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DP83848 and SFP interface

John Zukas
Prodigy 20 points
Other Parts Discussed in Thread: DP83620

Can the DP83848 interface to an SFP module?  I hope to use the pins associated with the magnetics and put the PECL termination resistors in their place  (kind of like in the DP83849) .  Is there anything else I should concern myself with?

I only need one interface, not 2 like the DP83849.

  • 0
    TI__Mastermind 19780 points
    Hi John,

    The DP83848 does not support 100BASE-FX which is typically used with SFP modules.

    If you need a single port 10/100 PHY with 100BASE-FX support, you could use the DP83620. The DP83620 EVM supports a fiber transceiver and can be used as a reference design.

    Best Regards,
  • 0 in reply to Rob Rodrigues
    Prodigy 20 points

    Thanks for the response.  I am looking through the DP83620 data sheet and noticed a signal, FXSD which is a signal detect to the fiber interface.  

    In the fiber network circuit Figure 9-2, It looks like the FXSD signal is connected as a PECL interface.

    I am planning on using the SFP standard (example Cisco GLC-FE-100EX)  which has a RX_LOS signal.

    RX_LOS: It is an open collector/drain output, which should be pulled up with a 4.7K resistor. Pull up voltage between 2.0V and TX Vcc. TTL logic HIGH when the receiver optical power is below the worst-case receiver sensitivity, logic LOW otherwise for normal operation. Connect to ground if not needed. In the low state, the output will be pulled to < 0.8V.

    Am I confusing two different things? Should these be connected together for operation?

  • 0 in reply to John Zukas
    TI__Mastermind 31600 points
    John,

    You will need to add a component between the transceiver and the DP83620. The LOS signal will need to be inverted and translated from TTL to LVPECL.

    Patrick