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TCA9517: TCA9517

Part Number: TCA9517
Other Parts Discussed in Thread: TCA9800, TCA9509,

Hi,

I connect wrongly two device side B to side B as you can see at the capture below:

<<  ??  >>

the secone device defected the I2C bus when I2C access is initated.

is there anything I can't do the prevent it (beside of course making ReLayout)?

when i insert the second device to Disable the I2C bus is working properly.

can you recomended on some soulation that can be work till we will make relayout (maybe with device to TCA9800)?

Best Regards

Shay Tevet

  • Hey Shay,

    "I connect wrongly two device side B to side B as you can see at the capture below:"
    It doesn't look like your picture was attached properly. You need to click on "Insert code, attache files, and more..." then click on attach picture to properly post a picture.

    Can you tell me what voltages you are using as well? TCA9800 supports up to 3.6V recommended (I don't think this device will work for you)

    I am assuming you place two buffers together with voltage offsets on both sides to each other. If this is the case, placing B side of TCA9800 and B side of TCA9517 will not work because nothing has changed. You could try TCA9509 [This device is the only one in our portfolio which has the offset on A side so it is likely your only solution if I understand your problem correctly] which has the buffered offset on the A side with a normal B side. One issue I could see is this device was not guaranteed to work when Vcca=Vccb so if this is the case for you, this solution may work but may not meet datasheet specs when you do this. Please be aware of that.

    Last thing to note is this device has an internal current source on the A side so you will need to remove and pull up resistors on the A side for this device to work.

    Thanks,
    -Bobby
  • Hi,

    Thanks for the Help,

    I hope now you can see the Scheme capture

    The Master I2C (2.5V) connected to First TCA9517 (U55) VCCA side.

    The VCCB (3.3V) of it connected to the I2C slaves device and to the Second TCA9517 (U62) VCCB side.

    If I understand your suggestion correctly, we can change the First TCA9517 (U55) to TCA9509 (removed the PU on side A) and it work properly,

    I'm I right?

     

    Best Regards

    Shay

      

  • Hey Shay,

    It looks like you can use TCA9509 to fix this problem now that I see the schematic. I would recommend using TCA9509 to replace U62 though. As the requirement is: VccA needs to be less than VccB-1V. Replacing U55 does not meet this requirement but replacing U62 does.

    Thanks,
    -Bobby
  • Hi,

    Thanks for quick respond and best solution.

    Regarding the Pull Up resistors on side A of TCA9509, I will removed it also as you mention.

    only for the knowledge if I don't remove it is it mean that it will not function well?

    Best Reagrds

    Shay

  • Hey Shay,

    "if I don't remove it is it mean that it will not function well?"

    That is correct, I suspect the device may oscillate if the pull up resistors are there (edit: when trying to pass a low from one side to another).

    Thanks,

    -Bobby