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SN65LVDS104: Parallel configuration of LVDS outputs

Josef Warta
Expert 4550 points

Part Number: SN65LVDS104

Hello Team,

customer has a question about lvds buffering.

"We need to be able to drive four 100Ohm terminated receivers in a multidrop configuration. The termination is internal so not removable thus leads to a 25ohm termination. To be able to drive this I was looking a parallel connection the four outputs of the sn65lvds104. There is an app  from ti describing this slld009 on page 3-7. Do you or any of your colleagues ever looked into this?"

Many Thanks

Josef

  • 0
    TI__Guru* 93570 points

    Hi Josef,

    Given the receiver termination is 100-ohm internal, in order to get the best signal integrity and thus a robust design, would one of these two options be acceptable:

    1). Use DS25CP104 or a similar device to drive each 100-ohm receiver separately.

    2). Use LVDS receiver with external termination.

    The issue with parallel termination of 100-ohm receivers is that it causes return loss degradation/reflections and thus not a stable design. Therfore it would be good to consider two options noted above.

    Regards,, Nasser

    Regards,, Nasser

  • 0 in reply to Nasser Mohammadi
    Prodigy 10 points

    Hi Nassar,

    Thanks for your answers, but we have several reasons to not be able to go over the routes you described :

    1). We need to reduce the number of signals going into a thermal chamber, as we will be testing 20 devices at the same time for several days on end.

    Each of these devices have four identical blocks, each with their own terminated LVD receivers. By linking the block of each device together, we could reduce the number of connections by a factor of 4.

    2). As described above each of the receivers has its own on-device termination.

    As the burn-in test does not require full speed functionality, we can highly reduce the actual speed of the device down to 1 or 10Mhz.

    I suppose TI has no LVDS buffers capable of running at +125C, as the chamber will be heated up to 125C degrees.

    Regards, Yves

  • 0 in reply to Yves Cantraine
    TI__Guru* 93570 points

    Hi Yves,

    I checked and there are multiple LVDS parts for 125degC operating temperature. Please follow link below and check for devices marked as Hi-Rel:

    https://www.ti.com/interface/lvds-m-lvds-pecl/products.html#!p404=Deserializer;SerDes;Serializer&p1389=LVDS

    Regards,, Nasser