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THVD1406: Baud rate 9600bps

ttd
Mastermind 9415 points

Part Number: THVD1406
Other Parts Discussed in Thread: THVD1400

Dear Technical Support Team,

I have questions about THVD1406DR.

Q1

Is the following understanding of the THVD1406DR’s automatic direction control correct?

  • When the “D” pin input to the IC changes from “L” to “H,” the driver output turns OFF after the “t_device_auto-dir” time.
  • The “t_device_auto-dir” time ranges from a minimum of 4 us to a maximum of 14 us (typ. 8 us)

Q2

Is communication possible at 9600 bps?

The time per bit would be 104 µs.

In this case, I am concerned that the driver output will turn OFF during the “H” period of a bit being output, which might prevent proper communication.

Considering the transceiver IC’s specification that the output turns OFF in a minimum of 4 µs,

is this device intended for use at 250 kbps or higher?

Q3

Is there a way to turn off “auto direction”?

If so, will it operate at 9,600 bps?

 

Q4

Are there any products that are pin-compatible with the THVD1406DR and operate at 9,600 bps?THVD1400DR,THVD1410DR？

www.ti.com/.../

The datasheet did not specify a minimum requirement.

image.png

Best Regards,

ttd

  • +1
    TI__Intellectual 2180 points

    Hi ttd,

    ttd said:

    Is the following understanding of the THVD1406DR’s automatic direction control correct?

    • When the “D” pin input to the IC changes from “L” to “H,” the driver output turns OFF after the “t_device_auto-dir” time.
    • The “t_device_auto-dir” time ranges from a minimum of 4 us to a maximum of 14 us (typ. 8 us)

    Correct (assuming SHDN! is high/open), feel free to read more about this in section 8.4 of the datasheet.

    ttd said:
    Are there any products that are pin-compatible with the THVD1406DR and operate at 9,600 bps?THVD1400DR,THVD1410DR

    This is likely not possible as the bit length is MUCH longer than the typical auto-direction timing (8 us). Though you are more than welcome to try it out in your own system. Section 2.2 of this app note talks a bit about using failsafe resistors to slightly extend the range of possible data rates.

    ttd said:
    Are there any products that are pin-compatible with the THVD1406DR and operate at 9,600 bps?THVD1400DR,THVD1410DR？

    You can refer to the app note above and also this other E2E post. There is a good chance you may be able to get as low as 125 kbps with failsafe biasing. Generally, though, you are correct that 250 kbps and higher would be better.

    ttd said:
    Is there a way to turn off “auto direction”?

    No

    ...

    The THVD1400 or 1410 are mostly pin compatible and you should be able to run it at your desired speed. Since they don't have the auto-direction feature you'd need at least 1 extra channel to your MCU to control a combined RE! and DE pin.

    -Ethan White