A 9.1 mW inductive displacement-to-digital converter with 1.85 nm resolution

Abstract

A displacement-to-digital converter (DDC) based on inductive (eddy-current) sensor is presented. The sensor is embedded in a self-oscillating front-end, whose 145MHz output is then digitized by a ratiometric ΔΣ ADC. Over a 10μm range, the DDC achieves 1.85nm resolution (1.02 pH), in a 2kHz bandwidth. It draws 9.1mW from a 1.8 V supply making it the most energy-efficient ECS interface ever reported.