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PCA9535

mark siejka
Prodigy 10 points
Other Parts Discussed in Thread: PCA9535

We are designing a product with mutliple PCA9535 I2C port expanders. To ensure a clean SCL signal at the PCA9535's, we drive the SCL from the master, with a pullup, into a clock driver. From the clock driver we drive directly into the SCL pins of the PCA9535. Since the input to the PCA9535 is not from an open collector anymore, but a clock driver, do we still need pullups on the SCL inputs? Also if the ports are outputs do they need pullups?

  • 0
    Mastermind 7395 points

    Hi,

    1) Did you see that the device is not recommended for new designs?

    2) You don't need a pull up for SCL coming from the clock driver. However, I am not sure that a clock driver is really needed and you should check what happens to the timing of the SDA vs. SCL signals since now SCL has a delay

    3) The outputs of the device are of the totem pole type, or push pull, namely they have high side and low side drivers so they DON'T need pullups