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MSPM0L1106: VDD-Pin is going very hot (SOT-16 Version)

Beat Brand
Prodigy 40 points

Part Number: MSPM0L1106

I've soldered a MSPM0L1106 on a SOT-16 pin-breakout-board. This helps  prototyping on a breadboard. The TI-document 'MSPM0 L-Series MCUs Hardware Development Guide' describes, how the processor has to be connected (Figute 1-1). For communicating with BSL, I used a USB-UART-controller (9600-8-N-1). Out of the box, pin 13 and 14 (PA22/PA23)  will be used for UART RX/TX.
After sending the HEX-Sequence "80 01 00 12 3A 61 44 DE" I received response "F8". After sending again, I received something else and so on just for about 3 minutes. Then the VDD Pin (3.3V) has become very hot and the chip has gone... -  No problem, it's protoryping and so I've taken another chip and resoldered VDD-Pinto prevent overheating by a weak soldering. But there was the same behavor: The VDD has become very hot.

I think, MSPM0L is a very low energy microprocessor. Why can the VDD Pin become so hot without any activities? - Is there a workaround?

  • 0
    Guru 42695 points

    "Why can the VDD Pin become so hot without any activities?"

    You have a short somewhere. Is it hot before you send the  hex sequence?

    How much current does it draw?

  • 0 in reply to Keith Barkley
    Prodigy 40 points

    Thanks for the quick response
    For test purposes, I have already tried leaving out the pull-up resistor and the capacitors (so that no external components cause the short circuit). I also disconnected the RX/TX connections.
    However, under the microscope, I could see that shortly after applying a voltage of 3.3V to the VDD pin, the solder resist started to melt...
    I will try to check the current. Maybe there is still a short circuit on the board under the soldered chip. But I won't be able to test that until tomorrow.

  • 0 in reply to Beat Brand
    Guru 42695 points

    In any case, if this is a bench supply, you should have the current limit set to 100 mA or so, which is plenty for these chips.

  • 0 in reply to Keith Barkley
    Prodigy 40 points

    Many thanks for the tip.
    A measurement of the resistances between the contacts revealed astonishing results. Even though no short was visible under the magnifying glass, the resistances between the connections were very low at a few kOhms. Much soldering flux was used to solder the chip on a SOT-23-THN footprint by hand. After a thorough cleaning of the board, the resistances were then > 5 mOhm.
    To protect the board (and the microcontroller) I will still install a PTC fuse.
    Thank you very much

  • 0 in reply to Beat Brand
    Guru 42695 points

    A few kOhms is not going to cause excessive heating.

  • 0 in reply to Keith Barkley
    Prodigy 40 points

    2.8 kOhm between VSS and VSD. This was a little low and led to continuous heating.
    After cleaning, the resistance is greater and the heating is also gone.
    Many thanks for your support. - I will set the issue to resolved.