8-Channel Neural Stimulation ASIC for Epidural Visual Cortex Stimulation

Abstract

This paper presents an 8-channel neural stimulator application-specific integrated circuit (ASIC) for biphasic stimulation of the visual cortex, fabricated in a 0.35[Formula: see text][Formula: see text]m AMS HV process. Each channel is composed of a standard SPI interface, an 8-bit current digital-to-analog converter (DAC) and 120[Formula: see text]V compliant HV output stage. Thus, it is possible to deliver to the tissue arbitrary current waveforms with amplitudes up to [Formula: see text]8.192[Formula: see text]mA with 32[Formula: see text][Formula: see text]A steps. The measured maximum differential nonlinearity (DNL) of the current output does not exceed 1.1 LSB. The on-board current reference provides the output current of 16[Formula: see text][Formula: see text]A with a very low temperature variation. The maximum anodic and cathodic current mismatch after calibration is 25[Formula: see text][Formula: see text]A. The measured interpulse leakage current does not exceed 60[Formula: see text]pA. The ASIC was also tested with the electrode–tissue model, which describes the PEDOT electrodes of 560[Formula: see text][Formula: see text]m diameter in the phosphate buffer saline (PBS). The measurement results approve the possibility to stimulate with arbitrary current amplitudes with frequencies up to 1.5[Formula: see text]kHz.