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

The first fully integrated inductive proximity sensor has been realized wit h a 75 nH, 1 mm side gold electrodeposited squared coil and with on-chip 1 mu m 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 mu m 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 in crease when approaching a conductive non-ferromagnetic target, thus enhanci ng strongly the sensor sensitivity. The new sensor microsystem has been suc cessfully applied for angular position measurements. (C) 1999 Elsevier Scie nce S.A. All rights reserved.