A holistic power saving concept for ultra-low-power microcontroller (MCU) systems involving application requirements, system architecture, and circuit design techniques is presented. The key of this concept is a digitally enhanced low dropout regulator (LDO) supplying the MCU digital core. By making use of known system power information, the LDO digitally adapts its maximum current drive capability up to 2.56 mA while its quiescent current is as low as 650 nA in light load conditions. In this way, the power management overhead is drastically reduced when operating at low clock speeds enabling system energy savings of 31% at 1 MHz. At the same time, a drastic reduction of the LDO output capacitance enables ultralow-power consumption during sleep and energy efficient wakeup, resulting in system energy savings up to a factor of 4.6.Index Terms-Digitally enhanced analog, energy harvesting, fully integrated voltage regulator, power management unit, ultralow-power microcontroller.

Abstract. This paper presents a first approach towards cooperative energy management in wireless sensor networks using online battery monitoring. Using a standard platform for wireless sensor networks, a simple concept for measuring the battery voltage on the mote with little additional hardware is shown. This is used for modelling of the battery discharge behaviour of Li-Ion batteries and deriving the remaining lifetime under given environmental conditions. As an application example this model can be incorporated into a topology control scheme for optimized network lifetime under variable environmental conditions.

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