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TMS320F28035: TZ signal routing long distance

Howard Zou
Genius 12365 points
Part Number: TMS320F28035

Hi,

my customer is WIRE-AND OCP signal and route it to TZ for over current protection to stop PWM output.

The schematic is as below: I.BST&CAP_OCP is the signal routing to TZ of F28035 on the same PCB board.

Below schematic is on another board and routing I.BST&CAP_OCP through a connector to TZ of F28035. The distance is long, tens of centimeters.

Are there any risk of doing this? Any consideration need to be taken at this kind of situation?

  • 0
    TI__Genius 12365 points

    Now my customer observed TZ short to GND for some of their equipment.

    I.BST&CAP_OCP is routed from upper board to lower board through the wire shown below and route to TZ.

    Is this kind of configuration risky? How can we solve the problem?

    We suspect that it's damaged by ESD.

    My proposed solution include:

    1. add esd protector on this pin, could you please advise proper esd device? Any side effect?

    2. or add a transistor to act as a buffer. Any side effect?

  • 0 in reply to Howard Zou
    TI__Expert 8105 points

    Hi Howard,

    I am contacting an ESD expert with this post, please stand by.

    Regards,
    Peter

  • 0 in reply to Peter Galicki
    TI__Expert 8105 points

    Howard,

                 it is very difficult to answer questions like this. Any meaningful analysis requires access to the board. Also, it is only conjecture that it is ESD damage. Only PFA can say with some certainty if the damage is ESD or EOS induced. A wire that is “tens of cms” long is never a good idea to carry a digital signal. It could act as an antenna and pick up all sorts of noises in the system. Without knowing what damaged the system in the first place, we cannot comment on the protection mechanism being considered.

    REgards,

    Peter

  • 0 in reply to Peter Galicki
    TI__Genius 12365 points

    Sorry what does PFA mean?

    Can we do PFA with the broken device? Or we need to get the whole board to do analysis?

  • 0 in reply to Howard Zou
    TI__Expert 8105 points

    Howard,

    FA stands for Failure Analysis where the silicon is exposed inside the package by etching and then observed with optical end electronic sensors to determine failure mechanism under certain test conditions.

    Regards,
    Peter

  • 0 in reply to Peter Galicki
    TI__Genius 12365 points

    Peter,

    if it's caused by ESD, then what do you suggest to solve this problem considering the tens of centimeters wire is there?

    1. add esd protector on this pin, could you please advise proper esd device? Any side effect?

    2. or add a transistor to act as a buffer. Any side effect?

  • 0 in reply to Howard Zou
    TI__Expert 8105 points

    Howard

    Based on the feedback you have received I will close this post for now. You can always reopen it later if needed.

    Regards,
    Peter

  • 0 in reply to Peter Galicki
    TI__Genius 12365 points

    Peter,

    but the email I received answered neither of these questions.

    My understanding is that the damage may be caused by ESD.

    So I need your direct answer to the question:

    if it's caused by ESD, what's the suggested method to help solve the problem if the tens of centimeters wire is there?

    If you do not have other suggestions, then could you please help answer:

    1.Are there any side effect of adding esd protector on this pin? what requirement of the esd protector?

    2. or add a transistor to act as a buffer. Any side effect?

  • 0 in reply to Howard Zou
    TI__Expert 8105 points

    Howard,

    I believe Hareesh already answered this question, I am going to close this post

    Regards,
    Peter