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SN65HVD230 Problems

Sean Overberger
Prodigy 10 points
Other Parts Discussed in Thread: SN65HVD230

Please help!

I have a problem with rounded edges on the canH and canL coming from the sn65hvd230. I have attached screen shots. I have termination both on the node as well as the end of the cable each of 120 ohms. has anyone seen this or have any suggestions on how to change the edges and make them sharp? has anyone seen this problem before? I have a tight deadline on this, and this is the last piece to the puzzle so anyones input would be greatly appreciated.

 

Thanks in adavance,

 

Sean

 

  • 0
    TI__Mastermind 28265 points

    Sean,

    do you have a schematic you can send us to very the function in the lab?

    thanks, Thomas

  • 0
    TI__Intellectual 970 points

    Hello Sean,

    Your observing a property of CAN devices.  CAN drivers actively drive dominant bits ("logical 0's) to VOD >= 1.2V, however recessive bits ("logical 1's) set the driver into High-Z by protocol (for bus arbitration).  That is the outputs are pulled back together via a very small internal leakage path.  This internal leakage current, in conjunction with the system RC, will determine the single-ended recessive wave-shape.  The good news is that the differential signal (CANH-CANL) will look more like what you're expecting [and consequently is what the CAN receiver will see].

    Regards,

    Bryce