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ISO1540: EMC testing and designing with the ISO1540

Part Number: ISO1540
Other Parts Discussed in Thread: SN6505B, SN6501, SN6505A

Good afternoon,

I was hoping you could provide any insight into designing with the ISO1540 for successful EMC testing. I am concerned about the emissions of the part and passing the testing.

Thank you,

Julia

  • Hi Julia,

    Thank you for posting your question on TI E2E, we'll be glad to help you out here .

    One of my team members will be posting a follow-up , but to get us started, could you please tell us a little bit more of your implementation, and system? A simplified block diagram is very helpful for initial discussions.

    For example, you could show how the isolated power supply is generated (can contribute to EMC as well depending on type), how the 1540 is configured - supply values, pull-up resistor values, data rates used etc. It is also useful to know if you are trying to meet any EMC standards in particular or are trying to use best practices in general to prevent EMC issues down the road.

    We can also look at a schematic *if*you need and if that's your preferred option. If so, this is best done over PM(private Message)/email, to protect the integrity of your IP. Please feel free to pick whichever option works best for you and we can support you and share some best practices for sure!

    Best regards, have a good day!
    Abhi
  • Power supply: PXC-M03-24WS05-A

    ISO1540:

    1kohm pullups

    0.01uF decoupling

    1-2 devices on the bus

    3.3V to 5.0V

    Generally I would like to use best practices to prevent EMC issues down the road. We will be trying to meet EMC, but I am not sure of the standard currently.

    Thank you

  • Hi Julia,

    Thank you for sharing additional information about your application. ISO1540 being a signal isolation device where the power levels of the signal are very low, we do not expect it to cause any issues in complying to radiated or conducted emissions standards like CISPR 11, CISPR 22, CISPR 32, etc. We also haven't heard any customers facing any such emissions issue due to ISO1540.

    As a good schematic and PCB layout practice, I would like you to refer to Section 10 & 11 in page 25 of ISO1540 datasheet. As suggested in Section 10, it is recommended to have 0.1µF of decoupling capacitors at VCC1 & VCC2 of ISO1540. Otherwise there shouldn't be problem. Thanks.


    Regards,
    Koteshwar Rao
  • Thank you for taking the time to respond. i will definitely make the update to the caps. I missed that when I changed my part over from a different MFG.
  • Just found out that we will be testing to CISPR 11 Class B.
  • Hi Julia,

    Thanks for sharing the emissions standard that you are trying to meet, CISPR 11 Class B. ISO1540 by itself doesn't cause any issues in meeting the standard but the power supply in the system may cause issues. Hence please do make sure the power supply is optimized to meet CISPR 11 Class B.

    One of the isolated power supply solutions from TI that meets CISPR 11 Class B is based on SN650x devices (SN6501, SN6505A & SN6505B). If you are looking for power supply solutions, you can have a look at these devices. Thanks.


    Regards,
    Koteshwar Rao
  • Thank you for taking the time to respond. I will look into the power supply.

    have a great day,

    Julia