In this chapter we present two different solutions of integrated photovoltaic energy harvesting, realized for discrete and continuous time working systems. The first solution is realized in a standard 0.35 μm CMOS technology: it collects light energy from the environment, by means of 2 mm~2 on-chip integrated micro-solar cells, and accumulates it in an external capacitor. While the capacitor is charging, the load is disconnected. When the energy in the external capacitor is enough to operate the load for a predefined time-slot, the load is connected to the capacitor by a power management circuit. The second solution is realized in 0.35 μm SOI CMOS technology. The energy harvesting elements consist of 35 trench-insulated p-n junctions, while the sensing system consists of a bandgap reference circuit, including an integrated high precision temperature sensor, and a high voltage low drop-out voltage regulator.
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