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DP83869HM: SGMII Interface Signalling

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Replies: 5

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Part Number: DP83869HM

We are planning to integrate the PHY chip DP83869HM with one of our controller with RGMII Interface MAC interface . Our basic requirement is to use the 1 Gbps Fiber optic  . Our PCB will be having a single directional optical communication  either Transmit or Receive .  Please clarify below queries.

  • Shall we use DP83869HM for the above described application?
  • What is the interfacing standard for the SGMII for optical fiber ( CML or LVCMOS or LVDS )?If not CML, how can I convert it in to CML using terminations.
  • In a single PCB either Tx channel or Rx channel will be present for the SGMII fiber optic interface. Does that cause any issue? or I can operate Tx  & Rx only one at a time?

  • Hi Sharvy,

    DP83869 supports RGMII-to-1000Base-X and RGMII-to-SGMII mode. Which mode are you planning to use? If only 1Gbps fiber is needed, then 1000Base-X can be used. Note that 1000Base-X is different from SGMII.

    Can you elaborate more on your 3rd question?

    Regards,

    Hung Nguyen
  • In reply to Hung Nguyen92:

    Hi Nguyen,

    Thanks for the feedback.

    We are planning to interface the optical transmit signal from the PHY Chip ( DP83869 ) to the ONET4291VAR Laser Driver Chip & this chip will drive the optical diode . On the other PCB, we will connect the receive signal of PHY chip with ONET4251PARGTR Limiting Amplifier which receives signal from PIN diode . In Both the PCB's, at a time only Transmit or Receive signal will present.

    • For the above application which interface  ( 1000Base-X  or  SGMII ) would be fine?
    • In a transmit PCB, no signal trace for the Receive. This will cause any issue to PHY Chip?

    BR
    Sharvy

  • In reply to Sharvy Mayan:

    Hi Sharvy,

    DP83869 will not work for your application. By standard, it needs to see incoming signal in order to establish the link with connected link partner. On your transmit PCB, if there is no receive signal, DP83869 would not have the link at all. Without link, it would not be able to send out any data.

    Regards,

    Hung Nguyen
  • In reply to Hung Nguyen92:

    Hi Nguyen,

    • Can we mask or override the Link status using Software?
    • Or using HW ( pull up or pull down ), can we override the link status?
    • Or suggest us if you have any other solution since TI is  dealing with Laser Driver devices.

    BR
    Sharvy

  • In reply to Sharvy Mayan:

    Hi Sharvy,

    There is no reliable way to force the link status.

    Typically, fiber media of the PHY is connected to Fiber Optic Transceiver, or SFP module. Please refer to DP83869 EVM for more details on fiber connectivity: www.ti.com/.../dp83869evm

    Regards,

    Hung Nguyen

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