Fully-integrated inductive power recovery front-end dedicated to implantable devices

Wirelessly powered implantable biomedical devices require a near-field inductive link to provide enough power for high current stimulation of large electrode-nerve impedances. In that situation, the induced voltage may be much larger than the compliance of low-voltage integrated circuits, especially during low-load conditions. In fact, most power recovery approaches limit the voltage with an inefficient off-chip solution using discrete components such as a Zener diode or a shunt regulator, or even on-chip voltage clipping. In this paper, we propose the approach where the induced voltage is not limited at all, using a high-voltage (HV) CMOS technology. In order to fully integrate the inductive power recovery stage, we report the design of a HV custom integrated circuit (IC) that includes a full-wave rectifier and a 10 V regulator using a multiple-outputs voltage reference. The IC has been fabricated in DALSA-C08G technology and the total silicon area including pads is 4 mm². This front-end stage can be driven by an input voltage as high as 50 V. Measurement tests are successful as the HV regulator shows good response to a power-on 50 V step, and good stability in presence of large input variations.