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ISO7721: Failure mode 1: High voltage across the isolation barrier

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Part Number: ISO7721


in the technical article below:

The failure mode 1 is fail short for capacitive isolation. Customer is worried about this failure mode, and says that magnetic isolation is fail open, which is better than capacitive isolation. How should we correspond?

  • Hi Howard ,

    As mentioned in the whitepaper, all isolator technologies fail short in mode 1 , when the rating of the barrier is exceeded. The difference is the level at which this failure happens. There are also multiple nuances to consider, such as working voltage, frequency of HV stress and so on, which affects the general operating lifetime of the barrier. Capacitive isolation retains several advantages here. 

    can you tell us more details of the end equipment the customer is using, and what type of fail modes are expected? It would also be good to know the type of energy applied and the level desired, such as IEC ESD. Feel free to engage with us over email if needed to protect any sensitive IP info, and we can summarize the conclusions at the end here on the forum. 

    often times, the failure rating of the barrier is higher than what is actually needed by the end application , thereby presenting a good engineering margin. 

    PS; the team is out for Thanksgiving holiday this week, so please expect a follow-up from us early next week.

    Best regards, Abhi