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TPS2378EVM-105: TPS2378

adiga
Prodigy 10 points
Part Number: TPS2378EVM-105
Other Parts Discussed in Thread: TPS2378

I have interfaced TPS2378 with one of the POE port (Ethernet switch with POE port) . MCT1 (+) and MCT2 (-) are connected to bridge. Not interfaced any adapter ckt.

I am not able to get continuous power across VDD and RTN. Power comes and goes off continuously.

As in reference board, all four MCT's are required to connect to bridge ?

pin 6, 7 and 8 are not used,  Is it required for any pullup/pulldown ?

Remaining interface is asper TPS2378EVM. Across o/p used 47uf/100v Electrolytic capacitor.

please suggest what may be the cause ?

  • 0
    TI__Intellectual 1695 points
    Hi Sudarshana,

    First of all, Pin 8 should be connected to RTN and Pin 6 and 7 can be floated.
    Second, It is OK to only connect MCT1 and 2 to the bridge if your PSE is using ALTA pair. If PSE is using ALTB pair, you have to connect all the MCT pins.

    From your description, it is OK to just connect MCT1 and 2 because you have seen the power on.
    The reason why the power comes and goes off is that you did't provide MPS to PSE so once the PSE powers on the PD, it didn't see maintain power signal then it will shutdown and then detect, class, power on again.
    It is suggested to add a dummy load paralleled with 47uF bulk cap which can provide over 10mA current.

    Best Regards
    Jack Chen