Study of Fully Integrated Energy Harvesting Power Management Units PMUs for Internet of Things IoT applications

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Design of a Fully Integrated Power Management Unit with a Multi-ratio and Multi-cell Switched-Capacitor DC-DC Converter

Publication . Madeira, Ricardo Falé de Carvalho; Paulino, Nuno; Oliveira, João

The Internet of Things (IoT) smart nodes deployment have been increasing rapidly in recent years, in a wide range of applications. These nodes are typically inserted in Wireless Sensor Networks (WSN), ranging from a few numbers to hundreds of nodes. Solutions using System-on-Chip (SoC) have been proposed for the nodes implementation, due to their low production costs. One import block of these SoCs is the Power Management Unit (PMU), used to power the node. Since the available energy is limited, efficient energy conversion is crucial to reduce the maintenance costs. To this end, Switched-Capacitor (SC) DC-DC converters have been proposed, since they can be fully integrated in CMOS technology, and offer a good trade-off between efficiency and power density. This thesis describes the design and test of two PMU Integrated Circuit (IC) prototypes in 130 nm bulk CMOS technology. The first is a 1 mW PMU composed by a multi-ratio SC converter with three voltage Conversion Ratios (CRs) 1/2, 2/3, and 1/1, covering an input voltage range of 1.1 V to 2.3 V, and generating a 0.9 V output voltage. It also includes a set of auxiliary circuits including a phase generator, a CR controller, the switch drivers, and a start-up circuit. The total circuit active area is 0.138 mm2 and a peak efficiency of 80.4% was measured. The second prototype is a fully integrated 16 mW PMU which includes a multi-ratio 1+3 binary-weighted SC converter, including the same CRs, and the same input voltage range and output voltage value of the previous prototype. The PMU is now completely fully integrated by removing the external decoupling capacitor and by integrating the voltage reference generator, both external in the first prototype. The decoupling capacitor was removed by employing a time interleaving scheme and by using capacitance modulation, according with the output power level and input voltage value, sensed through the clock frequency. The PMU includes the first prototype re-designed auxiliary circuits plus a cell controller and voltage reference generator. The total circuit active area is 5.12 mm2 and a peak efficiency of 74.3% was measured.

2012-12-02Tese de doutoramento

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Fundação para a Ciência e a Tecnologia

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OE

Número da atribuição

SFRH/BD/115543/2016