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A 12V-500µA neuron stimulator with current calibration mechanism in 0.18µm standard CMOS process

Functional electrical stimulation (FES) has high potential to partially repair or at least improve the physiological function of patients suffering from neuron damage. Stimulators for this purpose usually face two design challenges of the required high supply voltage for compliance voltage, and the residual charge which eventually causes electrode corrosion. Using a voltage limit technique, a stimulator which can withstand 12V supply voltage is proposed in this study. A current calibration mechanism is added to limit the amount of residual charge within a safe range. The simulator has been fabricated using TSMC 0.18µm technology. Experimental results show that stimulation current up to 500µA could be delivered, and the current mismatch is less than 0.2µA. The stimulator successfully generated a 80 Hz biphasic stimulation waveform, whose amplitude and pulse width were tunable. The circuit has been tested for more than 2 hours without any failure due to transistor breakdowns.