This paper presents an integrated power management unit (PMU) for battery-operated wireless endoscopic system. This PMU is integrated with a baseband chip in standard 0.18-μm CMOS technology. The integration of PMU promises low cost, eases PCB design, and miniaturizes the system size. Optimized power supply architecture is derived from comparison. Circuits of sub blocks are presented in detail. As a result, only five small off-chip capacitances are required by PMU with overall quiet current consumption less than 100μA. Moreover, digital calibration method is adopted to alleviate the effect of process variation. The achieved performance will be demonstrated with corresponding measurement results.