Selectable boost converter and charge pump for compliance voltage generation in an implantable stimulator device

Abstract

Improved compliance voltage generation circuitry for a medical device is disclosed. The improved circuitry in one embodiment comprises a boost converter and a charge pump, either of which is capable of generating an appropriate compliance voltage from the voltage of the battery in the device. A telemetry enable signal indicating whether the implant's transmitter, receiver, or both, have been enabled is received. A 'boost' signal from compliance voltage monitor-and-adjust logic circuitry is processed with the telemetry enable signal and its inverse to selectively enable either the charge pump or the boost converter: if the telemetry enable signal is not active, the boost converter is used to generate the compliance voltage; if the telemetry enable signal is active, the charge pump is used. Because the charge pump circuitry does not produce a magnetic field, the charge pump will not interfere with magnetically-coupled telemetry between the implant and an external controller. By contrast, the boost converter is allowed to operate during periods of no telemetry, when magnetic interference is not a concern, while obtaining the advantage of higher power efficiency.