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Original question:

TLK2711-SP: compatibility with TLK2501 ?

TLK2711-SP: AC coupled interface with other devices

Danilo Stefano Dias Alves
Prodigy 10 points
Part Number: TLK2711-SP
Other Parts Discussed in Thread: TLK2501,

Tool/software:

Hello,

We're planning to use a TLK2501 (CML) to interface with an existing product that uses the TLK2711 part (VML). This existing product currently interfaces with another TLK2711 part through an AC coupled interface.

I understand that this AC coupling is used to enable interconnection from a device with a wide variety of receivers. Only to confirm in this specific case, could you please review the understanding stated below and in the picture to ensure it's correct for this interface:

  • For the transmission circuit for the TLK2711, only the series AC coupling capacitors are required.

  • For the transmission circuit for the TLK2501, termination resistors are required in both lines, along with the series AC coupling capacitors.

  • For the receiver circuit for the TLK2711, only the series AC coupling capacitor is required, as the devices already have integrated termination resistors.

  • For the transmission circuit for the TLK2501, both series AC coupling capacitors and termination resistors in both lines are required.

Thanks in advance for your support.

Best regards.

  • +1
    TI__Genius 17325 points

    Hi Danilo,

    Your understanding is mostly correct. I made a few modifications to your diagram.

    TLK2501 Receiver: The CML receiver termination network requires VTERM = 2V, not 2.5V.

    AC Coupling: TLK2711-SP datasheet recommends using 1 nF -- 10 nF for AC coupling. TLK2501 datasheet recommends using 10 nF for AC coupling. Since this application places 2 capacitors in series, the total capacitance is 1/2 each capacitor value. Therefore I recommend using 22 nF capacitors (standard value) so the total capacitance on each net is close to 10 nF.

    Best,

    Lucas