Nano-things: Pushing sleep current consumption to the limits in IoT platforms

In this work we illustrate a novel power management architecture towards eliminating the power draw of IoT platforms during inactive periods. Our principle suggests the employment of an off-chip Real-Time-Clock (RTC) configured to control the power supply of the under consideration mote, by enabling or disabling its power in a power-gating fashion. The selected RTC features an ultra-low power profile and it is the only module that remains powered during sleep, hence the overall mote's consumption is substantially diminished. Additionally, we introduce an alternative topology in which the host MCU remains powered in sleep state while the power-gating scheme is applied only in the rest of the peripherals of the IoT node, in an effort to exploit the MCUs benefits such as RAM retention and ultra-fast wake-ups. The proposed principle can be adopted by any IoT mote, in order to extend the life expectancy of battery-powered applications, by pushing sleep currents an order of magnitude lower. Moreover, we demonstrate the ICARUS mote, the first sensor that draws a sleep current of only 22 nA on a 3 V supply. Direct comparison of power draw in sleep state with state-of-the-art sensors illustrates improvements of roughly 98 % - 99.8 %, while we demonstrate that the life expectancy of the same motes can be prolonged from 2.7 years to 19 years under specific duty-cycles.