One of the key differentiators for the C8051F9xx family is the integration of both an LDO and a DC/DC boost converter. This provides the capability of operating all the way down to 0.9V and the ability to use one or two batteries. By integrating these components, the F9xx family has a flat current vs. supply voltage curve. The internal voltage regulator (VREG0) is used to regulate the internal core supply to 1.8V from a supply of 1.8V to 3.6V. C8051F9xx devices include an on-chip DC/DC converter to allow operation from a single cell battery with a supply voltage as low as 0.9 V. The DC/DC converter is a switching boost converter with an input voltage range of 0.9 to 1.8V and a programmable output voltage range of 1.8 to 3.3 V with a default output voltage of 1.9 V. This converter can supply the system with up to 65mW of regulated power and can be used for powering other devices in the system. This allows the most flexibility when interfacing to sensors and other analog signals which typically require a higher supply voltage than a single-cell battery can provide. When operating from a single 1.5 V battery, the supply is generated by the DC/DC converter. When any supply voltage is less than the DC/DC converter output voltage, the MCU is put into boost mode. Ont he devices that operate over the full input voltage range (C8051F912/02), the DC/DC converter enters a bypass mode when the voltage is above the output voltage and the diode bypass switch remains on. The output voltage will be equal to the input voltage minus any resistive loss in the switch and all of the converter's analog circuits will remain biased.