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TLC1543: TLC1543

Michael Gadilov
Prodigy 30 points
Part Number: TLC1543

Hello, 

The subject ADC is part of our PWB’s that that are assembled by our subcontractor. Recently we’ve experienced constant failures during our final tests. The strongest hypothesis is that the failure caused by ESD damage. We are looking for TI failure analysis. Our request for Failure Analysis to the distributor (Rochester Electronics) was denied. The manufacturer's analysis is very crucial and is required to point us in the right direction. Any attempt without out it is a guess. We may introduce improvements, but we can't know if any of them will resolve the issue

Is there a way to send our parts for Failure Analysis, bypassing the distributor?

  • 0
    TI__Mastermind 24618 points
    Michael,

    I can help you with a failure analysis. Before we do this, however, can you send me a schematic of your design (or the section in question)? The main thing that I want to determine is if there are pins that go to external connectors, and/or are there pins that can have power applied before the supplies are powered up.

    Ideally with ESD/electrical overstress issues it is best to look for application issue first. If we see something in the application that looks like it may be a problem we can recommend an application fix.
  • 0 in reply to Art Kay
    Prodigy 30 points

    Hello Art,

    Thanks for your response and sorry it took me time to reply to you. We tried to look into our application based on your questions to see if there is an issue, but don't find any, yet.

    Please see attached schematic of our design. Item U92 is reference to TLC1543. On this PWB there are 5 similar ADC's, but only this location failing consistently.

  • 0 in reply to Michael Gadilov
    TI__Mastermind 24618 points

    Michael,

    Some observations that I make based on your schematic:

    1. The analog supply is 5V, and the reference is 2.5V. Based on this the absolute maximum input voltage is 5.3V. Any input exceeding 5.3V could damage the device.

    2. Most analog input is driven by an op amp. I don’t see the supply voltages on the amplifiers. Are the amplifiers supplied by more than 5V? If they are greater than 5V this could be what is causing the damage.

    3. Assuming the amplifiers are powered by 5V or less, it is possible that a transient input voltage is passed through the amplifier. Are the amplifiers damaged by the electrical overstress as well?

    4. There are two inputs (A4 and A5) that are connected to other signal sources. I doubt that these are the source of the electrical overstress as they have large series resistors on them (22.1k).   What are these lines connected to?

    5. Input A9 is connected to “PM1_FAN_VOLTS”. I do not see a series limiting resistor on this input. This input may be something to look at as I think of a fan monitor as potentially having an inductive kickback and potentially a large transient voltage. Can you add a series resistor here or a clamp diode?

    6. Generally I don’t expect the digital inputs to be a problem. Perhaps the only exception to this would be if the digital signals are connected to some external card or digital source as opposed to an microcontroller physically located on the same PCB.

    7. The only other considerations are:

      1. Power supply glitches. A TVS diode on the supply is usually helpful with this.

      2. ESD damage. Based on the fact that you have the same device in other locations that do not get damaged I doubt that it is ESD.

      3. Some kind of PCB layout issue that couples high energy magnetic field near this device and induces a large voltage.

    Please look through the list above and let me know if any of the items gives you some ideas as to the potential source of the issue. If we cannot find any application issue we can move to FA.  However, I think it is likely an applications issue as you are only seeing this problem on one of five sites.

    Thanks

    Art

  • 0 in reply to Art Kay
    Prodigy 30 points

    Hi Art,

    Thanks a lot for your detailed review. Although there are many interesting ideas that worth to look into, and our ENG team working on it already, but this design was working for several years with no issues. Also similar applications have been implemented in other design. This particular assembly have 5 TLC1543, and only this location is failing. Another piece of information that we got from our subcontractor that those parts were ordered from the alternative distributor Rochester Electronics. Replacement of this part is fixing the issue.  In the attached picture you can see the left part (SS) is the one that fails and on the left (NL) is a replacement. So it will be appreciated if we could go forward with the Failure Analysis and in addition to that would you be able to confirm if this is not counterfeit parts?

    Thanks again for your support,

    Michael