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ISO3088: ISO3088 & DS3695

pramod naik
Prodigy 10 points
Part Number: ISO3088

Dear all

I am trying to make a RS485 communication between ISO3088 and DS3695 . In the sense one of our controller board has ISO3088 and other has DS3695. For your reference both the end is terminated with 120 ohms resistor,

But when we connect pin number 12 of ISO3088  to pin no. 6 of DS3695 &   pin number 13 of ISO3088  to pin no. 7 of Ds3695  there is  no communication.But when we interchanged the pin numbers communication is established between two controllers.

Please clarify. 

  • 0
    TI__Mastermind 29595 points

    Hello Pramod,

    Thank you for reaching out.

    The initial configuration sounds correct.

    • Could you provide a schematic of the application?
    • Is the output RO inverted in the hardware or software? When you interchange the pin numbers, this will invert the data packet. 

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 10 points

    Hi Andrew ,

    I am attaching both the scematics for your refernce. For your kind information when we established communication between same board at both the ends we are not getting any isuues .I.e between ISO3088 to iso3088 and DS3695 to ds3695. 

  • 0 in reply to pramod naik
    TI__Mastermind 29595 points

    Hi Pramod,

    Based on the schematic alone, the only comment I have is to have one GND on the secondary side (tie ISO_GND and DIU_ISO_GND). If these grounds are kept separate and there is a shift in grounds it can cause the TVS diode to conduct prematurely.

    The ground pins of the ISO3088 should also be connected to the same planes/node.  

    Best,
    Andrew

  • 0 in reply to Andrew J
    Prodigy 10 points

    Hi Andrew

    Thanks for the suggestion . I have tied the both grounds but problem still there. One more thing I have connected shield of the cable to these ISO_GND to overcome EMI isuues.

  • 0 in reply to pramod naik
    TI__Mastermind 29595 points

    Hello Pramod, 

    Based on the schematic, I don't expect there to be any issues with the ISO3088. For further analysis, please provide a scope capture of the R, D, A and B pins. Preferably one with communication working and one without. 

    Best,
    Andrew