Low-power and high-resolution capacitance sensing using CMOS inverter-based RC oscillator by employing voltage-integration feedback

Abstract

Abstract In this paper, new circuit techniques are proposed and applied for low-power, high-resolution capacitance sensing. The first is a CMOS inverter-based resistor-capacitor oscillator that consists of a resistor, a capacitor, and three inverters, allowing it to operate at low supply voltage and low power with a wide sensing range. The second is a voltage-integration feedback (VIF), which suppresses low-frequency jitter noise generated by internal and external noise. As a result, a fabricated circuit with a 0.18 μm CMOS process technology exhibits the sensitivity of 10.5 μs pF−1 with 2.12 ppm resolution in the oscillation frequency, in addition to 7.52 μW power consumption under a 1 V power supply.