COMMON MODE TRANSLATION IN SIGMA-DELTA ANALOG-TO-DIGITAL CONVERTERS

摘要

System and method (400) for common mode translation in continuous-time sigma- delta analog-to-digital converters (100). An embodiment comprises a loop filter having an RC network (105) coupled to a differential signal input, a Gm-C/Quantizer/DAC circuit (GQD) coupled to the loop filter, a common-mode level adjust circuit coupled to signal inputs of the GQD (110), and a tuning circuit coupled to the GQD and the common-mode level adjust circuit. The GQD evaluates an input signal provided by the RC network, computes a difference between a filtered input signal and the feedback quantization signal to generate an error signal, measures the error signal, and compensates for the error signal with sigma-delta noise-shaping. The common-mode level adjust circuit alters a common-mode level of a differential input signal to be substantially equal to a desired common-mode level and the tuning circuit provides a compensation voltage to the common-mode level adjust circuit based on a difference between the common-mode levels.