Interface Circuit Design to Enable Miniaturization of Thermal-Piezoresistive Oscillators for Mass Sensing Applications

Abstract

This work focuses on the integrated circuit design for CMOS-MEMS-based thermal-piezoresistive oscillators (TPOs). Conventional TPOs necessitate bulky discrete circuit components, which impedes integration and miniaturization of the microsystems. The proposed circuit implemented using TSMC $0.18 \mu\mathrm{m}$ CMOS technology serves as sustaining amplifier and biasing circuit for our previously developed CMOS-MEMS thermal-piezoresistive resonators (TPRs), thus achieving TPOs with small form factor, targeted for mass/particle sensing applications. The previous version using commercial PCB electronics consumes 2.73 W while the proposed design greatly reduces the power consumption down to 15 mW. In addition, no harmonics have been found in oscillator output power spectrum while reaching 0 dBm (i.e., 1 mW). The far-from-carrier phase noise is demonstrated with −73.85 dBc/Hz and −80.06 dBc/Hz at 1 kHz and 100 kHz offsets respectively at a carrier frequency of 814.49 kHz in ambient pressure; as a result it is suitable for sensor applications. The miniaturized CMOS-MEMS TPO system features a frequency resolution of 65.9 Hz, thus corresponding to a mass resolution of 33.9 pg, which would potentially serve as aerosol (PM 2.5 ) sensors.