We are designing a PoE design to power our camera. The block diagram below is the basic design we are planning to implement.
I want to get some advice to make sure we will not be damaging our camera or harming the user before going any further. From my understanding the PoE Magnetics will isolate the earth ground thus after the PoE Ethernet Magnetics, there is a different ground lets call it ground A. The PoE PD interface IC has a DCDC converter that will output 12V, I read that it is a good idea to add an isolation transformer after the output of the DCDC converter to keep anything downstream of the transformer protected.
If I add the isolation transformer then the ground to my camera is different from ground A, lets call it ground B.
I have two questions:
The MDI Pairs will be going directly to the ethernet PHY on the camera. Does it not send ground A to ground B directly? Ground A and ground B will be the same because of the MDI pairs going to the PHY on the camera. If this is the case, would it not defeat the purpose of the isolation transformer?
Our camera is mounted against a metal chassis that the user will touch when connecting power. What effects will this have on the user and the camera since the user would have a different ground than ground B. We want to make sure the camera does not get damaged.
Please feel free to provide any suggestions or improves to the design to better protect the camera. Thank you in advance for any help or suggestions. I really appreciate it!