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Original question:

TCA6424A: What is the difference between TCA6424A and the TCA6424

TCA6424A: INT pin doesnt pull low

Gaurav Gothoskar
Prodigy 100 points
Part Number: TCA6424A
Other Parts Discussed in Thread: TCA6424

Tool/software:

Hello,

I am using the TCA6424A in the design.all ports are configured as inputs and the host is successfully able to detect the state change on each port. However, the INT pin stays high. it never asserts low even on pin state changes. I have two boards with 2 different versions of the IC. One chip is marked "L6524" which doesnt assert the INT and the other is marked "PH424A" which asserts the INT pin everytime. what is the difference in the markings and how can I fix it on t he IC on which the INT doesnt work.

  • 0
    Guru 278840 points

    When you want to know why the PCAL6524 does not work, you should ask NXP, not TI.

  • 0
    TI__Mastermind 31133 points

    Gaurav, 

    PH424A is the device marking for a TI device - TCA6424A. 

    For the L6524, this device is from NXP. It might be possible that the INT does not assert because you might need to enable the interrupts on power up. Otherwise, a change on the input might not reflect an interrupt. Double check their datasheet to see if that is the case. 

    Regards,

    Tyler

  • 0 in reply to Clemens Ladisch
    Prodigy 100 points

    While I am not expecting much customer service here, this reply is outright rude and derogatory. Maybe look at Tyler's reply and learn from him? Had I known this was a NXP part, I would have never asked on this forum (these boards were directly sent to me from the plant).

    Those people who are really smart are humble as well.....:)

  • 0 in reply to Tyler Townsend
    Prodigy 100 points

    yeah, I figured it out. Thanks for confirming. Maybe setting up a training session in customer service for our friend Clemens here wouldn't hurt too.   

  • 0 in reply to Gaurav Gothoskar
    TI__Mastermind 31133 points

    Hi Gaurav, 

    Thank you for your question. I am always glad to help out when it comes to semiconductors NXP or TI. If I don't know something about a competitor device, I can always refer to their datasheet or their tech service for additional help. 

    E2E is a public forum. There are engineers from a variety of different companies and organizations that can provide responses not just TI. Mr. Ladisch is a high contributor to multiple forums on e2e, however is not employed with TI. 

    If more questions arise, please feel free to direct message me on e2e. 

    Regards,

    Tyler

  • 0 in reply to Tyler Townsend
    Prodigy 100 points

    Hi Tyler,

    Is this issue only on the TCA6424 or is it present on the TCA6424A version as well. The exact part we are using is TCA6424ARGJR. should we be concerned about the INT issue?

    Thanks. 

  • 0 in reply to Gaurav Gothoskar
    TI__Mastermind 31133 points

    Hi Gaurav,

    It is recommended to stick with the TCA6424A version since the non-A is a NRND (not recommended for new design) device and has a couple of device errata. 

    TCA6424ARGJR should not present issues. The interrupt is enabled on power up, so a state change on the input should trigger the /INT pin appropriately. 

    I did look into the NXP device. I found this section in the datasheet. 

    It looks like on powerup for the NXP device, the interrupts are masked via register 54h/55/h/56h. In other words, the interrupts are disabled on system start-up. To enable the interrupts, the firmware would need to adjust so that it writes to these registers on power up for the NXP device. 

    Regards,

    Tyler