An impedance-tracking battery-less arbitrary-waveform neurostimulator with load-adaptive 20V voltage compliance

A 4-channel wireless and battery-less neurostimulator with impedance-tracking power-adaptive voltage compliance is presented. The device houses a 10 mm2 0.35μm HV-CMOS SoC (system on a chip) that performs current-mode arbitrary-waveform stimulation with voltage compliance of up to 20 V. An on-chip mixed-signal controller together with a 3-bit charge-pump maintain supply voltage at its minimum required value, resulting in up to 68.5% saving in power. An 8-bit current DAC is implemented in each channel, which together with adjustable supply voltage yield a current range from 23 μA to 95 mA (100Ω load). The device receives both power and configuration commands wirelessly using a near-field inductive link. The neurostimulator SoC is wire-bonded on a 2×2 cm2 PCB. Additional rigid and flexible PCBs of the same size provide wireless command and power interface. The 3-board 2×2×0.7 cm3 stacked system weighs 6 grams.