A power-optimized reconfigurable CT ΔΣ modulator in 65nm CMOS

This paper presents transistor-level design of a continuous-time (CT) reconfigurable ΔΣ modulator in a 1.2 V 65 nm CMOS process. Both architectural- and circuit-level power-optimization techniques, such as flexible loop order and quantizer bit, switchable OTA unit cells, and folding flash ADC, are utilized to achieve power efficiency over all bandwidths. As gate leakage current in 65 nm technology becomes prominent, a DAC biasing scheme that is robust to gate leakage current is employed. Simulation results show that the modulator achieves signal-to-noise-and-distortion-ratio (SNDR) of 73.3/76.5/77.4/84.4 dB for 20/10/3/0.5 MHz bandwidth (BW) with power consumption of 23.9/20.7/9.49/7.22 mW, respectively. The respective figure of merit (FOM) equals 0.16/0.19/0.26/0.53 pJ/conv.