A fully-differential, multiplex-sensing interface circuit monolithically integrated with tri-axis pure oxide capacitive CMOS-MEMS accelerometers

The integration of a CMOS multi-channel readout circuit and tri-axis capacitive accelerometers on a single chip has been demonstrated in this work. The tri-axis mechanical structure together with the monolithic tri-axis multiplexed accelerometer interface circuit is proposed and demonstrated for the first time. Such a system exhibits the following features: (1) the smallest chip size is realized by a timing-based readout circuit; (2) the signal-to-noise ratio (SNR) is enhanced by a fully differential sensing mechanism; and (3) the stacking of the pure oxide layers, serving as the mechanical structures, enhances temperature stability. As a result, the sensing system not only reduces the total chip size but significantly improves the overall system performance.