This application note presents and discusses essential thermal considerations regarding the use of PLC line drivers in real-world applications. The NCS5650 (a 2 A PLC Line Driver with Programmable 4th−Order Filtering, Output Current Warning/Limit plus Thermal Diagnostic Flags and Enable/Shutdown Control) comes in a 20−lead QFN (4x4 mm). To enable optimal thermal performance, this package has an exposed heatsink designed to be soldered directly to a metal pad on the application board. It will be shown that board thermal properties dominate the typical system in which the NCS5650 might be used. Therefore, external design choices will, in most cases, make the difference between what would otherwise be reasonable, plausible or impossible applications, at least when viewed from a strictly thermal perspective.