A biomedical implantable FES battery-powered micro-stimulator

Abstract

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 ~2.5µA and ~10mA. The stimulator communicates with an external master control unit through a 400MHz wireless link that can support a bit rate of ~2.5MB/s in high speed mode. The total number of stimulators that the communication system can support is 852. IEEE 2008 Custom Intergrated Circuits Conference (CICC)978-1-4244-2018-6/08/$25.00 ©2008 IEEE 13-1-1

High-voltage tolerant stimulation monitoring circuit in conventional CMOS process

“…In these applications, a twochip solution is usually required [2] such that the device may include a high voltage IC and a low voltage IC. Power management, stimulators and monitoring circuits, etc.…”

“…Examples of implantable systems that utilize FES techniques include retinal prostheses [1], arm rehabilitation [2], etc. FES utilizes pulses of electrical current applied in programmable patterns through electrical stimulators to different nerves or reflex centers to restore neurological functions.…”

High-voltage rectifier and voltage doubler in conventional 0.18μm CMOS process

“…These devices are usually powered by inductive coupling from an RF field directly [1] or from an inductively rechargeable battery managed by a battery management unit [3]. In both cases, a coil inside the implantable device is used for receiving power through magnetic coupling from an external magnetic field generator as shown in Fig.…”

“…High induced voltages are required in some applications. One example is the stimulation of the nerve tissue using current pulses [1][2][3]. A high DC supply voltage is required to accommodate different stimulation current amplitudes and tissue impedances.…”

“…Implantable biomedical devices have been developed for different applications such as retinal prosthesis [1], cochlear implant [2], arm rehabilitation [3], etc. These devices are usually powered by inductive coupling from an RF field directly [1] or from an inductively rechargeable battery managed by a battery management unit [3].…”