Abstract
An output-capacitorless inductive power transfer subsystem with bidirectional communication capability for implanted applications is presented in this thesis. The most popular topic in the field of implanted applications is inductive power transfer. Moreover, bidirectional communication is also essential to deliver closed-loop, smart implantable treatments, especially for biological signal monitoring and deep-brain stimulation. Therefore inductive power transfer subsystems with bidirectional communication capability are necessary in implanted devices. Usually, inductive power and data communication require multiple antennas to realize the closed-loop transfers between an implanted device and an external device. However, surgeons may have difficulties implanting a device with multiple antennas, therefore the minimization of device size is crucial. The number of antennas must be minimized and all external components that can be removed must be removed. We propose to minimize device size and realize fast transient response power regulation simultaneously, by implementing a single coil power and data transmission subsystem and an output-capacitorless power transfer subsystem. This thesis includes two major parts. In the first part, we present a single coil power and data transmission subsystem with a fast transient regulator for bidirectional neuroprosthetic applications. Both amplitude shift keying (ASK) and load shift keying (LSK) have been used in this design. LSK and time division multiple access (TDMA) techniques can enable single coil power and data transmission at the same time. The proposed implantable chip, fabricated using commercial 0.18 μm complementary metal oxide semiconductor (CMOS) technology, yielded a maximal output power of 15 mW. Operated with a 1.2 V power supply, the maximal overshoot and undershoot voltages were both less than 55 mV for a 15 mA full-load current that changed within an current change rising/falling edge time of 100 ns, and the recovery time of LDO regulator was less than 200 ns. The maximal transmission data rate of the proposed LSK transceiver was 2 Mbps at a load current of 3.3 mA. In the second part, we present an output-capacitorless power transfer subsystem with a high power supply rejection ratio (PSRR) regulator. The system does not require an external capacitor because it has an output-capacitorless power transfer subsystem with a high PSRR and a fast transient response regulator. The proposed implantable chip, fabricated using commercial 0.18μm CMOS technology, yielded an output power of 11 mW. The LDO regulator operated at 1.25 V, the maximum overshoot and undershoot voltages were both less than 42 mV for an 11 mA full-load current whose rising and falling time were less than 50 ns, and achieved high PSRR performance of 71.2 dB and 45.6 dB at 10 kHz and 1 MHz, respectively. We will detail circuits design and analysis of an output-capacitorless inductive power transfer subsystem with bidirectional communication capability that incorporates both the single coil power and data transmission subsystem and the output-capacitorless power transfer subsystem in this thesis.