• State
  • Locked Locked
  • Replies 3 replies
  • Subscribers 32 subscribers
  • Views 395 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TCA9546A: Channels not working on TCA9546A

Pelle Lund
Prodigy 40 points
Part Number: TCA9546A


So I'm having some strange behavior with a TCA9546A.

I have two PCB's that's identical, and on one it works perfectly. On the other one it worked during first startup and initial tests. However now I lost one channel. CH0 is not responding at all. I have a poor oscilloscope that's not able to trigger properly, but I can see something happens on the line when try to access the channel with a test script. With a logic analyzer nothing happens, line stays high.

During this trouble shooting I also lost channel 2. And then channel 1.. And then 5 minutes later channel 1 and 2 was back, working as usual, but channel 0 is still dead. And 5 minutes later channel 2 is lost again. Channel 3 has been stable throughout.

I'm a little bit lost what could've happen and why it behaves as it is.

Vcc to the TCA9546A is 3.3v, channel 0, 1 and 2 is pulled up to 5v, while channel 3 is pulled up to 3.3v. Pull up resistors used is 4.7k. There is nothing else then the TCA on the incoming I2c bus.

Any explanation for this behavior?

  • 0
    TI__Mastermind 35648 points

    Hey Pelle,

    Given that one of them is functioning properly and the other isn't, I lean towards believing this is either a damaged device or there is some other issue with the board and they aren't actually functioning as identical as you think. 
    If you haven't already, I would try removing the non-working device and put a new one on and see if it starts functioning as intended. You could even remove the knowns good one and place it on the board that isn't working and see if the issue is gone on that board. That would indicate that there is probably some damage on that 2nd IC. If you wanted to you could also put the non-working IC on the working board and see if it follows the issue but since there may be damage on the non-working device, I can't guarantee that putting it on the functioning board wouldn't damage some other component that may be on the board too though if there's somehow like a higher current path somewhere so I'd prefer if we could just swap out the non-working device with a new one or the known functioning one first to see if that helps.

    Thanks,
    Rami 

  • 0 in reply to Rami Mooti1
    Prodigy 40 points

    Hello!

    Thanks for your reply. I'll replace it and try again. I'm just curious what could've caused this damage to the component? I know the answer to that is pretty much anything, but I want to avoid another broken TCA

  • 0 in reply to Pelle Lund
    TI__Mastermind 35648 points

    Hey Pelle,

    It's not going to really be possible to give a definitive answer here given the information. It could be a short from a soldering job, or likely even some ESD damage from handling the device without ESD protection, or some transient. 
    Since it started working and then stopped, it could be some over-voltage transient event. Since it sounds like channel 1,2 and 3 are the ones that stopped working and all of those are pulled up to 5V so it could be something with that 5V source. I'd monitor it and make sure it doesn't have any strange behavior or spikes in it. 

    Thanks,
    Rami