Fast & Efficient Hysteretic Power Supplies for IoT Microsensors: Analysis & Design with Insight.

Integrating and conforming emerging wireless IoT microsensors into tiny form factors is challenging in many ways. To conserve energy, for example, the system should idle whenever possible, activating functional blocks on demand only. Internal power circuits must therefore supply and cut-off power quickly. In the interim, as these react, capacitors supply and sink the mismatch in power. The low capacitance that small capacitors afford, however, cannot supply or sink much power for long. Hysteretic power supplies are appealing in this respect because they respond quickly. But how fast and reliably they respond depends on design, which hinges on understanding. This paper uses and develops insight to explain and analyze the feedback dynamics and stability requirements of hysteretic current-mode dc-dc switched-inductor converters, which are largely abstract and algebraic in literature today. Moreover, this paper also outlines and analyzes possible practical design issues related to IC implementations. To this end, the paper derives accurate and insightful expressions, uses and applies them to a design, and validates them with SPICE simulations.