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An ultra-low power ISM-band integer-N frequency synthesizer dedicated to implantable medical microsystems

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Abstract

In this article, the architectural choices and design of a fully integrated integer-N frequency synthesizer operating in the 902–928 MHz Industrial, Scientific and Medical (ISM) band is presented. This frequency synthesizer, optimized for ultra-low power operation, is being integrated in the transceiver of an implantable wireless sensing microsystem (IWSM), which is dedicated to in vivo monitoring of biological parameters such as temperature, pressure, pH, oxygen, and nitric oxide concentrations. This phase-locked loop-based synthesizer includes a 1.830 GHz LC voltage-controlled oscillator (VCO) using a 10 nH on chip inductor. Varactors are implemented using P+ in N-well diodes for their linearity and high quality factor. The transistors of the VCO are operated in moderate inversion, and their bias point was chosen using the g m/I d design methodology. The output of the VCO, operating at twice the ISM frequency band, is divided by 2 to generate differential, quadrature versions of the carrier. Power minimization of the programmable divider was achieved by designing the latches and flip-flops using appropriate circuit techniques such as True Single Phase Clocking (TSPC) and first-type Dynamic Single Transistor Clocking (DSTC1) depending on their operating frequency. The power consumption of the proposed synthesizer is 580 μW under 1 V; almost an order of magnitude lower compared to that of recent synthesizer designs having a similar architecture.

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Acknowledgments

The authors would like to acknowledge financial support from NSERC and the Canadian Research Chair on Smart Medical Devices. Thanks are also due to CMC Microsystems for the design tools and fabrication support.

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Authors and Affiliations

  1. Polystim Neurotechnologies Laboratory, École Polytechnique de Montréal, 2500, Chemin de Polytechnique, Montreal, QC, Canada, H3T 1J4

    Louis-François Tanguay & Mohamad Sawan

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  1. Louis-François Tanguay
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  2. Mohamad Sawan
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Correspondence to Louis-François Tanguay.

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Tanguay, LF., Sawan, M. An ultra-low power ISM-band integer-N frequency synthesizer dedicated to implantable medical microsystems. Analog Integr Circ Sig Process 58, 205–214 (2009). https://doi.org/10.1007/s10470-007-9123-z

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  • DOI: https://doi.org/10.1007/s10470-007-9123-z

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