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Original question:

THVD8000: THVD8000

THVD8000: TCVD8000-Topology

Michele Ammendola
Prodigy 30 points

Part Number: THVD8000
Other Parts Discussed in Thread: THVD8010, , THS6222

Tool/software:

Hi Parker,

thank you very much for the detailed answer.

Let's keep the system with a main Central Unit and the 30 thermostats as an example.

Can I connect them in any way I want? Or is there a limitation?

Like the three topologies shown in the attached pifture? Are they OK?

Thanks,

Michele Ammendola

  • 0
    Guru 321460 points

    A high-speed bus should be linear, with termination at the two ends.

    Other topologies are possible, but the missing termination reduces signal quality and allows only lower speeds. (For those, use the THVD8010.)

  • +1
    TI__Guru 54042 points

    Hi Michele,

    Standard implementations of the THVD8000 are going to prefer either daisy chain or junction box topologies - please see below for a couple diagrams:

    Other network topologies typically have stub lengths that are too long to not terminate - but RS-485 based devices (like THVD8000) only support two terminations on each end of the bus (start and end node) of 120 ohms - which is why topology is generally limited to the above two. 

    However - a lot of THVD8000 based systems those topologies aren't always possible - to use them that would generally require all nodes to be terminated - but the THVD8000 cannot drive more than two 120 ohm resistors - so the answer is we need more drive current. Using a device like the THS6222 (differential line driver) on every THVD8000 pathway that needs to transmit messages will be able to meet that goal. Essentially in these systems the THVD8000 is only a demodulator/modulator as the data is driven on the bus by the line driver - we do have an application note on that which I have included below:

    THVD8000 in Star Networks

    Please let me know if you have any other questions and I will see what I can do!

    Best,

    Parker Dodson