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Original question:

ISO7821: Isolation forum

ISO7821: lifetime with 1500Vrms, f=20kHz condition

Hung Ching Hsu
Expert 3086 points
Part Number: ISO7821

Hi Team 

My customer is using ISO7821FDWWR with 1500Vrms, f=20kHz.

They want to know the lifetime of ISO7821FDWWR with the conditions mentioned above.

I've got the TDDB test information for 3500Vrms, f=10kHz from the thread below and provided to the customer.

https://e2e.ti.com/support/isolation/f/1013/t/906943

I know because of the HV equipment restriction, the experiment could only be done til f= 10kHz.

So they're asking if there are any way to estimate the lifetime with 1500Vrms, f=20kHz condition ?

Thanks.

  • 0
    TI__Guru 53025 points

    Hi Hung,

    The device ISO7821FDWW is TDDB tested to estimate its like at f = 60 Hz is 135 years, as stated in the datasheet.

    Looking at the lifetime vs frequency plot from the above referred E2E post, you can see that the lifetime remains almost the same for frequencies upto 10kHz. Since we don't have data for f = 20kHz, I will not be able to confirm any performance at that frequency but we do expect the lifetime to remain almost the same even at 20kHz. Please also know that there are many motor driver and solar inverter converters who are successfully using ISO78xx and ISO77xx without any issues and hence, we do not expect any issues. Thanks.

    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Expert 3086 points

    Hi Rao 

    Thanks for your reply and the success example for motor driver and solar inverter converters.

    I'm not quite familiar with motor driver and solar inverter converters, what the frequency range will they usually be used ? 

  • 0 in reply to Hung Ching Hsu
    TI__Guru 53025 points

    Hi Hung,

    Most motor drive and solar inverter applications use a switching frequencies between 10 - 20kHz and some applications might have higher frequencies as well. We have many of these customers ISO78xx and ISO77xx devices without any issues. Thanks.

    Regards,
    Koteshwar Rao