and the SI community. But, to =
start
>the
> > > ball rolling, please share any of your thoughts on:
> > >
> > > 1. Productive ways to communicate between the two communities =
both at
>work
> > > and in outside venues such as symposiums and publications.
> > >
> > > 2. Modeling and simulation in SI and EMI and how this facilitates
> > > understanding.
> > >
> > > 3. Measurements and terminology and how this must relate the =
models
>and
> > > simulation used across different technical disciplines.
> > >
> > > 4. How best to draw into this communication other technical areas =
that
> >will
> > > have to be involved in order for any of us to succeed.
> > >
> > > 5. The role of standards.
> > >
> > > I agreed to be a point of contact between TC10 and SI-LIST. It is =
my
>aim
> >to
> > > facilitate communication between the EMI community and the SI
>community.
> > >
> > > For item 4 above I'm thinking of component package design and =
modeling
>for
> > > circuits AND EMI effects. Plus, the same issues for the IC chips
> >themselves.
> > > Plus the participation of the PWB and standards communities.
> > >
> > > Recently, I attended EMC 2002 in Minneapolis. I sat in on the =
meeting
>of
> > > IEEE EMCS Technical Committee 10 (TC10) "Signal Integrity and
> > > Microelectronic Technology." It was well attended by your peers =
with
> > > outstanding reputations in EMI who know about SI-LIST, but don't =
have
>the
> > > bandwidth to be very active in it. The attendees felt that the =
two
> > > communities are being driven together by the press and progress =
of
> > > technology. They also felt the impossibility of succeeding in
>isolation
> >from
> > > each other. There is a long tradition of interest in EMI in the =
IEEE.
> >While
> > > their evident interest in SI is very recent, I believe it is =
genuine.
>I
> > > noted at least 15 papers presented at the seminar that touched on =
some
> > > aspect of EMI from chips and packages. The IEEE press bookselling
>booth
> >also
> > > had a brand new text:
> > >
> > > "Signal Integrity Effects in Custom IC and ASIC Designs"
> > > Raminderpal Singh
> > > IEEE Press & John Wiley & Sons, Inc., c2002
> > > ISBN 0-471-15042-8
> > >
> > > I'll share some of my perceptions and opinions (based on my
>experiences)
> > > below to start this discussion going. Your experience, therefore
>opinions,
> > > can be different. So much the better for the sake of the =
discussion.
> > >
> > > I believe the relations between the SI community and the =
product/logic
> > > design community plus the PCB design community already have a =
good
> >teamwork
> > > paradigm that allows them to meld together their separate talents =
and
> >skills
> > > in a highly effective way. This work involves a lot of modeling =
and
> > > simulation at the front end, a (virtual) verification of layout =
and
> >routing
> > > and as a diagnostic tool of physical board problems. A lot of
> >communication
> > > goes on between this team to meet their mutual and sometimes
>conflicting
> > > goals. To simplify a lot:
> > >
> > > The logic engineer would be happy with logic that is hooked up
>correctly
> >and
> > > has good timing (ideal ones and zeros with infinitely fast =
edges).
> > >
> > > The SI engineer wants good clean switching waveforms without =
noise,
> >ringing,
> > > etc., for reliable switching. Fast edges often cause problems.
> > >
> > > The board engineer wants to achieve the above seemingly =
unreasonable
> >demands
> > > at minimum cost and maximum producability.
> > >
> > > Driver strength and speed, physical structures that radiate, =
support
>EM
> > > fields, have losses and influence feedback effects insure that =
what
> > > engineers and designers do at every physical scale impacts every =
other
> > > physical scale. Particularly at today's speeds and complexity.
> > >
> > > As an SI engineer I've noted that after the product engineer, the =
PCB
> > > designer and I complete our concurrent tasks the design process =
enters
>a
> >new
> > > (often excruciatingly painful) phase called "trying to pass
>regulatory."
> >In
> > > this endeavor there doesn't seem to be a lot of modeling, =
simulation
>and
> > > communication that goes on between the SI engineer and the EMI
>engineer.
> >The
> > > EMI engineer might be happiest with no fast edges at all and lots =
of
> > > shielding. There also seems to be many iterations of
>build-test-find/fix
> > > problems-retry. During this phase, if successful, there is a lot =
of
>stress
> > > on everyone.
