A 36μW heartbeat-detection processor for a wireless sensor node

In order to provide better services to elderly people, home healthcare monitoring systems have been increasingly deployed. Typically, these systems are based on wireless sensor nodes, and should utilize very low energy during their lifetimes, as they are powered by scavengers. In this article, we present an ultra-low power processing system for a wireless sensor node for very low duty cycle applications. In the CoolBio system-on-chip, we utilized several power reduction techniques at both the architecture level and the circuit level. These techniques include feature extraction, voltage and frequency scaling, clock and power gating and a redesign of key standard cells. In the design of the ultra-low power processing system, we paid special attention to the memory subsystem, as it is one of the most power-consuming modules in a design. We also designed a clock manager in order to reduce the power consumed by clocking, and a power manager that is able to power-off unutilized modules. The proposed wireless sensor node processing system consumes 36.4μW at 100MHz and 1.2V supply voltage, for a heartbeat-detection algorithm with a 0.01% duty cycle.