STM32 Heating

[prakashram72]

I have been working on a SMT32H747 MCU based HV PCB board. The power supply pins of MCU is only supplied with 3.3V (max can supply 3A). Moreover, I also connected MCU's VDD1V2 (1.2V) pins with 3.3V.

Issue noticed so far, MCU is heating too much. And damaged couple of IC.

Note - MCU is not loaded with any firmware, still heats up. I'm suspecting short circuit on power supply pins of MCU.

Can anyone help me finding short circuit nets here? Also provide me your suggestions. Thanks

MCU Power supply section image (Sorry for confusing schematic net names) https://imgur.com/U8ChMLy

 

[Harald Kapp]

Moreover, I also connected MCU's VDD1V2 (1.2V) pins with 3.3V.

Looks like the obvious error, doesn't it?

I'm suspecting short circuit on power supply pins of MCU.

Instead of suspecting, measure that with an Ohmmeter.

At first glance nothing obviously wrong with the schematic. Doesn't mean your PCB is correct. There may be errors in the layout or during manufacturing.

• Check a bare PCB (no components assembled) for any short circuits that shoudln't be there.
• Check the placement and the orientation of all components.
• Check the layout for errors like mirrored pad layouts. Especially when using double sided pcbs, make sure the pad layout on bottom is mirrored becaus the components on bottom are placed mirroted, too.
  Check the schematic for any floating inputs on the mcu. You should never leave CMOS inputs floating (not connected to an output, pull-up or pull-down resistor).

 

[danadak]

Is this part in latchup ? Possibly due to power supply sequencing not correct, or out of spec
pin V per below.....




Part dissipates > 1W, so not exactly cool to the touch unless heatsink.


Regards, Dana.

 

[Keonte45]

It looks like you are supplying 3.3V to both the VDD and VDD1V2 pins of the MCU. This is not correct and could be causing the issue you are experiencing. The VDD pin should be connected to the main power supply for the MCU, which is typically a higher voltage (e.g., 3.3V or 5V). The VDD1V2 pin should be connected to a separate low-voltage power supply, typically around 1.2V.

It's also possible that there is a short circuit somewhere on the board, which could be causing the high current draw and resulting in the overheating of the MCU and damage to other components. To try to identify the source of the short circuit, you could try using a multimeter to measure the resistance between various points on the board. If you find a low resistance between two points that should not be electrically connected, then you may have found the source of the short circuit.

In addition, you should make sure that all components on the board are properly rated for the voltage and current levels they will be subjected to, and that they are properly soldered to the board. It's also a good idea to add bypass capacitors to the power supply pins of the MCU to help filter out voltage spikes and reduce the risk of damage to the MCU.

I hope this helps! Let me know if you have any other questions.