Abstract
This paper presents a battery-powered wireless ion sensing platform featuring complete sensing-to-transmission functionality. A 1 mm × 1.2 mm chip fabricated in 65 nm includes a 406 pW potentiometric analog front end, a 780 pW 10-bit SAR ADC, a 2.4 GHz power-oscillator-based wireless transmitter that consumes an average of 2.4 nW during a 10-sample/sec transmission rate, two timing generation oscillators that each consume 140 pW, and a 3:1 switched-capacitor dc-dc converter with 485 pW of quiescent power that achieves the efficiencies of 96.8% and 70.5% at 60 and 3.9 nW loads, respectively. The chip connects to a screen-printed ion-selective electrode responsive to sodium ions, and in vitro testing across an NaCl solution concentration range of 0.1-100 mM exhibited a linear near-Nernstian response with a slope of 71 mV/log10[Na <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ]. When all blocks are operating, the system consumes an average of 5.5 nW.
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