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DP83848 and RJ45 connector with magnetics

Ross Johnston
Prodigy 10 points
Other Parts Discussed in Thread: DP83848I

Currently working on debugging a design using the DP83848. I have checked all the relevant voltages at the various pins on the device and they are all correct. One thing I have discovered is we have missed off the magnetics - so I am planning on changing the existing RJ45 connector to a connector with integrated magnetics to see if this is the reason I have no activity. Can anyone advise on the most suitable integrated magnetics connector. We are not using PoE.

As our application does not need EMI fingers this cuts down the choice to J0011, J00-0014 AND J0026 options - so what will the different schematics J0011 and J0026 give?

Also - no activity on MDC and MDIO lines - and TX_EN is sitting about 0.4V.

PFBOUT and PFBIB1,2 voltages are correct.

25MHz clock is present

RBIAS is correct at 4K87

MDIO pull-up resistor is correct at 1K5

RESET_N is sitting High

  • 0
    TI__Mastermind 31600 points
    Ross,

    The J011D21 RJ-45 with integrated magnetics is used on some of our evaluation boards. You can see an example of the connections in the DP83848I schematic (www.ti.com/.../snlr022).

    Communications over a cable without magnetics are not likely to work. However, this should not affect register access.

    When you say there is no activity on MDC and MDIO, what do you mean? Are you saying that the PHY does not respond when the MAC attempts to read or write? Or are you saying that there is no signaling at all?

    Patrick