Accelerometer with digital representation

EU-funded scientists have developed an integrated circuit (IC) for resonant accelerometers that has both analogue and digital components to digitally display acceleration values.

Industrial Technologies

Resonant accelerometers are often microelectromechanical systems (MEMS) that measure acceleration by sensing the difference in the resonant frequencies of their two resonators. The fact that they are resistant to ionising radiation also makes them suitable for space applications. However, very few readout ICs for resonant MEMS accelerometers have been hitherto demonstrated, and often lack digital display. Against this backdrop, the EU-funded project RESACC (Development of a readout circuit for a resonant accelerometer) has developed an application-specific integrated circuit (ASIC), a microchip for a resonant MEMS accelerometer. RESACC combined an analogue sensor interface and a digital output on a single chip. The frequency-shift measurement of the MEMS provides input to the ASIC to deliver a digital display of acceleration. Focus was laid on the architecture of the sensor interface and the detailed design specifications of each block that the ASIC contains. Two oscillator blocks are each connected to a resonator of the MEMS. The ASIC also includes a damping block. Less critical parts, such as oscillator, voltage regulator and non-volatile memory, are not included; instead, external components are used. The project team built models of the oscillator and damping blocks during the project's specification phase. They also developed the layout of the ASIC. All sub-blocks have now been designed and separately validated, and assembled together for integration testing. RESACC has developed an integrated sensor interface circuit with digital output of acceleration that reduces the energy requirements of high-performance resonant accelerometers, with power consumption well below 100 mW. This ASIC has demonstrated satisfactory functional, noise and temperature stability performance and also served as a proof of concept for the system, including the MEMS. ASICs are likely to be useful in construction, where accelerometer-based sensor interfaces can be deployed to monitor structural health of large buildings, bridges and tunnels. They can also be used in vehicles, where sensors and interfaces are taking on increasing roles for safety and comfort. The machine industry can use them where miniaturised sensors and sensor interfaces allow efficient monitoring and maintenance. Sports/wellness and medical/health applications can include novel products for continuously monitoring body motions.