CCO-based analog front-end for iStents

This paper presents a low power analog front-end designed to be part of an intelligent stent for restenosis monitoring in a distal pulmonary artery. The heterogeneous front-end comprises a capacitive MEMS pressure sensors for the acquisition of physiological signals, as well as 0.18 μm CMOS electronics for wireless device powering and data transmission, performed using the ISM 433.92 MHz band. The architecture includes a voltage rectifier, a voltage reference, a voltage regulator, an oscillator and a MEMS pressure sensor. A modified Sawtooth oscillator has been designed to allow the operation of the system under ramped-voltage biasing signals. Post-layout simulations present a good correlation with the analytical model of the system, showing an average power consumption of 11 μW and a frequency-to-capacitance sensitivity of 0.1569 MHz/pF.