Near threshold pulse transit time processor for central blood pressure estimation

In this work a digital peripheral that can measure pulse transit time for central blood pressure estimation is presented. To do so, it processes ECG and BCG signals in real time by detecting the R-waves in the ECG and using this as time reference for measuring intervals of interest such as RJ, IJ and RR. The circuit was fabricated in a 180 nm process and experimental results are presented. The peripheral works at the near-threshold region and consumes 7 pJ/cycle with 0.43 V of supply voltage while operating at 8 kHz. We showed that state of the art performance can be achieved in the processing required for wearable estimation of central blood pressure while operating the digital circuit in the near-threshold region.