Electronic design of an eight-channel-stimulator for DSP-driven cochlear prostheses and prospective rehabilitation technique dedicated to deafness disability

In this article, the authors were interested in the design of an electronic circuit for a versatile stimulator dedicated to cochlear prostheses. As a first approach, the design was tentatively conceived with eight stimulating channels because it could be possible to provide additional channels. On the other hand, a prospective technique for patient rehabilitation was also studied in order to test as well as to prove the efficiency and the versatility of the conceived stimulator. This under-the skin micro-stimulator is dedicated to operate with any DSP- driven cochlear-prosthesis systems for executing numerical data with great flexibility. The major parts in this electronic circuit were designed around a logical processing unit for commanding the stimulation stage. It includes a transmission bus, which could differentiate the two main stages: the decoding stage and the stimulation stage. When receiving transmitted data from the external processing part, the logic unit decodes information for commanding the eight stimulation channels. Channels work independently and were merely formed by CMOS-current sources delivering positive and negative stimuli. After processing sounds, appropriate numerical data would be transmitted from the external sound analyser to the internal micro-stimulator through an inductive link (radio-frequency communication link), using an amplitude-modulated carrier. Transmitted data specifies stimulation current level to generate at each specified channel as well as stimulation rhythm. The external processing permits sound energy extraction through different calculation methods. For rehabilitation, a visual aided-tool illustrated on computer screen was designed to identify extracted energies, and hence to control clinically stimulating-pulse levels. With this dedicated process, clinicians could set up therapeutic experiments during rehabilitation, adjust correctly the device operation-parameters and assess electrical charges (current-pulse level) injected in cochlea's biological tissue.