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ISO7741: The output of ISO7741 is incorrect

Xu Derek
Prodigy 20 points
Part Number: ISO7741

Tool/software:

The part number I'm using is ISO7741DWR， I found the outputs does not match the input, not know the possible reason.

Please see my captured data:

  • 0
    TI__Genius 17355 points

    Hi Xu,

    Thanks for reaching out.

    Can you please provide the below details?

    1. Can you please describe more your application? are you using your own Board? or are you simply testing the isolator on the EVM?
    2. Can you please provide a schematic/PCB layout of the board/isolator you are using?
    3. Can you please show the similar waveform, but include VCC1 and VCC2 of the isolator?

    Regards,
    Aaditya V.

  • 0
    Prodigy 20 points

    Hi Aaditya V,

       Thank you for your quick reply! I am using my own board, not EVM.

       I captured more waveforms for your reference. 

       To avoid SPI bus cause the pin6 works abnormal, I lifted pin6 off the PCB and keep it floating, then, I re-do the test, there are still data lost.

  • 0 in reply to Xu Derek
    TI__Mastermind 28745 points

    Hello Xu,

    Thank you for the additional waveforms. I see that both supplies are stable. This rules out the device missing the transmission due to a transient.

    I realized that the time scale shows that missed transmissions appear less than 2us than from where the ENx was first enabled. ENx has to be active for more than 8.5us (max) before a non-default state transition can be recognized. 

    Therefore, this behavior is expected.  Please wait for 8.5us after ENx is 'high' before transmitting data.  

    Best,
    Andrew