A Dual-Mode Neural Stimulator with Two-Step Charge Balancing Scheme for Fast Residual Voltage Compensation

Abstract

Recent advance in bi-directional neural interface requires miniaturized neural stimulator for implantable applications. Charge balancing circuit is needed to minimize residual electrode voltage after stimulation, hereby avoid tissue damage in long-term usage. This manuscript proposed a dual-mode neural stimulator with charge balancing circuits. With combined continuous current and discrete current pulse compensation techniques, the compensation time is minimized without degradation of accuracy and hardware overhead. The proposed system is implemented in a typical <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.18\upmu \mathrm{m}$</tex> HV process, with integrated high voltage generator. The stimulator was able to deliver 14.4 V pulse and 3 mA current. Compared with conventional charge balancing method, the implemented system achieved 50% compensation time saving with power consumption lower than <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$18 \upmu \mathrm{W}$</tex> and final residual voltage lower than 7 mV.