TPS2375: Connection with Class 4 HUB

Hello Dice-K,

Before answering your question, I want to clarify something. For class 3, the PSE will source power at 15.4 W, while the PD will receive power at 13 W (for a 100m long cable). I am attaching a picture of a table below for reference, that goes over the power sourced and received for each different class.

Now, to your question about using a class 4 hub for a class 3 PD. Yes, a class 4 hub can be used for a class 3 PD. As long as the class of the PSE (i.e., the hub) is greater than or equal to the class of the PD, the connection should work. To ensure interoperability, some devices (both PSEs and PDs) have the Ethernet Alliance logo – if the logo shows the PSE’s class to be greater than or equal to the PD’s class, the devices should be interoperable. You can learn more about Ethernet Alliance certification here: Introduction to the PoE Certification Program | TI.com Video

When the PSE and PD are connected, the PSE is able to detect the class of power for the PD, and supply the appropriate power for that class. So, even if the PSE can supply a maximum of class 4 level power (30 W), if it detects that the PD takes class 3 level power, the PSE will only supply class 3 level power.

Let me know if I can be of further assistance.

All my best,

Atilla