Korner, Dominic (2024)
Fully Integrated Autonomous System-on-Chips with Wireless Energy and Data Transmission.
Technische Universität Darmstadt
doi: 10.26083/tuprints-00028813
Dissertation, Erstveröffentlichung, Verlagsversion

Kurzbeschreibung (Abstract)

Integrated autonomous System-on-Chips (SoCs) with wireless data and energy transmission enable applications in areas that were previously inaccessible due to size constraints or the lack of an energy source. Depending on the transmission medium, the integration of an energy source and communication into the Application-Specific Integrated Circuit ( ASIC ) requires specialized circuitry. Ideally, an autonomous SoC consists of a single ASIC, requiring no external components for operation, making it hereby particularly small. This work focuses on developing, designing, and fabricating autonomous SoCs with the smallest possible size and as few external components as feasible while still being capable of energy and data transmission. Four different ASICs have been designed and fabricated for three different applications. Two fabricated ASICs use ultrasound for energy and bidirectional data transmission, whereas the other two ASICs use visible light for energy and unidirectional data transmission. The ultrasonic-powered systems presented are a Sensor-integrated Machine element (SiMe) and a medical smart implant. The SiMe can generate a power of 60 mW, providing power to sensors even in fully encapsulated metal enclosures deep inside the machine. The medical smart implant focuses on minimal-sized implants for the human body. External piezoelectric crystals, required for ultrasound, consume much space compared to the size of an ASIC. Visible light as an energy and data carrier offers the possibility to integrate all components into a single die by using on-chip solar cells. The presented system for discovering novel drug candidates with an ASIC tag uses visible light as an energy and data carrier, and therefore requires no external components. It operates at a high illumination intensity of 10 Mlx, decreasing the overall system size to a minimum. A single solar cell generates voltages of up to 0.7 V, which is not enough to supply the ASIC. Instead of charge pumps, which consume energy and chip area, a serialization of solar cells in a Silicon-on-Insulator (SOI ) technology provides the required supply voltage. To predict the power generated by the solar cell array on the ASIC, different types of solar cells are fabricated and measured. Light encountering the ASIC generates leakage current on the p-n junctions in sensitive circuitry. A countermeasure was taken to reduce the light-induced leakage currents: Measurements show a reduction of the leakage current by over 90 % when using a metal shield and give instructions on how to design it. This thesis provides design and implementation recommendations for autonomous SoCs with wireless energy and data transmission. It considers light and ultrasound transmission principles for energy and data, as well as provides a system architecture overview for the implementation. The fabricated ASICs prove the effectiveness of the presented recommendations.

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