An implanted system for multi-site nerve cuff-based ENG recording using velocity selectivity

This paper describes the design of an implantable system for velocity-selective electroneurogram (ENG) recording. The system, which relies on the availability of multielectrode nerve cuffs (MECs) consists of two CMOS ASICs. One ASIC called the electrode unit (EU) is a mixed analogue/digital signal acquisition system which is mounted directly on an MEC in order to optimize the interface between the two. It is linked to the other ASIC by means of a 5-core cable through which it receives power and commands in addition to transmitting data. The second ASIC, called the monitoring unit (MU) manages the interface between the EUs (each MU can control up to three EUs) and an RF transcutaneous link to the external signal processor. The ASICs are fabricated in 0.8 mu m CMOS technology. The EUs measure 3 mm x 4 mm each and consume 105 mW (35 mW each), while the MU measures 1.5 mm x 2 mm and consumes 4 mW. The power consumption on the communication channels (including cable losses) between the MU and EUs is 129 mW. A digital communication strategy between the two parts of the implanted system and the external controller is described.