A 2.3 $\mu$ W Wireless Intraocular Pressure/Temperature Monitor

We present the design of an ultra-low power, wireless pressure/temperature sensing device for continuous intraocular pressure monitoring. The device is wirelessly powered and demonstrates a power consumption of 2.3 μW at 1.5 V during continuous monitoring. The chip converts both capacitance and temperature to frequency using a time-interleaved relaxation oscillator, which modulates RF backscatter to a reader for computation of measured samples. A significant reduction in power consumption results from the elimination of the digitization circuitry, time-multiplexed operation, and moving the signal processing burden to the external reader using analog IF-modulated backscatter. The chip exhibits measured capacitance and temperature standard deviations of 1.4 fF and 0.4°C, respectively.