An Energy-Efficient ΔΣ Modulator Using Dynamic-Common-Source Integrators

Hiroaki KOTANI
Takao WAHO

IEICE TRANSACTIONS on Electronics   Vol.E97-C    No.5    pp.438-443
Publication Date: 2014/05/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E97.C.438
Type of Manuscript: Special Section PAPER (Special Section on Fundamentals and Applications of Advanced Semiconductor Devices)
ΔΣ modulator,  data converter,  low power,  analog circuit,  dynamic circuit,  

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An energy-efficient ΔΣ modulator using a novel switched-capacitor-based integrator has been investigated. The proposed dynamic integrator uses a common-source configuration, where a MOSFET turns off after the charge redistribution is completed. Thus, only the subthreshold current flows through the integrator, resulting in high energy efficiency. A constant threshold voltage works as the virtual ground in conventional opamp-based integrators. The performance has been estimated for a 2nd-order ΔΣ modulator by transistor-level circuit simulation assuming a 0.18-µm standard CMOS technology. An FOM of 29fJ/conv-step was obtained with a peak SNDR of 82.6dB for a bandwidth and a sampling frequency of 20kHz and 5MHz, respectively.