Abstract
The development of microelectromechanical system (MEMS) processes enables the integration of capacitive sensors into silicon integrated circuits. These sensors have been gaining considerable attention as a solution for mobile and internet of things (IoT) devices because of their low power consumption. In this study, we introduce the operating principle of representative capacitive sensors and discuss the major technical challenges, solutions, and future tasks for a capacitive readout system. The signal-to-noise ratio (SNR) is the most important performance parameter for a sensor system that measures changes in physical quantities; in addition, power consumption is another important factor because of the characteristics of mobile and IoT devices. Signal power degradation and noise, which degrade the SNR in the sensor readout system, are analyzed; circuit design approaches for degradation prevention are discussed. Further, we discuss the previous efforts and existing studies that focus on low power consumption. We present detailed circuit techniques and illustrate their effectiveness in suppressing signal power degradation and achieving lower noise levels via application to a design example of an actual MEMS microphone readout system.
Highlights
Recent growth in mobile devices and the internet of things (IoT) market has led to an increased demand for various types of sensors [1]
Low power consumption is important for batterypowered devices that cannot operate for longer periods with their smaller batteries [2]
The system comprises an analog front-end interfaces with the sensor and converts the capacitance change caused by the change in which interfaces with the sensor and converts the capacitance change caused by the the physical quantity to be measured into voltage or current; an Analog-to-Digital Converters (ADC), which converts change in the physical quantity to be measured into voltage or current; an ADC, which analog signals digitaltosignals; and a post-processor for signal
Summary
Recent growth in mobile devices and the internet of things (IoT) market has led to an increased demand for various types of sensors [1]. Capacitive sensors have become a popular research topic as they are advantageous because of their small form factor and low power consumption [5,6,7]. Micromachines 2021, 12, 960 pressure sensor, etc.) are difficult to implement in small sizes because of problems such as the production, assembly, and durability of mechanical parts [7]. The readout system and sensor are very important in terms of the overall system performance readout system and sensor are very important in terms of the overall system performance and power consumption. Because the power consumption of the capacitive sensor is low, the power power consumptions of other circuits (analog front-end circuit, analog-to-digital conconsumptions of other circuits (analog front-end circuit, analog-to-digital converter, postverter, post-processor, etc.) of the readout system are dominant. Among the capacitive readout sysSNR or power consumption requirements. 4, we introduce the readout method through an actual example we introduce the readout circuitcircuit designdesign method through an actual designdesign example of the of the analog front-end the MEMS microphone
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