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  • TI Thinks Resolved

TCA9509: Connect TCA9517 to TCA9509

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Replies: 3

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Part Number: TCA9509

Hi Expert, 

Can we use the B port of TCA9517 to dock the B port of TCA9509, is there a problem?

Thanks,

  • Hi Oliver,

    B side of TCA9517 to B side of TCA9509 is okay. Just make sure you don't have series resistance infront of the TCA9509 B port as this may interfere with its VoL and become larger than the ViLc of the TCA9517. Assuming the logic levels are okay, I don't see a problem.

    Thanks,

    -Bobby

  • In reply to BOBBY:

    Hi Bobby,

    Customer add PCA9546A between PCA9306 and PCA9617,  but no detail input/output range in PCA9306 datasheet.

    Could you give a comment to below topology too? Thanks.

  • In reply to Oliver Ou:

    Hi Oliver,

    PCA9306 does not redrive a signal, it is basically the same thing as the PCA9546A acting as a passive through element when enabled. This is why there is no input/output data in the datasheet. There will be a slight shift up from the 'input' to the 'output' due to parasitic resistance between the two sides of the device. Basically the shift up will be a function of Vshift = IoL(through device) X Ron. This shift is typically very small because Ron of PCA9306 is also very low.

    Since this is all on the A side of the 9617 (thanks for choosing B version btw) I don't suspect we'll see issues in terms of input and output. 9617 has a VERY strong pull down so it should be able to pass a suitable low from A side (9617) to the 1.8V logic 'EXpander IC.' Minor shifts upwards due to 9546A pass element and 9306 pass element.

    -Bobby

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