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Original question:

ISO7041: IECEx and ATEX certification

ISO7041: Safety Limiting Values for IECEx/ATEX Certification

Glen Schmidt1
Prodigy 160 points

Part Number: ISO7041

I am an IS consultant working on a complex IS design and had planned on using the isolator clauses in the IEC 60079-11 standard for a serial IS interface.
I was thrilled to find that TI has achieved this certification. 

I have obtained the IEC and ATEX certificates from your web site.

However, there is a confusing detail.
Section "7.8 Safety Limiting Values" of the data sheet would tend to imply the TOTAL POWER for the part is 1.435 watts and de-rated accordingly.  I have always assumed this meant total, as in total between both sides.  However, the IEC certificate and ATEX certificate both say 1.3 watts each side for 70C and 1.1W each side for 85C.  No matter how you add it up, that does not make sense.

The Intrinsic safety standard is always more conservative, and would also requite a 1.5 safety factor.  SO even if testing improved the certification, I cannot imagine it flew by without the 1.5 safety factor on top of it.

I need more particulars and I am certain this will need to come from the person who handled the certification, as very few people are well versed in Intrinsic safety and it is a language all of its own.
Please either get me the full certification test report or please connect me directly with the person who handled the certification.

I already have the certificates. That is not enough info.  I have also read your "Application Report SLLA480–May 2020 Intrinsic Safety Compliance of Digital Isolators in Explosive Atmospheres" whichj also is not useful for real design work.

Thanks

Glen E Schmidt

AnalogIS LLC
Analog Design + Intrinsic Safety = AnalogIS
A UNIQUE COMBINATION OF TWO OF THE MOST DIFFICULT SKILLS TO FIND IN THE INDUSTRY

2513 Centre Rd
Bartlesville, OK  74003
glen@analogIS.net

  • 0
    TI__Genius 17100 points

    Hi Glen,

    Thank you for posting, and welcome to E2E! You are right: ISO7041 is a low-power digital isolator, and it does not consume 1.3W on each side during normal operation.

    Our team will follow up regarding the test report or specific test procedure tomorrow. Thank you for specifying what you are looking for.


    Respectfully,
    Manuel Chavez

  • 0 in reply to Manuel Chavez
    Prodigy 160 points

    Hello Manuel

    I agree it does not consume that power.  That was not my question.  The referenced section is how much power the part can take as a fault before the isolation is compromised.  The Intrinsic Safety Standard EN 60079-11 section 7.6 is lengthy but this statement says it all "

    "integrated circuits can fail so that any combination of short and open circuits can exist between their external connections."

    What this means is that if I power the part with 3.3V, I to prove that the  3.3V cannot somehow produce 1.3W into a failed part, or..cause a failure into the part that goes >1.3 watts.  FURTHERMORE...since it is a safety device upon which, literally, life or death depends, EN 60079-11 ALSO requires you have a triple redundancy so that two faults cannot allow the 1.3 watts.
    FURTHERMORE....my real question...did it somehow certify with this set of conditions of 1.3 watts on both sides?

    Think of it this way...if you took 115VAC from the wall socket and hooked it from power to ground on the part, what would happen?
    I think we can agree, the part would be destroyed.  In  that case, do you think the part would still maintain isolation?  I doubt it
    So then, what CAN it stand to have and still maintain isolation?  Well... the certificate for the part actually says 50V.  But not more than 1.3 watts...
    My question...one side or both sides?  Your data is not clear.

    This is life in the IS world.  I actually have to design low voltage equipment where you can accidentally put 250V to the inputs while the other side of the device is immersed in flammable gas and NOTHING explodes.  But we have rules to live by and that is EN 60079-11

    Please..please. pass the question on to someone who understands Intrinsic Safety. and the application specific to EN 60079-11.

    Best regards

    Glen

  • 0 in reply to Glen Schmidt1
    TI__Genius 12555 points

    Hi Geln,

    Thanks for your question. I'll send you an email shortly to discuss the details of IECEx & ATEX testing of ISO7041 device.

    We'll move the rest of this discussion to direct email communication.

  • 0 in reply to Saleem Marwat
    Prodigy 160 points

    Ok good deal!

    Thanks

    Glen

  • 0 in reply to Glen Schmidt1
    TI__Genius 12555 points

    Hi Glen,

    I hope our email communication resolved this issue.
    Let me know if you have additional questions.

  • 0 in reply to Saleem Marwat
    Prodigy 160 points

    Thanks so much for the help.  The certification report will be very helpful.
    I will also talk to our agency about the 1.5 safety factor rating for a component, since this is already "vetted" by its own certification.  Please let me know what your agency says as well.

    Best regards,

    Glen