What is the difference between a DCDC converter and a controller?

A DC/DC with a built-in driver FET is called a DC/DC converter.

Conversely, a DC/DC without a built-in driver FET that controls an externally attached FET is called a DC/DC controller.

When a power supply is configured with a DC/DC converter, it has few externally connected components, which reduces the mounted surface area. However, the driver FET built-in the IC, which is a heat source, and the junction temperature to increase due to power dissipation caused by the driver FET. Therefore, great care with the thermal design is required to ensure the junction temperature stays within the operation range.

A DC/DC controller can be used to build optimum circuits fitting a variety of power supply specifications by selecting the driver FET. However, compared to a DC/DC converter, there are more externally attached components, which increases the mounted surface area. In addition, since increasing the number of components also increases the mounted surface area, the expertise for creating a low-noise design and selecting the optimum peripheral components is required.