A 21.6μW inductively powered implantable IC for blood flow measurement

This paper presents a fully integrated inductively powered implantable circuits for blood flow measurement, which are embedded within vascular prosthetic grafts for early detection of graft degradation or failure. The ASIC interfaces with micro-fabricated pressure sensors and uses a 13.56MHz carrier frequency for power transfer and command/data communication. A backscatter-modulated passive telemetry is used for transmitting sensor readout information to an external monitoring device. The chip has been fabricated in 0.18μm CMOS process, occupies a total active area of 1.5×1.78mm
²
and consumes a total power of 21.6μW. The rectifier achieves an efficiency of 66% The sub-μW 10-bit SAR ADC achieves an ENOB of 8.5 bits at 106KS/s conversion rate.