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LMH1297: Lightning Transient Suggestions

Jeff Spencer
Prodigy 10 points

Part Number: LMH1297
Other Parts Discussed in Thread: TVS3300

Tool/software:

I am working on the design of an avionics box that will use the LMH1297 for SDI video. We have severe lightning induced transient requirements and I was curious if there were suggestions from TI on what approach to take for lightning transient suppression and if there was any idea of the transient survivability of the part.

  • 0
    TI__Mastermind 23141 points

    Hi Jeff, 

    Would IEC ESD test be a valid test?

    Best,
    J

  • 0 in reply to J
    Prodigy 10 points

    Hi J,

    It may be a good approximation with some adjustments. For my lightning requirement, full wave simulation on a representative cable bundle setup shows a peak short circuit current of about 6.5A and the test would allow no more than 750V common mode to develop at the SDI interface. The duration would be on the order of 100s of microseconds and there would be repetitive applications. That all said, we are somewhat in the neighborhood of ESD current levels but duration is what makes this a little tough.

    -Jeff

  • 0 in reply to Jeff Spencer
    TI__Mastermind 23141 points

    Hi Jeff, 

    We are not experts on lightning tests nor ESD tests, so I cannot speak much about it. But, after discussion with the ESD team, the IC's survivability will mostly depend on the TVS diode and a large value pulse proof of resistor before the input of the TVS to limit the current into it. 
    I have discussed little bit with the ESD team, and they discussed that TVS diodes like TVS3300 will enable lightning transient survivability of the sensitive ICs. 

    Best,
    J

  • 0 in reply to J
    Prodigy 10 points

    Hi J,

    I want to double check. So the LMH1297 will be able to survive seeing a clamping voltage of up to 38V common mode for the couple hundred microsecond duration of the transient? That's what's most unclear to me from the datasheet of the LMH1297. Is there a well defined maximum common mode transient maximum?

    Thanks,

    Jeff

  • 0 in reply to Jeff Spencer
    TI__Mastermind 23141 points

    Hi Jeff, 

    LMH1297 itself is able to survive with 6kV ESD without any ESD/TVS diodes as defined in the datasheet. If the ESD diodes are selected properly and clamps properly, LMH1297 will be able to survive the lightning transient wave. Unfortunately, we only have the ESD rating for this part. 

    Best,
    J