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ISO1640-Q1: Guideline for cable and connector selection

Chuqiang Wen
Expert 5385 points
Part Number: ISO1640-Q1
Other Parts Discussed in Thread: ISO1640

Tool/software:

Hi Team, 

My customer is considering to use ISO1640-Q1 for isolated I2C, it will connect to external I2C device. Could you please share the guideline for the connector and cable selection? 

Thanks!

Ethan Wen

  • 0
    Guru 295240 points

    There is no standard for I²C cables/connectors because I²C was designed for short distances on a single board.

    I²C has a limit of 400 pF for the total bus capacitance, and even that reduces the maximum achievable speed. So you cannot use connectors or cables that increase the capacitance too much.

    I²C has no error checking mechanism, and single-ended signals are sensitive to noise. In noisy environments, you have to use shielded cables, which increase capacitance.

  • 0 in reply to Clemens Ladisch
    TI__Expert 5385 points

    Hi Clemens, 

    Thanks! 

    Do you think if ISO01640-Q1 is suitable for off-board communication? Do you know if we have such use-case experience from other accounts? 

    Ethan Wen

  • 0 in reply to Chuqiang Wen
    Guru 295240 points

    Maybe. This depends on the total capacitance, which I do not know.

  • 0 in reply to Clemens Ladisch
    TI__Mastermind 24005 points

    Hello Ethan, 

    Clemens is correct, I²C is intended for short distances on the same board and as a result there are no official cable or connector recommendations in our datasheets. The transceiver and I²C team also confirmed that they haven't made any official recommendations regarding component selection. 

    Off board communication is okay for ISO1640 side 2 as long as the bus capacitance with the connector and cable are kept below 400pF limit stated in the datasheet.  

    Best,
    Andrew