A Modular 32-site wireless neural stimulation microsystem

This paper presents Interestim-2B, a modular 32-site wireless microstimulating ASIC for neural prosthesis applications, to alleviate disorders such as blindness, deafness, and severe epilepsy. Implanted just below the skull along with a high-density intracortical microelectrode array, the chip enables leadless operation of the resulting microsystem, accepting power and data through an inductive link from the outside world and inserting information into the nervous system in the form of stimulating currents. Each module contains eight current drivers, generating stimulus currents up to ±270 μA with 5-b resolution, ∼100MΩ output impedance, and a dynamic range (headroom voltage) that extends within 150 mV of the 5 V supply rail, and 250 mV of the ground level. As many as 64 modules can be used in parallel, to drive multiprobe arrays of up to 2048 sites, with only a pair of connections to a common inductive-capacitive (LC) tank circuit, while receiving power (8.25 mW/module) and data (2.5 Mb/s) from a 5/10-MHz frequency shift keyed carrier. Every 4.6 mm × 4.6 mm chip fabricated in a 1.5-μm, 2M/2P standard CMOS process through MOSIS, houses two modules and generates up to 65 800 stimulus pulses/s.