As mentioned earlier, a buck-boost can improve overall efficiency of a device that uses multiple LDOs. Efficiency of an LDO is directly related to the voltage drop across the LDO. In this example here if a 2.8 V LDO is powered directly from the battery, then the voltage drop is more than a volt when the battery is fully charged. By using the buck-boost to create an intermediate voltage of 3.4 V in this example, the efficiency is increased by 3%. The efficiency improvement will be even greater for lower voltage LDO outputs. The other advantage of adding a buck-boost is of course the device would stop functioning when the battery drops below the required input voltage of the LDO, whereas with a buck-boost, the device would run until the battery is fully discharged.