A Low-Cost CMOS Integrated Sensor Transducer Implemented as a Capacitance-to-Frequency Converter for Capacitive Measuring

In this paper, a low-cost CMOS integrated sensor transducer implemented as a capacitance-to-frequency converter for capacitive measuring is newly proposed. The proposed converter is attractive due to that a digitized signal is produced without realizing the analog to digital converter. Hence, the hardware cost could be reduced. Based upon the device parameters of 0.35 mum 2P4M CMOS technology with 3.2 V power supply, all the functions and performance of the proposed converter for capacitive measuring are tested and proven through SPICE simulations. The output frequency range is from 0.5 to 500 kHz under the variable capacitance of the detected sensor ranges from 4 to 24 pF. The area of this fabricated chip is 940 x 1080 mum² and the simulated power consumption is 5.917 mW. The proposed converter is suitable for capacitive measurement systems, for example, applied in the interfaces of pressure measurement, flow meter, humidity sensing, displacement sensors, etc.