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

摘要

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 1pm CMOS readout circuit. The measured nominal frequency output is of 9 MHz and increases up to11.6 MHz with an aluminum target placed at 50μm 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-ferromagnetictarget, thus enhancing strongly the sensor sensitivity. Furthermore a careful layout design leads to robustness towards the generated coil magnetic field.