A power management unit for ultra-low power wireless sensor networks

Wireless sensor networks become more and more attractive due to their ongoing miniaturization and decreasing costs. One of the major challenges concerning the design is the power consumption of the wireless sensor node. Low power consumption is mandatory to guarantee a long lifetime if a battery is used as a power source or to allow the use of an energy harvester. In this work a multi-stage power management for a wireless sensor node is presented. Energy-efficient power management is achieved by employing several state machines controlling different power domains which can be turned on and off separately depending on the operating mode of the wireless sensor node. A test chip has been produced in an Infineon 130nm CMOS process. The presented wireless sensor node consumes 240 nA in power down mode, most of which is leakage current. In different deep-sleep modes it consumes between 750 nA and 1.5 µA.