High dynamic range interface system for a micromachined integrated AC-power sensor

This paper describes a read-out system for a CMOS compatible integrated AC-power sensor. The system consists of two equal micromachined devices operated at the same power level in a closed loop configuration. The large dynamic range requirements are met by a novel oversampled A/D converter embedded in the feedback loop. The system uses a variable reference voltage, which is controlled and measured on chip. The large thermal time constant of the sensor introduces additional stability problems in the nonlinear system. Therefore, we optimized the proposed architecture by nonlinear analysis and numerical simulations. The complete system including the sensor was implemented in a 2 μm CMOS process on a single chip