A Battery-Powered Wireless Ion Sensing System Consuming 5.5 nW of Average Power

This paper presents a battery-powered wireless ion sensing platform featuring complete sensing-to-transmission functionality. A 1 mm x 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+]. When all blocks are operating, the system consumes an average of 5.5 nW.