If the DNL of a DAC is less than -1 LSB, the DAC will be non-monotonic (i.e. its transfer characteristic will contain maxima and minima) and if an ADC has DNL< -1 LSB it will have missing codes. Positive DNL>+1 LSB does not cause non-monotonicity or missing codes but does degrade INL, so as a general rule, converters should not have DNL magnitude of more than 1 LSB (i.e. they should obey the rule -1≤ DNL ≤+1 or, better but not absolutely essential, -1< DNL <+1). Of course small DNL magnitudes are better.

