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TCA6416A I2C issue

Kai Hsiao
Guru 12675 points
Other Parts Discussed in Thread: TCA6416A

Dear Sir 

When we use TCA6416A that I2C can't be communicated 

Below is our waveform ,you can see I2C voltage level is abnormal 

Do you have any idea about this issue ?? Thanks

  • 0
    TI__Genius 16510 points

    Hello,

    Could you explain your power supply sequence? Does VCCP come up first?

    We have seen an issue sometimes as a result of the power supply sequencing.

    Typically, we would recommend VCCI come high then VCCP. And to bring them both high as close together as possible.

  • 0 in reply to Jonathan Valdez
    Genius 4915 points

    Hi Jonathan,

    The waveform CH1 is VCCI/VCCP, there are the same source from +3.3V. The CH2 is SCL, CH3 is SDA.

    Actually, we found a lot of failure IC in the application, so do you think the power up waveform will cause the SDA/SCL pin damage?

    Thanks!

  • 0 in reply to Jerry Chu
    TI__Genius 16510 points
    Hello Jerry,

    It doesn't quite look like SDA/SCL damage since your voltage returns to normal afterwards.

    Does the device communicate as you would expect after the SDA and SCL lines come up to the expected voltage?

    How often do you experience this delay?

    Is it the same length of mid-voltage every time?

    Can you supply a scope shot zoomed in on your power supply ramp up? I would like to see the beginning waveform the most (as power comes up and then the SDA/SCL lines get stuck at mid voltage)
  • 0 in reply to Jonathan Valdez
    Guru 12675 points

    Dear Jonathan

    We just confirm the impedance on SCL/SDA pin and seems like the impedance abnormal 

    I will check other pin's impedance and your question!! 

    Thanks 

  • 0 in reply to Kai Hsiao
    TI__Genius 16510 points
    Very interesting data you have here.

    Thank you for taking it!

    I have a question, what are you measuring the resistance between? SCL and ground? SCL and VCC?
    Are you taking these measurements while the device is unpowered?
    Is the device removed from the board?

    One thing to keep in mind, is that there are ESD protection diodes on these pins, and if you are seeing a low impedance path from the pins to ground, it is possible that ESD cell damage occurred.