Evaluating DACs linearity and intermodulation errors through an ANOVA approach

In order to assess the performance of digital to analog converters (DAC) the attention is generally focused on the integral nonlinearity (INL). Useful diagnostic tools to detect the causes of poor linearity are the linearity and intermodulation errors, which can be evaluated from INL measurements. Linearity and intermodulation errors highlight and quantify erroneous calibration and unwanted interactions between current sources inside the DAC hardware. Unfortunately, their estimates, especially those related to high order intermodulation errors are characterized by high uncertainty. It is thus difficult assessing their relevance on the base of their very uncertain value. It is shown that by means of the analysis of variance (ANOVA) the relevance of intermodulation errors can be assessed from a limited set of INL measurements. ANOVA is in fact capable of distinguishing if the variance in INL measurements has to be addressed to active factors or noise, even if the effect of each factor is widespread upon different elements of the INL array and in different combinations with the other factors.