A Multi(bio)sensor Acquisition System With Integrated Processor, Power Management, $8 \times 8$ LED Drivers, and Simultaneously Synchronized ECG, BIO-Z, GSR, and Two PPG Readouts

A battery-powered multisensor acquisition system with five dedicated channels [electrocardiograph (50 $\mu \text{W}$ ), bioimpedance (46 $\mu \text{W}$ ), galvanic skin response (15 $\mu \text{W}$ ), and 2 $\times $ photoplethysmogram (134 $\mu \text{W}$ ) is presented. It includes an ARM Cortex M0, analog and digital filters, timestamp converter and sample rate converter (SRC), and generic interfaces to support additional sensor modalities. The timestamp module makes precise synchronization between the data streams possible. The SRC module makes the sample rates of data from the internal and external sensor readouts compatible with each other, and is up to a factor 35 more energy efficient compared with a software solution. These modules enable performing accurate and reliable (correlation) techniques. The power management includes two buck converters, an LDO, and eight LED drivers, supporting up to 64 LEDs in an $8 \times 8$ matrix organization. It makes this system the most complete and versatile sensor readout system with state-of-the-art performance (1073 $\mu \text{W}$ with all channels enabled).