From Less Batteries to Battery-Less: Enabling A Greener World through Ultra-Wide Power-Performance Adaptation down to pWs

This paper presents a holistic perspective on recent advances in silicon systems for distributed and decentralized systems (e.g., IoT, AIoT), whose count is trending towards the trillions exponentially. At such unprecedented scale, batteries impose severe scaling limitations in terms of form factor, system lifetime and uptime, sensor node cost, system cost (e.g., due to battery/sensor node replacement), and a heavy environmental impact at disposal time. Accordingly, sustained growth in the number of connected devices mandates drastic battery shrinking and ultimately elimination at scale. Beyond the straightforward reduction in the battery utilization via long sleep modes, this paper focuses on the prominent class of miniaturized (mm-scale) battery-indifferent and battery-less systems. Recent and unfolding design techniques are presented to enable purely-harvested operation, while still maintaining sensor nodes alert/available, long lived (e.g., beyond the battery shelf life), millimeter-sized and low cost. This paper and its keynote speech companion at ESSCIRC discusses how to achieve such goals through system peak power adaptation down to the nW level, rather than conventional average. Fundamental principles are demonstrated on silicon across all major sensor node sub-systems (e.g., processing, sensor interfaces, wireless communications). Overall, the design techniques described in this keynote paper aim to enable next-generation ubiquitous, low-cost, miniaturized yet alert sensor nodes for sustainable scale-up. From a technological viewpoint, the resulting advances aim to make scaling to the trillions economically and logistically sustainable. Even more importantly, they are crucially needed to make trillion-scale systems environmentally sustainable, addressing the gargantuan threat posed by trillions of batteries lying ahead, from production to disposal. Beyond the well-established notion of VLSI systems on a chip, sustainability in very large-scale (distributed/decentralized) systems really starts from design.