Design of a current-steering implantable stimulator with electric field shifting for deep brain stimulation

Active control over the electric field distribution during deep brain stimulation (DBS) can provide better focus of the stimulation field on target regions, beneficial to improve neural selectivity and reduce side effects arising from simulation of non-target regions. A current-steering tripolar electrode configuration can be adopted to achieve better selectivity in DBS. The tripole consists of a central cathode and two lateral anodes. The currents through the anodes are set by two complementary current sources. By varying the ratio between the amplitude of the anodic currents, the current can be steered toward one anode, while keeping the cathodic current constant. In this paper we present the design of a current-steering tripolar current source in 0.35 μm CMOS technology. The current source is capable of delivering cathodic currents up to 1.5 mA and generate exponential and quasi-trapezoidal pulses needed for anodal blocking. The average mismatch between sourcing and sinking currents is in the order of 0.4% and the output compliance ranges between 6.1V and 11.15V for a 12V supply, when the maximum and minimum anodic currents are supplied, respectively.