[SI-LIST] Pin vs. Die
- From: "Craciun, Liviu-Dumitru" <liviu-dumitru.craciun@xxxxxxxxxx>
- To: "twesterh@xxxxxxxxxx" <twesterh@xxxxxxxxxx>, "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 9 Jan 2015 09:10:09 +0000
Hi Todd.
I agree "signal quality at the die is what matters".
Yet I make simulation ONLY at the die and at some test points.
To compare the simulations results with the measurements
we place test points somewhere on the transmission lines.
The position is NOT important !!
Why ?
The simulation tool is able to show the waveform at the test point,
with and without the influence of the scope probe.
If the measurements at the TP are in concordance with the simulation results
WITH the influence (with the load) of the scope probe ... then the simulation
reflects the reality.
So, the waveforms at the die will be "identical" with the simulation results.
Clear, plus minus tolerances.
Best regards,
Liviu Craciun
Harman Becker Automotive Systems GmbH
D-76307 Karlsbad, Germany
-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von Todd Westerhoff
Gesendet: Donnerstag, 8. Januar 2015 21:26
An: si-list@xxxxxxxxxxxxx
Betreff: [SI-LIST] Re: Pin vs. Die
Conrad,
Interesting question. Ultimately, it's the signal at the die that matters,
because that's the signal that gets received and processed. Anything else is
well, just, something else.
My experience matches yours - having poor signal quality at the pin but
acceptable quality at the receiving die is common, but the other way around
is rare. Uncommon enough that I can't remember the last time I saw it.
In years past, I've seen metrics that assessed signal quality at the pin, in
an effort to assure that signal quality at the die was acceptable. This was
a measurement-based methodology and I don't think it's in use anymore.
My vote - signal quality at the die is what matters.
Todd.
Todd Westerhoff
VP, Semiconductor Relations
Signal Integrity Software Inc. • www.sisoft.com
6 Clock Tower Place • Suite 250 • Maynard, MA 01754
(978) 461-0449 x24 • twesterh@xxxxxxxxxx
“I want to live like that”
-Sidewalk Prophets
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Conrad Herse
Sent: Thursday, January 8, 2015 3:04 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Pin vs. Die
Historically, when performing PCB SI (ibis) simulations I've always focused
on the SI quality of a signal when measured at the die of a receiving
device, if a signal needs to be monotonic I've ensured it's monotonic at the
die rather than at the pin. On (rare) occasions I've encountered instances
where simulations show a signal to have acceptable SI at the pin but not the
die, for these cases I've always worked to find improvements to achieve
acceptable SI in the die waveform.
Questions have been raised recently as to whether achieving good SI at the
pin of a device is adequate, without careful regard to the SI of a waveform
at the die. The rationale behind this being that datasheet specifications
were traditionally considered at the pin of a device. The reasoning goes
that if good SI is achieved at a device pin this meets the datasheet
specifications and no further improvements should be needed.
I personally do not subscribe to this line of reasoning but would be
interested in hearing feedback from others on this.
Thanks,
--
Conrad Herse
Alcatel-Lucent
Conrad.Herse@xxxxxxxxxxxxxxxxxx
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