An efficient and stable power management circuit with high output energy for wireless powering capsule endoscopy

In this paper, a power management circuit (PMC) for wireless powering capsule endoscopy is presented. The PMC includes a RF Limiter, a CMOS rectifier and a low dropout (LDO) regulator. A bandgap circuit used as reference for LDO is optimized carefully and has a more than -50 dB PSRR at 2 MHz, which can effectively suppress the ripple of rectifier output used as input voltage of LDO. A voltage controlled current source (VCCS) is designed in LDO for frequency compensation in such a way that the stability of LDO is not dependent on the output capacitor´s Equivalent Series Resistance (ESR). The PMC is fabricated in a 0.35-μm CMOS process. The measurement results show that it can provide as high as 63.8 mA output current at a 3 V output voltage. The PMC has been used in a wireless powering system designed for capsule endoscope application. Experiment results show that the PMC can deliver as high as 191 mW DC energy to the load mimicking the physical condition in an biomedical environment in a human body.