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  • TI Thinks Resolved

TS3L4892: Not getting a 100b link

Part Number: TS3L4892

I am using ts3l4892 and I am having a problem getting a 100b link. Tester is reporting an unterminated issue, has anyone seen this issue

Thank You,

  • Martin,

    Do you have any more information on what a 100b link is? Do you have a schematic and scope captures of the signals going into and out of the device?

    Thank you,
    Adam
  • In reply to Adam Torma:

    Adam,

    Please see block diagram. 

    Regards,

  • In reply to Martin Corona:

    Martin,

    Thank you for the diagram that shows that one Ethernet PHY is connecting to two different connectors.

    Can you please describe how you are not getting a 100b link? Is this link made successfully without the switch?
    What are the scope shots of the waveforms going in and out of the switch?

    What are the voltages on the power supply and digital logic pins of the TS3L4892?

    Thank you,
    Adam
  • In reply to Adam Torma:

    Adam,

    The link is successful without the switch. The waveforms are sine wave without the switch and with the switch the wave gets clip, only positive wave. Does TI have any circuitry examples? Do I need to add a transformer on the I/O of the switch and what will the voltage for the center tap?

    The voltage for the device is 3.3V. Also, is there a way you can contact me directly?

    Thanks
  • In reply to Martin Corona:

    Martin,

    The TS3L4892 device recommended operating conditions states the voltage range is 0 V to Vcc. The switch will not pass signals < 0V and is why you are seeing clipping when the voltages reach ~ -0.5 V on the signal path. 

    All of our LAN switches have minimum recommended operating voltages of 0V and will have this issue so you will need to provide a common mode voltage. 

    Thank you,

    Adam

  • In reply to Adam Torma:

    Adam,

    The issue is not having transformers on the RJ45 I/O's. Does TI have a block diagram on recommended wiring and what transformers to use?

    Thank You,
  • In reply to Martin Corona:

    Martin,

    As far as the signal switch is concerned the only recommendation we have is the signal voltage needs to be > 0V.  The transformer recommendation would need to come from the transmitter or receive.  I don't have anything from a switch perspective.

    Thank you,

    Adam

  • In reply to Adam Torma:

    Adam,

    Would this be the best configuration for the TS3L4892? Two Ethernet Magnetic Transformers on PCB1, PCB2 is of the shelf and has its own Ethernet transformers. Please let me know.

    Thank You

  • In reply to Martin Corona:

    Adam,
    Another question, is it safe for the switch to be power off and have Ethernet lines being driven from the RJ45, external?
  • In reply to Martin Corona:

    Martin,

    The TS3L4892 does not have a spec that guarantees isolation like the TS3L501E where it states HiZ when Vdd = 0V and I/O voltage = 3.6 V.  We cannot recommended operating the TS3L4892 without power and voltages on the I/O pins.

    Thank you,

    Adam

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