A Fully On-chip 0.04mm² Power Management Unit with Low Output Ripple for Ultrasonic Wireless Powered Micro Implantable Medical Devices

This paper presents an area-efficient fully on-chip power management unit (PMU) for ultrasonic (US) powered implantable medical devices (IMDs). The PMU comprises a reconfigurable full-wave rectifier with integrated over-voltage protection (OVP), a power supply rejection (PSR)-enhanced output capacitor-less low dropout voltage regulator (OCL-LDO) with overshoot reduction (OVSR) and a reference generator (REF). The PMU is designed, simulated and laid out in 65 nm CMOS, occupying only $0.04 \mathrm{~mm}^{2}$ active area. The rectifier and OCL-LDO outputs 1.2 V and 1 V, respectively, achieving at least -35.3 dB PSR in the 1 MHz to 10 MHz range to suppress the MHz ripple generated by the rectifier. The PMU achieves OCLLDO output ripple of $0.8 \mathrm{mV} \mathrm{V}_{\mathrm{PP}}$ with a total of 146.5 pF on-chip capacitors at a US carrier frequency of 3.8 MHz. The OVSR improves the recovery time by $6.4 x$ for overshoot. The performance against varying storage capacitor values and US carrier frequencies is also investigated.