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ISO7841: how to define the operating lifetime?

Part Number: ISO7841

Hello,

In ISO7841 datasheet, there is a graph of operation lifetime, figure 1 and figure 2.

It is described operation lifetime is 135 years in figure 1 and operation lifetime is 34 years in figure 2.

What does the operation lifetime mean?

The customer feels 34 year is short number which is describe in figure 2 and how much is the operation lifetime under 1800Vrms case.

If operation lifetime is defined as TDDB line(<1PPM failure rate), then the answer will be 254 years.

Please let me ask the operation lifetime meaning and 254 years is the number of 1800Vrms case is.

I heard we are still keeping the test and no failure happens. I guess the green area will become much higher value but need time to update the number for test is done though...

Best regards,

Toshihiro Watanabe

  • Hi,

    Figure 1 shows operating lifetime of the isolation barrier for DW package (8mm Creepage) at 1500 Vrms (135 Yrs). The actual data shows lifetime of 254 years at 1800 Vrms but VDE standard requires 20% voltage safety margin and 87.5% lifetime safety margin, that's why we show operating lifetime of 1500 Vrms for 135 years.

    Figure 2 shows operating lifetime of the isolation barrier for DWW package (14.5mm Creepage) at 2000 Vrms (34 Yrs). The actual data shows lifetime of 63 years at 2400 Vrms but VDE standard requires 20% voltage safety margin and 87.5% lifetime safety margin, that's why we show operating lifetime of 2000 Vrms for 34 years.

    I hope this clarified any confusion.
  • Hello Saleem-san,
    Thank you for the explanation how to see the graph. Does the operating lifetime become longer when DWW package working voltage is 1800Vrms? If yes, how much longer lifetime is it?
    Best regards,
    Toshihiro Watanabe
  • Hello,

    How should we estimate the operation time under max working voltage? There is TDDB line in figure 2. Is the operating lifetime longer the same ratio as this line?

    Best regards,

    Toshihiro Watanabe
  • Both Figure 1 and Figure 2 have the same TDDB line. The difference in lifetime is due to working voltages for different packages. At 1800 Vrms, the insulation lifetime is 254 years.

  • Hello,

    I think 254 years at 1800Vrms working voltage is TDDB line cross point.

    I would like to know the year which operating zone: 1800Vrms, ?? years. Is it possible to know it?

    Best regards,

    Toshihiro Watanabe

  • Hi Watanabe-san,

    Did you mean to say that you are looking for DWW device lifetime at 1800Vrms with 87.5% margin on lifetime and 20% margin on working voltage which is mentioned as operating zone in datasheet?
    If so then the lifetime with margins for ISO78xx in DWW package for working voltage of 1800Vrms would be 59 years.

    To summarize,
    Lifetime at 1500Vrms -> 135 years
    Lifetime at 1800Vrms -> 59 years
    Lifetime at 2000Vrms -> 34 years


    Regards,
    Koteshwar Rao