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Design >> Mixed-Signal Design >> Internal Noise of ADC
https://designers-guide.org/forum/YaBB.pl?num=1326471539

Message started by singh on Jan 13^th, 2012, 8:18am

Title: Internal Noise of ADC
Post by singh on Jan 13^th, 2012, 8:18am

I have modeled ADC for 16 BIT and want to calculate Internal noise due to ADC.The ADC model description is given below:

ADC out = adc(input,freq,phase,OSR); % call ADC

inside adc function
[
KT/C noise (Integrators) random number generation
for i = 1 to OSR
input ADC = input;
ADC Integrators and compartor algorithm for MASH 1:1 with noise coefficients
end

filter section
output of ADC
]

How shud i calculate the internal noise Vrms Vs Vin for ADC.What si the procedure? When i give the DC ramp input i get the noisy output code as attached in figure (zoomed). how to measure rms noise for Dc input voltage ramp ?

the figure 4 in this pdf (link )gives plot of internal noise of ADC Vs Vin(analog) but i am not getting idea how to achive it.How to find rms noise value.
http://www.ti.com/lit/an/slyt339/slyt339.pdf

http://www.analog.com/library/analogDialogue/archives/40-02/adc_noise.html

http://www.analog.com/library/analogDialogue/archives/29-2/cnvtrnoise.html

Now if i give just one value of DC input say input = 2V, after OSR =256 cycles , i get one output code.How can i get the rms noise?

or shall i do the sin histogram test and calculate FFT? i have already done that and discussed in link :
http://www.designers-guide.org/Forum/YaBB.pl?num=1325873498
and founf fft using sin input,calculated FFt result..calculated Noise power from that but it dont comes in microVolts (it comes 0.2099) for 2.8 V input amplitude
PS: DNL INL is not good becoz i took less points to plot.

Title: Re: Internal Noise of ADC
Post by ywguo on Jan 15^th, 2012, 10:35pm

Short the differential input if the ADC is differential, or attach the input to ground. Measure the ADC output and it would be a gaussian distributed histogram if that is random noise and big enough in your ADC model.

I know this method only. In a lot of ADC datasheets, either Nyquist ADC or oversampling ADC, there are the histograms for Zero/Grounded input.

Title: Re: Internal Noise of ADC
Post by Dan Clement on Jan 16^th, 2012, 7:35pm

Also be mindful that the reference noise plays a big role also.