Input Load Adapting Charge Pump Interface

This Chapter presents the implementation of the input-load adaptive charge pump (ILACP) for interfacing \(\mu \)EH generators. As suggested in Sect. 2.4.2, two out-of-phase toggled flying capacitor arrays are used to realize the POPoC-window based continuous fractional voltage tracking (FVT). The design of this prototype chip has two major intentions: testing an on-chip realization of the introduced POPoC-based continuous tracking method as a proof of concept, and, in addition the presented design focuses on architecture development for beneficial and efficient harvesting with typical electromagnetic vibration transducers. An introduction in Sect. 6.1 names fundamental charge pump topologies and design techniques, and validates their applicability. In addition, this introduction gives an overview of related and most promising state of the art solutions. Then, Sect. 6.2 provides a concrete switching scheme for an event-triggered operation. Basic system parameters are defined, and the operation of the charge pump is represented as a state machine. Further on, Sect. 6.3 introduces a generic interface model of the input load adapting charge pump (ILACP). The generic scheme of this ILACP is studied to identify necessary system parameter optimization and to establish a corresponding design flow. It also gives an estimation on possible performance and operation limits. Next, Sect. 6.4 presents the actual implementation of the interface prototype chip. Details about the asynchronous low-power system architecture are given, as well as final dimensions of the main devices, and detailed operation loss estimations complete this section. Thereafter, Sect. 6.5 follows with chip characterization and performance results as well as a final loss analyses. This includes a comparative study based on measurements with real transducers. Beside main findings and insights, a conclusion gives recommendation and deduces next steps on further development necessary for autonomous operation in a real world environment.