Multistimulator backchannel communication link implemented for safety information and closed-loop power management

This paper describes the importance of having a backchannel communication link between a microstimulator ASIC and an external control unit for complete safety closure and closed-loop power management. An example of the overall microstimulation system with backchannel communication link for an epiretinal implant is provided. Additionally, the backchannel operation and protocol between the implant chip and the external control unit are given. The flexible multichannel stimulator was implemented and successfully tested in a 0.35 μm AMS HVCMOS technology. A test measurement setup is developed to test the functionality of bidirectional communication between the fabricated stimulator ASIC and the external control unit. Conducted measurement results on erroneous data packet, non-accomplished charge balancing and supply voltage adaptation validate the functionality of the bidirectional communication system.