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TPS23861: TPS23861 interrupt for detect function

Shuang Feng76
Expert 3310 points
Part Number: TPS23861

Hi,

Currently,  the semi-automatic mode we use is configured through the I2C bus, but the TPS23861 will always send out detection, resulting in a 19V voltage pulse on the network port.

(Any other solution to prevent the voltage pulse?)


I would like to ask, in the semi-automatic mode, can the detection negotiation be realized through interruption?

That is, after inserting the PD device, the detection is performed by interrupt mode.
When the PD device is not inserted, or other non-POE network port devices, the detection action will not be performed.

if nor, any other software solution?

  • 0
    TI__Mastermind 41760 points

    Hi Shuang, the open circuit voltage is expected per the standard and allows up to 30W max in the IEEE spec. There is no other way to prevent the voltage pulse as detection is ongoing and PSE must always to check to see if there is a connection to the port. 

    Unfortunately i don't see another way around this other than some non standard solution where a specific PSE and PD end to end solution will be used.

  • 0 in reply to Darwin Fernandez
    TI__Expert 3310 points

    Thanks Darwin,

    The reason why we check due to that this signal will affect the ethernet compliance test.(Any comments or suggestion here?)


    If PSE works in manual mode, will it not actively send this detection?
    If so, what is its application mechanism? Do we need to cooperate with the MCU and ethernet controller to realize the function of POE?

  • 0 in reply to Shuang Feng76
    TI__Mastermind 41760 points

    Hi Shuang,

    When you say ethernet compliance test do you mean SIFOS or EA logo? The spec is 30V max so a 19V OC voltage should still be compliant to the standard.

    In manual mode, you are right, detection would NOT occur unless the MCU forces detection on that port through I2C; however, in this case, there is no way for the MCU to know when to initiate detection after a PD is connected. Also, it can't be done through the LLDP since the PD wouldn't be powered ON by the PSE yet so the MCU on the PD side wouldn't be able to negotiate with the PSE. 

  • 0 in reply to Darwin Fernandez
    TI__Expert 3310 points

    Understood.

    The test is ethernet signal integrity test. for this, do you have any comments?

  • +1 in reply to Shuang Feng76
    TI__Mastermind 41760 points

    Hi Shuang, the PoE power is common mode, I don't expect this to affect the data since what goes through the data transformer to the data side is the differential signal. I don't believe the OC voltage would be affecting this. 

    Can you make sure the data transformer is rated for PoE and the ethernet data rate customer is using? Also, this could be a noise issue as well, does customer have filtering on the ports? Lastly it could be how the center taps are terminated on the data side and PoE side of the data transformer. 

    Do you have schematic we can review? Note this is fundamental architecture for PoE (Power + Data) so I don't expect the PSE OC voltage to be the issue. Thanks!