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ISO7720: Is there any aged deterioration in ISO7720?

Kazuya Nakai59
Guru 20080 points
Part Number: ISO7720

 Hello guys,

 One of my customers is considering using ISO7720 for their new interface products. They have a few questions about ISO7720as the followings. Could you please tell me your answers?

Q1. Is there any big aged deterioration in ISO7720? Especially, how about switching characteristics because they care about it. In other words, Does any ISO7720 switching characteristics become worse in aging?

Q2. Is there any point which customers need to pay attention to use ISO7720 in their design except using the device under the recommended operation conditions?

Q3. Is there any failure case of ISO7720 in the past. They want to know. If there is failed cases, they can use that information to avoid failure.

 Your answers would be much appreciated.

 Best regards,

 Kazuya Nakai.

  • 0
    TI__Mastermind 49415 points
    Hello Kazuya-san,

    I am glad to know that your customer is interested in using ISO7720 in their product. Please find below my comments to the questions you have listed out.

    A1. The specifications given in device datasheet cover all the variations due to external factors including aging. We do not expect the device to violate any of the datasheet specs for the life of the device. Hence there is no degradation expected from datasheet limits for any of the specs, particularly switching characteristics.

    A2. The device doesn't have any specific requirements from design point of view, the generic schematic and PCB layout guidelines that apply to most devices will also be applicable to ISO7720 as well. One of such important guidelines is to keep the decoupling capacitors on VCC/GND to close to the pins of IC and on the same layer as ISO7720.
    The device already has very good EMI/EMC performance like ESD, EFT, Surge, etc. But if customer requirements are much higher than usual then customer may need additional external protection.

    A3. We haven't heard about failures from any customer who is operating the device under its recommended operating conditions.

    The above points should answer your question, let me know if you have any other questions. Thank you.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    Guru 20080 points
    Hello Rao,
    Thank you for your prompt reply.
    Could I ask you a few additional questions?

    1. Is the X axis title of Figure 2 and 4 graph on page 12 in ISO7720/21 datasheet (SLLSEP3B) wrong? I think the title should be "Safety Limiting Power (mW)" not "Safety Limiting current (mA)"?

    2. The maximum ambient temperature in the customer case is +85 degree C. According to Figure 1 graph, the device DW-16 package can dissipate about 120mA with VCC1=VCC2=5.5V at the temperature as the maximum. I can understand the mean of the graph.
    But I don't know which case can dissipate such large current in ISO7720 in the device reccomend conditions even if the current is total of input current, output current and IC supply current,.
    Could you please tell me how to calcurate the current or dissipation power of ISO7720?

    Thank you and best regards,
    Kazuya Nakai.
  • 0 in reply to Kazuya Nakai59
    TI__Mastermind 49415 points
    Hello Kazuya,

    Please find below my inputs for the additional questions you have posted.

    1. Yes, your understanding is correct. The Y-axis of the plot for Figure 2 & 4 should have been "Safety Limiting Power (mW)". Thank you for bringing this to our notice, we will get this fixed.

    2. Please refer to section 6.8 titles "Safety Limiting Values" on page 7 of ISO7720/21 datasheet. Section 6.8 explains that if there is a damage local to a particular die and not to isolation barrier, then the current into device or power dissipation on overall package should be limited to avoid damage to isolation barrier due to overheating. This is not a typical operating condition rather this is a spec for the situation where a local damage has already occurred.

    I hope the above points cleared your questions, please let me know if something was not clear. Thanks.


    Regards,
    Koteshwar Rao
  • 0 in reply to Koteshwar Rao
    Guru 20080 points
    Hello Rao,

    Thank you very much for your answers. Your answers are very helpful.

    Best regards,
    Kazuya Nakai.