5V Auxiliary Power Supply Teams LDO and Charge Pump

To provide low-current 5V power in a 3.3V system, use a regulated-LDO chip to reduce 3.3V to 2.5V, then employ a charge-pump chip to double the 2.5V to 5V. To counteract the effect of high source impedance in the charge pump, provide feedback from the output to the LDO.