A 13.56 MHz 40 mW CMOS High-Ef ficiency Inductive Link Power Supply Utilizing On-Chip Delay-Compensated V oltage Doubler Rectifier and Multiple LDOs for Implantable

Abstract

In this paper, a 13.56 MHz CMOS near-field inductive link power supply (ILPS) that can deliver 20 mA output current for implantable medical devices (IMDs ) is proposed and fabricated. In the proposed ILPS, the pair of inductive link coils is constructed in the sp iral shape with a ferrite core to save space and increase ef- ficiency. Experimental results have shown that the near- field coils can transmit power at the resonant frequency of 13.56 MHz with the transmission ef ficiency up to 76.3%. The CMOS power regu- lator is composed of active voltage doubler recti fier (VD) and low- dropout regulators (LDOs). In th e active VD with the comparator, the input offset voltage is adjustab le for delay compensation and a start-up control circuit is added to achieve robust start-up mecha- nism. On-chip delay compensation control with SR-latches is pro- posed to prevent from error glitch switching on offset voltage con- trol and achieve accurate delay compensation so that the reverse current conduction can be avoided and the ef ficiency can be in- creased. Three fully-integrated LDOs with recti fier output voltage of 2 V to 1.8 V are realized for analog (ALDO), digital (DLDO), and reference-voltage (RLDO) circuits. Thus the performance of individual LDO can be optimized. The measured output ripple voltage of the active VD is 10.4 mV. The power conversion ef fi- ciency (PCE) is 85% under 20 mA output current. The measured dropout voltage is 384 mV. As compared with other designs, the proposed