Monopolar Biphasic Stimulator With Discharge Function and Negative Level Shifter for Neuromodulation SoC Integration in Low-Voltage CMOS Process
Chia‐Chi Hsieh, Ming‐Dou Ker
Abstract
A 16-channel monopolar biphasic stimulator chip with discharge function for biomedical applications is proposed and designed. To provide monopolar biphasic stimulus currents, the positive (6V) and the negative (-6V) voltage sources are supported to generate the desired current pulses of ±3 mA. The monopolar biphasic stimulator chip was fabricated in a 0.18-μm 1.8-V/3.3-V CMOS process with the common grounded p-type substrate. The overstress and reliability issues on the low-voltage transistors in the stimulator circuits were fully overcome by circuit design. The silicon area of each single channel only occupies 0.08 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and the output level of stimulus current is up to ±3 mA. By applying the discharge function, safety concern of unbalanced charge in neuro-stimulation can be dealt properly. The residual average dc current is less than 3.42 nA after discharge is activated. Moreover, this chip has also been verified with both in-vitro imitation measurement and in-vivo animal test.