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Original question:

THVD8000: Concerning the maximal number of node when using THVD8000.

THVD8000: How the number of nodes affect the communication distance?

Mac Te
Prodigy 50 points
Part Number: THVD8000


Hi, team

Could you please make some comments on how the increase in the number of nodes affects the communication? And then, we can estimate the approximate communication distance based on the number of nodes.

Thanks.

  • 0
    TI__Mastermind 25705 points

    Mac,

    It's a good question. What's the potential data rate, distance and node number in the application? Generally speaking increasing the number of nodes will increase the bus load, while increasing the cable distance has the same effect. However in the operation range of THVD8000, the load can be considered mainly resistive. Only when the cable loss is in the ball park of the total node load, the tradeoff would be meaningful. For example, each THVD8000's input resistance is about 96kOhm, while the cable resistance is about 20Ohm per 100 meter.

    Regards,

    Hao

  • 0 in reply to Hao L
    Prodigy 50 points

    Hi, Hao

    Thanks for your valuable comments. I have already read the datasheet and design guide of THVD8000, as we know, the additional stub can cause the signal loss problem, does it can also affect the communication distance? If so, how it affect the communication distance? And what is the design consideration?

    Thanks.

  • 0 in reply to Mac Te
    TI__Mastermind 25705 points

    Hi,

    Like RS485 applications, the rule of thumb is that the stub length should not be longer than 1/10 of the driver’s output rise time. You can find the detailed discussion in this app note (section 6, page3).

    www.ti.com/.../slla272c.pdf

    Regards,

    Hao