Dual-Stacked Current Recycling Linear Regulators With 48% Power Saving for Biomedical Implants

This paper demonstrates a dual-stacked current recycling linear power supply circuit for biomedical implants. Implantable neuro-stimulators often require high-voltage power supplies for electrode actuation purposes while most of the electronic implant sub-systems require low-voltage supplies which are often generated by linear regulators with poor power efficiency. The proposed current recycling technique and circuit allow linear regulators to be stacked, dividing the high-voltage power supply into two low-voltage supply domains; current can be recycled between these two power supplies and power efficiency in the low-voltage powered circuits can be close to doubled. The power supply circuit is implemented in 0.35 μm high-voltage CMOS process and occupies an active silicon area of 0.45 mm
²
, achieving maximum power saving factor and current efficiency of 48.6% and 97.2%, respectively, with quiescent current of only 45 μA.