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DP83822I: Transformerless parallel RJ45

Koshi Ninomiya
Expert 5745 points
Part Number: DP83822I


Tool/software:

Dear Team,

My Customer uses the DP83822I with Transformerless Configuration with reference to the application note below.
AN-1519 DP83848 PHYTER Transformerless Ethernet Operation
  4 Transformerless Configuration
      Figure 5. Transformerless Configuration

In order to perform compliance and conformance tests on the communication line (EtherCAT) of the DP83822I that is connected without transformer, they are considering a jig that can monitor the signal by adding parallel RJ45 connectors between capacitors and connectors as shown in the figure below.

In that case, do they need to connect a resistor or capacitor to the NC pin of the additional RJ45 connector, as shown in the "Figure 5. Transformerless Configuration"?
If so, what is the Resistance value or the Capacitance value?

* There are no resistors or capacitors inside the additional RJ45 connector.
   It just passes the signal as it is.

Best Regards,

Koshi Ninomiya

  • +1
    TI__Mastermind 20696 points

    Hi Ninomiya-san, 

    Transformerless configuration was meant to be used for one connection between the PHY and the RJ45 connector. Putting a parallel RJ45 connector in such setup will cause a lot of reflection and possible impedance mismatch. Therefore, this setup will not provide useful signal for compliance tests. We do not recommend such modification. 

    Please let me know if you have any questions. 

    Best,
    J