A calibration method for current steering digital to analog converters in continuous time multi-bit sigma delta modulators

This paper describes the general idea of a calibration method for a current steering digital-to-analog converter (DAC) in continuous time multi-bit ΣΔ modulators. Based on the application of the so called linear regression algorithm (LRA), this method improves the linearity of the DAC´s characteristics. Simulations under MATLAB on a fifth order continuous time 4bit ΣΔ modulator for signal frequencies up to 2MHz demonstrate the effectiveness of the presented algorithm compared to the data weighted averaging (DWA) method. The algorithm´s independence from the oversampling ratio makes it very attractive for modulators with low oversampling ratios.