Hello I'm new to STM32L152 MCU,
I had a custom board made after working on STM32L152-DISCO. My board was working well, was able to work on stlinkv/2 and IAR. After couple of days of working my STM32L152 , then all of a sudden few days later MCU got really hot and eventually my STLINKv/2 could not recognize the MCU (IAR throws this error) . MCU does not smoke nor leave black residue on the pcb just really hot.
Now I started to investigate as per the following.
- Put the boot0 pin to high and connected it to STLINK utillity , its able to detect the MCU.
- Tried erasing the chip thinking that some faulty line of code could be a problem. I use the STlink utillity to erase but it throws me a error stating Readout Protection enabled.
- Checking Option byte thing to disable the Readout Protection.
- So as to troubleshoot I checked the 3.3V on my switching regulator it was fine.
- Regulator was not getting that hot that was ok.
- So to speak that something wrong from the pcb or bridge is ruled out. I reconnected the power source thinking that there must be temporary glitch. Again the MCU gets really hot. So now I'm thinking may be MCU is bricked and I have a spare STM32L152VCT6 with me and removed the bricked MCU and re soldered the new one. Now the new one also gets really hot.
- Again repeated steps 1 to 5 with the new IC just get the same things.
Now I'm really freaking out, coz I could have bricked my replacement IC as well.(Not really sure though)
I had another spare pcb with me , so wanted to investigate if there is any pcb side issues.
- Checked the 3.3V and GND continuity. No beep sound that was good.
- Quickly resoldered all the required essential components.
- Before transferring the IC from PCB old to new, I again checked continuity 3.3V to GND , NO short.
- Transferred the IC from PCB Old to new. Now I get Beep sound between 3.3V to GND.
- Now 95% I'm convinced the replacement IC is also smoked.
- There are some peripherals connected to MCU like PCF8574 which should not draw lot of current. However could not verify it since I don't know how much current its drawing.
- Replacing a new IC on the new PCB will also yield failure and double blow.
If there is some one who can tell me what the problem is please let me know.