Hi Guys,

Many literatures state that DNL < 1 LSB guarantee ADC monotonicity. We often use code density (histogram) method to measure the DNL/INL. Can this method insure ADC monotonicity? Furthuremore, as indicated in the tutorial http://www.analog.com/zh/content/0,2886,761%255F795%255F91286%255F0,00.html, there are code transition noise. So how do I identify if the ADC is monotonicity when there are code transition noise? Is code density method enough to detect any non-monotonicity?


Thanks
Yawei

Ah! That one confirms a long-standing suspicion of mine. Thanks for that link Frank.

However, I have to say that a reasonably well-designed ADC ought not to have such weird flips. After all, it is not so
easy for 2 adjacent codes to get flipped without any visible impact on the other codes.

Don't you think?

Regards
Vivek

Yes, you will have to look at the ADC output directly.

A missing code is defined as a code with DNL≤-0.9 by IEEE Standard 1241-2000. I believe that Boris Murmann is referring to the fact that these codes may be much easier to find in the INL plot, which is the integral of the DNL plot and where the missing codes appear as downward steps. This is especially true if you have very many codes like in his example so that there may not be a pixel in the plot for every single code. I cannot tell you where exactly he is seeing the 5 missing codes, however.