A Capacitance-to-Digital Converter Integrated in a 32bit Microcontroller for 3D Gesture Sensing

This paper describes a capacitance-to-digital converter (CDC) integrated in a 32bit microcontroller. The analog part of the CDC that we propose is only composed of a voltage down converter, current mirror circuit, and current-controlled oscillator. Since its analog part is so simple that our CDC can be easily ported to various kinds of processes with which microcontrollers are fabricated. RF noise immunity of our CDC is enhanced by using the random phase shift scheme that we developed. The effectiveness of the scheme was experimentally verified with a CDC integrated in a 32bit microcontroller which was fabricated in 130nm CMOS process. Our CDC meets level 3 of IEC 61000-4-3 and IEC 61000-4-6 standards. With our CDC structure, users can select resolution under a trade-off between the resolution and measurement time. If the measurement time is increased up to 50ms, its resolution is as high as 2aF. 3D gesture sensing was realized using the 32bit microcontroller in which the proposed CDC was integrated.