A Biomedical Implantable FES Battery-Powered Micro-Stimulator

The integrated circuit (IC) designs of an implantable functional electrical stimulation (FES) battery-powered micro-stimulator are presented in this paper. The battery is recharged by receiving power magnetically through a coil under supervision of a power management unit. To limit the heat generation on the stimulator when a large magnetic field is present, an on-chip rectifier is capable of limiting the induced voltage and reducing heat generation by providing a low impedance path. The same coil is also used for generating and receiving magnetic fields such that the distances among 16 different stimulator pairs can be estimated simultaneously. To facilitate different clinical applications, a bio-potential sensor is also included. The micro-stimulator can output mono-phasic stimulation current from an 8-bit exponential digital to analog converter (DAC) that has a range between ~2.5 ??A and ~10 mA. The stimulator communicates with an external master control unit through a 400-MHz wireless link that can support a bit rate of 2.486 MB/s in high speed mode. The total number of stimulators that the communication system can support is 852.