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PCA9539: Some question about how to use PCA9539

Andy Liu3
Intellectual 2500 points
Part Number: PCA9539

Hi team,

I have some questions about how use PCA9539, please help me check, thanks.

1. Does the INT pin and the 16 IOs P0_0~7/P1_0~7 have to use VDD power? Is it possible to use different VDD power?
2. After the chip is reset during use, how will the subsequent 16 IO levels change? Will they change at the same time? Is it possible to latch the level status of some IOs and reset only one or a few IOs?
3. How to deal with the unused IO pin, can it be left floating directly? Will this affect other IOs of 9539?

Thanks a lot.

Best regards.

  • 0
    Guru 317280 points

    1. The I/Os tolerate voltages higher than VCC, up to 5.5 V, when they are configured as inputs (see section 8.2.3). Voltages lower than VCC will greatly increase the power consumption (see the ΔICC specification). The /INT output is open drain and can be pulled up to any voltage, up to 5.5 V.

    2. A reset changes all register to their default values. So all I/O pins are configured as inputs, i.e., they will float.

    3. Unused inputs should have a pull-up or pull-down resistor, or can be connected directly to VCC or GND if they will be never configured as outputs. Unused outputs can be left open.