This paper presents a CMOS fully-integrated resonant regulating rectifier (IR3) for inductive power telemetry in implantable devices. Employing PWM and PFM feedback, the IR3 achieves 1.87% of ΔVDD/VDD ratio despite a tenfold change in load with a 1nF decoupling capacitor. At 1V regulation of a 100μW load from a 144MHz RF input, the measured voltage conversion efficiency is greater than 92% at under 5.2mVpp ripple and 54% power conversion efficiency. Implemented in 180nm SOI CMOS, the IR3 circuit occupies 0.078mm2 active area.