Abstract: In an implantable human tissue stimulator with a volatile memory an arrangement is provided to protect against the stimulating circuitry producing pulses as a function of unknown parameters in the memory, as a result of inadequate power to the memory from a rechargeable power source, e.g. a rechargeable battery. The arrangement includes voltage sensors, so that when the voltage from the battery drops below a selected level the stimulating circuitry is disconnected from the battery and only the memory is powered. If the voltage from the battery first drops, so that insufficient power is supplied to the memory and thereafter rises, as a result of recharging, to a level sufficient to power the memory, the memory is first reset with known parameter values. Only thereafter when the voltage level reaches the selected level, is the rest of the circuitry, including the stimulating circuitry, reconnected to the battery.

Abstract: An implantable hermetically sealed living tissue stimulator which includes a coil in which current is induced by an external alternating magnetic field is disclosed. All the stimulator circuit components except for one or more electrode leads are hermetically sealed within a hermetic container formed of a biocompatible metal of a thickness T, and having an electrical resistivity .rho., where T/.rho. .ltoreq. 0.03, T being in mils and .rho. in microhm-cm. The metal thickness T is not more than 5 mils and preferably not more than 3 mils, and the electrical resistivity .rho. is not less than 75 microhm-cm and preferably not less than 100 microhm-cm, in order to reduce the portion of power induced in the stimulator by the magnetic field which is dissipated as heat in the hermetic metal container and to increase the portion of the induced power which penetrates the container and induces the current in the coil.