• State Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 1 answer
  • Subscribers 32 subscribers
  • Views 305 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

SN65MLVD206: How many receiver device can SN65MLVD206 drive?

Sunny Qin
Expert 4890 points
Part Number: SN65MLVD206
Other Parts Discussed in Thread: SN65MLVD207

Hi Team,

My customer use SN65MLVD206/207 between CPU board and daughter board for communication:

they have 1 CPU board(1 sn65mlvd206), 1 mother board(2 100 ohm terminal resistor on the right and left), 7 daughter boards(each one has 1 SN65MLVD207, no terminal resistor), but customer found if they only inject 5 daughter board, the communication is good, but if they inject 7 daughter boards, then mistake code happened some time, so here we need your comments:

 How many receiver device can SN65MLVD206 drive?

How to fix this issue?

Thanks very much.

Regards, Sunny

  • 0
    TI__Mastermind 35130 points

    Hi Sunny,

    It can theoretically drive up to 32 receivers. However, this number is highly dependent on a number of design variables (data rate, distance, stub length,  PCB traces, etc.) all of which can affect signal integrity and drastically lower the amount of receivers supported. 

    Also note that the architecture of their system is not correct. Since there is 1 driver (CPU board with MLVD206) and multiple receivers (daughter boards with MLVD207) then this is a multidrop connection. There should only be 1 termination resistor at the last receiver farthest away from the driver. The driver should also not be in the middle, but should be at one of the end points of the mother board, like below:

    Also, the termination resistor should match the characteristic impedance of the transmission line (they can measure it with a TDR), and will not necessarily be 100-ohms. 

    Regards,

    I.K.

  • 0 in reply to Ikechukwu Anyiam
    TI__Expert 4890 points

    Hi I.K,

    Thanks for your comments, now customer`s system can not change, so may still need you help on below question:

    1, can we change the left and right resistor to 150ohm?

    2, if system not changed, so you suggest customer still use 2 terminal resistor, or remove the left one or right one?

    Thanks.

    Regards, Sunny

  • +1 in reply to Sunny Qin
    TI__Mastermind 35130 points

    Hi Sunny,

    Customer can experiment with different resistor values and placement to see if it improves the issue, sure. The limitation is due to their system architecture though, so there's not much else that can be done without changing the system (aside from trying slower data rates).

    Regards,

    I.K. 

  • 0 in reply to Ikechukwu Anyiam
    TI__Expert 4890 points

    Hi I.K,

    Thanks very much, one more question, do you think customer need to keep both left and right resistor(they will change the value), or just keep one resistor on left or right?

    Thanks.

    Regards, Sunny

  • +1 in reply to Sunny Qin
    TI__Mastermind 35130 points

    Hi Sunny,

    It'd be better to keep both resistors for their architecture. But again, their architecture is still not correct (reference first reply). 

    Regards,

    I.K. 

  • 0 in reply to Ikechukwu Anyiam
    TI__Expert 4890 points

    Hi I.K,

    Got it, thanks so much.

    Regards, Sunny