Ultra Low Power Low Voltage ASIC design and implementation For a Novel Bone Conduction Implant (BCI) system

Abstract

Patients who are suffering from conductive hearing loss, single sided deafness and mixed hearing loss, cannot be rehabilitated by conventional air conduction hearing aids due to the functionality losses in the middle ear. Since in these hearing impairments, the cochlea functions perfectly, a bone conduction hearing aid is used for transmitting sound data to the cochlea. Today, percutaneous Bone Anchored Hearing Aid (BAHA) is an important alternative for such individuals. These devices use a percutaneous snap coupling and bone anchored implant that incurs skin infections, requires a life-long commitment of care every day, and there is a risk for implant damage due to trauma. A novel Bone Conduction Implant (BCI) system is designed as an alternative to the percutaneous system, because, it leaves the skin intact. The BCI system comprises digital and analog signal processing units and applying amplitude modulation technique, sound information is transmitted to a permanently implanted transducer via an inductive link system through the intact skin. A coupling insensitive efficient inductive power and data link is designed that can deliver maximum force output to the transducer. The BCI system uses a 1.3 volt standard hearing aid battery that provides power to the entire electronics and the transducer. In the process of designing and implementing the electronics of the BCI, the most critical, challenging and interesting focus is to have a very high efficiency system. Using ultra low power low voltage electronics circuit design and implementation with matured technologies, the power dissipation can be reduced and the whole device will be high efficient and the battery lifetime will be increased. The power amplifier design is another important part of the electronics that must be designed very efficiently. The proposed high efficiency switching power amplifiers are Class-D and Class- E. Studying and designing an application-specific integrated circuit for BCI system that covers all the demands on the power and efficiency is the main goal of this project. This Project has been divided into two different parts. In the first Part, Two different prototypes which use Class-D and Class-E as their Power Amplifier have been designed and implemented. The results proved Class-D amplifier as a better topology for this specific application with current consumption bellow 4mA which is significantly lower than 22mA which is consumed by Class-E for similar RF load. Spartan 3 board has been used as FPGA board to produce Clock signal and Pulse-density-Modulation (PDM) to Pulse-Width- Modulation conversion. In the second part, integrated version of proved circuit was designed in 0.35um Standard CMOS Technology and it was submitted for fabrication in SOIC 20 standard die frame.