IBIS Macromodel Task Group
Meeting date: 30 July 2024
Members (asterisk for those attending):
Achronix Semiconductor: Hansel Dsilva
Amazon: John Yan
ANSYS: Curtis Clark
* Wei-hsing Huang
Aurora System: * Dian Yang
Raj Raghuram
Cadence Design Systems: * Ambrish Varma
* Jared James
Dassault Systemes: Longfei Bai
Google: Hanfeng Wang
Gawon Kim
Intel: * Michael Mirmak
* Kinger Cai
Chi-te Chen
Liwei Zhao
Alaeddin Aydiner
Sai Zhou
Keysight Technologies: Fangyi Rao
Majid Ahadi Dolatsara
Stephen Slater
Ming Yan
Rui Yang
Marvell: Steve Parker
Mathworks (SiSoft): Walter Katz
Graham Kus
Micron Technology: Justin Butterfield
Missouri S&T: * Chulsoon Hwang
* Yifan Ding
Zhiping Yang
Rivos: Yansheng Wang
SAE ITC: Michael McNair
Siemens EDA (Mentor): * Arpad Muranyi
* Randy Wolff
Signal Edge Solutions Benjamin Dannan
Teraspeed Labs: [Bob Ross]
Zuken USA: Lance Wang
The meeting was led by Arpad Muranyi. Randy Wolff took the minutes.
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Opens:
Kinger noted he would like to start discussing again the topic of power
delivery including refining models of components of the PDN. Arpad added an
item to the agenda.
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Review of ARs:
- Yifan: Prepare draft2 of BIRD220.1 and send it to the ATM list.
Done
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Call for patent disclosure:
- None.
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Review of Meeting Minutes:
Arpad asked for any comments or corrections to the minutes of the July 23rd
meeting. Randy moved to approve the minutes. Chulsoon seconded the motion.
There were no objections.
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New Discussion:
BIRD220.1:
Yifan shared the updated BIRD draft (bird220.1_v2_0729.docx). Keyword names
were updated. The example tables were updated. Randy noted the comment in the
examples showing the units needed updating to (s) from (V/s).
Yifan said that in the last meeting there was a question about whether to put
the keywords under [Model] or under the V-t waveforms. She showed some slides
with data looking at the PSIJ of pre-driver and final driver separately. With
only pre-driver noise, the PSIJ was consistent between 3 different test loads.
When applying noise to the output stage as well, there was some difference, but
this could be accounted for due to load dependencies. The conclusion was that
the PSIJ could be located under [Model], since the values were not sensitive to
load.
Arpad asked about the condition with a common pre-driver design made of two
inverters separately driving the gates of the final driver transistors. Yifan
had not studied that case. Arpad said this design was commonly used to
separately adjust pullup and pulldown timing to avoid crowbar currents during
final driver switching.
Randy noted the difference in the PSIJ values with the C_fixture test load are
likely due to RC time constants, and changing the C_fixture value would likely
show a direct effect on PSIJ. He recommended using only R_fixture values to
characterize PSIJ.
Arpad will share a SPICE circuit used in his IBIS modeling classes (found on
the IBIS website) with Yifan so she can use it for further study [AR].
SPIM Transient Analysis:
Kinger updated his proposal to use a PWL source defined by a [SPIM icct File]
keyword. An external text file contains the icct current information in two
columns, time and current. Generation of the current is with an ideal voltage
source powering the silicon circuit. How to use the icct profile needs to be
defined in the specification. The keyword also defines a delay time and repeat
time.
The spec will define how EDA tools could use a second-order G-element POLY
source to add the icct profile in simulation.
Kinger sent his slides to the ATM email reflector already.
Ts4file Discussion:
Michael reminded everyone the discussion was about updating descriptions of
Ts4file usage in the specification. He proposed some new language describing
Tx_R and Rx_R. He also proposed new language on page 315, describing that
Ts4file completely replaces [Model] data such as C_comp, I-V curves, and
[Ramp]. The impact is that the parser should not check for I-V and V-t
mismatches and I-V and [Ramp] mismatches.
Ambrish asked if the language is present with [External Model]. Michael was
not sure. Arpad found text on page 136 of IBIS 7.2 that [Ramp] in the scope of
[External Model] provides the EDA tool with a first-order estimate of driver
switching characteristics. Arpad was concerned with completely ignoring [Ramp]
values in the Ts4file context given this statement. We may need to also fix
the contradiction on page 136 with other IBIS statements regarding [Ramp] as
being ignored when using [External Model].
Michael commented that [External Model] is not widely used. But a common use
of [Ramp] is for bandwidth estimation. Do we still need [Ramp] to be valid?
It is probably too much trouble to remove the keyword.
Arpad noted that you can get time domain waveforms when using Ts4file. He
thinks it is useful to have reasonable [Ramp] values when using Ts4file.
Michael noted you could do several cross-checks of Ts4file with I-V and [Ramp],
but that would require more complex parser behavior.
Ambrish noted you could have bad [Ramp] data and never know it.
Arpad planned to collect quotes from the spec related to [Ramp] usage for
further discussion [AR]. Michael will wait to share his slides until further
discussion from Arpad is completed.
Michael noted he also wanted to be sure to clarify that [Ramp] is not meant to
be part of the stimulus definition for Ts4file.
- Ambrish: Motion to adjourn.
- Michael: Second.
- Arpad: Thank you all for joining.
New ARs:
Arpad will share a SPICE circuit with Yifan for further study [AR]
Arpad to collect quotes from the spec related to [Ramp] usage for further
discussion [AR]
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Next meeting: 6 August 2024 12:00pm PT
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IBIS Interconnect SPICE Wish List:
1) Simulator directives