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TLK1501 twisted pair (CAT5/6/7) termination and coupling

Other Parts Discussed in Thread: TLK1501

Hello everyone,

i'm new to gigabit transmission of data and want to use the TLK1501 for the transmission of my data between two devices.

The datasheet makes different suggestions for the Rref and termination resistors and line coupling. Poorly there are no suggestions for (shielded) twisted-pair cables such as CATx network cables. Different data sheets and other sources say CAT5/6/7 cables have an impedance of about 100 Ohm (i found values from 80-120 Ohm).


How do I to choose my termination resistors for the twisted pair case. In the datasheet there are only cases for single shieded lines, or is it the same and i have to use a 50 Ohm pullup resistor on both, the positive and negative wire, to the termination voltage on both sides for the twisted pair cable.

I guess the best case would be to use the ac-coupled interface as found on page 23 in the datasheet. Do there have to be capacitors at both sides of the cable as in the manual of the evaluation module on page 15 (chapter 2.2)?

Kind regards,

Jonas Eberhard

  • Hi Jonas,

    Cat5/6/7 are suitable with BASE-T, unfortunately the TLK1501 is not compliant with BASE-T. Even, now, we do not have TLK devices that support this protocol. On the other hand, if you provide more information about your aplication, we could provide a better feedback.

    Best Regards,
    Luis Omar Morán Serna
    High Speed Interface
    SWAT Team
  • Hi Luis,

    thanks for your quick reply.

    I wanted to use the TLK1501 in a measurement device which is located next to the sensor. The measurement device will consist of some ADC, DAC and an FPGA. The data of the measurement device have to be send to a control unit which will handle the received data (ADC measurements and other data) and send control commands to the measurement device.

    The idea was to use CAT5/6/7 cables for the connection of the two devices, because they are cheap and can handle the data rates.
    I don't want to use any layer of the ethernet standard (protocol or physical interface), i just want to use the CATx cables for the connection. The data will be send and received by two TLK1501.

    But for every cable you need a termination and i wanted to know how the termination has to be done on both sides of the cable, if it is possible to use the CATx cables for such a connection.

    Kind regards,
    Jonas
  • Hello Jonas,

    Please take a look into this application note:

    www.ti.com/.../slva531a.pdf

    I hope this helps.

    Regards,
    Luis