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DP83869HM: Magnetics and cetertap connections

RAJENDER DUSA
Prodigy 10 points
Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869, TPD4E05U06

Hi,

We are using DP83869HM in our deisgn.

Can you please let us know that  0826-1X1T-GH-F magjack can be used with this phy?

And also there is a confusion regarding center tap connection of the magjack. What should be the center tap connection? Should it be connected to VDDIO or ground?

Thanks,

Rajender.

  • 0
    TI__Guru**** 192309 points

    Hello Rajender,

    Thank you for the query.

    Please refer to magnetics requirements and magnetics connection section of the datasheet and also the DP83869 EVM.

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Prodigy 10 points

    Hi thanks for your reply. I have gone through the datasheet but for some PHYs center tap is connected to VDDIO also so to clarify this I raised a query.  And regarding requirements, in magjack datasheet they haven't mentioned crosstalk but they mentioned common mode to common mode rejection. So just want to check regarding the usage of the mentioned part number. Can you please check the magjack and let me know whether it can be used or nor? Thanks.

  • 0 in reply to RAJENDER DUSA
    Prodigy 10 points

    And in the dp83869 evm the connections are made to pulse transformer. Do magjack's center tap also should be connected to ground along with bypass capacitor? www.belfuse.com/.../part-details please go through this magjack once and let us know it can be used or not, as we would like finalize it for production. Your reply will be really helpful for us. Thanks

  • 0 in reply to RAJENDER DUSA
    TI__Guru**** 192309 points

    Hello Rajender,

    Thank you for the additional inputs and query.

    Yes, the center tap needs to be grounded for the magjack as recommended in the EVM or data sheet.

    Do you have a schematics to review the connections.

    If you are planning production, i assume you have done the functional and other performance tests on the magjack? Is the magjack meeting your product requirements.

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Prodigy 10 points

    Hi sreenivasa,

    Thanks for confirming the magjack connections.

    By production I mean prototype production sorry for the miscommunication.

    We don't have any testing results to confirm the magjack usability so that's why reached out to you. What is your thought on the selected magjack based on PHY requirements?

    I have few other questions also. Please answer those also.

    1) As DP83869 has internal MDI and MAC termination resistors we are not connecting any external termination resistors. Is that fine? Or do we need to connect external termination resistors?

    2) MDI pins of DP83869 are voltage line driven right?

    3) what is the voltage swing of MDI pins in 10/100/1000 Mbps mode? Does the differential voltage go to negative level also? ( In the datasheet it's mentioned tha voltage level of MDI pin is -0.3v to 6.5v). We need this to confirm our TVS diode selection for PHY as we need to pass compliance test of surge as per iec 61000-4-5 level 4 i.e. +-8KV. ( Can SP3051-04HTG be used?)

    Thanks,

    Rajender.

  • 0 in reply to RAJENDER DUSA
    TI__Guru**** 192309 points

    Hello Rajender, 

    Terminations are available for RX_D[3:0], RX_ER, RX_DV, RX_CLK  and should be fine to use the same. I assume the required  terminations on the host side are provided.

    The  -0.3v to 6.5v is the absolute max voltage not the operating range. The operating levels are based on standards (It can support IEEE802.3 10BASE-Te, 100BASE-TX, and 1000BASE-T Copper Ethernet protocols, along with 100BASE-FX and 1000BASE-X Fiber Ethernet protocols). This voltage level should not be a concern in selection of protection devices.

    Are you looking for 8KV surge ? Can you please check the specifications mentioned.  The surge current should be rated based on the surge impedance assuming 42 ohms as a typical impedance.

    Regarding the Magjack, you should be able to use the solution provided you are ok to validate and do the required optimization ( if required).

    If you are looking for a tested solution, please follow the device recommendations provided in the EVM.

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Prodigy 10 points

    Hi thanks for the reply. As the absolute maximum rating of the MDI pin is 6.5V, then while selecting protection devices the clamping voltage of the protection device must be considered. So what should be the maximum allowable clamping voltage for specific Ipp.

    In the EVM pulse transformer is used not magjack so we don't have any reference to magjack selection. What kind of optimizations may required during testing? 

    Thanks

  • 0 in reply to RAJENDER DUSA
    TI__Guru**** 192309 points

    Hello 

    Thank you for the inputs. Please select tpd4e05u06 or similar devices.

    As i said above, during validation, based on the functional and other tests including EMI/EMC if required you might have to do some optimization (mostly layout). This is a good practice when changing key components.

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Prodigy 10 points

    Hi sreenivasa,

    Thanks for the inputs.

    One last question regarding MDI termination resistors, it's just mentioned as a point in the first page that MDI termination resistors are integrated in to ethernet phy. 

    Do we need any external 100ohm termination resistors for MDI differential pair?

    Regards,

    Rajender.

  • 0 in reply to RAJENDER DUSA
    TI__Guru**** 192309 points

    Hello Rajender,

    Thank you for the inputs. If you are not constrained by space, it would help if you provision for external terminations and start with o0R mounted.

    MDI differential pair, you will have to take care of control impedance routing.

    We should be able to support you with review as required.

    Regards,

    Sreenivasa 

  • 0 in reply to Kallikuppa Sreenivasa
    Prodigy 10 points

    Hi sreenivasa,

    Thank you for the answers.

    For MDI termination the connection should be 49.9ohm resistor to the ground right as the pins are voltage driven line drivers?

    And one more doubt regarding JTAG. For DP83869HM, no specific JTAG Reset pin is available, can we use RESET_N for JTAG also? We have already connected RESET_N to MAC Gpio.

    Thanks

  • 0 in reply to RAJENDER DUSA
    TI__Guru**** 192309 points

    Hello  

    Thank you for the query.

    I would recommend that you provide a provision to disconnect the reset_n  from the MAC GPIO as required  for initial testing as the behavior depends on the host with MAC

    DP83869 specifies as below : Integrated MDI Termination Resistor. the datasheet does not recommend an external termination.

    Regards,

    Sreenivasa