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[help] pll simulation in spectre

reddevil011

I am trying to run a PSS analysis of a closed-loop PLL in spectre, but encounter   converge problems.

Is it possible to run a PSS analysis of a closed-loop PLL?

thanks! 

Parents

  • thanks, Andrew.  I managed to simulate s-domain model of closed-loop PLL. But now my PLL is formed as follows:

    integer-N PLL;

    ideal PFD&CP, Loop filter and divider model written in veriloga language;

    implimenting real VCO schematic.

    And I am trying to run a PSS and Pnoise analysis of this PLL to estimate the VCO's pnoise contributition, but always failed in PSS analysis. simulation log shows that Converge  problems exits.

     I also run a trans analysis of this PLL. The result shows that the input voltage of VCO has small ripples when PLL is locked. The ripple voltage is 400uVpp.  Is it the reason why PSS analysis has converge problems?

     regards.

     

Reply

  • thanks, Andrew.  I managed to simulate s-domain model of closed-loop PLL. But now my PLL is formed as follows:

    integer-N PLL;

    ideal PFD&CP, Loop filter and divider model written in veriloga language;

    implimenting real VCO schematic.

    And I am trying to run a PSS and Pnoise analysis of this PLL to estimate the VCO's pnoise contributition, but always failed in PSS analysis. simulation log shows that Converge  problems exits.

     I also run a trans analysis of this PLL. The result shows that the input voltage of VCO has small ripples when PLL is locked. The ripple voltage is 400uVpp.  Is it the reason why PSS analysis has converge problems?

     regards.

     

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