A Healthier World, One Data Point at a Time
A variety of biosensor modules and biopotential analog front-ends (AFEs) are designed to be integrated into health wearables. Figure 2 shows an example. The biosensor modules integrate various components—LEDs, photodetectors, and low-noise electronics with ambient light rejection, for example—to enable mobile and wearable devices to measure ECG, pulse oximetry, and heart rate. The biopotential AFEs can be used to create solutions such as wearable health and fitness monitors that provide clinical-grade ECG monitoring. Examinations were done that utilize a two-chip solution consisting of an ECG AFE and a PPG sensor to measure, via a wearable form factor, pulse arrival time (PAT), which is equal to the sum of PTT and the pre-ejection period. In this study, engineers configured the hardware and performed detailed register configuration settings to allow the two chips to acquire ECG and PPG data synchronously to derive PAT.
The ECG AFE’s interrupt registers were configured to generate a synchronization pulse after each ECG sample was placed in its data FIFO. The PPG sensor is configured to wake up with each ECG synchronization pulse and acquire a sample. After the PPG sensor completes a measurement and sets its FIFO interrupt, the micro-computer unit reads both the ECG and PPG FIFO data registers over an SPI interface. The process is repeated at the sample rate selected for the ECG AFE.