Monopolar Biphasic Stimulator With Discharge Function and Negative Level Shifter for Neuromodulation SoC Integration in Low-Voltage CMOS Process.

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 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.