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ISO7742: IIC isolated interface

Cooper Zhang1
Expert 2190 points
Part Number: ISO7742
Other Parts Discussed in Thread: ISO1541, ISO1540, ISO7241C

Dear ,

Can I use ISO7742 to monitor ISO1524 function for i2c isolated ?

  • 0
    TI__Guru 54245 points

    Hi Cooper,

    Thanks for reaching out.

    ISO1524 is not a valid part number, did you mean to refer to ISO1540 or ISO1541?
    Could you please elaborate on what exactly you meant by monitoring? ISO154x is already an isolator and you probably wouldn't require another isolator for the same interface.

    Let me know, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Expert 2190 points

    sorry， i meant I am using ISO7742 now, I do not add new part ,so i want to know whether ISO7742 can apply for i2c isolated ? 

  • 0 in reply to Cooper Zhang1
    TI__Guru 54245 points

    Hi Cooper,

    I2C requires bidirectional channels where each channel should be able to transmit signal both directions. ISO77xx only supports unidirectional channels and hence, it doesn't support I2C as is.

    In some applications, the MCU has split SDA channels as SDAO and SDAI. If this is also the case with your application and SCL is only need to be unidirectional, then ISO77xx can be used with an additional open-collector buffer to isolate I2C. Please refer to TPS2388EVM-612 which implements I2C using ISO7241C which can also be done using ISO77xx. I am copying below the schematic from EVM for your quick reference.

    Even if the MCU doesn't have SDA line split into two, you can still use a digital isolators some more additional external circuit as shown in the below application note.

    Designing an Isolated I2C Bus interface by using digital isolators

    But since we already have I2C isolators, we do not recommend using digital isolators for I2C isolation. ISO164x is our latest family of I2C isolators. Let me know if you have any questions, thanks.


    Regards,
    Koteshwar Rao