[SI-LIST] Re: IBIS Model Quality (or lack thereof)
- From: "Peterson, James F (FL51)" <james.f.peterson@xxxxxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Tue, 26 Mar 2002 07:18:47 -0500
Hello,
great question...I recently had an ASIC house create some models for an =
ASIC
they were making for us. I could tell by our talks that they were =
fairly new
to IBIS ("we've done a few of them, but the guy who used to do them is =
now a
manager").
how did we qualify the models? I had them take their spice model, which =
they
were very confident in, and create a 1 foot long 50 t-line. They sent =
me the
plots and I compared them with my sim's using their ibis model in the =
same
type of circuit. I look closely at the porch at the driver (source Z) =
and
the rise and fall times at the same place in both circuits. I also try =
to
make sure nothing else is significantly different.
this test would have been very easy for the semiconductor vendor to do =
- but
they first need very good spice models.
best regards,
Jim Peterson
-----Original Message-----
From: Todd Westerhoff [mailto:twester@xxxxxxxxxxx]
Sent: Monday, March 25, 2002 6:28 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: IBIS Model Quality (or lack thereof)
Oh no, here we go ...
For the record, we've had *VERY* good luck getting HSpice to correlate =
with
IBIS simulations - the problem is, we've had to create most of the IBIS
models ourselves ir order to get things to match.
Please, let's save the "ultimate HSpice accuracy" arguments for another
thread (preferably one that gets redirected to /dev/null). I'm well =
aware
of IBIS' limitations, and we've done lots of real-world comparisons for =
our
current applications. IBIS will work just fine if we have decent =
models ...
AND, I'll be able to do all the post-route analysis I want.
The question remains, folks ... what semiconductor vendors are willing =
to
"step up the plate" and tell us how they test their IBIS models to =
ensure
correlation to a known source (measurement or HSpice)?
Inquiring minds want to know!
Todd ;-)
Todd Westerhoff
Signal Integrity Engineer
Hammerhead Networks
5 Federal Street - Billerica, MA - 01821
email:twester@xxxxxxxxxxx - ph: 978-671-5084
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
"I=92m starting With the man in the mirror
I=92m asking him to change his ways
And no message could have been any clearer
If you wanna make the world a better place
Take a look at yourself, and then make a change"
- "Man in the Mirror", Michael Jackson
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Chris Cheng
Sent: Monday, March 25, 2002 5:18 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: IBIS Model Quality (or lack thereof)
Why use IBIS at all ?
If you are convinced that IBIS is not good enough (which I am), don't
simulate and just follow whatever the vendors design rules say. After =
=3D
all,
if you deviate from the rules based on your incorrect IBIS models, do =
=3D
you
think the vendor will really take responsibility if it doesn't work ? =
=3D
If you
follow the design rules, what value does the simulation add to you =3D
design ?
If you are serious enough to simulate, you must be working on something =
=3D
that
is unique about your own system that needs to be custom optimized =3D
beyond
what the component guideline can tell you. Get the SPICE model and do a =
=3D
good
job of modeling your own system. If a small little start up like mine =
=3D
can
get SPICE model from vendors, anyone can. Its just a matter of a few =
=3D
NDA and
extra effort.
-----Original Message-----
From: Todd Westerhoff [mailto:twester@xxxxxxxxxxx]
Sent: Monday, March 25, 2002 12:59 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] IBIS Model Quality (or lack thereof)
Hi all,
We have been doing a lot of comparisons between IBIS and HSpice models
lately, with a lot of less-than-satisfactory results.
I have an open question for the semiconductor suppliers among us:
What testing is performed after an IBIS model is created, to ensure =3D
that the
completed model behaves as expected? I'm interested in responses from
vendors that actually SIMULATE the IBIS model before distributing it =
=3D
for
customer use. It looks to me as though many of the models I've =3D
received
were never used in a simulation before being released ... and, as a
potential customer, I find that quite disheartening.
So the question is - what processes are being used to test IBIS models =
=3D
and
ensure they function properly before their release to customers?
As always, replies both on and off the list are greatly appreciated.
Todd.
Todd Westerhoff
Signal Integrity Engineer
Hammerhead Networks
5 Federal Street - Billerica, MA - 01821
email:twester@xxxxxxxxxxx - ph: 978-671-5084
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D
=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D=
3D=3D3D=3D3D=3D3D=3D3D=3D3D
"I=3D92m starting With the man in the mirror
I=3D92m asking him to change his ways
And no message could have been any clearer
If you wanna make the world a better place
Take a look at yourself, and then make a change"
- "Man in the Mirror", Michael Jackson
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