A 23ppm/°C readout circuitry improvement for capacitive sensor acquisition platforms

This paper presents a high performance analog front-end for conditioning and acquiring raw sensors signals for a frequency based converter platform, with very low power consumption aim. This platform consists of specific circuits designed to interface capacitive sensors with high efficient frequency to code converters. The whole system shapes a readout integrated circuit (ROIC). This ROIC integrates a specific capacitance to frequency converter based on a high performance voltage reference circuit. Thanks to compensation of the channel length modulation effect and the suppression of mobility dependence it presents a low power consumption (only 149 μA at full power mode) and the temperature coefficient achieved is 23 ppm/°C. This novel frequency acquisition and conditioning techniques proves to be very precise, versatile and useful for signal sensor acquisition in scalable structures, which can improve the monitoring system reliability and performance.