A 2.45?W patient-specific non-invasive transcranial electrical stimulator with an adaptive skin-electrode impedance monitor

This paper presents a power-efficient non-invasive 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 0.18μm CMOS with an area and power consumption of 0.035mm² and 2.45μW, respectively.