A 16-CHANNEL CMOS NEURAL STIMULATING ARRAY

This paper describes a probe designed for the highly selective long-term stimulation of neuronal assemblies in the central nervous system. The micromachined multishank probe incorporates CMOS circuitry to control the output current on 16 iridium oxide (IrO) electrode sites. Serial site addresses and current amplitude data are loaded into the probe at 4 MHz and converted to analog stimulus currents over a range of +/- 254 muA using 16 on-chip 8-b DAC's. The probe circuitry dissipates only 80 muW from +/- 5-V supplies when not delivering stimulus currents and uses five external leads. It permits the IrO sites to be activated by voltammetry from off-chip, provides per-channel pulse time-outs to prevent accidental overstimulation of the tissue, and signals the external world, using a status bit, in the event of certain trouble conditions. The stimulating site impedances and the stimulus currents can be measured from off chip on demand. The circuitry is implemented in a single-metal, single-poly, CMOS process with 3-mum minimum features using 7100 transistors in an area of 11 mm2.