Dynamic calibration of feedback DAC non-linearity for a 4th order CT sigma delta for digital hearing aids

Abstract

In this paper we present a calibration scheme for calibrating the 2^nd order harmonic distortion of feedback DAC used in a 4^th order CT-ΣΔ. This scheme was implemented in a 0.25um CMOS process with a supply voltage of 1.2V, the 4^th order CT-ΣΔ was able to achieve 68dB measured SNR, while the 2^nd order harmonic was reduced by about 20dB suppressing it to the thermal noise floor.