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PCA9557: about PCA9557 and TCA9557

Vera Mao
Expert 5065 points
Part Number: PCA9557

Hi dear supporting team,

I heard there is a bug on PCA9557 , and it is revised on TCA9557, may I know what the bug is? 

and are these two chips fully pin2pin compatible?

Customer found PCA9557 has very high requirement on POR,  from d/s, if the residual voltage is lower than 0.2V than it can be POR sucessfully, so just double confirm with you, if the residual voltage is 0.1V, could the POR work normally?

and for the reset pin, could it  work well to reset the internal stae machine? 

tks a lot!

  • 0
    TI__Mastermind 49110 points
    Hello Vera,

    "I heard there is a bug on PCA9557 , and it is revised on TCA9557"
    -It doesn't seem like we have a TCA9557.

    "may I know what the bug is? "
    -The two issues on the PCA9557 are the POR errata and the RESET errata both in the datasheet.

    "are these two chips fully pin2pin compatible? "
    -What are some of the requirements the customer has for their I/O expander? Maybe we can find a P2P replacement? What package are they currently using(size too).

    "Customer found PCA9557 has very high requirement on POR, from d/s, if the residual voltage is lower than 0.2V than it can be POR sucessfully, so just double confirm with you, if the residual voltage is 0.1V, could the POR work normally?"
    -POR is required to be pulled below 0.2V, so 0.1V will work assuming the ramp up time is also followed.

    "and for the reset pin, could it work well to reset the internal stae machine? "
    -reset pin does reset the internal state machine.

    -Bobby