DC/DC Converter Application Note
Internal or External Output Driver Transistor
Ricoh has DC/DC converter types available with an internal output transistor and external output transistor. In internal types have an Lx pin and are called DC/DC converters, the external types have an EXT pin and are called DC/DC controllers. (If a specific product has both types available it is listed as a DC/DC converter)
When using an external output transistor, select a power MOSFET. When efficiency at high loads is important select a MOSFET with a low ON resistance, but when efficiency at a low loads is more important select a MOSFET with small gate capacity. Please use a MOSFET that has a maximum drain current higher than the maximum coil current (ILmax).