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LVDS multidrop analysis report

Other Parts Discussed in Thread: SN65LVDS34

Currently we are using below IC in multidrop configuration

Driver IC : SN65LVDS389DBT

Receiver IC : SN65LVDS34

I gone thru slaa054a.I could not able to give the definite values at my scenerio mentioned below

Cable length : 13 meters , Signaling rate : 10 Mbps , no of loads : 26 cable used : CAT3

required data

%jitter, max load allowed on case(Iout,Iin,Cout,Cin), max cable length i can acheive,common mode voltage is in acceptable range



  • Senthil,


    LVDS is a very good signaling technology for point to point links however it is not really recommended for multi-drop applications beyond one or two drops at lower frequencies.  Another type of signaling technology to consider is MLVDS ( which is a standard that was developed to address the need for LVDS type of multi-drop signaling. As for LVDS data you requested, we do not have data for that specific case please refer to the attached document which provides information about LVDS performance over different cable types.





  • 3225.LVDSquery.txt
    I gone through the applications notes you mentioned (SLLA053b+SLLA054b).Every data seems to be good for
    the conditions i mentioned
    i) jitter & %jitter
       40ps is acceptable & % jitter mentioned in graph is also good vs signaling rate
    ii) number receivers in multidrop
        %jitter+signaling rate required also managable
    iii) Loading analysis for multidrop - good margin
         SN65LVDS389 - sourcing 4mA
         SN65LVDS34D - 20uA * 24 = 0.48mA
    iv) common mode range - good margin
              SN65LVDS389 - -50mV to +50mV
              SN65LVDS34D - -4V to 5V (even under ground level shift of 1V it seems managable)
    some possible pitfalls
    i) stub length mismatch in receiver -
        will cause more VOD change
    ii) characteristic impedance of cable
    iii) ISI caused due capacitive loading 
          SN65LVDS389 - cout - 9.4pF
         SN65LVDS34D - Cin - 5pF * 24nos= 120pF
    since conditions seems to be good & managable.Kindly mention strong pitfall LVDS with respect to my requirement
     why do we need to go for M-LVDS?



     please find the query attached with mail



  • Hi Senthil,

    M-LVDS will be a better fit for the application since it was specifically designed to handle multi-point and multi-drop topologies.  It has a larger signal swing so that it is less susceptible to loss/noise, and it generally has slower rise and fall times so that longer stubs are permissable.  That said, there is nothing intrinsic to LVDS that will prevent it from working in your application.

    A signaling rate of 10 Mbps over 13 meters of CAT-3 cable should be achievable as long as the application can tolerate the jitter added by the cable.  The leakage current into the LVDS34 is small enough that the loading caused by many parallel receivers should not substantially degrade the signal.  Each drop will add a stub to the line, so you will need to make these as short as possible to minimize their impact on signal integrity.

    Even with these factors accounted for, though, it is hard to say with confidence that a given multi-drop system will work reliably just based on transmitter and receiver characteristics.  Interconnect properties and system topology will have a major impact on the performance.  If possible, it would be a good idea to try to simulate (or prototype) the full communications link.  Such a simulation should take into account the transmitter and receiver properties, as well as the properties of the cabling, connectors, and PCB traces that the signal will go through.

    Please let me know if you have any additional questions.

    Best regards,
    Max Robertson
    Analog Applications Engineer
    Texas Instruments