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ISOW7841: EMI issues

Statham Su
Genius 4990 points
Part Number: ISOW7841
Other Parts Discussed in Thread: ISOW7741

Hello Sir:

We need your help to check our EMI results.

We had been followed up below link to modify our schematic and layout.

https://www.ti.com/lit/pdf/slla368

We don't want to discuss our design on public.

Can we discuss and check schematic/layout by private message?

The other we have other questions on Pin9, can we let pin9 floating? Just let it connected by IC internal. 

Looking forward your feedback.

Thanks a lot. 

  • 0
    TI__Guru 55815 points

    Hi Statham,

    Thank you for reaching out and sorry to hear about issues.

    Statham Su said:
    The other we have other questions on Pin9, can we let pin9 floating? Just let it connected by IC internal. 

    Floating pin 9 is okay for lab testing but for reliable operation in noisy conditions, we recommend that pin 9 is connect to ground externally on PCB as well.

    Statham Su said:
    Can we discuss and check schematic/layout by private message?

    Sure, before that I would like to ask / give a few points.

    ISOW7841 is our first-generation device family while we now have second-generation device ISOW7741 which offers significantly improved overall performance including radiated emissions performance. If customer is currently evaluating ISOW7841 for a new project then we recommend that they consider ISOW7741 for their design and use the simple guidelines specified in below application note to meet their emissions requirements without any issues.

    How to Meet CISPR 32 Radiated Emissions Limits With ISOW7741

    If customer still like to use ISOW7841 then I recommend that they follow the guidelines provided in the E2E at below link, especially the use of CMC. This should help improve their radiated emissions significantly.

    https://e2e.ti.com/support/isolation-group/isolation/f/isolation-forum/806938/isow7841evm-isow7841evm

    Please share these inputs with customer and let me know if customer is going to consider either of these inputs. If they have any further questions, then let me know so that I can reach out to you over your email. Thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Genius 4990 points

    Hello Koteshwar:

    Customer puts CMC on input and output side already.

    Please accept my friendship request, I can send schematic and layout for you.

    It's a follow that guide line of "Low-Emission Designs With ISOW7841 Integrated Signal and Power Isolator".

    Looking forward your feedback.

    Thanks a lot.

  • 0 in reply to Statham Su
    TI__Guru 55815 points

    Hi Statham,

    Thank you for the friendship request on E2E. I have accepted it, you can send me the files so that I can review.
    Please make sure to include the values and/or part numbers of components in the schematic, especially the CMC. Thanks.


    Regards,
    Koteshwar Rao