A Low-Power Delta-Sigma Capacitance-to-Digital Converter for Capacitive Sensors

A Low-Power Delta-Sigma Capacitance-to-Digital Converter for Capacitive Sensors

This paper proposes a low-power delta-sigma capacitance-to-digital converter (CDC) for a capacitive sensor. The input of the capacitive sensor employs a zoomed-in technique with the offset capacitor to extend the input capacitance range. The proposed CDC uses a third-order switched capacitor delta-s...

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Bibliographic Details
Main Authors: Rongshan Wei, Wanjin Wang, Xiaoxia Xiao, Qunchao Chen
Format: Article
Language:English
Published: IEEE 2019-01-01
Series:IEEE Access
Subjects:
Capacitive sensors
delta-sigma modulation
low power
Online Access:https://ieeexplore.ieee.org/document/8736289/
Description
Summary:This paper proposes a low-power delta-sigma capacitance-to-digital converter (CDC) for a capacitive sensor. The input of the capacitive sensor employs a zoomed-in technique with the offset capacitor to extend the input capacitance range. The proposed CDC uses a third-order switched capacitor delta-sigma modulator to provide a digital output, based on a cascade of integrators with a feed forward (CIFF) structure. The current-starved operational transconductance amplifiers (OTAs) are applied in the delta-sigma modulator's first integrator to improve the current efficiency and reduce the power consumption. An auto-zeroing technique is used in the OTAs to reduce their offset and noise. The circuit was implemented in a 0.18-&#x03BC;m CMOS technology and occupies an area of 0.496 mm<sup>2</sup>. The measurable capacitance range of the CDC can be varied from 0 to 8 pF. In a measurement time of 0.8 ms, the delta-sigma CDC achieved a 12.7 effective number of bits while consuming 18.6-&#x03BC;A current from a 2-V supply voltage.
ISSN:2169-3536

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