LTC4278　how to achieve PoE dominace

Have same question )

Hi Leo,

Apologies for the late response. What is the voltage range for the auxiliary supply? Do you want PoE Priority even if the auxiliary is connected first? Assuming the auxiliary supply is between 42V to 57V:

This circuit inserts power before the LTC4278 interface controller. In this configuration, it is necessary for the wall adapter to exceed the LTC4278 UVLO turn-on requirement. This option provides input current limit for the adapter, provides a valid power good signal and simplifies power priority issues. As long as the adapter applies power to the PD before the PSE, it will take priority and the PSE will not power up the PD because the external power source will corrupt the 25k signature. If the PSE is already powering the PD, the adapter power will be in parallel with the PSE. In this case, priority will be given to the higher supply voltage. If the adapter voltage is higher, the PSE should remove the port voltage since no current will be drawn from the PSE. On the other hand, if the adapter voltage is lower, the PSE will continue to supply power to the PD and the adapter will not be used. Proper operation will occur in either scenario.

Hi, 
It is a pleasure to hear back from you. we will try the above circuit.

Additional information added below, 
>What is the voltage range for the auxiliary supply?
- We  want to use 10V to 57V. does this circuit still work as you mentioned above?

> Do you want PoE Priority even if the auxiliary is connected first?

-Yes

Best Regard,