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Power Analysis via Innovus

Mehregan

I faced two issues when I ran power analysis through Innovus.

Firstly,  according to"Basic" tab in "Run Power Analysis" window, the unit of Dominant Frequency is MHz, while it shows GHz during Static/Dynamic power analysis. For example, I put 10 in the "Dominant Frequency " blank space which i expected a frequency of 10MHz but during simulation it shows the frequency of 10GHz in console window.

Secondly, when I double the frequency  (let say changing from 10MHz to 20MHz), I expected the total switching power and internal power doubled (as explained in Innovus user guide, the switching power has a direct relation with frequency).
Actually by increasing the frequency the total switching power decreases!!
I am wondering if it is a bug of the power analysis in Innnovus or I have missed some set-up points during the analysis.

Thanks, Mehregan 

  • Dear Cadence Support,

    I would be thankful if you could help me with the aforementioned issues I faced in power analysis. I really need your help since we are blocked in this stage and we are limited in time for upcoming tape-out. 

    Thanks,

    Mehregan

  • in reply to Mehregan

    Hi Mehregan,
    the GUI form you are using is effectively using the command set_default_switching_activity.
    In the tool command reference the following is stated for this command:  
    "Specifies the switching activity for all primary inputs, nets, and other devices in the design whose activity has not been previously defined through user attributes, the toggle count format (TCF) file, the value change dump (VCD) file, or the tracing of the clock network."

    Hence, doubling the default switching activity will not necessarily double the total power, as it is only applied where no other activity is set with either set_switching_activity, or where a clock is propagated to.

    It is indeed strange that increasing the default activity is decreasing the total power consumption.I would suggest you to try using the native commands instead of the gui to make sure you are not changing any other settings that might affect the results.

    I should point out that these forums are responded to by volunteers. If you need an urgent response you should go via the official support channels.

    Dimo

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