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TCA9509: Looking for I2C devices for long I2C bus

Penny Xu
Genius 15685 points
Part Number: TCA9509


Hi team,

I am planning to build a board which can be extendable. For example, I can connect 6 boards by connecting the I2C lines and power lines together to expand the port number in the system. However, I only want to install the host launchpad to on of the boards which means the I2C line from the last board to the host launchpad could be very long(60 inches). I am looking for some I2C devices to protect the data. Is TCA9509 the right device for this application? Thanks. 

Best regards,

Penny

  • 0
    TI__Intellectual 1925 points

    Hi Penny,

    thanks for reaching out. In general the TCA9509 should work. To give a better understanding I put togheter the basics below.

    The I²C standard defines at the transmission speed up to 400 kbps a total load of 400 pF on the BUS. Otherwise the timings get delayed too munch. 

    Every node adds a certain amount of capacitance and the cable itself. Every cable has a specific capacity per length usually pF/m so the more cable length the more load on the BUS. Once you determined the load it is necessary to calculate the value for the pull up resistors. Please take a look here to find out more: 

    /cfs-file/__key/communityserver-discussions-components-files/138/4807.slva689.pdf

    Also how you build up your network matters. Examples are shown on chapter 10 Application and Implementation on page 10 of the datasheet. If you could provide a simple block diagram we can take a closer look at your application.

    I hope this is helping you out, don't hesitate to ask further questions.

    Kind regards 

    Dierk

  • 0 in reply to Dierk Bronner
    TI__Genius 15685 points

     Hi Dierk,

    Thank you for the reply. Can I contact you offline regarding my system design? Thank you. 

    Best regards,

    Penny