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Problem occured when TLK105L is connect with Repeater Hub.

g.f.
Guru 15520 points
Other Parts Discussed in Thread: TLK105L

Hi,

I have question about Ehter PHY TLK105L.

My customer are using TLK105L on their customer board. When they connected the board(without Power ON) to the Ether Repeater Hub via Lan Cable(straight cable), the LED(LINK LED) on the Hub linked. Because the board power state is off, we don't know why the LED on theHub linked.

The customer also checked with AM437x EVM(IDK) which have TLK105L on the board. The result was same as the customer board. The LED on the repeater hub linked. But this issue doesn't occure when they tried with the other customer board which have LAN8710 on the board(not TLK105L). They captured TD/RD signal of TLK105L side from RJ45 connector. It looks that TLK105L is outputting pulse from TD port. Please take a look at attached file.

This issue occued when they used following Ether Repeater Hub.

Manufacturer: Corega

Model: HUB5PL

www.onino.co.uk/.../corega_hub_5pl_cd_hub5pl.html

By the way, this issue doesn't occure when they used Switching Hub.

Maybe this is TLK105L side issue or maybe not. Is there a possibility with the problem in TLK105L?

best regards,

g.f.

TLK105L TD_RD signal .pdf

  • 0
    TI__Mastermind 31600 points
    It appears that some signal is being reflected onto the cable. Per the IEEE 802.3 specification, this signaling should be rejected by the receiver (the hub in this case) if the amplitude of the signaling is less than 585mV.

    It may be possible to reduce this signaling below the receive threshold of the hub using a series common mode choke on the device side of the transformer. Many times, transformers include series common mode chokes inside the package. Therefore, it may be possible to reduce the signaling below the receive threshold of the hub by changing the transformer component.

    Patrick
  • 0 in reply to Patrick OFarrell
    Guru 15520 points
    Hi Patrick,

    Thank you for the reply.

    So, can I understand that TLK105L isn't outputting a signal?

    By the way, the customer are using RJ45(TM11RD-5TANA-FN-88-LP) and
    it have common mode choke inside the package.
    Should they try other RJ45 or is there any other solution to reduce this signal?

    best regards,
    g.f.
  • 0 in reply to g.f.
    TI__Mastermind 31600 points
    The TLK105L is not transmitting. Regarding the magnetics, the customer could try another part number. Many times, vendors have footprint compatible versions with different configurations of the magnetics inside the case.

    On another note related to the magnetics current being used, we recommend using symmetric magnetics. That is to say, the common mode chokes should both be on the same side of the transformer cores. For the magnetics currently being used in this application, one common mode choke is on the device side of the transformer and the other common mode choke is on the cable side of the transformer.

    Patrick
  • 0 in reply to Patrick OFarrell
    Guru 15520 points
    Hi Patrick,

    Thank you for the reply.
    I understood.

    By the way, is there recommended magnetics which have common mode chokes
    on both side of transformer cores for TLK105L?

    best regards,
    g.f.