A 2.45μW Patient-Specific Non-Invasive Transcranial Electrical Stimulator with an Adaptive Skin-Electrode Impedance Monitor

Abstract

This paper presents a power-efficient noninvasive transcranial electrical stimulator (tES) with patient-specific impedance adaptation. The proposed tES exploits the varying skin-electrode impedance which results in different RC relaxation time, where the tES adapts the number of pulses to deliver a constant charge. This eliminates the need of an additional current source for impedance monitoring widely used in conventional stimulation techniques, thereby reducing power consumption. To ensure safety for patients, a charge balanced bi-phasic stimulation is implemented with maximum current of < 1mA. The proposed tES is implemented in 0.18 mu m CMOS with an area and power consumption of 0.035mm(2) and 2.45 mu W, respectively.