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Problem in doing pss pnoise simulation to get PFD CP output current noise

macanfeng11

I tied an ideal voltage source to the output of my charge pump and selected this voltage source as the port of my pnoise simulation. However, after my pss pnoise simulation is finished, the output noise of my simulation is in voltage type not in current type.  I want to get the output current noise of my design.   My cadence version is IC6.17. Cry The test bench is shown below.

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  • Dear macanfen11,

    Is there a reason you did not include a current probe in series with your ideal voltage source and specify its input node as the pss output? When you specified the voltage source, the pss output is specified as a voltage and not a current.

    Does this make sense and help?

    Shawn

  • in reply to ShawnLogan

    Shawn, it's fine to use voltage source as the probe - there should be no difference from using an iprobe (which is in effect a zero-volt source). This should (and does) give an output current.

    macanfeng11 didn't say which sub-version was being used (which is rather useful information), unfortunately.

    I started with the latest IC618 hot fix (ISR15) and this worked fine. Then having picked a random (earlyish) IC617 ISR (ISR8) I see the problem. By a bit of a binary search of versions, I found that the issue is resolved in IC6.1.8 ISR10 (so 6.1.8.500.10).

    In the affected versions, it's the units that are wrong - the value are actually in A/sqrt(Hz) or A^2/Hz, but the labelling is in volt units.

    So the solution is to move to a newer version - this was a temporary bug, fixed long ago.

    Andrew.

  • in reply to Andrew Beckett

    Dear Andrew,

    Andrew Beckett said:
    Shawn, it's fine to use voltage source as the probe - there should be no difference from using an iprobe (which is in effect a zero-volt source). This should (and does) give an output current.

    Thank you for correcting my error! Please accept my apologies Andrew and macanfeng11.

    Shawn

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