First integrated inductive proximity sensor with on-chip CMOS readout circuit and electrodeposited 1 mm flat coil

Abstract

The first fully integrated inductive proximity sensor has been realized with a 75 nH, 1 mm side gold electrodeposited squared coil and with on-chip 1 μm CMOS readout circuit. The measured nominal frequency output is of 8.95 MHz and increases up to 11.60 MHz with an aluminum target placed at 50 μm of the coil. The on-chip electronic interface is based on a differential relaxation oscillator designed to be fast and to have a frequency output increase when approaching a conductive non-ferromagnetic target, thus enhancing strongly the sensor sensitivity. The new sensor microsystem has been successfully applied for angular position measurements.