Can anyone help me look into the PCB power supply issue?

Cisjy

Can anyone help me look into the PCB power supply issue? [Copy link]

I want to connect an external power supply to the finished STM32. I plugged in a 12V power supply. When the VCC GND in the picture is not connected, the voltage can be measured to be reduced to 3.3V. However, the red line VCC GND in the picture seems to burn out when it is connected to the STM32 development board AMS1117. I tested it again and the output is 12V (my development board also burned out ). Is there something unreasonable about my power supply design? Please advise

吾妻思萌

Is the right vcc connected to vout?

吾妻思萌

Vin is 12v? It seems to be connected in reverse.

beyond_笑谈

The internal equivalent circuit block diagram and pin definition of AMS1117 are as follows. The second pin is VOUT. According to the failure description, it seems that the fourth pin is floating?

Cisjy

Azuma Simeng posted on 2024-5-25 15:00 Is the right vcc connected to vout?

I don't quite understand. The VCC on the right is 3.3V after voltage reduction.

Cisjy

beyond_笑谈Published on 2024-5-25 15:57 The internal equivalent circuit block diagram and pin definition of AMS1117 are as follows. The second pin is VOUT. According to the failure description, it seems that the fourth pin is floating ...

I have tested it with a multimeter, and both pin 2 and pin 4 of AMS1117 can step down and output 3.3V. As soon as the red part in the picture is connected to STM32 (I have also tested the two pins of the red part with a multimeter, and they are normal 3.3V GND), AMS1117 burns out directly. Are there any other problems with the circuit?

Cisjy

Azuma Simeng posted on 2024-5-25 15:01 Vin is 12v? It seems to be connected in reverse

Vin is 12V and vout on the right is 3.3V, so connect it to VCC

damiaa

There is something wrong with your idea.

Although the AMS117 can input a maximum of 12V, the output is 3.3V. The voltage difference is so large, and the AMS117 is a voltage regulator, so a lot of power is consumed on it. Of course, it is easy to burn out.

It is best to use DCDC. The voltage regulator is suitable for circuits with small input and output voltage difference, such as 5V input and 3.3V output. That is generally no problem.

The simple solution is for the OP to find a 5V power supply and plug it in to solve the problem of large input and output voltage difference.

If there are other problems such as reverse wiring, please correct them yourself.

Cisjy

damiaa posted on 2024-5-28 09:06 Your idea is wrong. Although the ams117 can input a maximum of 12V, the output is 3.3V. The voltage difference is so large. The ams117 is a voltage regulator...

Thanks, I'll buy a 5V one and try it out