A distributed transducer system for functional electrical stimulation

Implanted transducers for functional electrical stimulation (FES) powered by inductive links are subject to conflicting requirements arising from low link eflciency, a low power budget and the need for protection of the weak signals against strong RF electromagneticJields. We propose a solution to these problems by partitioning the RF transceiver and sensor/actuator functions onto separate integrated circuits. By amplifying measured neural signals directly at the measurements site and converting them into the digital domain before passing them to the transceiver; the signal integrity is less likely to be affected by the inductive link. Neural stimulators are afected to a lesser degree, but still benejit from the partitioning. As a test case, we have designed a transceiver and a sensor chip which implement this partitioning policy. The transceiver is designed to operate in the 6.78MHz ISM band and consumes approximately 360pW Both chips were implemented in a standard 0.5 ,um CMOS technology, and use a 3 V supply voltage.