A 56fJ/Conversion-Step 178dB-FoMS Third-Order Hybrid CT-DT Δ∑ Capacitance-to-Digital Converter

Abstract

With the advent of the internet of things (IoT) and wearable devices, demands of various environmental, motion, and proximity sensors have rapidly increased. Most environmental sensors employ certain transducers to modify their output capacitance value with respect to physical quantities such as humidity, pressure, strain, and proximity. Because of the nature of the transducers, the sensitivity of the environmental sensor is relatively low, and the differential capacitance values induced by the physical quantities are tiny compared to baseline capacitance values. To detect the small capacitance difference in a noisy environment and thus accurately detect the desired physical values, sensor interface ICs following the capacitive sensors should have low noise and high capacitance resolution characteristics. In addition, there is growing interest in power-efficient capacitance-to-digital converters (CDC) because of their wide usage in battery-powered IoT and wearable devices.