STM32L4 Fault Power (over current)

[Doc97]

Hi,

my dear STM32L4 (BL475E-IOT01A) was working until yesterday, but for an unknown reason today it does not work anymore.

When i connect the micro usb to the ST-LINK the LD7 is turned on and remains red.

 

the datasheet says it is a Fault Power.

 

The connector is getting hot pretty fast: indeed I measured the current on the IDD pins by removing the jumper from JP5 and it reports around 650mA, which (correct me if I'm wrong) is too high.

 

I think the ST-LINK part of the board is still working since i can connect it to STM32CubeIDE and even perform a firmware upgrade, but the MCU part is not recognized at all; I can read the FAIL.TXT file from the PC which contains "The interface firmware FAILED to reset/halt the target MCU ".

Since I'm not a genius at electronics I'll ask you: do you have any idea of what could have happened? What steps should I perform to figure out the problem? Do you think the board is fried?

I've also tried to powered it up (changing the power jumper) with an external power supply either from the Vin pin (9V) or the 5V pin but in these cases nothing happens, not even a single led light.

Any help is appreciated.

[Uwe Bonnes]

When powered from an external power source, does the target get hot? In that case, it is broken, often caused by overvoltage on some pin.

[Piranha]

Check the current consumption while holding the RESET button. If it's normal, then try "Connect Under Reset" and do a full erase of the MCU.

[Doc97]

Tried, still ~630mA.

STM32CubeProgrammer can see the board but fails to connect with "Error: No STM32 target found!", therefore every action such as "full chip erase" fails.

I suspect there's an electrical failure or short circuit somewhere...

[Uwe Bonnes]

Consider you fried the STM32!