Stats

  • Locked Locked
  • Replies 5
  • Subscribers 63
  • Views 15197
  • Members are here 0
This discussion has been locked.
You can no longer post new replies to this discussion. If you have a question you can start a new discussion

tstab method in hb with mmsim12

Aldo2

Hello,

In the old versions of mmsim (now I'm using the v12) it was possible to set the method used by the initial transient (tstab). How can I set it in mmsim12?

In my simulations transient gives a correct result whereas hb/tstab predicts a strange behaviour that prevents the hb simulation to converge. Which are the default methods of the 2 analysis, tran and hb/tstab? Are there other different settings?

Thank you very much

Best regards

Aldo

  •  Sorry, I mean the integration method (euler, gear2only...)

    BR

    Aldo

  • Hi Aldo,

    As before, there's tstabmethod (on the Accuracy tab in the hb options form). From "spectre -h hb", it says:

     23      tstabmethod       Integration method used in stabilization time. The
                              default is `traponly' for autonomous circuits, or is
                              derived from `errpreset' for driven circuits. Possible
                              values are euler, trap, traponly, gear2, and
                              gear2only.

    And if I remember rightly, the settings for driven circuits match those for transient.

    That said, just because the initial tstab is running, doesn't mean that the hb will necessarily converge. Did you try using the new "auto" methods (not sure which IC subversion you're using - you have to have (I think) IC615 ISR14 or later to get that).

    Regards,

    Andrew.

  • Hi Andrew,

    In my Accuracy tab I do not have the tstab method (there is only time step). I added it as additional parameter.

    These are the versions of ic and mmsim I'm using

    ic          06.15.171
    mmsim 12.10.457

    Thank you

    BR

    Aldo

  • Hi Aldo,

    Not sure how that's happened. I don't have that version of spectre, I have slightly earlier and later versions - but not that one.

    Ah, I think I have it. It only shows up if there's a single tone in HB. Not sure why that is, because if you're doing a Transient Assist with multitone (only one tone is enabled during the tstab), it still needs to have an appropriate integration method.

    But that does highlight one important difference between transient and initial transient (tstab) of HB; for transient, all sources are enabled, whereas in HB only one tone (the first one) is enabled - the point is you only have the one that causes the most non-linearity enabled, and there wouldn't be much benefit in having more than one enabled because you'd have to simulate over the common period of the tones to be useful. So maybe that's related to your issue (rather than the setting of tstabmethod)?

    Regards,

    Andrew.

  • Hi Andrew,

    Yes, now I understand: I'm simulating the IP3 of a mixer but tstab make me see only LO leakage at the output.

    Thank you

    Best regards

    Aldo

Community Guidelines

The Cadence Design Communities support Cadence users and technologists interacting to exchange ideas, news, technical information, and best practices to solve problems and get the most from Cadence technology. The community is open to everyone, and to provide the most value, we require participants to follow our Community Guidelines that facilitate a quality exchange of ideas and information. By accessing, contributing, using or downloading any materials from the site, you agree to be bound by the full Community Guidelines.