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Design of Switched Capacitor DC-DC Converters Suitable for Wireless and Bio Sensor Applications

Periodic Reporting for period 1 - SCDCDC (Design of Switched Capacitor DC-DC Converters Suitable for Wireless and Bio Sensor Applications)

Reporting period: 2015-04-01 to 2017-03-31

The main objective of this research is to analyze and design highly efficient, scalable and cost effective integrated circuits for highly integrated wireless systems, energy harvesters and bio-sensors. Specifically, it focuses on analyzing and designing Switched Capacitor DC-DC converters as the main goal. These converters can be implemented fully integrated on silicon, which opens up the possibilities for designing Nano-sensor-nodes that can be used in applications ranging from smart-cities to health monitoring. These sensors are vital for building up the future where resources are optimized by close monitoring of health and needs of masses. This is the gateway to utilizing limited resources most efficiently.

As part of this research, Switched Capacitor DC-DC Converters have been designed and integrated with an ultra-low power transmitter on a single silicon die. These Nano-nodes will be the building blocks of smart sensor networks that can be deployed massively. Future work is to integrate energy harvesters on the same system to create a fully autonomous sensor node to be used in bio-sensors and for smart homes/cities.
As part of this project, we first started by analyzing the design of switched capacitor DC-DC converters. We’ve identified all the loss sources for the switching regulator and came up with derivations to estimate the losses. This is very critical for coming up with a systematic way to design these converters. Two DC-DC converters that work at light-load and heavier load conditions have been designed. Several methods have been utilized to reduce the output ripple of the DC-DC converters. These regulators were designed in 65nm CMOS process, fabricated and measured. As a follow up, a transmitter that consists of a radio transmitter has also been designed in 65nm CMOS and integrated with one of the SC DC-DC converters as the supply. A Class-AB linear regulator was designed and connected in parallel to the DC-DC converter to achieve fast supply modulation when the SC DC-DC converter is slow to respond. The design has been sent to fabrication for verification of the design.

As part of dissemination, 2 journal papers are in review for publication and 2 patents have been filed with the Turkish Patent Office with an option to extend to international IP protection.
As part of this research, a systematic way of designing Switched Capacitor DC-DC converters has been developed. This method was used to design a DC-DC converter that was integrated with a radio. This project is the first step to a fully developed sensor node that harvests its own energy and communicates its sensor data to the neighboring nodes. Using the foundation that was built during this project, another research funding was secured to develop a tribo-electric based energy harvester and a sensor node integrated with the harvester. Such nodes have promise to be used in smart homes/cities and bio-sensor applications. These applications are critical for optimal use of resources or continuous health monitoring for individuals.
A systematic approach to Switched Capacitor DC-DC Converter Design
Chip photo (2mm-by-2mm)