A system including a current loop in serial connection with a field device is disclosed. The system includes a power management circuit connected in serial with the current loop and configured to cause a regulated voltage drop across the serial connection at an insertion voltage. The power management circuit is configured to output an electrical power derived from the insertion voltage. The power management circuit includes an energy pump, a control circuit, and a power consuming circuit. The energy pump is a voltage converter that receives a first voltage and converts the first voltage to a second voltage that is either higher or lower than the first voltage. The energy pump includes an input for receiving at least a portion of the insertion voltage and an feedback input for accepting a feedback sense.