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Original question:

DP83869HM: Media converter mode not working

DP83869HM: Media convertor strap, SD polarity and Differential termination

Yansheng Yue
Intellectual 370 points
Part Number: DP83869HM
Other Parts Discussed in Thread: DP83869

Hi, I'm using DP83869 as a 1000M media convertor for . I'm not sure for the following questions. 

1. .Is SD(Pin no. 24) pin a high valid or a low valid input?  The datasheet did not specify the polarity or functionality of the SD pin. The LOS pin is a low value when the signal is good for SFP modules but SD pin is high for a SFF module. And then, should I connect DP83869's SD pin to SFP's LOS directly and with an inverter to SFF's SD, or in an opposite way?

2. Do I need to place 100-Ω termination resistor between the differential pair lines link SGMII and Magnetics copper PHY? It did not say if the termination resister is needed or not. There's no terminal resister in EVM schematic.

3.I only want to have the media convertor with resistor straps and don't want to use any MCU. Can be DP68389 used as a media convertor only with strap pins configuration? It's not very clear in datasheet and the saying is opposite in this form. John confirms that it work well with just strapping pins but Aniruddha said software access is needed to work in media convertor mode.

https://e2e.ti.com/support/interface/f/138/t/769396?tisearch=e2e-sitesearch&keymatch=DP83869

https://e2e.ti.com/support/interface/f/138/p/791559/2927891?tisearch=e2e-sitesearch&keymatch=DP83869%2520media%2520convertor%2520sw#2927891

100-Ω termination

  • 0
    TI__Expert 7040 points

    Hello Yansheng,

    Thank you for your questions. 

    1. The default polarity of the Signal Detect pin is Active Low, which means SD is expected to be '0' by DP83869 when fiber cable is connected or Fiber signal is present.
    2. 100-Ω termination is not needed for either SGMII or Magnetics differential pairs.
    3. The DP83869 can be strapped into Media Converter mode without the need for MDIO communication. One important note is that device must be Fiber setting must determined through straps, the device will not negotiate the Fiber setting to match the Copper mode selected through auto-negotiation

    Regards,

    Justin

  • 0 in reply to Justin Lazaruk
    Intellectual 370 points

    Hi, Justin. Your timely reply resolve my confusion. Thank you!