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chungmnig

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Posts: 37

parameter "flkmod=?(0 or 1)" to simulatie circuit?
May 19^th, 2006, 9:57am

Hi ~~~
I simulate sigma delta modulator's noise using PSS & Pnoise analysis.
I using TSMC 0.35um , but the model has no flicker noise.
So i added by my self , but i don't know the parameter flkmod=? , the defult is "0"
but i see .25um is set "1" .
setting "1" the result is better.
I also see "An Oscillator Puzzle,An Experiment Community Authoring" by Ken Kundert ,
there said flkmod=1 is regarded , but i don't know the condition is suit to me?
Can someboy help my?
thanks~~~

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ACWWong

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Posts: 539
Oxford, UK

Re: parameter "flkmod=?(0 or 1)" to simulatie circ
Reply #1 - May 19^th, 2006, 10:27am

In reference to BSIM3v3:

flkmod=0 means Ids based model
flkmod=1 means gm based model

You can get the full meaning and equations by looking it up in the spectre model guide in your installation path.
<Cadence_Installation_path>/doc/spectremod/spectremod.pdf

I think what you really need though is some measurement data for you to correlate your flicker noise modelling to. This should (?!?) be provided by your foundary. Often foundaries will release models for flicker noise parameters and show you graphically how well or badly they fit. Unfortunately flicker noise is one parameter which is often poorly fitted....

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Geoffrey_Coram

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Posts: 1999
Massachusetts, USA

Re: parameter "flkmod=?(0 or 1)" to simulatie circ
Reply #2 - May 25^th, 2006, 4:35am

With flkmod=1, as ACWWong wrote, you get the gm-based model, which has a spectral density in Amps/Hz^2 of
KF * gm*gm / (Cox * W *L * f^AF)

Note the pre-factor of KF, which needs to be set. If you set flkmod=1 and get flicker noise, then KF must be set, because it defaults to zero. But this conflicts with your statement that "the model has no flicker noise" before you changed flkmod.

You may also want to look at the value of NOIMOD; if it is set to 2 or 3, then the model uses the "unified flicker noise model" with parameters NOIA, NOIB, NOIC (and the parameter KF has no effect). I don't recall offhand whether NOIMOD takes precedence over FLKMOD.

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