An energy-efficient readout circuit for resonant sensors based on ring-down measurement

Area of Science:

• Electrical Engineering
• Sensor Technology
• Microelectromechanical Systems (MEMS)

Background:

• Resonant sensors are crucial for various applications, but their readout circuits often face challenges with energy efficiency and parasitic capacitance.
• Existing oscillator-based readout methods can be limited in detecting resonator quality factor (Q) and are susceptible to parasitic effects.

Purpose of the Study:

• To develop and demonstrate an energy-efficient readout circuit for resonant sensors utilizing a transient measurement technique.
• To enable accurate measurement of both resonance frequency and quality factor (Q) in resonant sensors, even with significant parasitic capacitance.

Main Methods:

• A transient measurement method where the sensor is driven near resonance and then allowed to "ring down".
• Zero-crossing detection of the decaying oscillation to determine resonance frequency.
• Envelope analysis of the ring-down response to extract the quality factor (Q).
• Integration of a prototype circuit in 0.35 μm CMOS technology.

Main Results:

• The prototype circuit achieved high energy efficiency, consuming only 36 μA at 3.3 V for a 2 ms measurement.
• Accurate determination of resonance frequency and quality factor (Q) for a micro-machined SiN resonator, validated against impedance analysis.
• Demonstrated sensitivity to ethanol flow, showcasing the system's potential for chemical sensing applications.

Conclusions:

• The proposed transient readout circuit offers an energy-efficient and robust solution for resonant sensor characterization.
• This method effectively measures key resonator parameters (frequency and Q) and is suitable for practical sensing applications, including environmental monitoring.
• The CMOS-integrated circuit provides a versatile platform for developing next-generation resonant sensor systems.