IBIS Macromodel Task Group Meeting date: 29 October 2024 Members (asterisk for those attending): Achronix Semiconductor: Hansel Dsilva Altair: Junesang Lee 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 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 Samsung: Jun-Bae Kim 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. Curtis Clark took the minutes. -------------------------------------------------------------------------------- Opens: - None. ------------- Review of ARs: Michael: Prepare a new proposed update to the language surrounding Ts4file and Ramp and related cross checking that incorporates comments from the meeting. - Done. Yifan: Perform additional investigations into the applicability of BIRD220.1 for devices with independent pre-driver stages. - Done. -------------------------- Call for patent disclosure: - None. ------------------------- Review of Meeting Minutes: Arpad asked for any comments or corrections to the minutes of the October 22nd meeting. Jared moved to approve the minutes. Michael seconded the motion. There were no objections. -------------- New Discussion: Ts4file and [Ramp]: Michael reviewed his latest change proposal, which incorporated Ambrish's feedback from the previous meeting and had been sent to the ATM list shortly after the last meeting. Ambrish requested one additional change. He asked that "if present" be added to the last sentence of the new Ts4file language for extra emphasis on the fact that waveforms and I-V tables are optional when Ts4file is used (slide 4 - "Proposed New Language (2 of 6)"). Michael agreed. No other comments were offered. Michael said he would create a BIRD draft now that the language had been reviewed. Arpad suggested one final review cycle in ATM. Michael agreed. Arpad commented on the history of the possible confusion about [Ramp] and Ts4file. He said some early models that utilized s4p files, prior to the adoption of the Ts4file AMI parameter, had distributed the s4p files as stand- alone files that users manually imported into their schematics. In those early pre-approval models, the IBIS model ([Ramp]) was trying to drive an ideal step into the external (to the IBIS model) s4p files. Those pre-release models may have led to the confusion. If they were properly implemented as Ts4file models, then [Ramp] would not have served that "ideal stimulus" purpose. Arpad recalled that as part of these discussions we had considered the idea of extending [Ramp] with a few additional subparams. He said the idea would be to allow [Ramp] to be checked against all waveforms. He said it was reasonable to do this as a separate BIRD, but he asked whether people wanted it done. Ambrish said he didn't think it was necessary, and he asked why we would want to resurrect [Ramp], which is largely superseded by new keywords. BIRD220.1 update: Yifan reviewed the presentation IBIS_validation_1029.pptx. Previously, Yifan had found that the following equation for output pad PSIJ: PSIJ_total = PSIJ_pre-driver_power_noise + PSIJ_final_driver_power_noise did not hold in general for devices with independent pre-drivers. It held for experiments with the test load connected to GND but had not held when the test load was connected to Vcc. At the previous meeting, the group suggested the loading conditions used in the experiments might explain the unexpected Vcc results. The group had suggested redoing the experiments with the test load always connected to Vddq. That is, when measuring the pre-driver PSIJ by varying the voltage on the pre-driver rail, the test load would be connected to the nominal Vddq. When measuring the final driver PSIJ by varying the Vddq provided to the final stage, the test load would be connected to the varying Vddq. Yifan had redone the experiments under these conditions, and she reported that for all of her test cases, including single pre-driver stages, independent pre- driver stages with similar delays, and independent pre-driver stages with differing delays, the equation holds when the PSIJ values are measured with the test load tied to Vddq. In addition, for single pre-driver cases, the pre-driver PSIJ may be measured at the pre-driver output or the final output pad. For devices with independent pre-driver stages, both the pre-driver PSIJ and the final driver PSIJ should be measured at the output pad. With the new results, Yifan said that the previous restrictions on the device types for which the BIRD could be applied were no longer required. Yifan said she would prepare a new draft of the BIRD and remove the language regarding any restrictions on the use of its algorithm. Per Arpad's request at the previous meeting, Yifan shared several waveforms from experiments comparing SPICE results to IBIS results with the new PSIJ algorithm applied. Yifan noted that her baseline IBIS model was non-power-aware, due to limitations in the SPICE->IBIS toolset she used. However, given that starting model, she was able to demonstrate that the IBIS model with the new PSIJ algorithm successfully demonstrated the edge shifts due to pre-driver PSIJ that the SPICE model exhibited. She showed results for test loads of 50 Ohms to Vcc, 50 Ohms to GND, and 20pF to GND, and the IBIS model with the PSIJ enhancement matched the SPICE model's predicted edge shifts. Arpad and Randy thanked Yifan for her tireless investigations. - Curtis: Motion to adjourn. - Ambrish: Second. - Arpad: Thank you all for joining. New ARs: Michael: Create a BIRD draft incorporating the Ts4file and [Ramp] language changes. Yifan: Create a new draft of BIRD220.1 that removes the previous restrictions on its applicability. ------------- Next meeting: 5 November 2024 12:00pm PT ------------- IBIS Interconnect SPICE Wish List: 1) Simulator directives