IBIS Macromodel Task Group

Meeting date: 21 October 2008

Members (asterisk for those attending):
  Ambrish Varma, Cadence Design Systems
  Anders Ekholm, Ericsson
* Arpad Muranyi, Mentor Graphics Corp.
  Barry Katz, SiSoft
* Bob Ross, Teraspeed Consulting Group
  Brad Brim, Sigrity
  Brad Griffin, Cadence Design Systems
  David Banas, Xilinx
  Donald Telian, consultant
  Doug White, Cisco Systems
  Essaid Bensoudane, ST Microelectronics
  Fangyi Rao, Agilent
  Ganesh Narayanaswamy, ST Micro
  Gang Kang, Sigrity
  Hemant Shah, Cadence Design Systems
  Ian Dodd, Agilent
  Joe Abler, IBM
* John Angulo, Mentor Graphics
  John Shields, Mentor Graphics
  Ken Willis, Cadence Design Systems
  Kumar
  Lance Wang, Cadence Design Systems
  Luis Boluna, Cisco Systems
* Michael Mirmak, Intel Corp.
* Mike LaBonte, Cisco Systems
  Mike Steinberger, SiSoft
* Mustansir Fanaswalla, Xilinx
  Patrick O'Halloran, Tiburon Design Automation
  Paul Fernando, NCSU
* Pavani Jella, TI
* Radek Biernacki, Agilent (EESof)
* Randy Wolff, Micron Technology
  Ray Comeau, Cadence Design Systems
  Richard Mellitz, Intel
  Richard Ward, Texas Instruments
  Sam Chitwood, Sigrity
  Sanjeev Gupta, Agilent
  Shangli Wu, Cadence Design Systems
  Sid Singh, Extreme Networks
  Stephen Scearce, Cisco Systems
  Steve Pytel, Ansoft
  Syed Huq, Cisco Systems
  Syed Sadeghi, ST Micro
* Terry Jernberg, Cadence Design Systems
  Todd Westerhoff, SiSoft
  Vikas Gupta, Xilinx
  Vuk Borich, Agilent
* Walter Katz, SiSoft
  Zhen Mu, Cadence Design Systems


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Opens:

- None


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Call for patent disclosure:

- No one declared a patent.


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Review of ARs:

- Walter prepare presentation on final stage proposal

- Arpad send Fangyi Rao presentation to Mike L for posting
  - Done
  - Arpad will sent a notice

- Arpad:  Write parameter passing syntax proposal (BIRD draft)
          for *-AMS models in IBIS that is consistent with the
          parameter passing syntax of the AMI models
          - TBD

- TBD:    Propose a parameter passing syntax for the SPICE
          - [External ...] also?
          - TBD

- Arpad:  Review the documentation (annotation) in the macro libraries.
          - Deferred until a demand arises or we have nothing else to do

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New Discussion:

Michael M gave a Synopsys update:
- We have cleared 6 of 7 legal hurdles
- It should be approved this week
- Synopsys provided technical feedback to us:
  - Todd has a copy of this
  - Edits will be made once permission is granted

Walter presented his slides "Final Stage Subckt":
- Slide 2: Michael M proposal:
  - IBIS B element with Freq-Volt dependent C_comp at pad
  - Michael M had also proposed parameterized RC ladder circuit model
  - Arpad: Would the B element include original C_comp?
    - Walter: No, all C_comp would be in the new block
    - Box with B element should mention "C_comp removed"
- Slide 3: Walter's proposal:
  - The Final Stage subckt has 2 pad nodes:
    - The Pad_IBIS connects to the B element
    - The Pad goes to the outside world
  - The Final stage has Stim, En, Vdd, Vss nodes
  - SiSoft has found certain features necessary:
    - s-param models
      - These connect Pad_IBIS to Pad
      - Stim, En, Vdd, Vss ports are not used
    - Arpad: Wouldn't this make it non-LTI?
      - Walter: It doesn't matter here
  - This enables statistical models
- Slide 4: Differential models
  - The Final Stage has 2 B elements, 4 pad nodes
  - The Stim, En, Vdd, Vss ports connect to each block
  - Also present is a Vcm node (common mode voltage)
  - This enables true differential model using 2 B elements
- Slide 5: Differential Rx model
  - Same as Differential Tx, but with no Stim or En
  - Arpad: This can be done with [External Circuit]
    - Walter: [External Circuit] can't have I-V curves
    - This can support s-param models
    - Michael M: John had suggested s-param within [External Circuit]
    - John: You also need the B element
    - Arpad: Not sure if I-V tables are excluded with [External Circuit]
      - John: It is excluded
    - Maybe the BIRD for this should be revived
- Michael M: Are we building mansion-style extensions on a shack?
  - Maybe we need to start clean
  - This may be too complicated to see it through
- Radek: What about V-T tables?
  - Walter: It uses good ol' IBIS models (except C_comp)
  - Maybe "IBIS IV" is confusing (Walter changed the slide to just "B element")
- Arpad: Are V-T tables needed for Hi-Z,Lo-Z, etc. transitions?
  - Walter: IBIS was not designed for those transitions
    - The proposal captures the dominant behavior
    - It is an incremental change
  - Bob: One assumption is that this has more impact on Rx
    - But technically we should de-embed this load from V-T tables in the Tx
    - Michael M: With the original approach the model extractor didn't worry
      about this detail
      - We would model C_comp at the pad looking in
      - The de-embeding requirement would make model making more difficult
    - Walter: Without changes IBIS may become irrelevant for high speed
- Arpad: Which is better, algorithmic or SPICE-like?
  - Walter: It may be a subset of HSPICE, but we can add other elements

Walter showed a Final_Stage_Subckt syntax description:
( Walter was disconnected for a minute )
- The syntax adds the Final_Stage_Subckt IBIS keyword
- There would be rules for the SPICE contents
- Arpad: Why not use [External Circuit]?
  - Walter: That is fine as long as it has the described functionality
- The differential circuit includes V_Shunt for pad pass-through
- Arpad: We should ask ourselves what can be done with [External Circuit]
  - John: I can present something like that
- Arpad: Is this simpler than a mansion on a shack?
  - Michael M: We have to insure this does not conflict with other proposals
    - Arpad: We might need to add more controlled sources
- Arpad: We seem to be returning to keyword explosion
  - Walter: Some enhancements have interfered with IBIS
    - Package additions, [External Model] are fundamentally flawed
    - AMD handles packages well
    - With this addition IBIS can become more relevant again
    - The best part of IBIS remains the B element and pin information
  - Arpad: So we should get rid of newer IBIS features and use subckts?
    - Walter: Yes, industry needs this
    - Michael M: Who is the industry?
      - We have to be careful in saying what is useful
      - We have more EDA representation than IC in this group
    - Walter: That is a fair critique
    - Arpad: How do we get a correct view?
      - Randy: We have been testing the effects of lossy C_comp
	- So far there is no noticable difference in the results
      - Walter: Effects begin at 3GHz
	- Arpad's 3D graph shows effects starting at 5GHz

- Arpad: What do we discuss next week?
  - John could summarize his BIRD idea

AR: John prepare summary of [External Circuit] enhancements for next meeting

Next meeting: 28 October 2008 12:00pm PT

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