Theoretical design and implementation of a transcutaneous, multichannel stimulator for neural prosthesis applications

The development of a transcutaneous, implantable, multichannel neural stimulator is described. This was originally dedicated to the stimulation of the auditory nerve in profoundly deaf persons, but is sufficiently flexible in design and operation to be applicable to other areas of neural prosthetics. Control of both the amplitude and time of stimulation for up to fifteen independent channels is possible with a maximum stimulation rate of 1 kHz. Particular attention is given to the design of the transcutaneous link stage which allows both power and data to be transferred to the implanted device using a compact coupling inductor configuration. All circuit timing is derived from a single clock in the external transmitter unit, resulting in stable operation with predictable stimulus output characteristics. The implantable device, realised using thick film hybrid techniques, employs CMOS logic extensively to reduce power consumption. One such device has been implanted in a profoundly deaf volunteer for a period exceeding two years and has continued to operate reliably in conjunction with the complete prosthesis system.