An Ultra-Low Power Variable-Resolution Sigma-Delta Modulator for Signals Acquisition of Biomedical Instrument

Chen-Ming HSU  Tzong Chee YO  Ching-Hsing LUO  

IEICE TRANSACTIONS on Electronics   Vol.E90-C   No.9   pp.1823-1829
Publication Date: 2007/09/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.9.1823
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Electronic Circuits
sigma-delta modulator,  variable-resolution,  ultra low power,  biomedical,  

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In this paper, an ultra-low power variable-resolution sigma-delta (ΣΔ) modulator for biomedical application is presented. The resolution of proposed modulator can be adjusted by switching its sampling frequency and architecture. The architecture is switched between second-order single-loop modulator and fourth-order cascaded second stage noise shaped modulator to reach different resolution requirement. The proposed sigma-delta modulator is implemented by single phase integrators based on a fully differential switched-capacitor circuit. The digital cancellation logic is embedded in the chip so that it would easily be integrated with biomedical instrument for effective acquisition. Experimental results of the proposed variable-resolution ΣΔ modulator fabricated in standard CMOS 0.18 µm technology confirm the expected specifications from 65 dB signal-to-noise distortion to 96 dB with 1 kHz bandwidth and power consumption range from 48 µW to 360 µW with a 1.8 V battery supply.