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Problem in plotting I/O waveform in Cadence

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Nigidita

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Hello

I want to plot the I/O characteristics of PFD to see the dead zone. I got to know from the previous post that I have to plot the current and sweep variable, but can anyone please elaborate the process on how to sweep the variable.


Thanks

Nigidita
 

By cadence I mean using cadence EDA tool.
 

Actually I am new in this.. I am using cadence virtuoso...
 

I want to sweep the phase of Fref and Fdiv .... I have done dc analysis in cadence virtuoso ADE enviroment..... I am not sure which parameter to sweep and how to sweep. Is it AC phase or delay time? I have attached the picture below.. Please have a look.
plotingproblemofphase.jpg
 

Can you undestand your circuits ?

DC Analysis is not useful.

You have to do Transient Analysis or Shooting-Newton-PSS Analysis.

Show me netlist.
 
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I have done the transient analysis and checked the working... but I was not able to get current vs phase plot...please see the netlist.

cHARGEPUMP pfd.png
 

Nigidita said:
Hello

I want to plot the I/O characteristics of PFD to see the dead zone. I got to know from the previous post that I have to plot the current and sweep variable, but can anyone please elaborate the process on how to sweep the variable.


Thanks

Nigidita
Click to expand...

Connect a capacitor to your charge pump output. Make sure its large enough so that when the CP turn on, the voltage does not change too much.

Start with two vpulse sources that have a phase offset between them as a parameter. Run a transient simulation and see how much charge is dumped into your capacitor (the difference in voltage before up or down went became high and voltage after both of them became low multiplied by the capacitance). And then you do a parametric sweep on the offset.

Ideally, for a 20ps phase offset, the amount of charge dumped will be 2x charge dumped for a 10ps offset.

By the way, I really don't see the point in measuring deadzone like this. The thing you need to ensure is that for your minimum reset pulse width, both the current sources turn on and settle to their final DC values in the slowest corner.
 

I have taken vpulse source it has AC phase and delay time.... which one should I take?
 

I have done the transient analysis I got this result.... How can I get phase in X-axis?
1.png
 

Use the delay function to plot the delay between the two wave-forms and then do a Y vs Y plot.
Alternatively you can save both your voltage/current/charge waveform and your delay waveform in csv files and plot them in Matlab/Python/Julia etc

Here is an example of a sample delay function:

Code: 
delay(?wf1 v("/feedback" ?result "tran"), ?value1 0.5, ?edge1 "rising", ?nth1 1, ?td1 0.0, ?tol1 nil, ?wf2 v("/ref" ?result "tran"), ?value2 0.5, ?edge2 "rising", ?nth2 1, ?tol2 nil,  ?td2 nil , ?stop nil,  ?period1 1 ?period2 1 ?multiple t ?xName "trigger" )
Make sure you select multiple and not single.
 
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