A Low-Power Interface for Eddy Current Displacement Sensors in Sub-Micron Applications

In this paper we present a low-power interface for eddy current displacement sensors with digital output. A measurement method and a new front-end circuit are proposed. The front-end circuit demonstrates an excellent thermal stability, high-resolution and low power consumption. The demodulation principle, as well as the interface implementation, is addressed. This interface is introduced for measuring sub-micron displacements in medium to high-resolution applications. The system will consume less than 12 mW, and will have an extremely low thermal drift. The interface circuits will be implemented as a system in a package (SIP). The full-scale range of displacement is 1 mm with 50 KHz signal bandwidth and 11 bits resolution (less than 500 nm). The signal conditioning circuit utilizes a standard 0.35 mum CMOS technology. The discussions are based on simulations and preliminary experimental results, promising a proper operation of the sensor.