IBIS Macromodel Task Group

Meeting date: 10 February 2015

Members (asterisk for those attending):
Altera:                       David Banas
ANSYS:                      * Dan Dvorscak
                              Curtis Clark
Avago (LSI)                   Xingdong Dai
Cadence Design Systems:     * Ambrish Varma
                              Brad Brim
                              Kumar Keshavan
                              Ken Willis
Ericsson:                     Anders Ekholm
IBM                           Steve Parker
Intel:                      * Michael Mirmak
Keysight Technologies:        Fangyi Rao
                            * Radek Biernacki
Maxim Integrated Products:    Hassan Rafat
Mentor Graphics:            * John Angulo
                            * Arpad Muranyi
Micron Technology:          * Randy Wolff
                              Justin Butterfield
QLogic Corp.                  James Zhou
                              Andy Joy
eASIC                         Marc Kowalski
SiSoft:                       Walter Katz
                              Todd Westerhoff
                            * Mike LaBonte
Synopsys                      Rita Horner
Teraspeed Consulting Group:   Scott McMorrow
Teraspeed Labs:             * Bob Ross

(Note: Agilent has changed to Keysight)

The meeting was led by Arpad Muranyi.

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Opens:

- None


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Call for patent disclosure:

- None


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Review of ARs:

- Arpad to review IBIS spec for min max issues.
  - In progress.


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New Discussion:

C_comp enhancements:

- Michael M showed a proposed BIRD AMI Reserved Parameters for Buffer Directionality
- Arpad: This should be posted in the TAM archive.
- Michael M: This adds 2 new parameters.
  - It is implied that only Input-only and Output-only buffers can be associated with AMI.
  - The tool needs to know the capabilities and the current state.
  - Two parameters are added:
    - AMI_Model_Type
    - AMI_Model_Direction
  - The parser would flag models that are I/O but are missing these keywords.
  - This would help detect circuits with no TX or no RX.
  - AMI_Model_Type has 4 values.
  - This will not invalidate existing models.
  - A single model could handle both TX and RX.
  - Direction can not change during a simulation.
  - Tools would configure state at simulation time.
  - For 3-state Direction can be "Ignore".

- Ambrish: Can multiple models be used with this by selector?
- Michael M: The tool would have to adjudicate.
- Radek: What about Res Par that are specific to TX or RX?
- Michael M: The parser should check for TX or RX.
  - For I/O it might flag missing parameters, not sure.
- Radek: We have not seen those parameters mixed so far.
- Michael M: We could have a table of allowed/prohibited parameters by model type.
- Ambrish: Is I/O one model or two models?
- Michael M: IBIS assumes there is one block.
  - Maybe we could have [AMI Model Selector]
- Ambrish: We have run into this question before.

- Michael M: We are sneaking in an enable switch as part of Reserved_Parameters.
  - We could have a selector to point to different AMI files.
  - Should a single DLL family be state-aware?
- Ambrish: We would like a single model to function for both.
- Mike L: The Executable line could be extended to say when each line would be used.
- Michael M: Or a selector might override the existing Executable line.
- Mike L: That would be better.
- Arpad: Two mechanisms are possible:
  - One for choosing the analog model
  - Another to select among algorithmic models.
  - The first one requires no GUI.
- Michael M: One question is if the selection is implicit based on something else.

- Michael M: We have 3 suggested methodologies.
  - This draft should be tabled until we have resolved some questions.

AR: Michael M send BIRD proposal to Mike L for posting.


C_comp enhancements:

- Randy showed Improved C_comp Case Study.
- Randy: This was shown at the summit.
- slide 3:
  - Randy: One question is if we need a series element.
- slides 4 to 10:
  - Randy: These show VNA measured vs. simulation of the enhanced model.
- slide 13:
  - Randy: We need to look at voltage margin.
- slide 14-16:
  - Randy: These are different loss and drive situations.
- slide 17:
  - Randy: This shows a need for an improved model.

- Arpad: Are the models IBIS or SPICE?
- Randy: IBIS for die load, SPICE for package.

- Arpad: Was the V-T compensation point moved?
- Randy: This was an input model, it ignores that.
  - The series element question is important.
- Michael M: The need for series resistance occurs in real devices.
  - This complicates I-V model extraction.
- Bob: We assume it is a fixed resistance.
- Arpad: The inductor on slide 5 is a regular inductor?
- Randy: An AC resistance is calculated proportional to sqrt(freq)
  - It really is a skin effect model.
- Arpad: Is the inductor in the ISS box for C_comp?
- Randy: It is independent.
- Bob: We could allow W element.

- Arpad: What conclusions are we making here?
- Randy: We need buy-in before going forward.
- Michael M: We agree on the need for this.

- Arpad: Walter had a simplifying proposal.
- Radek: Did that address C_comp?
- Michael M: It did but it assumed compensation would not be changed.
  - There was disagreement about that.
- Bob: Correspondence with the V-T signal has to be checked.
  - Model makers would have to do an extra rigorous step.
- Arpad; Did Walter post his BIRD?
- Mike L: It was put in the archive Dec 2.

- Bob: There should be an automatic mechanism to determine when to use the new model.
  - Also to say when C_comp should be ignored.
  - We would have to look at Typ/Min/Max issues.
  - Walter added terminals for differential connections.
- Arpad: We might consider implementing proper differential termination.
- Bob: It might be a C_diff keyword, separate from C_comp.
  - It probably would still be averaged for de-embedding.
  - That complicates the problem.
- Arpad: Would Bob's presentation be helpful here?
- Bob: It's not about compensation, it's about K(t) adjustment.

AR: Mike L post link to Randy's presentation

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Next meeting: 17 Feb 2015 12:00pm PT
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IBIS Interconnect SPICE Wish List:

1) Simulator directives
