• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 33 subscribers
  • Views 359 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.

SN65HVD888: Power over RS485 protection

Rajan
Intellectual 270 points
Part Number: SN65HVD888
Other Parts Discussed in Thread: TIDA-00527

Hi,

We have chosen SN65HVD888 chip for 24V power over RS485 communication.

Kindly suggest suitable protection device at output (D+ , D- ) terminal point.

Thank You

Rajan

  • 0
    TI__Guru 62920 points
    Hi Rajan,

    How are you combining the data and power lines? Is it similar to TIDA-00527?

    Also, what are your system's requirements with respect to transient immunity? I ask because the SN65HVD888 device already has a relatively high level of ESD protection integrated. If you wanted immunity beyond what the transceiver supports, it would be good to know the exact target so that I can verify that the TVS is designed to support it.

    Regards,
    Max
  • 0 in reply to Miguel Robertson
    Intellectual 270 points

    Hi Max,

    Thank you for your support.

    Yes, same concept of TIDA-00527 link.

    Normal 5V or 3.3V RS485 communication we can provide TVS diode (SM712 series) and Pulse proof resistors.

    But Power over RS485 power lines VCC have 24V, so we can't use SM712 Tvs diode for this application.

    Please suggest suitable protection, as well as we want to protect from the 230VAC supply. Can we add fuse at D+ or D- data line as series?

    Kindly suggest the same.

    Thank You

    Rajan

  • 0 in reply to Rajan
    TI__Guru 62920 points
    Hi Rajan,

    If you put the TVS diode between the transceiver and the AC-coupling capacitor (rather than between the AC-coupling capacitor and the cable connector) then it would not experience an DC/low-frequency stresses from teh power line. So, the existing SM712 solution could likely be used even with the 24 VDC or 230 VAC power coupling. Let me know if this doesn't make sense.

    Regards,
    Max