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Hi, I designed a POE+ PD device and tested it. it works fine with POE+ PSE, But when I connect it to a POE PSE, then also it works. The PSE should detect this as POE+ and shouldn't source power to PD. Rclass is R29, and resistor value used is 30.9ohms.

Class 4 is also defined in 802.3af, where it will deliver 13W. The difference has to be detected by the application using the nClass_at pin, which will be pulled down only when the PD is connected to an 802.3at PSE. The application can then decide to disconnect everything, or start up in a limited mode that consumes less power. Answered by:
ON Semiconductor
2013-04-17 08:27:45.426