STM32 Nucleo-64 for STM32L073 gets very warm

[KKark]

I got a STM32 Nucleo-64 for STM32L073 board from Farnell. A few seconds after I had connected it to my PC via USB, it got so warm that I could not touch the CPU. They then send me another one, but it has exactly the same problem. I have tried setting JP1 on, which should limit the max current to 100 mA, but then the PC says that an USB device need more power. The board also gets warm with J1 on.

I then tried with an external 5V supply with current limiter, without USB connected. But it draws more than 2A when I turn off the current limiter.

[Uwe Bonnes]

You have some hidden way to fry your CPUs. Are you talking about the F103 CPU in the stlink part or the L073 target. You can easily fry some CPU by applying a voltage to high to some pin. If beside the USB cable nothing(!) was connected to the Nucleo, check the voltage on the USB cable. If something was connected, try on a new board with nothing(!) connected and having checked the USB voltage before.

[KKark]

Hi Uwe I have checked my USB power and it is spot on 5.0V. I connected an other ST Eval board (STM32F7508-DK) also with nothing else connected, and measured the USB power on that one. I have just received and unpacked the second STM32 Nucleo-64 for STM32L073. Connected it with nothing else but the USB connector, and the problem was there after a few seconds. It is not only the STM32L073 that get warm, it’s also the stlink chip, but especially the U1 chip (the 3.3V regulator) gets extremely warm. It is strange, that I now have two similar boards that has the same problem, and I have not applied anything to any of the other pins. Best regards, Klaus Karkov KK Data Danmark ApS Munkebakke 13 DK-3230 Graested Denmark Mobile: +45 4084 0833 klaus.karkov@kkdata.dk <> www.kkdata.dk Member of www.konsulent-klyngen.dk