Minimizing heat can be especially challenging at higher power levels. Linear Technology’s latest generation of PoE controllers use external key components whenever applicable. For PSEs, this means using external low R_DS(ON) MOSFETs and 0.25 Ω sense resistors. For PDs, an external low R_DS(ON) MOSFET also maximizes the amount of power delivered to the load. Not only can the user size components per the application’s heating and efficiency requirements, but they can also focus their thermal dissipation efforts on the sources of heat rather than the entire PSE or PD controller. For multi-port PSEs, external MOSFETs also provide increased reliability since adjacent ports will be unaffected by a port with a damaged or nonfunctional MOSFET.