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Original question:

DS26LV31T: Backward compatibility

DS26LV31T: Data Signaling Rate vs Cable Length

Liu Yang
Expert 5915 points

Part Number: DS26LV31T

Hi Team,

Figure 3. shows the "Data Signaling Rate vs Cable Length" on page 4 of following Application Report
https://www.ti.com/lit/an/snla137a/snla137a.pdf

However the Data Signaling Rate is up to 10M but I want to know the "Data Signaling Rate vs Cable Length" up to 20M when using DS26LV31T and DS26LV32AT.

Beat Regards,
Tom Liu

  • 0
    TI__Mastermind 48215 points

    Hi Tom,

    This is a general figure to outline the relation and soft limitations of cable length and data rate. There are many more variables that can extend the range of a given bus, or limit the length earlier. For specific info and some data sets, check out this application report. 

    Let me know if you have any questions on this material. 

    Regards,
    Eric Schott

  • 0
    Prodigy 10 points

    Mr.Eric

    Thank you for your answer.

    However, I have confirmed the answer, but I do not think it is a sufficient answer to the question.

    I will ask you the following questions again, so please answer.

    What is the data transmission distance when the RS422 communication circuit with a link speed of 20 Mbps can be correctly designed using RS422 driver: DS26LV31TM and RS422 receiver: DS26LV32ATM respectively?

    Should I extend the RS-422 BALANCEDV line in Figure 3 of snla137a.pdf and think it will be greater than or equal to the read value (20FEET at 20Mbps)?

    Regards,
    Anegawa
    MITSUBISHI ELECTRIC CORPORATION KAMAKURA WORKS

  • 0 in reply to Kenji Anegawa
    TI__Guru 60392 points

    Kenji,

    Since the RS422 standard only specifies up to 10Mbps, there isn't measurement data available to know if these can work up to 20Mbps.These transceivers are technically specified to work up to 32Mhz, which would equate to 64Mbps, but again, the RS422 standard is only defined up to 10Mbps, so the standard distance vs. data rate plots are only going to show 10Mbps. looking at the plot,

    if you extrapolate the curve beyond 10Mbps to 20Mbps in the log-based plot from the application note, 20Mbps would seem to work up to 30 feet, but again, that's not real data, but just from extrapolating the curve that exists beyond the 10Mbps limit. I've notified our RS422 expert to look at this thread and comment further, thank you for your patience.

    Regards,

    Eric Hackett 

  • 0 in reply to Eric Hackett
    TI__Mastermind 25705 points

    Kenji,

    These two devices work with 20Mbps. Like Eric said, the maximum distance depends on some variables, for example the cable loss. As a rule of thumb, the limit of the cable is 9dB loss at the data rate (10MHz in your case). In this app note, there are some 20Mbps lab data for your reference.