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Original question:

ISO7740: iso7740 lost of isolation

ISO7740: ISO7740

christophe duchemin
Prodigy 80 points
Part Number: ISO7740
Other Parts Discussed in Thread: ISO7820

Hi,

Yes, we've already seen the TDDB plot and we will continue to discuss that, but idealy we need Failure Modes and Distribution with the item 'lost of isolation'. Is it possible for TI to provide this FMD: 'lost of isolation' of ISO7740, ISO7820... (double capacitive barrier devices)?

Inside 'slla508_iso7740' document there is also a note below the FMD table 3-1 where it is written 'The FMD in Table 3-1 excludes short circuit faults across the isolation barrier. Faults for short circuit across the isolation barrier can be excluded according to ISO 61800-5-2:2016 if the following requirements are fulfilled...'. The issue is that we don't have ISO 61800-5 yet.

Best regards,

Christophe

  • 0
    TI__Mastermind 22760 points

    Hello Christophe,

    Could you clarify what you mean by "lost of isolation"? Are you looking for a Failure Mode Distribution where the isolation barrier is damaged? What data or information are you needing exactly?

    As long as the recommended operating conditions are followed, there should not be any damage or failure of the isolation barrier. The SLLA508 document includes Failure Mode Distribution of random failure events but does not include failures due to misuse or overstress.

    The requirements for exclusion that you referenced from the SLLA508 document are listed out further in the table note in the numbered list. If you need more details, please refer to the standard itself.

    Regards,
    Darrah

  • 0 in reply to Darrah Merillat
    Prodigy 80 points

    Hi Darrah,

    "Lost of isolation" will be a short circuit (from any pin from non iso side to any pin to iso side). I do not consider failures due to misuse or overstress.

    It could be a figure like 0.1% occurence of a short circuit and 99.9% of a fail-safe state (open).

    Regards,

    Christophe

  • 0 in reply to christophe duchemin
    TI__Mastermind 22760 points

    Hello Christophe,

    Thanks for explaining what you are looking for. Unfortunately, we do not have data similar to what you have described. Our Failure Mode Distributions are created with respect to potential outputs of the device and do not include events like shorts across the isolation barrier

    All our isolators offer a reliable level of isolation and have been certified to many standards by certification agencies such as VDE and UL. As long as proper operating conditions are met, you should not see any issues with the isolation barrier failing. Is there any information other than a Failure Mode Distribution and the certified specs that would reassure you of the robustness of our isolators?

    Regards,
    Darrah