Design and Analysis of a High Bandwidth Rectifying Regulator With PWM and PFM Modes

We propose a novel rectifying regulator to wirelessly power a neural stimulator in 65 nm CMOS process. The regulating rectifier operates at 13.56 MHz and has two operating modes. In the high power pulse width modulation (PWM) mode, it regulates the output voltage by controlling the conduction time during every cycle of the incoming HF signal. The PWM mode is designed with a high bandwidth feedback loop to satisfy the transient time requirements of the stimulator. The rectifier also incorporates a pulse frequency modulation (PFM) mode to power the stimulator in sleep mode wherein it controls the frequency at which the rectifier conducts to efficiently deliver low output power. We present the theory and develop an analytical model for the rectifying regulator and validate the model for both PWM and PFM operating modes.