A 19.8-mW Eddy-Current Displacement Sensor Interface with Sub-Nanometer Resolution

Vikram Chaturvedi*, Johan Vogel, Kofi A.A. Makinwa, Stoyan Nihtianov

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

12 Citations (Scopus)
52 Downloads (Pure)

Abstract

This paper presents an eddy-current sensor (ECS) interface intended for sub-nanometer (sub-nm) displacement sensing in hi-tech applications. The interface employs a 126-MHz excitation frequency to mitigate the skin effect, and achieve high resolution and stability. An efficient on-chip sensor offset compensation scheme is introduced which removes sensor-offset proportional to the standoff distance. To assist in the ratiometric suppression of noise and drift of the excitation oscillator, the ECS interface consists of a highly linear amplitude demodulation scheme that employs passive capacitors for voltage-to-current (V2I) conversion. Using a printed circuit board-based pseudo-differential ECS, stability tests were performed which demonstrated a thermal drift of <7.3 nm/°C and long-term drift of only 29.5 nm over a period of 60 h. The interface achieves an effective noise floor of 13.4 pm Hz which corresponds to a displacement resolution of 0.6 nm in a 2-kHz noise bandwidth. The ECS interface is fabricated in TSMC 0.18- μm CMOS technology and dissipates only 19.8 mW from a 1.8-V supply.

Original languageEnglish
Pages (from-to)2273-2283
Number of pages11
JournalIEEE Journal of Solid-State Circuits
Volume53
Issue number8
DOIs
Publication statusPublished - 2018

Bibliographical note

Accepted Author Manuscript

Keywords

  • Amplitude demodulation
  • chopping
  • displacement
  • eddy current
  • inductive
  • oscillation
  • sensor

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