Patent ID: 7944385
Filing Date: 2011-05-17
Classification: H03M

Abstract:
1. A continuous-time sigma-delta analog-to-digital converter for converting analog signals into digital signals, comprising i) a signal path comprising at least one combiner adapted to combine analog signals to be converted with feedback analog signals, at least two integrators mounted in series and adapted to integrate said combined analog signals, a quantizer adapted to convert said integrated signals into digital signals, a decimation filter for filtering digital signals, and ii) a feedback path comprising at least a digital-to-analog converter (DAC) adapted to convert said digital signals output by said quantizer into feedback analog signals intended for said combiner, characterized in that at least one of said integrators comprises variable capacitance means and/or variable resistance means arranged to be set in chosen states depending on values of a digital word to present chosen capacitances and/or chosen resistances, and in that it also comprises a self-calibration control means arranged a) to generate a digital word with a chosen first value, b) then to estimate in-band noise IBN from said filtered digital signals and to compare said in-band noise IBN) to the preceding in-band noise IBN, c) then to modify the value of the digital word in order to decrease said capacitance and/or resistance of each concerned integrator from a chosen decrement, when BN is smaller than IBN, d) then to iterate steps b) and c) till IBN is equal to or greater than IBN, and to choose as calibration digital word value the value corresponding to the preceding in-band noise IBN in order to set said calibration state.