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tdnoise or pnoise?

PeppeW90

Hi,

I'm simulating a test bench consisting of a crystal oscillator, followed by several inverter stages that act as buffers.

I want to simulate the phase noise at the output of the last buffer, and eventually see how the added buffers contribute to the total phase noise.

What is the most accurate analysis to do in this case? PSS+PNOISE(sources option) or PSS+PNOISE(timedomain option)?

I don't want to see the integrated jitter or the noise in V^^2/Hz, but the phase noise at the output of the last buffer.

Thanks

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  • Andrew Beckett

    The tdnoise isn't going to give you phase noise - so you'd have to numerically convert the jitter back into phase noise if you were to go down that route.

    Instead, I think what you should do is use MMSIM151 or later, together with IC617, and then pick noisetype=timeaverage (this is a new implementation that supersedes noisetype=sources) and pick one of the options on the form that gives "PM" - it's on the bottom of the pnoise form). Then you can plot phase noise.

    The closest you have with older versions is to pick noisetype=modulated and pick the PM results from that - but I would definitely recommend using a more recent version and getting the improved noise analyses there. There's been a lot of work to ensure that the settings are more logical, more accurate, and it's clear what you're getting when you simulate and plot something afterwards.

    Regards,

    Andrew.

Reply
  • Andrew Beckett

    The tdnoise isn't going to give you phase noise - so you'd have to numerically convert the jitter back into phase noise if you were to go down that route.

    Instead, I think what you should do is use MMSIM151 or later, together with IC617, and then pick noisetype=timeaverage (this is a new implementation that supersedes noisetype=sources) and pick one of the options on the form that gives "PM" - it's on the bottom of the pnoise form). Then you can plot phase noise.

    The closest you have with older versions is to pick noisetype=modulated and pick the PM results from that - but I would definitely recommend using a more recent version and getting the improved noise analyses there. There's been a lot of work to ensure that the settings are more logical, more accurate, and it's clear what you're getting when you simulate and plot something afterwards.

    Regards,

    Andrew.

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