Buck-Boost is a DC to DC power converter that is used when the input voltage can be higher or lower than the required output voltage. A typical example is when using a single cell Li-Ion battery and the load needs a regulated 3 V, 3.3 V or 3.6 V, for example. Very often a buck-boost converter is also used as a pre-regulator in front of a multi-rail PMIC or Power Management Unit with integrated LDOs. A sudden high current demand from a wireless connectivity or from other fast load transients will wear the battery voltage so low that LDOs supplied directly from the battery may fall out of regulation and force the system into an undesired Reset. A buck-boost converter as pre-regulator protects the battery and ensures a stable regulated system supply.