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calculating and ploting INL,DNL (Read 1296 times)

singh

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calculating and ploting INL,DNL
Dec 15^th, 2011, 9:51am

Hello,

I am working on 8 bit analog to digital converter and beginner in matlab

I swept dc input from

for vin = 0 : dv :3
save_input(i)= vin;

then ADC function is called which returns output code in array Vdout(i) = ADC_out;
i am able to get staircase output when i plot out vs input

now i want to plot DNL, which is ((Vdout - Vdoutprevious)/LSB)-1; how to plot it against digital output as there are less points in DNL array as compared to vdout?

also how to plot INL , how to calculate it and plot against input voltage?

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Sharath Raju

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Re: calculating and ploting INL,DNL
Reply #1 - Oct 24^th, 2012, 1:53pm

By definition, the DNL is not defined for the first and the last codes. Therefore, an 8-bit ADC will have DNL values only for ADC codes 1 through 254. (dropping the 0th and the 255th code.)

Then INL can be shown to be the cumulative sum of the DNL. i.e,

INL(code1) = DNL(code1)
INL(code2) = DNL(code2) + DNL(code1), and so on.

Note INL(code0) is undefined, and INL(255th code) = 0.

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