IMPLANTABLE TISSUE-STIMULATING PROSTHESIS

An implantable tissue-stimulating prosthesis, such as a cochlear prosthesis, which can be implemented in single-chip form, and permits great flexibility in stimulation strategy and data transmission format. Only sixteen electrodes are required for stimulating fifteen different sites. Each site is stimulated by a biphasic pulse under control of two adjacent electrodes whose polarities are reversed in the middle of the site stimulation cycle. Although the transmission scheme requires a pulse-width modulation format, the precise form of the format can be varied in order to accommodate widely different stimulation strategies. For example, only a single site may be stimulated during each transmission frame or multiple sites may be stimulated during the same frame. Although only one site can be stimulated at any instant of time, the system cycling is for fast that "simulataneous" site stimulations are perceived. The system is designed for minimum power usage, and its operation is fail-safe in that no site may be stimulated for longer than a pre-set time interval.