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PCA9535: Application issues of chips

Tonyx.wu
Expert 2905 points
Part Number: PCA9535

The gpio of pca9535A was pulled down, causing an i2c abnormality

The P6 of the expansion chip was pulled down causing an i2c anomaly

There has been no change in the same design. The customer feedback before that the old batch of materials is fine, but the new batch of materials has this problem. The initialization of io expansion chip also fails.

Now we will temporarily remove R23 to solve this problem

Please help to think about what might be the problem and provide a solution, thank you!

  • 0
    Guru 276290 points

    The PCA9535A is not made by TI. Please clarify what chips you were using and are are using now.

    What exactly is the problem with the failed initialization? What are you trying to write, and what are the actual register contents?

    What happens on the I²C bus when P6 goes down?

  • 0
    TI__Mastermind 30453 points

    Hi Tony,

    Can we double confirm the chip in use? PCA9535 or PCA9535A by NXP? 

    Tonyx.wu said:
    There has been no change in the same design. The customer feedback before that the old batch of materials is fine, but the new batch of materials has this problem. The initialization of io expansion chip also fails.

    For the new batch of materials, is this issue repeatable across all devices of the new batch? 

    Is the customer using the power-on-reset functionality of this device? What specifically is the customer doing that causes the failure mode? 

    Regards,

    Tyler