The Pennsylvania State University The Graduate School HIGH-PERFORMANCE INTEGRATED CIRCUITS FOR ULTRSOUND NEUROMODULATION AND POWER MANAGEMENT OF MEDICAL IMPLANTS A Dissertation in Electrical Engineering by Hesam Sadeghi Gougheri © 2020 Hesam Sadeghi Gougheri Submitted in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy May 2020 The dissertation of Hesam Sadeghi Gougheri was reviewed and approved* by the following: Mehdi Kiani Assistant Professor of Electrical Engineering Dissertation Advisor Chair of Committee Ram Mohan Narayanan Professor of Electrical Engineering Bruce Gluckman Professor of Engineering Science and Mechanics Seyedehaida Ebrahimi Assistant Professor of Electrical Engineering Kultegin Aydin Department Head of Electrical Engineering and Professor ii Abstract In general, this Ph.D. thesis aims at developing innovative technologies for interfacing with the central and peripheral nervous systems. More particularly, this thesis is focused on the design, development, and testing of novel circuits and systems for ultrasound neuromodulation and power management of those implantable medical devices (IMDs) which are powered by wireless power transmission (WPT) via inductive coupling. First, a new class of integrated power management (IPM) application-specific integrated circuits (ASICs) is proposed for efficient, robust, and long-range inductive power transmission. Unlike conventional IPM ASICs with voltage-mode (VM) operation, a current-mode (CM) IPM structure is proposed in which the receiver coil is employed as a current source. Several features have been added to the CM IPM structure to noticeably improve performance of the wireless IMDs in terms of voltage regulation, maximum provided output power, and lifetime. In the second part, the concept of microscopic ultrasound stimulation (μUS) is proposed in which either an electronically phased array of ultrasound transducers or several millimeter-sized focused transducers can directly be placed on the brain surface with partially removed skull (or over thinned skull) to deliver a focused ultrasound pressure to the neural target. A comprehensive study of ultrasound transducer characterization is presented to find optimal design of the transducers for μUS application. An ultrasound neuromodulation ASIC is designed and fabricated to drive the transducer with sufficient power, and finally a couple of preliminary animal experiments with commercial off-the-shelf (COTS) components are carried out. In chapter 1 of this dissertation, the proposed technologies for ultrasound neuromodulation and power management of IMDs are briefly introduced, and an overview over current technologies for neuromodulation and WPT to IMDs is presented. Also, the main contributions of this thesis are briefly described. In chapter 2, a current-based resonant power delivery (CRPD) technique is presented for extended-range WPT. In chapter 3, a self-regulated reconfigurable voltage/current-mode integrated power management (VCIPM) is presented for robust inductive WPT. In chapter 4, optimal wireless receiver structure for omnidirectional WPT is discussed. A self-regulated seamless-voltage/current-mode IPM with energy recycling capability is presented in chapter 5. To improve maximum output power provided to IMDs, a dual-output reconfigurable shared-inductor boost-converter/current-mode IPM is presented in chapter 6. In chapter 7, a comprehensive study of ultrasound transducer characteristics in μUS is presented. An ASIC for ultrasound neuromodulation is proposed in chapter 8. Finally, in chapter 9 preliminary animal experiments and future works are discussed. This research has resulted so far in 6 journal papers, 8 peer- reviewed conference papers, 1 pending US patent, and 1 book chapter. iii Table of Contents List of Figures ............................................................................................................................................. ix List of Tables ............................................................................................................................................ xxi List of Abbreviations .............................................................................................................................. xxii Acknowledgements ................................................................................................................................ xxiv Chapter 1 Introduction ............................................................................................................................. 1 1.1 Ultrasound neuromodulation ............................................................................................ 1 1.1.1 Current state-of-the-art neuromodulation technologies ................................................ 1 1.1.2 Transcranial focused ultrasound stimulation ................................................................ 2 1.1.3 Proposed microscopic ultrasound stimulation .............................................................. 3 1.2 Wireless power transmission to implantable medical devices (IMDs) ............................ 5 1.2.1 Proposed IPM ASICs for wireless power transmission to IMDs ................................. 5 1.3 Contributions .................................................................................................................... 6 1.3.1 Integrated power management ASICs .......................................................................... 6 1.3.1.1 Current-based resonant power delivery ASIC .......................................................... 6 1.3.1.2 Self-regulated reconfigurable voltage/current-mode IPM ASIC .............................. 7 1.3.1.3 An inductive voltage/current-mode IPM ASIC with seamless mode transition and energy recycling .......................................................................................................................... 7 1.3.1.4 A dual-output reconfigurable shared-Inductor boost-converter/current-Mode inductive power management ASIC ........................................................................................... 8 iv 1.3.2 Microscopic ultrasound stimulation ............................................................................. 8 1.3.2.1 A comprehensive study of ultrasound transducer characteristics in microscopic ultrasound neuromodulation ....................................................................................................... 8 1.3.2.2 An ASIC for microscopic ultrasound neuromodulation ........................................... 9 Chapter 2 Current-Based Resonant Power Delivery with Multi-Cycle Switching for Extended- Range Inductive Power Transmission..................................................................................................... 10 2.1 Proposed current-based resonant power delivery (CRPD) technique ............................ 12 2.1.1 CRPD Concept ........................................................................................................... 12 2.1.2 The circuit theory behind CRPD ................................................................................ 14 2.1.3 Theory vs. Simulation................................................................................................. 17 2.2 Measurement results ....................................................................................................... 19 2.3 Conclusion ...................................................................................................................... 24 Chapter 3 Self-Regulated Reconfigurable Voltage/Current-Mode Inductive Power Management 25 3.1 VCIPM modeling and operation .................................................................................... 26 3.2 VCIPM chip architecture ............................................................................................... 32 3.3 Measurement results ....................................................................................................... 36 3.4 Conclusion ...................................................................................................................... 44 Chapter 4 Optimal Wireless Receiver Structure for Omnidirectional Inductive Power Transmission to Biomedical Implants ..................................................................................................... 46 v 4.1 Omnidirectional inductive power transmission to mm-sized implants using three Rx coils… ....................................................................................................................................... 47 4.2 Different Rx structures using three Rx coils .................................................................. 49 4.3 Conclusion ...................................................................................................................... 51 Chapter 5 A Self-Regulated Seamless-Voltage/Current-Mode Inductive Power Management with Extended Input Voltage Range and Energy Recycling ......................................................................... 52 5.1 Proposed power management concept and structure ..................................................... 52 5.2 Measurement results ....................................................................................................... 56 5.3 Conclusion ...................................................................................................................... 59 Chapter 6 A Dual-Output Reconfigurable Shared-Inductor Boost-Converter/Current-Mode