A Fully Integrated Eddy-Current Sensor With Dual Stages for Absolute Angle Measurement

This article presents a fully integrated absolute angular position sensor based on the eddy current effect. The noncontact principle based on extraordinary magnet detection is immune to dust, oil, and stray magnets. The sensor achieves a more accurate absolute position measurement by two-stage coils on the printed circuit board. Due to the orthogonal channel design, the demodulation performance is robust under amplitude vibration because of the ratiometric principle. Programmable gain and offset adjustment lessens the installation and manufacturing process requirements. The tracking ADC based on the pseudo-linearization achieves a high conversion speed. The whole eddy-current sensor (ECS) has been fabricated in the 180-nm process. The converter occupies 14.45-mm2 silicon area and consumes 55 mA under a 5-V supply. The measurement results prove that the maximum error is 0.05° within [0, 360] after harmonic compensation.