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ISO7742: Work with LAN Magnetics for Ethernet 10/100-T?

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Replies: 6

Views: 130

Part Number: ISO7742

Hi,

As the suggested solution as the following link, "", ISO7742DBQR has been designed in, but MSP432E401Y has no response to the Ethernet after plugging in RJ45 cable. Any idea to the issue?

By the way, if the ISO7742 is replaced with another magnetics, the communication among MSP432E401Y, the 2 magnetics and Ethernet is OK.

Thanks.

Ming

  • Hi Ming,

    Thank you for your post! As Koteshwar mentioned in the referenced thread, ISO77xx isolators support standard, logic-level digital CMOS signals on their inputs and outputs. Please let us know the following:

    • Can you share a schematic of the system that is not responding to the Ethernet? If this is proprietary, please feel free to send me a Request to Connect and PM
    • What are the voltage levels of the signals being isolated and what are the power supply levels of ISO7742?
    • Which magnetics allow the system to communicate instead of ISO7742?



    Best,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Manuel,

    1. Please refer to the attached schematic. ISO7742 OUT/A/B connects to magnetics TX pair and INC/D to magnetics RX pair.

    2. ISO7742 VCC1 (V_MCU_3V3) and VCC2 (V_ETH_3V3) are all 3.3V; the 2 supplies are separately isolated from 2 isolated DC/DC converters (5.2KVDC isolation and 2.4pF isolation capacitance).

    3. Pulse HX1198FNL is the magnetics.

    Thanks.

    Ming

  • In reply to Ming Liao:

    Hi Ming,

    Thank you for sharing the schematics and part numbers. It's possible that propagation delay or skew is affecting communication timing. Can you show how signals are connected to the Pulse transformer and share waveforms of the inputs and outputs? I apologize for the delay in my response.


    Respectfully,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Ming,

    Hopefully all is going well on debugging this Ethernet system. Please post an update at your earliest convenience and include the requested waveforms if possible.


    Thank you,
    Manuel Chavez

  • In reply to Manuel Chavez:

    Hi Manuel,

    We built 6pcs PCBA this time, and 5pcs' ISO7742 were reworked to replace with magnetics (the other 1pcs is in SMT factory due to SMT issues); I didn't record waveforms with 7742.

    So far, the 5pcs' Ethernet communication is quite good, but I am not sure right now what the ADC noise level, interfered by AC 60Hz, will be. I will do more test.

    Thanks.

    Ming

  • In reply to Ming Liao:

    Hi Ming,

    Thank you for letting us know. Feel free to contact us again and share test data or any additional questions.


    Have a great weekend!


    Respectfully,
    Manuel Chavez