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ISO1642: Can our Digital I2C isolator also support isolated CJTAG?

Zoe Yang
Intellectual 1820 points
Part Number: ISO1642
Other Parts Discussed in Thread: ISO1540,

Customer is using 2 MCU structure.(One for communication and another for power driver) and would like to check if our I2C isolator could support to use in isolated CJTAG application?

Is it possible to use some I2C isolation like ISO1540 which is bidirectional?

  • 0
    TI__Mastermind 49445 points

    Hi Zoe,

    Thanks for reaching out.

    ISO1642 is a open-drain bi-directional channel isolator. The most common interface that would require such isolator is I2C and hence, is best suited for I2C. Since the device is only a physical layer device, it can be used to isolate any other bi-directional interface as long as its electrical and switching specifications including datarate meet application requirements. It looks to me that ISO1642 can be used for cJTAG but do note that ISO1642 requires external pull-up resistors which could slow down the max datarate that solution could support.

    Let me know if you have any further questions, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    TI__Intellectual 1820 points

    Thanks Rao for detailed reply! May I know how much it would affect if using iso-i2c to transfer iso

    -CJTAG? You mentioned max data rate influenced, How much about that influence? Do we have any better solution right now?

  • 0 in reply to Zoe Yang
    TI__Mastermind 49445 points

    Hi Zoe,

    ISO1642 supports a maximum datarate of 1.7MHz as stated in the datasheet. The actual datarate of the overall system depends on external pull-up resistors used, acceptable rise/fall times of customer application and I/O capacitance of the GPIOs. If customer datarate requirement is not very high, then it should be okay to use this device. If you can share customer datarate requirement then I maybe able to comment if ISO1642 still works for them.

    Let me know, thanks.


    Regards,
    Koteshwar Rao