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Original question:

ISO1644: SPI Interface

ISO1644: Competitive advantage for EMC?

Bryan McLaughlin
Expert 1110 points
Part Number: ISO1644
Other Parts Discussed in Thread: ISO1640

Hello, 

I'm deciding whether to use the ISO1644 (or similar) for I2C isolation to break DC current paths on a 5V electrochemical sensor system. Multiple ISOs (data+power) would be used to connect various hot-swappable I2C sensors to an MCU. The distance from MCU to ISO is 5-10cm on a PCB, but from ISO to sensor is a wired connection up to 30cm. 

We really like the competitor's ADM3260 which has an integrated DC/DC, but their extensive application notes about reducing EMI from the high frequency coupling circuitry make me feel like it's going to cause more problems than it's worth. 

Can you share any advice about how the EMC of TIs coupler technology compares with similar products on the market, and what should be done to control EMI.on the load-side wired connection? Thanks! 

  • +1
    TI__Mastermind 23065 points

    Hello Bryan,

    Thank you for looking into ISO1644. There should be no EMI concerns with these parts, but the below guidelines will help avoid any problems at the system level. 

    • The distance of 5-10cm on the PCB is okay, and I do not expect any issues here. 
    • The wire connection length from the ISO1644 to the sensor should also be okay as well.
      • Please note that side 2 of ISO1640 has 8kV ESD protection. Make sure to use side 2 to connect to the sensor, and side 1 to MCU. 
    • The device internals do not cause any radiations, however, the data switching in the wire could cause radiations. If these violate your emissions requirements, you can slow down the rise and fall times by increasing the pull-up resistance values on the datelines.
      • This should help you address your EMI concerns. 

    Best,
    Andrew