Electromechanical Sigma-Delta Modulators ( \Sigma \Delta } ) Force Feedback Interfaces for Capacitive MEMS Inertial Sensors: A Review

Analog-to-digital converters based on sigma-delta modulators (ΣAM) are a popular choice for high resolution conversion from the analog to the digital domain. With relatively small modifications, they can also be used as electromechanical ΣAM (EM-ΣAM) force feedback interfaces for capacitive micro-electromechanical systems (MEMSs) inertial sensors. Such interfaces are able to combine the benefits of force feedback and analog-to-digital conversion at relatively modest circuit cost. This paper provides a comprehensive review of EM-ΣAM interfaces for capacitive MEMS inertial sensors. The principle and the design methodology of EM-ΣAM interfaces are introduced. A classification of EM-ΣAM accelerometers and gyroscopes is presented, and a detailed analysis of different EM-ΣAM architectures is given. The most representative EM-ΣAM inertial sensors systems are discussed and compared with regard to their performance characteristics. In particular, the properties of various discrete and continuous-time techniques and a system parameter optimization methodology are illustrated through specific examples. Finally, current challenges and future development trends of EM-ΣAM interfaces for inertial sensors have been identified.