Design of Safe Two-Wire Interface-Driven Chip-Scale Neurostimulator for Visual Prosthesis

Visual prostheses with a high number of electrodes are now of great research interest driven by the successful recent clinical trials. High channel devices are confronted with numerous challenges many of which can be addressed by adopting a multi-implant architecture. However now the difficulties lie in ensuring safety of the inter-implant interface by addressing the associated risks, often neglected in the past. This paper presents a multi-implant architecture-based 98-channel neurostimulator with an inter-implant interface consisting only of two wires, carrying both power and semi-duplex data. The interface is ac-coupled both to prevent high levels of dc current in the presence of insulation failures and to maintain a charge-balanced interface. The interface is also monitored within the stimulator itself for added means of safety. The stimulator is fabricated using a 0.35-mu m HVCMOS technology and occupies 4.9 x 4.9 mm(2) without any external discrete components, making it suitable for a chip-scale packaging.