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. -------------------------------------------------------------------------------- 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. ------------- Review of ARs: - Yifan: Prepare draft2 of BIRD220.1 and send it to the ATM list. Done -------------------------- Call for patent disclosure: - None. ------------------------- 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. -------------- 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] ------------- Next meeting: 6 August 2024 12:00pm PT ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives