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ISOW7821: Question about high isolation voltage condition

Guru 14080 points

Part Number: ISOW7821

Customer is require high isolation voltage condition below;

・Isolation voltage: 5500Vac / 1min


 ※DC/DC: 5Vin ⇒ 5Vout / 10mA

Please let me know about three points below for ISOW7821.

ISOW7821 is 1414Vdc, but isolation voltage is 5000Vac / 1min.

 I think that cascade two ISOW7821 became to increase isolation voltage, is it correct?

 I want to know any idea for ISOWxxxx  series match 5500Vac / 1min.  

②Is there specification graph for Isolation capacitor Life time? (Graph of Time of fail vs Stress voltage)

③Is there test data for Failure mode?

 (I want to know these test data based on Vac or Vdc)

Best regards,


  • Hi Satoshi-san,

    Thanks for using our E2E forums.

    1). Technically, yes - one can cascade isolators to achieve higher isolation voltage ratings. However, before we consider that option, there might be better solutions available based on end equipment needs. For example, one can use the ISO7821 (no W in the part name; only data isolator without power), which can support 2121V (DC) and 5700V rms (1 minute) in the same footprint (16DW). You can then use an SN6505 part to drive a transformer to get isolated power. The 10mA load current budget at 5V should be easily handled since the 6505 can provide up to 1A of current.

    Can you please share more details on the end equipment that needs this high isolation voltage Vac spec? 

    2) We will follow-up with you on this. The ISO7821  (no "W") part linked above contains the capacitor lifetime data in the datasheet, but this is for data path only. We will try to see if we can provide a similar curve for the W parts also [data + power].

    3) This data unfortunately cannot be shared on a public forum. Sharing this will require an NDA and we will have to pursue this offline over PM/email.  Is this something you wish to pursue? If yes, can we please reach out to you/your end customer over email to route this through the correct channels?

    Best regards,


  • Guru 14080 points

    In reply to Abhi Aarey:


    Thank you for reply,

    About answer 3), I confirm to customer that consider NDA or not.
    I will get back to you.

    About answer 2), I didn't find life time graph on ISO7821 Datasheet, is there the other document?
    ISO7821 isolation voltage is higher than ISOW7821, is ISOW7821 life time the same(near) as ISO7821?

    Best regards,
  • In reply to Satoshi:

    Hi Satoshi-san,

    Abhi is going to be Out Of Office, so please allow me to help you while Abhi is away.

    1) Abhi already addressed this question.

    2) ISO7841 datasheet has the lifetime data published in Section 6.18 as Insulation Characteristics Curves, this will equally be applicable for ISO7821 as well. ISOW7821 lifetime curve will be slightly different from ISO7821 for the reason that ISOW7821 includes an integrated DC/DC converter as well. Like Abhi asked earlier, can I reach out to you through on your email that you have used for E2E profile creation for sharing you lifetime curve?

    3) Regarding the failure mode, before I comment on this can you please describe more about what exact data are you looking for?
    If it is about whether the isolation barrier is going to fail-open or fail-short, then please refer to the white paper at below link.

    Koteshwar Rao
  • In reply to Koteshwar Rao:

    Hi Satoshi-san,

    Please do help me with your inputs so that I can support you further, thanks.

    Koteshwar Rao
  • Guru 14080 points

    In reply to Koteshwar Rao:


    Thank you for many advice,
    And sorry for my reply delay.

    About your answer 1) and 3), these were cleared.
    About answer 2); Yes, please share lifetime information to my email.

    Best regards,
  • In reply to Satoshi:


    I have sent you an email with the requested information. I will go ahead and mark this thread as closed. If you have other questions, please create a new E2E post. Thanks.

    Koteshwar Rao