A fully differential switched-current delta-sigma modulator using a single 3.3-V power-supply voltage

This paper presents the design of a fully differential second-order delta-sigma modulator using a single 3.3-V power supply voltage. At the system level, we tailor the modulator structure considering the similarity and difference of switched-capacitor and switched-current realizations. At the circuit level, we propose a new switched-current memory cell and integrator with improved common mode feedback, without which low power-supply-voltage operation would not be possible. Other building blocks such as 1-bit A/D and D/A converters are presented as well. The whole modulator has been implemented in AMS´ 0.8-μm double-metal digital CMOS process. It occupies an active area of 0.53×0.48 mm² and consumes a current of 0.6 mA