Arduino nano every burnt a onboard chip

Using Arduino Microcontrollers
1

Dear community,

I have a small problem with a big consequence.
I made a PCB that can control led strings using a IRLB8721.
Also i have a 5v Power regulator a 7805C.
I use a power supply of 12v, the 12v is connected to the vin of the arduino.
The power regulator is powered from the 12v also, and is connected to the 5v of the arduino.
From this point i tried to test the PCB and the first connect nothing happends, the arduino works fine.
After i had disconnected it and connected it again it fries.

Maybe do you guys know what can be the case?
And can anyone tell me what chip this is, and what it is used for.

Hope that you folks can help me out here!

2

You can find the schematic in the documentation section here

3

Already found my problem. thanks for advance.

4

that's the 5V regulator module. for when you're using Vin to power the board.
Did you figure out why it fried? It's probably not happy with:

I use a power supply of 12v, the 12v is connected to the vin of the arduino.
The power regulator is powered from the 12v also, and is connected to the 5v of the arduino.

You should not connect both Vin and 5V...

5

Thanks for your answer, thats exactly what i thought what happend there!