A biomedical implantable FES battery-powered micro-stimulator

The 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 reducing the Q factor of the coil using a time-varying method. 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. The stimulation current is produced from an 8-bit exponential DAC that has a range between ~2.5 muA 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 ~2.5 MB/s in high speed mode. The total number of stimulators that the communication system can support is 852.