A 900 mV 66 µW Sigma-Delta Modulator Dedicated to Implantable Sensors

Zhijun LU  Yamu HU  Mohamad SAWAN  

Publication
IEICE TRANSACTIONS on Information and Systems   Vol.E88-D   No.7   pp.1610-1617
Publication Date: 2005/07/01
Online ISSN: 
DOI: 10.1093/ietisy/e88-d.7.1610
Print ISSN: 0916-8532
Type of Manuscript: Special Section PAPER (Special Section on Recent Advances in Circuits and Systems--Part 1)
Category: Biomedical Circuits and Systems
Keyword: 
sigma-delta modulator,  low-power,  low-voltage,  switched-OTA,  half-delay integrator,  

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Summary: 
In this paper, a low-voltage low-power sigma-delta modulator dedicated to implantable sensing devices is presented. This second-order single-loop sigma-delta modulator is implemented with half-delay integrators. These integrators are based on new fully-differential CMOS class AB switched-Operational Transconductance Amplifier (switched-OTA). An on-chip voltage doubler is introduced to locally boost a supply voltage at the input stage of a conventional OTA in order to allow rail-to-rail signal swing. Experimental results of the modulator fabricated in CMOS 0.18 µm technology confirm its expected features of a peak signal-to-noise ratio (SNR) of 72 dB, a signal-to-noise distortion ratio (SNDR) of 62 dB in a 5 kHz signal bandwidth, and a power consumption lower than 66 µW with a 900 mV voltage supply.