A 144-MHz Fully Integrated Resonant Regulating Rectifier with Hybrid Pulse Modulation for mm-Sized Implants

This paper presents a fully integrated resonant regulating rectifier (IR³) with an on-chip coil used to wirelessly power mm-sized implants. By combining rectification and regulation in a single stage, and controlling this stage via a hybrid pulse-width modulation and pulse-frequency modulation (PFM) feedback scheme, the IR³ avoids efficiency-limiting cascaded losses while enabling tight voltage regulation with low dropout and ripple. The IR³ is implemented in 0.078 mm² of active area in 180-nm Silicon oxide insulator (SOI) CMOS, and achieves a 1.87% ΔV_DD/V_DD power supply regulation ratio with a 1-nF decoupling capacitor despite a tenfold load current variation from 8 to 80 μA. A 0.8-V V_DD is maintained at a 8-kΩ load for 144-MHz RF inputs ranging from 0.98 to 1.5 V. At 1-V regulation, the voltage conversion efficiency is greater than 92% with less than 5.2-mV_pp ripple, while the power conversion efficiency is 54%. The measured overall wireless power transfer system efficiency, from the primary coil to V_DD output of the IR³, is 2% at 160-μW load, and reaches 5% at 700 μW.