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A VCO-Based CMOS Readout Circuit for Capacitive MEMS Microphones
Andres Quintero1, Fernando Cardes2, Carlos Perez3
1Department of Electronics Technology, Carlos III University of Madrid, 28911 Leganes, Spain. andres.quintero@uc3m.es.
Sensors (Basel, Switzerland)
|September 27, 2019
Summary
This study introduces a novel, low-power digital readout circuit for Microelectromechanical systems (MEMS) microphones. The new voltage-controlled oscillator-based analog-to-digital converter (VCO-ADC) achieves high performance, enabling advanced always-on applications.
Area of Science:
- Electrical Engineering
- Materials Science
- Acoustics
Background:
- Microelectromechanical systems (MEMS) microphones are crucial for modern electronics.
- Existing switched-capacitor readout circuits have limitations in power consumption for battery-powered devices.
- There is a growing need for low-power, high-performance readout electronics for MEMS microphones.
Purpose of the Study:
- To develop a new, low-power readout circuit for MEMS microphones.
- To implement a mostly digital Sigma Delta analog-to-digital converter (ADC) approach.
- To improve the performance and reduce the power consumption of MEMS microphone readout electronics.
Main Methods:
- A novel readout circuit based on a mostly digital Sigma Delta analog-to-digital converter (ADC) was designed.
- The circuit couples the MEMS sensor to an impedance converter modulating a stacked-ring oscillator (voltage-controlled oscillator - VCO).
- A time-efficient design methodology optimized oscillator sensitivity and noise performance, with prototyping in a 130 nm CMOS process.
Main Results:
- The proposed VCO-based analog-to-digital converter (VCO-ADC) achieved a peak signal-to-noise and distortion ratio (SNDR) of 77.9 dB-A.
- A dynamic range (DR) of 100 dB-A was measured.
- The circuit demonstrated low current consumption (750 μA at 1.8 V) and a small effective area (0.12 mm²).
Conclusions:
- The developed VCO-ADC offers a significant advancement for low-power MEMS microphone applications.
- This technology enables the development of battery-powered, always-on devices.
- The circuit's performance characteristics make it suitable for low-cost digital MEMS microphones.
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