Sensors, Vol. 19, Pages 4126: A VCO-Based CMOS Readout Circuit for Capacitive MEMS Microphones

Sensors, Vol. 19, Pages 4126: A VCO-Based CMOS Readout Circuit for Capacitive MEMS Microphones Sensors doi: 10.3390/s19194126 Authors: Andres Quintero Fernando Cardes Carlos Perez Cesare Buffa Andreas Wiesbauer Luis Hernandez Microelectromechanical systems (MEMS) microphone sensors have significantly improved in the past years, while the readout electronic is mainly implemented using switched-capacitor technology. The development of new battery powered “always-on” applications increasingly requires a low power consumption. In this paper, we show a new readout circuit approach which is based on a mostly digital Sigma Delta ( Σ Δ ) analog-to-digital converter (ADC). The operating principle of the readout circuit consists of coupling the MEMS sensor to an impedance converter that modulates the frequency of a stacked-ring oscillator—a new voltage-controlled oscillator (VCO) circuit featuring a good trade-off between phase noise and power consumption. The frequency coded signal is then sampled and converted into a noise-shaped digital sequence by a time-to-digital converter (TDC). A time-efficient design methodology has been used to optimize the sensitivity of the oscillator combined with the phase noise induced by 1 / f and thermal noise. The circuit has been prototyped in a 130 nm CMOS process and directly bonded to a standard MEMS microphone. The proposed VCO-based analog-to-digital co...
Source: Sensors - Category: Biotechnology Authors: Tags: Article Source Type: research
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