An Energy-Efficient Interface For Resonant Sensors Based On Ring-Down Measurement

This paper presents a resonant-sensor interface that operates based on transient measurement of the resonator's exponential decay after a brief excitation at a frequency close to its resonance frequency. In contrast with oscillator-based interfaces, the presented readout circuit is capable of detecting the resonator's quality factor (Q) in addition to its resonance frequency, and can be used in the presence of large parasitic capacitors. A prototype of the interface's front-end circuit has been integrated in 0.35 mu m CMOS technology, and consumes only 36 mu A from a 3.3V supply during a measurement time of 2ms. Measurement results on a clamped-clamped beam resonator obtained using this prototype are in good agreement with results obtained using impedance analysis.