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PCA9546A: PCA9546A and PCA9517ADP schematic review

Mike Hsu
Intellectual 300 points
Part Number: PCA9546A
Other Parts Discussed in Thread: PCA9517,

Hi 

Can you help to review the following cirucit?

We find there is no ACK from slave device.

  • 0
    Guru 282670 points

    In that circuit, there is no slave device connected to the PCA9517.

    Anyway, please show an oscilloscope trace of the SDA/SCL signals at the slave.

  • 0 in reply to Clemens Ladisch
    Intellectual 300 points

    Could you review the circuit first?

    I will provide the waveforms later 

    Thanks

    Mike

  • 0 in reply to Mike Hsu
    Guru 282670 points

    There is no obvious problem in the part of the circuit that is shown.

  • 0 in reply to Mike Hsu
    TI__Mastermind 32693 points

    Hi Mike,

    PCA9546A:

    The schematic pinout seems to match up with the datasheet pinout. 

    SDA/SCL lines are properly pull-up through resistors to VCC. I do want to make sure that pull-ups are present on pins 12 and 13 on the input side of the PCA9546A. I think they are probably part of a different page in the schematic. 

    Local decoupling capacitors are present on VCC's. 

    It is unnecessary to tie address pins to VCC through 10kohm pull-up. These address pins can be directly shorts to VCC or GND. 

    /RESET is biased.

    PCA9517:

    The schematic pinout seems to match up with the datasheet pinout. 

    SDA/SCL lines are properly pulled-up through resistors to VCC.

    Local decoupling capacitors present on VCCA and VCCB. 

    As of now, I am not seeing any glaring issues with the schematic. Per Clemens' request, please provide scope captures of the I2C bus for further examination. 

    Regards,

    Tyler