Pololu 5V Step-Up/Step-Down Voltage Regulator S10V4F5

This switching regulator uses the SEPIC topology to produce 5 V from input voltages between 2.5 V and 18 V. The wide input range coupled with its ability to convert both higher and lower input voltages makes it useful for applications where the power supply voltage can vary greatly, as with batteries that start above but discharge below 5 V. The compact (0.4″ × 0.575″) module can supply over 400 mA in typical applications.