Effects of capacitors non-idealities in un-even split-capacitor array SAR ADCs

Abstract

This paper studies the effects of capacitors non-idealities in the performance of un-even split-capacitor SAR ADCs. Also, election of the m and l bits of MSB and LSB capacitors banks, respectively, is studied to reduce SAR errors. To exemplify and quantify the non-idealities, MOM capacitors are used. In particular, MOM layout parasitics and effective capacitors' value is obtained with an electrical extraction tool using a flattened view of the MOM. Effects of capacitors layout placement in the SAR and their surroundings in the effective capacitance value are quantified. A quantitative study of a 10-bit un-even split-capacitor SAR is done for different combinations of m and l bits. Finally, a qualitative set of guidelines to choose the distribution of these bits is listed.