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ISOW7840: DC/DC Switching Frequency

user5163865
Genius 4140 points

Part Number: ISOW7840
Other Parts Discussed in Thread: ISOW7821, , ISOW7741

Hi,

What is the switching frequency of the built-in isolated DC/DC converters in the ISOW7840 and ISOW7821?

www.ti.com/.../slla561.pdf
According to this infomation, the ISOW7741's frequency is 25MHz.

Do these two products have the same frequency?

Best regards,

Hiroshi

  • 0
    TI__Genius 17760 points

    Hi Hiroshi,

    Thanks for reaching out.

    The ISOW784x is older generation of devices which uses 60MHz switching frequency.

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Genius 4140 points

    Varun-san,

    Thank you for your support.

    Just to be sure, the only difference with the ISOW782x is the number of channels, so it's the same generation product as the ISOW784x, right?
     In other words, are all the ISOW78xx from the same generation?

    Best regards,
    Hiroshi

  • 0 in reply to user5163865
    Genius 4140 points

    Sorry for the multiple posts.

    Additional Question
    The CISPR22 EMI results have been published.
    Isolated RS-232 With Integrated Signal and Power Reference Design

    I understand that the two products in question are similar, and that the EMI peak trends are the same?
     Also, would a 3.3V supply voltage instead of a 5V supply tend to reduce EMI?

    If possible, I would appreciate any information on board layout or other methods for reducing EMI.

     Background of the Question

    They were using a competitor's product, but due to the high EMI, they are considering replacing it with a TI product.

    Best regards,
    Hiroshi

  • +1 in reply to user5163865
    TI__Genius 17760 points

    Hi Hiroshi,

    user5163865 said:
    Just to be sure, the only difference with the ISOW782x is the number of channels, so it's the same generation product as the ISOW784x, right?
     In other words, are all the ISOW78xx from the same generation?

    Yes, that is correct.

    user5163865 said:
    I understand that the two products in question are similar, and that the EMI peak trends are the same?
     Also, would a 3.3V supply voltage instead of a 5V supply tend to reduce EMI?

    Yes, the EMI performance is same in both the products as they use same generation of DC-DC switching power supply.

    And yes, the 3.3V operation is expected to have lower EMI due to less energy transfer through internal DC-DC power supply.

    user5163865 said:
    If possible, I would appreciate any information on board layout or other methods for reducing EMI.

    You can refer following appnote on product page: Low-Emission Designs With ISOW7841 Integrated Signal and Power Isolator (Rev. C)

    Please note that CISPR32 is the latest and updated standard version which is based on CISPR22 and as of today CISPR22 no longer exists.

    Regards
    Varun