Power-Efficiency Evolution of Capacitive Sensor Interfaces

Zhichao Tan, Hui Jiang, Huajun Zhang, Xiyuan Tang, Haoming Xin, Stoyan Nihtianov

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Abstract

Recent years have witnessed an improvement in the energy efficiency of capacitive sensor interfaces by more than three orders of magnitude. This article reviews the architectural and circuit innovations that have contributed to this progress. The fundamental limit on the energy consumption of capacitive sensor interfaces is discussed, as well as the widely used figure-of-merit (FoM). Interfaces based on period modulation feature simple circuitry, but their power efficiency at higher resolution deteriorates. Those employing Δ Σ modulation achieve high resolution with improved efficiency but require operational transconductance amplifiers that do not easily scale with process and supply voltage. Interfaces using successive approximation techniques feature mostly digital circuitry achieving good power efficiency at medium resolution. To achieve higher resolution, they can also be employed as the front-end in a hybrid architecture, where a back-end based on Δ Σ modulation or a voltage-controlled oscillator (VCO) performs a fine measurement on the front-end's residue, resulting in high resolution and excellent energy efficiency simultaneously.

Original languageEnglish
Article number9245583
Pages (from-to)12457-12468
Number of pages12
JournalIEEE Sensors Journal
Volume21
Issue number11
DOIs
Publication statusPublished - 2021

Keywords

  • Capacitive sensor
  • energy efficiency
  • period modulation
  • SAR
  • VCO
  • zoom

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