[LTPoE LT4293] Implementation and configuration when LT4293 works Ultramode

To whom may it concern,

Hi I'm HS.

LTPoE PSE(LTC4279) works in ultamode and it will source power to LTPoE PD(LT4293).

But the datasheet denotes that LT4293 supports up to 90W.

I would appreciate if you elaborate how to configure and design the LT4293 with respect to ultra power mode and DCDC .

Thank you!

Parents
  • 0
    •  Analog Employees 
    on Mar 3, 2021 8:34 PM

    Hi HS,

    UltraPWR is a specific mode of the LTC4279. It should only be used in a closed system. It will aggressively power any valid PDs, and it will set the current limit to 2950mA typical. The LT4293 will identify an LTC4279 in UltraPWR mode as an LTPoE++ PSE, but since this is a closed system the PD could assume it will always receive an UltraPWR allocation.

    An UltraPWR PD should have a very low RDSON Hotswap FET, and we highly recommend using an ideal diode bridge such as the LT4321 in this application, with low RDSON FETs. The PSMN4R8-100BSE or similar low RDSON FET with good SOA can be used for the Hotswap FET, and the PSMN040-100MSE should work for the ideal diode FETs.

    Best Regards,

    Eric

Reply
  • 0
    •  Analog Employees 
    on Mar 3, 2021 8:34 PM

    Hi HS,

    UltraPWR is a specific mode of the LTC4279. It should only be used in a closed system. It will aggressively power any valid PDs, and it will set the current limit to 2950mA typical. The LT4293 will identify an LTC4279 in UltraPWR mode as an LTPoE++ PSE, but since this is a closed system the PD could assume it will always receive an UltraPWR allocation.

    An UltraPWR PD should have a very low RDSON Hotswap FET, and we highly recommend using an ideal diode bridge such as the LT4321 in this application, with low RDSON FETs. The PSMN4R8-100BSE or similar low RDSON FET with good SOA can be used for the Hotswap FET, and the PSMN040-100MSE should work for the ideal diode FETs.

    Best Regards,

    Eric

Children
No Data