[SOLVED] How to use PSS of Cadence Spectre ?

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arminakkk

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pss convergence

Hi
I'm designing a frequency divider by 1.5 and I need to find the noise floor of this divider. It seems to be working fine in time domain, but pss does not converge. I'm using ideal input sources (freq=4GHz) and using Spectre Simulator in Cadence. This is my first time simulating such things in Cadence... can anyone help me?!

ps. pss and pnoise simulation is the only thing I can think of in order to find my divider's noise floor, is there any other way to do it?
 

Re: pss convergence

it maybe need set a correct beat frequency for simulation, such as fclock/1.5
 

Re: pss convergence

rambus_ddr said:
it maybe need set a correct beat frequency for simulation, such as fclock/1.5
Click to expand...
Wrong.

Don't use a term of "beat", if you mean PSS of Cadence Spectre.

See "spectre -h pss", if you mean PSS of Cadence Spectre.
There is no "beat" in analysis statement for PSS of Cadence Spectre.
"beat frequency" of PSS setting UI is not beat frequency. It is a "fundamental frequency" not beat frequency.

arminakkk said:
I'm designing a frequency divider by 1.5 and I need to find the noise floor of this divider.
I'm using ideal input sources (freq=4GHz) and using Spectre Simulator in Cadence.
Click to expand...
Set fundamental frequency of PSS as fin/3, here fin=4GHz.

See https://www.designers-guide.org/Forum/YaBB.pl?num=1268969030/7#7
 
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if it does not converge even after using proper fund.freq and tstab period,you can use initial conditions from the transient settled op as ic for pss...
also you can play with steadyratio and tolerances to make pss converge..once pss converges make you sure you got the correct outputs from your circuit...

rampat
 

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