The RF circuit design for magnetic power transmission dedicated to cochlear prosthesis

Wireless remote powering of implants is usually achieved with a transcutanous link. Such a link consists of two resonant circuits, an external transmitter and an implanted receiver. The inductances are realised by two coils, facing each other. The radiated power received by a small coil in implantable telemetry systems must not exceed a few ten of milliwatts to avoid the damage of the biological tissue. This requires a very efficient RF to DC converter, as well as the lowest possible power consumption for the biomedical sensor and data acquisition/transmission system. This paper describes the design of a CMOS 0.35 mu integrated circuit that includes a numeric control unit, a DE amplifier class, a voltage doubler/rectifier, as well as a low power voltage regulator. Numeric control unit included a Manchester encoder operating with a VCO (voltage controller output).