> > >
> > > I know that EMI engineers are often every bit {and often more)
>technically
> > > sophisticated as I am. I presume that they would like to see
>simulations
> >at
> > > the system level with multiple boards, different data patterns,
> >enclosures,
> > > attached cables, etc., that would match their test bench data.
> > >
> > > For starters there is an extremely important missing area of =
models
>and
> >data
> > > that prevents this match up between system simulation and test =
stand
> > > measurements. That missing link is the EMI modeling of the chips =
and
> > > components on a board. Without it there is virtually no chance =
that
> > > simulation and measurement will ever match. Package modeling
>information
> >is
> > > often considered competitive and proprietary. However, in the =
IBIS
> >spec/data
> > > exchange approach we have the possibility of rendering the =
information
> > > behavioral and non-process specific as we go up from
> > > chip-package-board-system scale.
> > >
> > > Also, the above complex system level simulation might be =
impractical
> >without
> > > a lot more computing power than we have today.
> > >
> > > Lastly, such a system level simulation involves many different
>software
> > > capabilities. For example chip, board and system level components =
and
> > > structures probably involves several different modeling =
techniques.
>For
> > > example: SPICE, IBIS, S-parameter models plus different methods =
to
>handle
> > > radiation, (TLM, FDTD, MOM, PEEC?) non-ideal grounds, etc.
> > >
> > > What this really implies is cooperation between several competing
>software
> > > companies. Because, a company that attempted all this at once =
would
>lack
> > > focus and technical excellence. I see a number of such =
partnerships
>being
> > > discussed. But, potentially competing companies are just =
beginning
>such
> > > discussions.
> > >
> > > However, we are all missing an opportunity here if we wait for =
the
>system
> > > solution.
> > >
> > > That is an opportunity to inject increased modeling, simulation,
>design
> > > intelligence and communication into the step between SI and =
passing
> > > regulatory. We need to take the software tools as they are (or =
soon
>will
> >be)
> > > and use them apriori and diagnostically to knock down EMI risks =
and
> >problems
> > > on an individual net level. Then, proceed to feed the behavioral
> >information
> > > up/down to/from the next level of scale: =
chip-package-board-system.
> > >
> > > Simulation is critical in addition to a rules-based approach =
because
>you
> > > must get down to predicting/diagnosing what is actually going on
>amongst
> > > many possible physical mechanisms. The discussions on this list =
often
> > > involve heated advancement of different theories (rules) unaided =
by
>data.
> > > Models used in the simulation must be based on reality and then =
be
> >verified
> > > by measurement. Or, the models can be recognized as speculation =
when
>that
> >is
> > > an appropriate initial problem solving strategy.
> > >
> > > Design rules and standards have their place in this discussion. =
We
>would
> > > like to avoid paralysis by analysis.
> > >
> > > That which is considered physical is considered behavioral at the =
next
> > > physical level down. Ohms law (V, I, and R) involves electrons =
and
> >material
> > > properties at a more fundamental physical level and is considered
> >behavioral
> > > down at that level. I believe we need to investigate using =
voltage,
> >current
> > > and voltage-time curves plus auxiliary information as the data
>exchange
> > > format between the different physical scales.
> > >
> > > I recently participated in an exercise using modeling and =
simulation
> >apriori
> > > and diagnostically to knock down EMI risks with a client and =
their
>team.
> >It
> > > was very successful in terms of time, cost and performance vs. =
the
> > > traditional pass regulatory paradigm. They doubled their clock =
speed
>and
> > > were cleaner on EMI emissions than the older product on a much =
more
> > > compressed schedule. They didn't have to add an expensive =
shielding
>box.
> > >
> > > Simulation and modeling tools do not have to be perfect and =
complete
>to be
> > > of great benefit. You do need to know their limitations. All they =
have
>to
> >do
> > > is to assist you in the steady application of good design =
principles,
> > > problem solving and the implementation of design intent.
> > >
> > > The above experience also reinforced my belief that the best =
engineers
>use
> >a
> > > combination of simulation and measurement to meet their design
>challenges.
> > >
> > > Best Regards to All,
> > >
> > > Roy Leventhal
> > >
> > > =
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> > > List archives are viewable at:
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> > >
> >
> >--
> >Fred Balistreri
> >fred@xxxxxxxxxxxxx
> >
> >http://www.apsimtech.com
> >
> >
> >
> >
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