Two-wire industrial process field device power supply circuitry

An industrial process field device includes first and second loop terminals configured to couple to a two-wire process control loop. Device circuitry is powered from the process control loop and monitors a process variable or controls a control device. A current regulator is in series with the loop terminals, and regulates a loop current. A first shunt voltage regulator regulates a voltage across the device circuitry. Supplemental circuitry is connected in series with the first shunt voltage regulator and the second loop terminal, and is powered by power from the two-wire process control loop shunted through the first shunt voltage regulator. A second shunt voltage regulator is connected in series with the first shunt voltage regulator and the second loop terminal, and in parallel with the supplemental circuitry, and regulates a voltage across the supplemental circuitry.