A wide dynamic range sigma-delta modulator with automated coefficients adaptation

A fourth order, low power sigma-delta modulator (SDM) with dynamic range (DR) extend technique is presented. The SDM was implemented as a sensing circuit for hearing aids systems instead of the traditional complex analog front end (AFE). The wide dynamic range sigma delta modulator (WDSDM) is implemented with a feed-forward architecture, order of 4, oversampling ratio (OSR) of 32, and an 1-bit quantizer under a sampling frequency of 1.44 MHz. The TSMC 0.18 μm 1P6M CMOS process is employed. Without the DR extended technique, the measured signal-to-noise distortion ratio (SNDR) and DR are 63.5 dB and 75 dB, respectively. By applying the DR extended technique, the measured DR can be extended to 88dB and its power consumption is 49.5 μW under the supply voltage of 1.8V.