A Capacitive-to-Digital Converter With Automatic Range Adaptation for Readout Instrumentation

Capacitive sensors have profoundly found their way in everyday life. Devices and instrumentation ranging from specialty equipment to smartphones all employ in one way or the other a capacitive sensor and its associated readout circuit, making the latter ubiquitious. We present a capacitive readout system that automatically adapts its range to the unknown measured capacitance, thereby extending its functional input range, as well as its application and instrumentation compatibility. The proposed system achieves a constant resolution for a range of input capacitance up to 690 pF.