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Built-in Power Calculation

moralope

Hi,

I am trying to find out how Cadence calculates the "pwr" operating point parameter of a MOS transistor, and it is almost imposible to get that information.

In a previous forum, it was mentioned that the "pwr" was calculated by the transistor model and not by Spectre. However, I cannot find any information of power calculation in the BSIM4 model for example.

I want to get this information because I have observed that the power calculation in Cadence does not have into account leakage currents (e.g. gate-tunneling current), which are not negligible in scaled technologies. For example, when simulating a large MOS cap, the reported "pwr" is 0, while it is consuming quite some current. Thus, the total "pwr" does not match the power reported by the VDD source.

I have found a paper that reports this issue:

ihome.ust.hk/.../j16.pdf

But still it is not clear for me who has to solve this issue (foundry, BSIM4, Cadence?) and how. Is there a way to include these contributions to the "pwr" calculation of individual transistors?

As I am simulating a quite large circuit and I want to find out the power consumption of each subcircuit, I cannot check manually each transistor to do that calculation.

Regards,

 moralope

 

  • Moralope,

    In the MMSIM11.1 and MMSIM12.1 documentation, the Device Model Equations manual does list (for bsim4) the equations used to compute the operating point parameters. For pwr, it says:

    49 pwr (W)
    Power at op point. pwr = abs(ids * vds) + abs(ibulk * vbs).

    Unfortunately these equations have gone missing in MMSIM13.1 documentation. I filed a CCR about that a few weeks ago (CCR number 1287725).

    If there's anything wrong with this calculation, then it is the implementation of the model in the simulator that needs to be fixed - so you should contact customer support.

    Kind Regards,

    Andrew.

     

  • Thaks Andrew. I have contacted the custumer support.

    Regards,

    moralope

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