A high resolution current stimulating probe for use in neural prostheses

The authors describe a high resolution monolithic current stimulating probe which is a multichannel microprobe capable of delivering precisely controlled charge to highly-localized regions of tissue (for example, the auditory nervous system) on a chronic basis. This chip has 8 stimulating sites and provides 7 bits of current level control, that is -126 mu A to +126 mu A with 2 mu A resolution. In order to improve controllability and reduce the cost of the circuitry, the integrated stimulating microprobe is addressable and self-testing. Implemented features include self-test capabilities, a bipolar current forcing scheme for the effective stimulation of the tissue and a user-specified time-out scheme which makes the microstimulator safe. The total number of pads is 14, eight of which are stimulating sites, with the others being used for overall circuit control and power supplies. The chip is designed in an n-epitaxial, p-well, 1.2 mu m, double metal CMOS process with an area of 0.24 mm/sup 2/ excluding bonding pads.<>