[SI-LIST] Re: EMC versus SI, or EMC + SI?
- From: "Peterson, James F (EHCOE)" <james.f.peterson@xxxxxxxxxxxxx>
- To: <olaney@xxxxxxxx>, <Chris.Cheng@xxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Mon, 24 Mar 2008 07:59:53 -0400
Orin,
Regarding your "yellow tab" comments. I'm guessing you were overstating
the point (90% of SI work can be done on a yellow pad), because of your
frustration with folks simulating without understanding the results and
the theory behind it. I get frustrated also... and worried. But the
bottom line is in these days we really need our SI tools (rules of thumb
are just way too conservative).
At DesignCon in 2007 (two DesignCons ago) I attended a presentation
where the CEO from SiSoft mentioned the "Hat Trick" for Signal
Integrity. (For us non-hockey fans, a Hat Trick in Hockey is when you
get 3 goals.) In SI, it occurs when the simulation, theory, and
measurement align. His point was that when these 3 things line up, only
then can you proceed confidently in your design. You have to understand
what you're simulating, and back it up with verification in the lab
(maybe the verification in the lab is not your own).=20
Regards,
Jim Peterson
Honeywell
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of olaney@xxxxxxxx
Sent: Monday, March 24, 2008 1:48 AM
To: Chris.Cheng@xxxxxxxx
Cc: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] EMC versus SI, or EMC + SI?
The field of EMC engineering is evolving from the classic test-and-fix
paradigm. The test lab guys will always be needed, but the new
perspective recognizes that many EMI problems are symptoms of underlying
SI faults best addressed at the design level rather than by slapping EMI
bandaids on a black box. Really good SI practitioners have some EMC
competence, and really good EMC engineers understand SI. At that level
of expertise the areas blend together because it's the same physics,
with
the difference that SI deals with the management of milliamps inside the
box while EMC deals in microamps leaking outside. The essential factor
that separates the men from the boys in either area is as stated:
"adequate understanding of the underlying principles" rather than
"iterat(ing) empirical designs into something workable". Software is
supposed to be a tool, not a crutch, and a yellow pad is for conceptual
work, not "accuracy down to -50dB" (assuming that is meaningful
information). Engineers who come to me waving simulation results but
cannot explain what makes the plots the way they are, can be very hard
to
help. In any instance, I presume we are agreed that digital is just a
special case of analog. The techniques and analog components necessary
for high speed designs prove it.
That is also why I have to disagree that "analog is analog". Opamps and
LC filters are one thing. A thing of a different kind is the ability to
inspect a layout to discern the hidden schematic of parasitic components
that govern many EMC/SI performance issues, the ability to visualize the
invisible fields that result, and the ability to gain useful information
from symptoms that change simply from moving a hand or touching a
surface. This is what makes EMC/SI seem like a black art to the
uninitiated. If you accept that RF engineering has long been a
specialty
not to be taken lightly, surely the ability to design competent audio or
power supply circuitry (both nontrivial tasks, based on the
specification
of competent as opposed to adequate) is not of itself qualification for
dealing with microwave rate bit streams.
Here's a thought for this forum: EMC has a recognized credential in the
form of NARTE certification for those who demonstrate relevant
experience
and pass a qualifying exam. Is the SI field ripe for an equivalent?=20
Should they be separate?
Orin Laney
P.S. Thank you, Roy, for the reference list.
On Sun, 23 Mar 2008 19:30:02 -0700 "Chris Cheng" <Chris.Cheng@xxxxxxxx>
writes:
I walked many miles in EMI and still do.
My company had never and will never have EMI only design engineers. I am
responsible for anything that is not 1 and 0 in our system. I don't care
if it is call SI or EMI. Analog is analog. Any engineer who work for me
is capable of doing both.
> As things stand today any EMI engineer can tell you that they can
> make an entire
> career on fixing prototype SI/EMI problems based on the same
> half-dozen principles
I am still waiting for you to tell me how your EMI engineer can make
their career out of my examples below.
From: Charlotte and/or Roy Leventhal [mailto:crleventhal@xxxxxxxxxxx]
Sent: Sun 3/23/2008 8:08 PM
To: Chris Cheng; olaney@xxxxxxxx; Roy.Leventhal@xxxxxxxx
Cc: avtaarenator@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Best Signal integrity Schools in the USA
Chris,
I'm heavily into using modeling and simulation. Check my website:
http://www.semiconductorsimulation.com. I'm also a great advocate of
combining EDA tools with the yellow pad for maximum efficiency and
understanding.
I recently had/have the opportunity to do some EMI engineering. Before
either SI engineers cast aspersions on EMI engineers or vice-versa I
suggest they walk in the others' moccasins a few miles.
You are right that EMI engineers will have to be better tool users in
the
future. Why don't you help them get started, as I am trying to do?
Best Regards
Roy
-----Original Message-----
From: Chris Cheng [mailto:Chris.Cheng@xxxxxxxx]
Sent: Sunday, March 23, 2008 7:52 PM
To: olaney@xxxxxxxx; Roy.Leventhal@xxxxxxxx
Cc: avtaarenator@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Best Signal integrity Schools in the USA
I would love to learn how to model a multi-giga bit channel with
accuracy
down to -50db with a yellow pad.
I would love to learn how to predict eye openings of heavily loaded
DDR2/3 buses with multiple loads and multiple branches and driving
positions under sso and crosstalk conditions with a yellow pad.
I would love to learn how to model package interconnects that has
imperfect return reference planes with a yellow pad.
I would love to learn how to deliver power to a multi-giga hertz IC
where
the power grid and via structure is inherited 2 1/2 and 3D with a yellow
pad.
Are you sure we are talking about the same SI work here ? What does your
average EMI engineer knows about the above anyways ?
From: si-list-bounce@xxxxxxxxxxxxx on behalf of olaney@xxxxxxxx
Sent: Sun 3/23/2008 2:07 PM
To: Roy.Leventhal@xxxxxxxx
Cc: avtaarenator@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Best Signal integrity Schools in the USA
The symptom we see today is that many designers are heavily reliant upon
really big, expensive software tools to iterate empirical designs into
something workable. The same designer, given adequate understanding of
the underlying principles, can often do 90% of the work on a yellow pad,
then use software for cleanup and as a sanity check. When I see SI
related job descriptions that want work experience with a big list of
tools, I can readily guess what the company mindset is: substitution of
tools for competence, and bring in the consultants when they get into
trouble.
Orin
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