• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 34 subscribers
  • Views 658 views
  • Users 0 members are here
Support feedback
Options
Options
Related

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.

Long run of TTL serial cleanup

Keith Barkley
Guru 42215 points


I have a system that outputs a 2.5 Mega Bit per second data stream with TTL signal levels. In the lab with short cable runs it works fine. However, in the field we need a 100 ft (or so) run of cable.

With coax, it is pretty clear that the driver has some issues driving the capacitance, and attenuates the level enough so that the high level is solidly in the noise margin.

With twisted pair, we don't have the capacitance issues, but the attenuation still puts us in the noise margin.

Any thoughts as to a good way to clean up our datastream? We cannot put a driver at the sender end of the cable, because reasons. (We have a similar system with 5MB/s with RS422, and it works fine.)

Sorry if this is the wrong area of the forum.

  • 0
    TI__Mastermind 25705 points
    Keith,

    I'm afraid I'm not the right person to answer your question, but would like to chip in. Where does your output come from, a microcontroller? If you don't want to alter the driver side, you may want to add some equalization (high pass filter) at the receiver end to compensate the loss. The function can be implemented by passive components, but the DC loss won't be recovered without amplification.

    Regards,
    Hao
  • 0 in reply to Hao L
    Guru 42215 points
    It is not a microcontroller, but it is a black box to us that puts out a TTL output stream. I am afraid I cannot go into too many details. To solve the attenuation problem, I thought I might just try a 3.3 to 5 V level shifter as a first cut try.
  • 0 in reply to Keith Barkley
    TI__Mastermind 25705 points
    Keith,

    Yes, you could do that. If you had the flexibility of breaking the signal chain, a SN74 signal gate buffer might work as well.

    Regards,
    Hao