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PCA 9555 problem

JM Esc.
Prodigy 20 points
Other Parts Discussed in Thread: PCA9555, TCA9555

hello,

I have a strange behaviour with PCA9555, this on is connected to ULN2003 driver and to relays, when switching some charge sometimes PCA9555 loose his configuration , in my case the 16 I/O are output, so it comes back to power reset configuration where I/O are input, I have decoupling capacitor everywhere needed, any idea to help me ?

regards

John

  • 0
    TI__Genius 9085 points

    Hello John,

    I don't understand. Sometimes the PCA9555 resets the registers to the default value in your system when you do not expect it? 

    Sometime when the PCA9555 is power cycled, or powered down and then powered up again rapidly, the registers can be set to random values. The TCA9555 does not do this. Switching to the TCA9555 may change what you are seeing, but I am still not sure what you are seeing in your system.

  • 0 in reply to Hattie
    Prodigy 20 points

    Hello Hattie,

    You understood correctly, sometimes for some unknown reasons, the PCA9555 lost his configuration so it returns to default config which are all inputs I/O, from my knowledge TCA9555 and PCA9555 was same design, but they might be some difference ?? I will try with TCA9555 and keep you informed.

    Thanks

    John