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 0.35μm CMOS technology, and consumes only 36μA 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.