An online fully-digital calibration of leakage noise in MASH continuous time ΔΣ modulators

This paper presents an online background calibration technique for eliminating the quantization noise leakage in MASH continuous-time delta-sigma modulators (CT-MASH). By using a system identification approach, the signal and noise transfer functions of each stage in CT-MASH are fully identified. This information is used to adaptively tune the coefficients of the digital noise cancellation filters (NCF) and therefore eliminate the leakage noise. This technique enables the design of high performance CT-MASH modulators despite the large variations in process and environment parameters. The accuracy of matching required to achieve a given signal-to-quantization-noise ratio (SQNR) is analyzed and verified through simulation.