画像 – IC design lab

New switching devices and circuit design
Clock frequency of microprocessor has reached the point where power is limited by thermal budget for package with recent extremely scaled CMOS transistors, even though microprocessor runs at 0.5V that is almost the lower bound of CMOS LSI. There are efforts on power reduction at various levels from device to system. In this research theme, we would like to focus on circuit design based on more-than-Moore switching devices for low power. Tunnel and negative conductance transistors have been vastly researched at a device level. Design consideration has just started. We would like to contribute to integrated circuits engineering in this area.
We have started with research on an analysis on lower bounds of supply voltages for enhanced-swing Colpitts oscillators, which was presented at IEICE general conference in March of 2018.

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Key circuit for energy harvesting
Energy harvesting powers up Internet-of-Things (IoT) devices to operate autonomously by harvesting power from ambient or extends the battery life for the IoT devices. DC power generated by photovoltaic cells and thermoelectric generators is converted by DC-DC converter. AC power generated by vibration and electromagnetic wave is transformed into DC power by AC-DC converter. Another area of interest in power converter is healthcare. Integrated circuits implemented in human body are better to be powered by wireless power transfer than by battery that needs to be exchanged by surgery. Having sufficiently high power conversion efficiency at extremely low power input is a key of the research. We would like to contribute to circuits and systems design in this research area.

We have started with researches on a minimum-operating-voltage design of DC-DC charge pump circuits for energy harvesting and on a clocked AC-DC voltage multiplier for increasing the power conversion efficiency in vibration energy harvesting, both of which were presented at IEICE general conference in March of 2018.　Developed clocked AC/DC charge pump has successfully operated with magnetostrictive energy transducer to generate 4uW at 2V with vibration acceleration of 0.1G.