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ISO7821: Isolation structure

cafain
Mastermind 6615 points
Part Number: ISO7821
Other Parts Discussed in Thread: ISO7842

Hi,
Please provide documentation on the structure of ISO7821FDWW

1.Provide structural diagram of ISO7821FDWW
　Datasheet (sllsem2f) We would like you to disclose such materials that you can see the structure of the
　　insulating part "SiO2 based Capacitive Isolation Barrier" shown in Figure11.
　(structure of primary, secondary and secondary insulation).
　In particular, the physical distance of Isolation Barrier is also required.

2.Offering "Reinforced Isolation Capacitor Life Time Projection for Devices"
  Another device, ISO7842 data sheet page15 Figure1 and Figure2 shows the characteristics about lifetime and reliability due to insulation degradation.
  Can you prepare the same data with ISO7821FDWW?

best regrads
cafain

  • 0
    TI__Guru 55155 points

    Hi Cafain,

    Thank you for using E2E Forum and for your interest on ISO7821FDWW. Please allow me to help you with the data you have requested.

    1. The physical construction of TI's OOK isolators (includes ISO7821FDWW) is explained in detail in the whitepaper titled "Enabling high voltage signal isolation quality and reliability". Figure 1 in the whitepaper shows dimensions of the isolation capacitor. You can find this article at the link here: https://www.ti.com/lit/wp/sszy028/sszy028.pdf
    Please also refer to the whitepaper with title "Understanding failure modes in isolators" for related information, you can find this whitepaper at the link here: http://www.ti.com/lit/wp/slyy081/slyy081.pdf

    2. The TDDB data given in Figure 1 and FIgure 2 of ISO7842DWW datasheet is equally applicable for ISO7821FDWW as well. You can refer to the same figures for TDDB data of ISO7821FDWW.

    Please let me know if you have any other questions, thank you.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Mastermind 6615 points

    Hi, Rao-san

    I appreciate the detailed explanation.
    Please let me ask the question of 2 additionally.

    Please tell me the formula used to create ISO7842 TDDB-data (Figure 1 and 2).

    best regards
    cafain

  • 0 in reply to cafain
    TI__Guru 55155 points
    Hi Cafain-san,

    There isn't any direct formula used to create the TDDB data rather it is an extrapolation of the practical test data conducted on ISO78xx devices. Please allow me to explain more details about TDDB.

    TDDB test is a device isolation barrier lifetime test where various set of samples are subjected to various stress voltages for continuously and are monitored for the amount of time they sustain the stressed voltage with a rate of 1 dppm. For example, ISO78xxDWW withstands about 8kV of stress voltage for about 1000 seconds with a dppm of less than one. 7kV for about 10,000 seconds, 6kV for about 100,000 seconds and so on. Once these tests are done for a reasonable of time (for days & months), it will be extrapolated to find out the isolation barrier lifetime at 2400Vrms. With quite some margin, we claim the isolation barrier lifetime of ISO7821DFWW at 2kVrms as >40 years.

    I hope the above explanation helps clarify the questions you had. Please let me know if any of the above points are not clear to you. If you have a separate independent question, please post it as a new query. Thanks.


    Regards,
    Koteshwar Rao