Studying the influence of critical parameters and elements of the ΣT-analog-to-digital converter on the linearity of the conversion function

Background. Numerous studies have shown that one of the critical elements of low-bit integrating analog-to-digital converters (ADC) is a capacitor included in the integrator, the dielectric absorption of which limits the maximum achievable linearity of the conversion function. The relevance of studying its influence today is determined in connection with the development of multi-bit integrating analog-to-digital converters of the Σ- architecture, in which the summation of the conversion results of adjacent partial cycles is carried out for a full cycle. The execution of the operation of summation of partial and full conversion cycles leads to the emergence of a methodical component of the error from edge effects due to their asynchronism, which can lead to inequality of the integral values of the converted and reference voltages for a full conversion cycle. Materials and methods. These issues are investigated based on the developed ΣT-ADC using simulation modeling in the NI Multisim environment. An experimental study was conducted and the values of the root mean square deviation (RMS) of the linearity of the ADC conversion function were obtained using an ideal integrating capacitor, as well as with the addition of an integrating capacitor equivalent circuit with a number of absorption coefficient values to the model. The algorithm performance was assessed and the effect of the absorption coefficient on the final conversion result was analyzed for different numbers of partial cycles in a full cycle. Results. The study of the linearity error of the conversion function was conducted taking into account the effect of dielectric absorption achieved by including elements of the equivalent circuit of the integrating capacitor in the converter model. The values of the RMS of the conversion linearity were calculated for different numbers of partial cycles in a full conversion cycle. Conclusions. The obtained RMS values indicate the ability of the proposed structural and algorithmic solution to completely eliminate the influence of the instrumental component of the error caused by dielectric absorption phenomena in the integrating capacitor. For all values of the number of partial conversion cycles in a full cycle, absorption phenomena do not affect the final conversion result. For all values of the absorption coefficient, the mean square error of the linearity of the ΣT-ADC conversion function remains unchanged.