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LAUNCHXL-F28027F: F28027F gets very hot

Lotfi BAGHLI
Intellectual 870 points
Part Number: LAUNCHXL-F28027F


Hi

My student had some voltage issues on the connexion pins (I don't know exactly what)

but now when powering from USB / emulator it consumes 0.9A and USB voltage drops to 4.8V... then the launchpad stops working (I thing the emulator can't maintain the 3.3V )

I tried powering from an external 10V DC power through an EVM8301 that I put on TOP of the Launchpad, this way (I think that the voltage regulator 3.3V on the EVM is much powerful and maintain the voltage even if there is a large current that is thrown from the 10 DC supply : 0.5 A ! of course without any BLDC motor on the EVM )

and the F28027F gets very very hot after 2 seconds.. you can't touch it

so I cut the power, tried several times, same, there is no visible damaged parts (C5 L4 C20...) near the 27F

Do you think if I just desolder and solder another 27F, I will get the board working or I just throw away the Launchpad ?

  • 0
    Guru 30330 points
    Lotfi,

    Yes, try that out. You can check for shorts after the MCU has been removed. Also, please check the LDO electrical damage there.

    Worst case, you have to order a new LAUNCHXL-F28027F. However you may be able to find the failing component and replace it. Looks like a great teaching experience on soldering and HW debugging for the student :)

    Thanks,
    Mark
  • 0 in reply to Mark Labbato
    Intellectual 870 points
    Hi Mark,
    What is puzzling me is that the 27F stil works (4 PWM Leds are switching) while it temperature is rising, I just let it powered for 3 or 4 seconds max... so the device is not all dead, the LDO is ok because when I unplug the JP1 3.3V jumper and power form the USB, I have 3.3V steady state
    and when I power from the EVM8301 I have the 27F operting but drastically increase its temperature until I switch the power off after few seconds
    very strange
    I checked the ti estore 27F cost more than 7 USD !
    I asked for free sample account, I am waiting for the answer but if it is negative, it is better to buy a whole launchpad than trying to desolder/resolder such tiny DSC.
    Bye
  • 0 in reply to Lotfi BAGHLI
    Guru 30330 points
    Lotfi,

    If the student potentially put excessive voltages on a pin, that specific pin may have some internal damage. You can probably check for shorts between that device pin to ground if you remove it (by carefully touching each pin with an ohmmeter referenced to a GND pin). If a single pin is sinking an excessive amount of current, the junction temperature will creep up until it exceeds the Datasheet limits and finally fails. Without having the part in my hands, that sounds like what is likely happening.

    Thanks,
    Mark