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The relationship between DNL and SNR

Charles-Chen
Genius 11836 points
Part Number: ADS9224R

Hi team,

How to understand the following sentence mentioned in application report "SLAA013"?

"The limit of a 1/2 LSB differential linearity error is a missing code condition which is equivalent to a reduction of 1 bit of resolution
and hence a reduction of 6 dB in the SNR"

Why 1/2 LSB DNL equals to a reduction of 1bit resolution rather than 1LSB DNL?

  • 0
    TI__Guru 57336 points

    Hi Charles,

    Thank you for your post. I've edited the title as this question can apply to all data converters in general.

    Of course, data converters have a finite number of codes in their transfer function, so there is a possible range of input voltages that could produce the same code in an ADC. The ideal voltage is at the center of the code "step." Each step is 1/2 LSB away from transitioning to the previous or next code (hence +/- 1/2 LSB from the ideal input voltage). If your non-linear error is greater than 1/2 LSB, this is enough to cause the ADC code to transition to the previous or next code, depending on the sign of the error.

    Regards,

  • 0 in reply to Ryan Andrews
    TI__Genius 11836 points

    Hi Ryan,

    Thanks for your answer.