28.5 A 0.6V 0.015mm2 time-based biomedical readout for ambulatory applications in 40nm CMOS

Emerging applications in personal healthcare require sensor SoCs with low area, low power and a high dynamic range. Design in small-scale technologies can reduce the power and area of digital processing. However, due to the accompanied reduced supply voltage (VDD), the analog front-end (AFE) faces significant challenges in maintaining a large dynamic range in a power- and area-efficient manner [1-3]. A large dynamic range is important to handle the large signals expected during motion [1]. In this paper, we demonstrate a 0.6V ECG readout in 40nm technology for ambulatory applications. It can handle up to 40mVpp AC-signal and up to 300mV DC-electrode offset while consuming 3.3μW power and 0.015mm2 area. These results are achieved by implementing a time-domain-based readout architecture that focuses on scalable design techniques and especially avoids high-gain opamps and large passives. The AFE achieves more than 5× increase in AC dynamic range compared with previous work with similar silicon area and similar VDD [2], without compromising on the power consumption (see Fig. 28.5.6).