• State TI Thinks Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 2 answers
  • Subscribers 15 subscribers
  • Views 240 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

ISO1644: ISO1644 master side

ahugron hugron
Prodigy 240 points
Part Number: ISO1644

Hi,

For ISO1644, what is the recommend side for the master I2C?

Thanks,


Arnaud

  • 0
    TI__Mastermind 49495 points

    Hi Arnaud,

    Thanks for reaching out and for your interest in ISO1644.

    The Side1 (VCC1 side) of ISO1644 supports lower load current (3.5mA) and capacitance (80pF) compared to the Side2 (VCC2) which supports 50mA and 400pF. This is done allow connection of only one node on Side1 and multiple nodes on Side2, hence, we recommend connecting the I2C leader device on Side1. I hope this is clear, thanks.


    Regards,
    Koteshwar Rao

  • 0 in reply to Koteshwar Rao
    Prodigy 240 points

    Hi,

    Thanks a lot for your answer. In my configuration, I have a remote master and multiple slaves (up to 16). Each slave has their own ISO1644 isolator that are then connected to the common I2C bus.

    (Master may not have an isolator). In this case, should I still use VCC1 for the master? The problem is that all slave have to be isolated from each other and from the master. Any recommendation if you have a better part?

    One more question, can the ISO1644 works with either 3.3v and 5v bus. In order word, if I set VCC to 3.3v, can it supports 3.3v and 5v I2C bus or if I set VCC to 5v, can it supports 3.3v and 5v I2C bus. We only provide an isolated slave device, customer master may use 3.3v or 5v for I2C level.

    Regards,

    Arnaud

  • 0 in reply to ahugron hugron
    TI__Mastermind 49495 points

    Hi Arnaud,

    Thanks for providing further clarification.

    I understand that you have one leader located remotely and not isolated while there are 16 followers where each one is isolated and then connected to the common I2C bus. Since the 16 followers need to be isolated, the isolator should be used with each one of those nodes which I believe you are already considering to do so.

    When you you use ISO1644 with each of these nodes, you connect one side of ISO1644 to one of these nodes while the other side of ISO1644 is connected to the I2C bus which has multiple nodes. Since only Side2 of ISO1644 supports I2C bus with multiple nodes, Side2 should be connected to the I2C bus with multiple nodes while the Side1 should be connected to the individual node (follower).

    ahugron hugron said:
    One more question, can the ISO1644 works with either 3.3v and 5v bus. In order word, if I set VCC to 3.3v, can it supports 3.3v and 5v I2C bus or if I set VCC to 5v, can it supports 3.3v and 5v I2C bus. We only provide an isolated slave device, customer master may use 3.3v or 5v for I2C level.

    As you may have already noticed, the device supports operation from for both 3.3V and 5V but it is recommended that the I/O voltages match the supply voltage. I would also like to mention that when VCC2 is 5V, the SDA2 and SCL2 can work with either 3.3V or 5V, although we recommend to use the same I/O voltages as the VCC2 so that the I/O signals have high noise margin.

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


    Regards,
    Koteshwar Rao