DP83822HF: DP83822HF without isolation transformer connection issue

Part Number: DP83822HF

Hi Support team,

We have a problem to connect the TD_M, TD_P and RD_MP, RD_P terminals and connect to another RD-, RD+ and TD-, TD+ and thought the DC doubling capacitor for transformerless connection. However, it did not work. Please advise what is the problem of the connection.

TD_M  >> RD-

TD_P >> RD+


RD_P >> TD+

3 Replies

  • Hi Kelvin,

    Which of the devices in your schematic are the DP83822HF? The pin numbers for TD and RD are not correct on either side.

    Please also specify what you mean by did not work. Is there no link? Is link not stable? Is data not transferred reliably?

    Finally, for transformerless operation, the front end of the DP83822 should be put into class A amplifier operation. This setting is in register 0x0404, table 70 of the datasheet.

    Note that register 0x0404 is in the extended register space which is accessed via the extended register method as described in section of the datasheet.

    Best Regards,

    Rob Rodrigues

    EFL (Ethernet & FPD Link) Applications Engineer

  • In reply to Rob Rodrigues:

    Hi Rob,
    1.The attahed schematics is not relative 83822. we just mentioned the connection how to connect berween two PHY IC s for our circuit . Do you have a reference circuit and connect two PHY IC IN/OUT ports without use the isloation transformers and RJ45 connectors.

    Do you need to provide the DC- Bias to another PHY IC port (RD-.RD+,TD-.TD + ) with 51 ohm pull up resistors,

    TD_M >> RD-

    TD_P >> RD+

    RD_MP >>TD-

    RD_P >> TD +

    2.No link mean the link led ( LED0,pin 17 ) is no any indication and only have some waveform on those pins.(
    TD_P, TD_M, RD_P,RD_M )

    3.The MDC and MIDO are no connection and not able to change the internal register. Pleae advise.

    Best Regards
    Kelvin Lo
  • In reply to Kelvin Lo:

    [View:Hi Rob:      this is Huaiming that came from same team with Kelvin, attached are the details for the connection between DP83822HF and WiFi Module and the unstable waveform both for TD_P/N and RD_P/N signal after power on for your better understanding and checking. thanks.:1230:0]