A Parasitic Insensitive High-Frequency Capacitance-to-Voltage Converter ASIC for Dielectric Measurements

This article presents a capacitance-to-voltage (C2V) converter circuit for high-frequency capacitance measurement. The circuit uses the sensor capacitor in a switched capacitor network and converts it to an equivalent voltage. The proposed C2V converter circuit uses only switches and logic circuits. The C2V converter offers good parasitic insensitivity for ${R}_{s} \geq $ 5 $\text{k}\Omega $ compared with the reported literature and is validated experimentally in the 180-nm CMOS technology with an active area of 0.005 $\text {mm}^{{2}}$ . Measurement results show that it is insensitive to parasitic resistance and consumes a minimal power of 2.7 mW at the highest frequency, 250 MHz. Also, it can estimate the sensor capacitance with 10.6 fF resolution in the range of 4.5–24 pF in the presence of offset capacitance. The effectiveness of the circuit is demonstrated using a printed circuit-based coplanar capacitive sensor and tested with reference liquids and soils.