A microcontroller system includes a main voltage regulator and a low power voltage regulator having a static current consumption less than the static current consumption of the main voltage regulator. A power state controller enables the low power voltage regulator during a power saving mode. On exiting the power saving mode, the power state controller enables the main voltage regulator and disables the low power voltage regulator after determining that the main voltage regulator is ready. The switching circuitry can be asynchronous.