The internal DC-to-DC converter is controlled by the voltage on the Vcc pin. A voltage of 4.5V to 5.5V activates an oscillator circuit used to magnetically transfer power to the secondary side of the transformer. The induced voltage is then linearly regulated and used to power the electrically isolated data circuitry. Some users may wish to use the device with the DC-DC converter disabled. In this case, an operating voltage of 3V to 3.7V should be applied to the Vcc pin to disable the converter and an isolated power supply should be connected to the VISO pin to power the secondary side.