The configured scale for the regulator voltage(VOS bit field). The returned value can be one of the following: - @arg PWR_REGULATOR_VOLTAGE_SCALE1: Regulator voltage output Scale 1 mode - @arg PWR_REGULATOR_VOLTAGE_SCALE2: Regulator voltage output Scale 2 mode - @arg PWR_REGULATOR_VOLTAGE_SCALE3: Regulator voltage output Scale 3 mode