A Neuromodulator Frontend With Reconfigurable Class-B Current and Voltage Controlled Stimulator

This letter presents a neuromodulator frontend that features a reconfigurable current and voltage mode stimulator for a bidirectional, neural interface. By implementing a capacitive high voltage (HV) to low voltage (LV) converter, a single-bit quantizer in the LV domain can be used to compare the difference between the electrode potential and the output of a 7-bit digital-to-analog converter. The digitized signal is integrated to generate a digital feedback signal, which controls a constant current stimulator in order to generate the desired output voltage by adjusting the output current. Thereby the stimulator can deliver up to ±10 mA of output current and ±6 V of stimulation voltage. The stimulation unit is connected over HV protection switches to a neural recorder that features a tunable high-pass cut-off frequency and impulsebased bioimpedance estimation, to form a bidirectional channel. The total consumed silicon area of the frontend is 0.45 mm
²
for recording and stimulation. In standby mode the stimulator can be completely disconnected from its biasing, which leads to a power consumption of less than 1 μW. The class-B operation during voltage stimulation yields an active power consumption, which is dominated by the stimulator output current in both voltage and current mode.