This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

POE Power

Other Parts Discussed in Thread: TPS23861

Hi,

I am new to Power on Ethernet. We want to connect two units using POE. Can i connector Negative 48 Volts (-48V) using POE as in specification of POE standard it is only Positive supply can be transferred using POE

My current consumption is 48 Volts @0.5 A Can we transfer 25W using POE. Please suggest some PD and PS chips. 

Regards

Neelam

  • Hi Neelam,

    You can use TPS23861 as the PSE device and connect your gnd to Vpwr pin and connect -48V to gnd pin. On the PD side, can you provide more information that help us understand your applications better?

    Model or End Customer
    Power Requirement
    (W Delivered or Class Level)
    Class 1 < 3.84W Delivered
    Class 2 = 3.84<x>6.49
    Class 3 = 6.50<x>13.0
    Class 4 = 13.0<x>25.5
    Isolation Required?
    (Y or N)
    Output #1
    (voltage, current)
    Efficiency Goal (%)
    Bridge included
    Efficiency Goal (%)
    Bridge Excluded
    Adapter Voltage?
    IEEE Compliant?

    Thanks,
    Penny
  • Hi
    Thanks for Quick Reply. We required a distance of 100 meter and IEEE 802.3 Compliant .IEEE 802.1Q
    Supported protocol: IEEE 802.1ad (Q-in-Q) and IEEE 802.1d. Regarding Power at PD side we required around 10-15W .We required Isolation also.I have one more query, basic one but i have not clarity that we can transmit Power as well as Ethernet data on the same Ethernet connector(RJ-45) or we have to use two Ethernet connector one for power and other for Ethernet data.

    Regards
    Neelam
  • Hi Neelam,

    WIth PoE enabled, you can definitely transmit date and power through the same Ethernet cable and same RJ45 connector.  You will need a Type 2 PSE and PD. So on the PSE side, TPS23861 is a good fit for your application. On the PD side, I will discuss our PD applications engineer and get back to you later. Thanks. 

    Best regards,

    Penny

  • Hi Neelam,

    What is your output voltage requirement? For 15W this will need to be a Type 2 PD.
  • Hi,

    We are transmitting -48V (15W) through RJ45 (POe) from one board to another board and on Poe Receiving board we are generating different voltages from -48Volts.

    I want Pin configuration on RJ 45 connector

    1-2 ,3-6 Data lines

    4-5 +Supply
    7-8 -Supply

    Please suggest reference circuit We required Two Port POE

    Can i give directly power to Pin no 4-5 of RJ 45 connector without using center Tap pin of Transformer.

    Regards
  • Hi Neelam,

    For type 1 power levels, data is sent through the data pair while power is sent through either data or spare pairs. In this case, pairs45 and 78 are connected directly to the diode bridge and not a data transformer center tap. For type 2, data can be sent through four pairs; since this is a type 2 design, this means you will still need to have a center tap connection on the data transformer.

    When you say dual port poe; are you talking about redundancy or UPOE, or pass through? Do you have block diagram of what you are trying to achieve?

  • Hi,

    If i want to transmit only 15W through each POE then i think it is Type 1 , in that case i do not need on transformer .

    Please find attached Block Diagram

    Regards

    Neelam

  • Hi Neelam,

    If the max power at the PD input is limited to 13W max, then yes it can be type 1; which means you need at least one data transformer on two of the 4 pairs. You still need to power directly the other two pairs as shown in EVM below as an example.