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how to simulate transient noise ?

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Mar 30, 2007
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transient noise

i want to know, how to run a simulation of transient noise analysis?

i see someone use pss and pnoise analysis to do this, but error always occurs for me, then is there other way to simulate transient noise of a relative big circuit(about 500 transistors)? and more than one clock signals are used.

can anyoe help me or give me some advice,pls?


Transient noise is now supported by many simulators which simply add to each noisy component an equivalent noise source. The source value is calculated to be equivalent to the noise properties of the component. Because in most cases the noise get comparable to the truncation noise of the simulator there are artificial boost factors which are applied to all sources at make the noise effect visible and measureable.

To my understanding there are some shortcomings with "pss" and "pnoise" because only a small number of harmonics sources could be used at the hidden problem is that storage and jitter transport effects could not be simulated.

That is overcome with "transient noise"


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can you speak more clearly?

but how to simulate transient noise in circuit, such as for spectre simulator?

can anyone tell me more,pls?

You can download this application papers in cadence souce link:
Application Notes on Direct Time-Domain
Noise Analysis using Virtuoso Spectre
Hi Dashun,
Cannot reply in your private message.

If your intrinsic noise is small. Try errpreset=coservative, in order to reduce numerical noise for both tran and tran-noise runs. Or try to scale up physical noise by setting noisescale=100 or higher.

if you want to run Spectre Transient Noise analysis and want to ensure that the noise value is accurate, you should make sure:

1-To turn on white noise sources
- Set noisefmax
- Rule of thumb: noisefmax=2xBandwith_DUT
2- To turn on colored noise sources
- Set noisefmin
- noisefmin will be adjusted so that noisefmax / noisefmin is an integer power of 2
- make sure that that you specify the right value for the noisefmin as it will be a lower limit for the range of frequency for which the noise
will be calculated .
- Make sure Tstop > 1/noisefmin
You will find that on reducing the noisefmin , you need to simulate the circuit for a larger time to meet the above criteria.
There is a tnoise checkbox in later Spectre (Analog Environment)
transient analysis. It adds time domain noise. However, getting
the noise scale factors right is on you. You may have to touch
the model files and add scale factors to dial in device noise to
match the data (you do have data, right?).

Since the capability is relatively new, you can't trust your foundry
PDK to have things right for it. You should ask before trusting,

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