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SM470R1B1M-HT bare die and light

Anders Engman
Prodigy 60 points
Other Parts Discussed in Thread: SM470R1B1M-HT, TMS470R1B1M

Hi,

I'm using SM470R1B1M-HT bare die, and when debugging I use a microscope with ring-light. Question is if running the device under light might damage it? Does anyone have experiance with bare die TI microcontrollers and light?

Best regards,

Anders

  • 0
    TI__Guru 62930 points

    Photon exposure can increase leakage and possibly cause functional issues.   It is not expected to cause permanent damage.  However, it is possible that a bad functional state could cause damage.  We believe this would be unlikely.

    Regards,

    Wade

  • 0 in reply to Wade Vonbergen
    Prodigy 60 points

    Thanks Wade. You are probably right, the light is not the problem. The problem for us is that our chips keeps breaking.

    We have developed a couple of boards to evaluate functions for this product before the final board. We have one board where we can place both an LPQF-144 TMS470R1B1M and wirebond a bare die version of the same TMS470R1B1M or the high temp variant SM470R1B1M-HT.

    We also have the product version of the board where only the bare die versions can be placed. This product and the custom evaluation boards use both CAN interfaces avaliable on the uC.

    With the LPQF-144 TMS470R1B1M we have not seen any problems related to this, but both types of bare dies break thier CAN interface in the uC.

    After a short time of operation (minutes) the CAN connection to our PC software is lost. And if we measure with an oscilloscope on the R-pin on one of the CAN transievers, it is pulled quite hard to ground, while the other is driven to 3.3V. The one with R-pin at 3.3V seems to transfer data ok when the CAN is talking. But the one seemingly pulled low switches between 0.2V and ground when the PC talks over the CAN interface. Lifting the pin of the CAN driver makes the CAN driver function normally again. This tells me it is the uC that pulls the signal low, and must be broken.

    We are running the exact same code on the bare die versions and the LPQF. The LPQF works and the bare die dies, on both board types. 9 units of the TMS470R1B1M and one of the SM470R1B1M-HT has died this way. The units still accept programming and the code seem to be running.

    The Errata mentions problems with one of the CAN pins during self-test. But we never use the CAN selftest. And there is no mentioning of the symptoms.

    Could there be a problem having the CAN connected while reprogramming or something like that?

    Please assist me getting forward with this problem, thanks!

    /Anders

  • 0 in reply to Anders Engman
    TI__Guru 62930 points

    Anders,

    I am not aware of a problem like this happening before.

    Do you have a unit to test that you can shield from the light that you would expect to fail within minutes?

    There may be an influence from the light that we have not experienced prior.

    I would not expect any issue with connection to CAN while reprogramming.

    Are your schematic connections equivalent between all versions?

    It may be beneficial to move this thread to email vs forum.  Please reply to w a d e v b (at) t i . c o m.

    Regards,

    Wade