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Cadence IC5.1 and MMSIM10.1 (Read 143 times)
Naga Kishan
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Cadence IC5.1 and MMSIM10.1
Aug 19th, 2015, 12:32pm
 
Hi,

I am using Cadence IC5.1 with MMSIM10.1 and simulating for phase noise using PSS/Pnoise analysis.

The simulation runs well for PSS, but it shows 2 warnings as shown below for Pnoise:

1) Warning from spectre at freq = 100 MHz during PNoise analysis `pnoise'.
   WARNING (SPECTRE-16518): Arithmetic exception in analysis `pnoise' .
..
2) Warning from spectre at freq = 1 Hz during PNoise analysis `pnoise'.
   WARNING (SPCRTRF-15037): Infinite flicker noise is ignored.

I will be obliged for your help.

Regards,
Naga
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Naga Kishan
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Re: Cadence IC5.1 and MMSIM10.1
Reply #1 - Aug 20th, 2015, 1:22pm
 
Hi,

I am using the following specifications to calculate the CMOS ring oscillator (Inverter-5stage)

PSS
Engine: Shooting
Fundamental frequency 3.1GHz
Number of Harmonics 64
errpreset: moderate
tstab: 333ns
Oscillator . clk, gnd!

pnoise
sweeptype. relative
relative harmonic: 1
output frequency sweep range: 100K - 100MHz
sweep type: log
points per decade: 200
Maximum sidebands - 64
output - voltage - clk, gnd!
Noise type - sources
Noise separation - yes

I get the below attached phase noise value.

So, my main questions are:

1. Does this plot look reasonable?

2. what should be the phase noise value for a best ring oscillator (or in a range of dBc/Hz)

3. It is used for a divider circuit which CML logic which uses differential clocks ( clk and clkb ), so i designed with a inverter at the output of the oscillator. So, my question is does the phase noise differ for clk and clkbar (complement). does i need to use clkb for reference node in both pss as well as pnoise.

Thanks for your quick reply in advance.

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PHasenoise_clk_3_1G_-42dBc.png
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