A 200-μW Interface for High-Resolution Eddy-Current Displacement Sensors

Journal article (2021)

Authors

Matheus Pimenta Infineon Technologies
C. Gürleyük Electronic Instrumentation - EEMCS
Paul Walsh Infineon Technologies
Daniel O’Keeffe Infineon Technologies
M. Babaie Electronics - EEMCS
K.A.A. Makinwa Microelectronics
Research Group
Electronic Instrumentation (EEMCS) (TU Delft)
Copyright: © 2021 Matheus Pimenta, C. Gürleyük, Paul Walsh, Daniel O’Keeffe, M. Babaie, K.A.A. Makinwa
DOI: https://doi.org/10.1109/JSSC.2020.3044027
Low power Displacement Phase-locked loop (PLL) Digitally controlled oscillator (DCO) Eddy-current sensor interface
More Info
expand_more

Published Date

2021

Language

English

Reuse Rights

Other than for strictly personal use, it is not permitted to download, forward or distribute the text or part of it, without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license such as Creative Commons.

Faculty

Electrical Engineering, Mathematics and Computer Science

Department

Microelectronics

Research Group

Electronic Instrumentation

Abstract

This article presents a low-power eddy-current sensor interface for touch applications. It is based on a bang-bang digital phase-locked loop (DPLL) that converts the displacement of a metal target into digital information. The PLL consists of a digitally controlled oscillator (DCO) built around a sensing coil and a capacitive DAC, a comparator-based bang-bang phase/frequency detector (PFD), and a digital loop filter (DLF). The PLL locks the DCO to a reference frequency, making its digital input a direct representation of the sensing coil inductance. To compensate for the coil inductance tolerances, the DCO's center frequency can be trimmed by a second capacitive DAC. This approach obviates the need for a reference coil. When combined with a 5-mm-diameter sensing coil located 500μm from a metal target, the interface achieves a displacement resolution of 6.7 nm (rms) in a 3-kHz bandwidth. It consumes 200μW from a 1.8-V power supply, which represents the best-reported tradeoff between power consumption, bandwidth, and resolution.