The robustness of a PoE design is especially important when dealing with many cables, high voltages, high currents or high temperatures. Linear Technology has designed a low cost circuit protection scheme that is scalable to match the IEC61000 cable discharge voltage requirements. Shown on this slide is a single transient voltage suppressor, or TVS, and 8 clamping diodes protecting the 4-port LTC4266 PSE controller. Linear Technology’s PSE controllers also have an 80V absolute maximum rating on all analog pins to provide native protection against transients, as well as a 4-point PD detection scheme that uses two forced voltages and two forced currents to ensure excellent immunity from false PD detection. For PD controllers like the LT4275, a single TVS and a 100V absolute maximum port pin provide more than enough protection against cable discharge events. The LT4275 operates over a wide -40°C to 125°C temperature range and is also equipped with overtemperature protection for the device during momentary overload conditions. With this much protection, it is easy to see that these devices were designed with rugged environments in mind.