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ksnf3000

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ENOB SINAD SNR Calculations of ADC in Cadence
Aug 13^th, 2013, 3:44am

Hi All,

I know this is a very recurring topic but sadly till now I have not found any conclusive answers anywhere.
I am trying to calculate the figures of merit (ENOB,SINAD,SNR) of a sigma delta ADC. �The steps to be followed are:

1. Acquire a signal.
2. Calculate the DFT of the waveform.
3. Normalize the DFT such that it is suitable for power
measurements.
4. Identify the DFT bins that contain the powers of the
elements shown in Figure 2.
5. Calculate the total power of these components
6. Calculate the figures of merit using the powers
calculated above.

Now,as per the steps I have obtained the DFT of my transient signal. But now I am in a fix as to how to obtain the remaining parameters.
Could someone please shed some light on this?
FYI...I am using Cadence Version 6

Thanks,
ksnf3000

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sheldon

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Re: ENOB SINAD SNR Calculations of ADC in Cadence
Reply #1 - Aug 13^th, 2013, 6:10pm

knsf3000,

� �Not sure what Cadence version 6 is. If you mean Virtuoso IC615
or IC616, then just use the spectrum function in the Calculator. The
input to the spectrum function is the transient waveform and the
output is the standard measurements: SFDR, SNR, THD, SINAD,
and ENOB. If you are using earlier version then there is another
function spectremeas(?), i think. It works but requires some manual
intervention, for example, clipping the transient waveform.

� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �Sheldon

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ksnf3000

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Re: ENOB SINAD SNR Calculations of ADC in Cadence
Reply #2 - Aug 15^th, 2013, 3:22am

Hi Sheldon,

Thanks for your reply. I am using Cadence Virtuoso IC6.1.5.500.1 32
You mentioned that spectrum function is sufficient. Does this mean that this function first takes the DFT and calculates the remaining parameters or should the input to the spectrum function be a DFT of the output?

Regards,
ksnf3000

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sheldon

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Re: ENOB SINAD SNR Calculations of ADC in Cadence
Reply #3 - Aug 15^th, 2013, 7:24pm

KSNF3000,

The spectrum function supports two modes of operation:
1) Perform a Fourier Transform and calculate the parameters
If the input is transient data, then the Fourier Transform is
performed
2) Calculate the parameters
If the input is the frequency spectrum, then the parameters
are calculated. This mode is useful when you use the Fourier
Integral to perform the frequency translation.

Sheldon

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ziikzak

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Re: ENOB SINAD SNR Calculations of ADC in Cadence
Reply #4 - Jan 31^st, 2014, 9:56am

May I have question about this topic?
I am working on a Flash ADC using TIQ technique, so I do not use clock in my design.
I am confused about the configuration of spectrum function. I did use it for some times, but I am not sure the result is correct.
My ADC is 4 bit with sampling rate of 1GSs.
@Sheldon: Can you give me a hint ? or do you have any related references?
Thanks

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sheldon

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Re: ENOB SINAD SNR Calculations of ADC in Cadence
Reply #5 - Feb 17^th, 2014, 3:54pm

Ziikzak,

Could you explain the source of your confusion? The setup is
roughly equivalent to the setup for the standard FFT based
measurement. The user sets the start time, the stop time, and
the number of points for the FFT. Assuming that you are using
a Verilog-A DAC with a output level of 1 to create the reconstructed
analog signal, there should be nothing else to do.

Sheldon

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