Analysis of a charge redistribution SAR ADC with partially thermometer coded DAC

This paper presents an analysis of capacitor mismatch of a partially thermometer coded charge redistribution SAR ADC. Thermometer coding of only the most significant bits effectively improves the linearity of a binary weighted capacitor array without exponential growth of decoder and interconnection effort at high resolutions. Distribution based calculations and an implementation example demonstrate the increase of chip yield or the possible reduction of circuit area. The proposed approach can be applied to different conventional architectures and requires only small additional decoder logic.