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TCA9545A: TCA9545APWR working not as expected

Kiran V Pillai
Prodigy 50 points
Part Number: TCA9545A
Other Parts Discussed in Thread: TCA9548A

Hi,

We are using TCA9545APWR - 4 channel I2C bus for two of our applications.

But sometimes we are facing the issue that I2C communication is not working properly.

We are enabling all the output channels, but we are using only one channel and the remaining channel interfaces are not populated on the PCB. Will this have any impact on the working channel ? Or is this a capacitance driven issue on I2C bus ?

If we bypass the IC,I2C is working as expected. TCA9545A.pdf

Please find the attached implementation of schematics & suggest the root cause of this.

Thanks & Regards

Kiran

  • 0
    Guru 317730 points

    Unused channels do not matter.

    Please show oscilloscope traces of the failing I²C signals.

  • 0
    Prodigy 50 points

    I2C is not failing every-time, but whenever it is failing we are just getting active 3.3V on SDA and SCL, there is no data transfer.

  • 0 in reply to Kiran V Pillai
    TI__Mastermind 26826 points

    Kiran,

    Sorry to hear that you're having some trouble. Without knowledge of specifically what is causing the failures and exactly what is happening, it's hard to address the situation. Unfortunately there are many ways to have a non-functioning I2C bus!

    When you say that there is no communication at all, do you mean that the TCA9545A is not responding to a read command? Is the I2C controller failing to communicate? Is there any abnormal ACK/NACK behavior that you're seeing?

    Note that the TCA9548A is an I2C responder. The controller on the bus provides SCL, even during reads. If you are not seeing any SCL signal, then this likely means that the controller is not executing a read command.

    Providing oscilloscope traces is helpful because it allows us to see potential problems with the integrity of the I2C signal.

    Best,

    Danny