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TCA9539: TCA9539 interrupt issue

Pavel Heyets
Prodigy 40 points
Part Number: TCA9539
Other Parts Discussed in Thread: TCAL9539

Hi,

I'm using TCA9539QPWRQ1 for my application. 

The issue that I have is that TCA9539 is not raising INT when input state is changed.

According to datasheet, steady state of the IOs is INPUT. When I'm reading the input states via I2C everything is correct. If the input is LOW I read 0 if its HIGH I read 1. When I change the state of the INPUTS it should raise an INTERRUP on the INT pin but its not happening. 

The INT pin is pulled-up externally in my design, according to datasheet. 

Is there a need to configure it somehow? 

 

  • 0
    Guru 317370 points

    The interrupt output is active only while the current input state is different from the last read state, i.e., when an input changes and then goes back to its old value, the interrupt will deactivate.

  • 0
    TI__Mastermind 48308 points

    HI Pavel,

    Clemens is correct here. 

    TCA9539 asserts an active low interrupt on /INT pulling the pin to logic low state when an input changes state from its previously read state. 

    i.e. if the input pin changes from a 1 to a 0, the interrupt will assert, and /INT will fall to a logic low state. If the input pin changes back to a logic 1 before the input port register is read, the interrupt will de-assert, and /INT will rise back to a logic high through the pull up resistor. 

    If you find this a problem in your application, please refer to using the TCAL9539 which has the ability to latch the input state, preventing this issue on the interrupt pin. 

    Regards,

    Tyler