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PCA9548A: PCA9548A reset

Guangyan Liu
Intellectual 2130 points
Part Number: PCA9548A

Hi Team 

Good day !

My customer use the PCA9548A as the IIC switch , in their application , they found that , after the power on , the device work fine , It can work with the configuration , after they switch the channel and communicate with the load  , the PCA9548A will reset itself  and do not active , the only way to recover the problem is power off -on .

They want to test the load side signal , but if they use the Oscilloscope probe , the device will reset and stop communication. Multimeter is OK.

Here is the schematic 

Do you have any suggestions about this query ?

BR,

Leon.liu

  • 0
    TI__Mastermind 22835 points

    Hello,

    I'd love to help out. I have a few questions surrounding this issue.

    "...after they switch the channel and communicate with the load  , the PCA9548A will reset itself  and do not active..."

    Is this happening with every load, or with just one load? Is the customer activating one channel at a time, or is the customer activating multiple channels at once?

    "...the only way to recover the problem is power off -on ."

    Do you mean that using the RESET pin has no effect, but the device resumes working properly only after a power-on reset?

    What are your estimates for the capacitances of the buses? If bus capacitance is high (including total sum of capacitance for all selected buses), then it might result in the pull-up resistors being too weak. Section 9.2.2 Detailed Design Procedure of the PCA9548A datasheet (and the TI Application Note I2C Bus Pullup Resistor Calculation) offer detailed descriptions of the method of selecting your pullup resistors.

    Best,

    Danny