# INL DNL of sigma delta ADC

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#### avinash

##### Full Member level 3 how can we measure the SNR,INL and DNL of sigma-delta converters at simulation level.any document regarding this will be highly appreciated.

#### Syukri

##### Full Member level 5 inl dnl definition

Can u specify the type of tools that u wanted to simulate this......

If it's Matlab just use the equation of DNL,INL and SNR.

### avinash

Points: 2

#### avinash

##### Full Member level 3 but i wanted it to measure from hspice.can you please tell me the matlab commands to calculate the INL,DNL and SNR of sigma delta.
thanks

#### Syukri

##### Full Member level 5 use m.file function and just rewrite the formula

DNLm=Vm+1-Vm - δ

INL = ∑ DNLm ( from 0 to 2n-1) n is power not multipllication

SNR = 20 log [ Vin rms / √( Vq²+Vnoise²+Vdistortion²)]

u need a matlab basic m.file programing and this is not accurate due to mathematical modeling

#### swicap

##### Member level 5 matlab measure snr sin cos

to get inl dnl, u need adc output data, not modulator output.
inl,dnl simulation need long time. I dont think hspice can do that.
If u really understand the definition of inl and dnl, you can easily get their value from the output data.
search in maxim's application nots, u will get many valuable infomation.

#### llci413

##### Newbie level 4 definition of dnl and inl

U just need to measure SNR, THD, SNDR and DR, and not nessary to measure INL and DNL for sigma delta modulator. and the SNR only contain noise, no need for distortion. the distortion is measure by SNDR and THD. u can use the following matlab script to exact the signal from the digital bit stream.
then do the PSD of (in-outx), u can get the quantization noise PSD. integrate the inband noise u get the IBN. then u can calulate the SNR,SNDR, THD ...

function [outx,amp,ang] = sinusx(in,f,n)
%in=bitstream ; f = normoize freq; n=number of point
%outx= Extraction of a sinusoidal signal; amp=amplitude; ang=phase
%
sinx=sin(2*pi*f*[1:n])';
cosx=cos(2*pi*f*[1:n])';
in=in(1:n);
a1=2*sinx.*in;
a=sum(a1)/n;
b1=2*cosx.*in;
b=sum(b1)/n;
outx=a.*sinx+b.*cosx;

angTemp=atan(b/a);
ang=angTemp/(2*pi*f);
amp=a/cos(angTemp);

#### HanGu

##### Junior Member level 3 inl and dnl simulation level

llci413 said:
U just need to measure SNR, THD, SNDR and DR, and not nessary to measure INL and DNL for sigma delta modulator.
;

Hi,llci413 , It's very appreciate to explain that why not nessary to measure INL and
DNL for sigma delta modulator

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