A 30 ppm < 80 nJ Ring-Down-Based Readout Circuit for Resonant Sensors

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Abstract

This paper presents an energy-efficient readout circuit for micro-machined resonant sensors. It operates by briefly exciting the sensor at a frequency close to its resonance frequency, after which resonance frequency and quality factor are determined from a single ring-down transient. The circuit employs an inverter-based trans-impedance amplifier to sense the ring-down current, with a programmable feedback network to enable the readout of different resonant sensors. An inverter-based comparator with dynamically-adjusted threshold levels tracks the ring-down envelope to measure quality factor, and detects zero crossings to measure resonance frequency. The excitation frequency is dynamically adjusted to accommodate large resonance frequency shifts. Experimental results obtained with a prototype fabricated in 0.35 μm standard CMOS technology and three different SiN resonators are in good agreement with conventional impedance analysis. The prototype achieves a frequency resolution better than 30 ppm while consuming less than 80 nJ/meas from a 1.8 V supply, which is 7.8x less than the state-of-the-art.
Original languageEnglish
Pages (from-to)187-195
Number of pages9
JournalIEEE Journal of Solid State Circuits
Volume51
Issue number1
DOIs
Publication statusPublished - 10 Sep 2015

Bibliographical note

Accepted author manuscript

Keywords

  • ring-down measurement
  • Energy efficiency
  • frequency tracking technique
  • inverter-based front-end
  • MEMS resonant sensors readout

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