Diode bridge design for LTPoE++ PD

Hi,
My customer is designing the LTPoE++ PD using the LT4275A for 90W power application.
The customer is designing with reference to the DC2093A-A demo board.
   1. Do they have to use two diode bridges for each pairs ? why ?
   2. Can they use only one diode bridge by combining data pairs and spare pairs? why?
Thnaks.
JH
Parents
  • 0
    •  Analog Employees 
    on Feb 25, 2019 6:15 PM

    Hey JH,

    IEEE 802.3af/at/bt requires the PD to be capable of receiving power from either pairset, the data or spare pairs, and to polarity correct the input. Polarity correcting requires a diode bridge, and receiving power from both pairsets requires two diode bridges. I would recommend your customer to use the LT4321 ideal diode bridge controller, this part was specifically designed for high power PoE.

    • Yes, they should use two diode bridges or an ideal diode controller. This maintains compatibility with IEEE standards, which allows PSEs to power different pairs with different polarities.
    • This would no longer be IEEE compliant, and would limit interoperability with different PSEs. If this is a closed system and your customer knows exactly which pairs will be powered and what polarity, then interoperability and compliance may not be required.

     

    Best Regards,

    Eric

Reply
  • 0
    •  Analog Employees 
    on Feb 25, 2019 6:15 PM

    Hey JH,

    IEEE 802.3af/at/bt requires the PD to be capable of receiving power from either pairset, the data or spare pairs, and to polarity correct the input. Polarity correcting requires a diode bridge, and receiving power from both pairsets requires two diode bridges. I would recommend your customer to use the LT4321 ideal diode bridge controller, this part was specifically designed for high power PoE.

    • Yes, they should use two diode bridges or an ideal diode controller. This maintains compatibility with IEEE standards, which allows PSEs to power different pairs with different polarities.
    • This would no longer be IEEE compliant, and would limit interoperability with different PSEs. If this is a closed system and your customer knows exactly which pairs will be powered and what polarity, then interoperability and compliance may not be required.

     

    Best Regards,

    Eric

Children
No Data