Analog-to-digital conversion with multiple charge balance conversions

Abstract

Performing a coarse conversion of an analog signal to a coarse digital representation using a first analog-to-digital converter, transferring the coarse representation to a second converter, and performing a fine analog-to-digital conversion of the signal using the coarse representation as a starting value for a fine digital representation. The fine conversion can include a redundant portion that can be used to correct a mismatch between the coarse and fine conversions, and this correction can operate according to a combinatorial transfer function. The fine conversion may include switching from a coarse reference to a fine reference after transferring the coarse representation. The fine conversion can also include comparing an amount of charge in a sampling capacitor after performing the coarse conversion. Also disclosed is converting an analog signal to a digital representation having a first resolution level, adjusting a bandwidth of the converter circuit, and then continuing to convert the analog signal to a second, higher resolution level. The adjusting can include adjusting a bandwidth of a comparison circuit. Further disclosed is evaluating the amount of charge stored in a second sampling capacitor while tracking an analog signal with the first sampling capacitor. The amount of charge stored in the first capacitor is evaluated while tracking the signal with the second capacitor. Evaluating the amount of charge in the first capacitor can include comparing performed in part by a first comparator input stage, evaluating the amount of charge in the second capacitor can include comparing performed in part by a second comparator input stage. Analog-to-digital conversion circuitry can be multiplexed between the sampling capacitors.