High-Power-Efficiency Readout Circuit Employing Average Capacitance-to-Voltage Converter for Micro-Electro-Mechanical System Capacitive Accelerometers

Abstract

A capacitance-to-voltage converter (CVC) is proposed in this paper and applied to a readout circuit for a micro-electro-mechanical system (MEMS) accelerometer to improve the power efficiency. In a traditional readout circuit, the front-end CVC has to operate at a high sampling frequency to resist thermal noise deterioration due to the large parasitic capacitance introduced by the mechanical sensing element. Thus, the back-end analog-to-digital converter (ADC) also has to operate at a high sampling frequency to avoid noise aliasing when sampling the output signal of the CVC, which leads to high power consumption. The average CVC technique is proposed in this paper to reduce the sampling frequency requirement of the back-end ADC and thus reduce the power consumption. Both the traditional readout circuit and the proposed readout circuit are simulated with a commercial 0.18 μm BCD process. The simulation results show that noise aliasing occurs, and the noise power spectral density (PSD) of the traditional readout circuit increases by 12 dB when the sampling frequency of back-end ADC is reduced by 24 dB. However, in the proposed readout circuit, a noise aliasing effect does not occur. Moreover, the proposed readout circuit reduces the power consumption by 53% without thermal noise deterioration. In addition, the proposed CVC circuits are fabricated in an 0.18 μm BCD process, and the test results show that the presented readout circuit based on the average CVC technique can obtain better performance than the traditional CVC-based readout circuit.

A Current-Mode Analog Front-End for Capacitive Length Transducers in Pneumatic Muscle Actuators

“…The structure of this Capacitive-MKM (C-MKM) overcomes the drawbacks intrinsic of the abovementioned solutions since it: (i) directly measures the distance between the two ends of the muscle without the need of mechanical sensors; (ii) does not suffer from external electrical and magnetic disturbances; (iii) is easy to be mounted between the two muscle end caps; (iv) respects the compliance of MKM muscles. To take full advantage of the properties of the C-MKM, the present paper aims to describe the design, implementation, and characterization of a Capacitance-to-Voltage Analog-Front-End (CV-AFE) circuit capable of measuring the value of the C-MKM capacitance whose output voltage is directly proportional to the pneumatic muscle length during both its elongation and contraction phases in real-time [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. In particular, CV-AFE circuits are employed in a large variety of medical [ 24 , 25 , 26 , 27 , 37 , 39 ] and industrial [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ] applications.…”

“…To take full advantage of the properties of the C-MKM, the present paper aims to describe the design, implementation, and characterization of a Capacitance-to-Voltage Analog-Front-End (CV-AFE) circuit capable of measuring the value of the C-MKM capacitance whose output voltage is directly proportional to the pneumatic muscle length during both its elongation and contraction phases in real-time [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ]. In particular, CV-AFE circuits are employed in a large variety of medical [ 24 , 25 , 26 , 27 , 37 , 39 ] and industrial [ 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 , 36 , 37 , 38 , 39 ] applications. The integration of analog and digital electronic paradigms identifies the Capacitance-to-Digital Converters (CDC) that enable efficient digital data processing and data transmission [ 24 , 25 , 29 ].…”

“…The integration of analog and digital electronic paradigms identifies the Capacitance-to-Digital Converters (CDC) that enable efficient digital data processing and data transmission [ 24 , 25 , 29 ]. On the other hand, when the specific application requests the output of the CV-AFE be a DC or AC voltage signals, the design architecture mainly employs a fully-analog approach; for example, this is the case for driving high-refresh-rate AMOLED displays [ 28 ], to control accelerometer, gyroscopes and positioning sensors [ 35 , 36 , 38 ]. The proposed CV-AFE circuit belongs to the latter class of converters since its DC output voltage can be employed to control the variations of the pneumatic muscle elongation or contraction with respect to a C-MKM initial value or rest condition by using suitable analog actuators [ 40 , 41 , 42 , 43 , 44 ].…”