Research and design of a power management chip for wireless powering capsule endoscopy

Abstract

This paper describes a power management chip for wireless powering capsule endoscopy, including over-voltage protection circuit RF limiter, CMOS rectifier and low dropout regulator (LDO). Bulk commutation technique is applied to suppress the substrate leakage current problem of CMOS rectifier. A bandgap circuit used as reference for LDO is optimized carefully and has a more than −50dB PSR at 2MHz, which can effectively suppress the ripple of rectifier output used as input voltage of LDO. It incorporates a voltage controlled current source (VCCS) compensation network to make sure the loop’s stability is not dependent on the output capacitor’s Equivalent Series Resistance (ESR). The proposed chip has implemented in 0.35μm CMOS technology and the measurement results show that it can provide as high as 63.8mA output current at a 3V output voltage. The PMC has been used in a wireless powering system designed for capsule endoscope application. Experiment results show that the Power Management Chip (PMC) can deliver as high as 191mW DC energy to the load, imitating the physical condition in a biomedical environment in a human body.