Switched Capacitor Circuits - PSS/PAC

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Puppet123

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Hello,

I already have the paper by Ken Kundert, but I am looking for a tutorial on how to do PSS/PAC simulation for Switched Capacitor Amplifiers in Cadence Spectre/Virtuoso.

I am not looking for the theory, rather a step by step tutorial on how this is simulated and set up in Cadence Virtuoso/Spectre.

Thank you.
 

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Hello,

Thank you for your response.

As I said he wrote a tutorial - that is theoretical - about this topic.

But I am looking for a practical tutorial on this subject.

Thank you.
 

Hello,

Thanks, but this document does not talk about Switched Capacitor simulations.

Thank you.
 

Hello,

Thanks for your response.

I read the course notes and understand the simulation procedure except for one thing.

How do I:

– Divide results by sinc(f/fs) to correct for ZOH distortion?

Thank you.
 

Puppet123 said:
– Divide results by sinc(f/fs) to correct for ZOH distortion?
Click to expand...
This is true for Transient Analysis.
Howerver, this is not required for PSS/PAC.

See https://www.edaboard.com/showthread.php?364294

Post Processing of Roll-Off-Compensation for Transient Analysis Result
Code: 
selectResult('tran)

time_vec = drGetWaveformXVec( v("/Vout") )
tstop = drGetElem( time_vec, drVectorLength(time_vec)-1 )
printf("tstop = %g[usec]\n", tstop/1u)

fmax = 25M

tw_in = 1.0/(5*fmax)
froll_off = 1.0 / tw_in
fnyquist = 2*froll_off

delta_f = 1.0 / tstop
maxstep = 1.0 / fnyquist
N = round(2*fnyquist * tstop)
ip = round(log(N)/log(2))
NN = 2**ip
if( NN < N then NN=2**(ip+1) )
fnyquist = NN / (2.0*tstop)
printf("N = %d --> N = %d\n", N NN)

k = tstop / (2.0 * tw_in)  ;  Amplitude Compensation

Vout_freq = dft(v("/Vout") 0 tstop N "Rectangular" 1 1)

Vref_freq = dft(v("/Vref") 0 tstop N "Rectangular" 1 1)

xvec = drGetWaveformXVec(Vout_freq)
len  = drVectorLength(xvec)
printf("len = %d\n", len)

bid = currentSubwindow(1)
plot( db20(k*Vout_freq) ?expr '("tran-S21 without roll-off compensation") )
plot( db20(Vout_freq/Vref_freq) ?expr '("tran-S21 with roll-off compensation") )
 
Last edited:

Puppet23 - are you required to use PSS/PAC or are you free to use any other simulation environment?
 

Hello,

Must use Cadence and must use PSS/PAC.

That is why I asked the question originally.

Thank you.
 

I must use Cadence Spectre as my simulator from Cadence ADE on Cadence Virtuso Design Framework and use the PSS/PAC type simulations.
 
Last edited:

Yes, I am required to use:

Cadence Design Framework as my design environment, Cadence Spectre as my simulator and Cadence ViVA from Cadence ADE for Post Processing.

Also, @pancho_hideboo, what is the code you posted earlier - is that MATLAB ?

Thank you.

--

Post Processing of Roll-Off-Compensation for Transient Analysis Result

Code:

Code dot - [expand]
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selectResult('tran)
 
time_vec = drGetWaveformXVec( v("/Vout") )
tstop = drGetElem( time_vec, drVectorLength(time_vec)-1 )
printf("tstop = %g[usec]\n", tstop/1u)
 
fmax = 25M
 
tw_in = 1.0/(5*fmax)
froll_off = 1.0 / tw_in
fnyquist = 2*froll_off
 
delta_f = 1.0 / tstop
maxstep = 1.0 / fnyquist
N = round(2*fnyquist * tstop)
ip = round(log(N)/log(2))
NN = 2**ip
if( NN < N then NN=2**(ip+1) )
fnyquist = NN / (2.0*tstop)
printf("N = %d --> N = %d\n", N NN)
 
k = tstop / (2.0 * tw_in)  ;  Amplitude Compensation
 
Vout_freq = dft(v("/Vout") 0 tstop N "Rectangular" 1 1)
 
Vref_freq = dft(v("/Vref") 0 tstop N "Rectangular" 1 1)
 
xvec = drGetWaveformXVec(Vout_freq)
len  = drVectorLength(xvec)
printf("len = %d\n", len)
 
bid = currentSubwindow(1)
plot( db20(k*Vout_freq) ?expr '("tran-S21 without roll-off compensation") )
plot( db20(Vout_freq/Vref_freq) ?expr '("tran-S21 with roll-off compensation") )
 
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