TQFP Atmega328p gets hot and won't let me upload the code

[Plecto]

Hi. I've used the TQFP atmega328p with my arduino a couple of times without any problems, but this last one is impossible to handle The circuit is very simple, I have the atmega328p TQFP chip, 16M crystal with two 22pF caps going to ground. I also have a 10k pull-up from the reset pin. Aside from this there are traces going different places (to two different ADC's, a temp sensor and to a LCD module), but none of these are connected. I have two 1uF decoupling caps on the board also. When I first tried it, I just couldn't upload the code (I get avrdude: stk500_getsync(): not in sync: resp=0x00). After testing both this and that I finally replaced the MCU with a brand new one (with a bootloader on it of course). I also tried to upload a code on this chip using a arduino shield I made and this worked fine. After soldering it to my PCB I was happy that I could finally upload my code, but after some seconds, the program stopped and the MCU started heating up! I replaced the chip again with an Atmega328 that I have previously used (which I knew worked), but the problem was still there. When I had the chip de-soldered I ohmed just about everything and I couldn't find any shorts or low impedance paths. I've also checked the PCB layout, made sure there are no shorts between the pins, the right voltages where it should be etc...

 

[nagkiller]

Post your hardware... Check the power supply voltage.

 

[Plecto]

Here's a picture: https://i44.tinypic.com/35mh3kj.jpg

The voltage is from the arduino board itself, I measure it to be 5.05V

 

[nandhu015]

The chip gets heated only when the supply voltage is higher in my experience.

Try changing power supply..

 

[pranam77]

If the chip get heated, 90% the chip is blown off or 10% chance that you are a bit above the margin of the Maximum specified voltage of the device.
Cheers

 

[josiphal]

For me, increased micro temperature during power up is related to somehow damaged chip (if everything else on board is OK).

 

[Plecto]

I can't see how the supply voltage is too high. First off, the voltage comes from USB and it goes through a regulator after that. Even if the voltage was too high, it wouldn't allow me to use the arduino with the standard DIP28 chip. I have measured it to 5.05V so the supply isn't the issue.

What I thought about was if several of the outputs were shorted to GND or +V (even thought I haven't found such a short), but I guess the outputs of the MCU is current limited? Also, what if I have a faulty crystal that has a higher frequency than what it says on it, can that create heat?

After talking about this issue on the freenode's #electronics chat, people seemed to start thinking that I've bought a bad batch of Atmega's. Thing is that the third chip I tried was taken from another project and the chip worked just fine on that previous project! And I also mentioned that I can burn the bootloader and upload code prior to soldering it to my PCB, the heating and errors occur after it is on the board. I guess I could try yet another chip

- - - Updated - - -

I solved it (I think)! While the chip was soldered to the PCB I checked if all the GND and +V pins were connected to the supply, and they were. To my suprice, when inspecting it while the chip was removed, GND pins 3 and 21 were not connected! I then checked Eagle and strangely enough, even though the schematic had wires going to these pins, they weren't actually connected I can now upload the code, but I still don't know how this could have been the reason for it heating up though, nor do I know why it needs so many ground pins

edit: Never mind, the success was short lived. The same symptoms have started appearing on this chip as well, I can no longer upload any code.

edit: I figured out something. The heating of the last three chips came after I uploaded a code that communicates with an ADC using I2C. I tried to connect the PCB to the arduino and then upload a clean code straight away and it worked, it doesn't heat up if there is no code on the chip. This is somehow caused by trying to use I2C.

 

[Plecto]

I would really like to know what to do here :S Is there anything to limit the current if I write I pin LOW and then connect it to +V? If it is, the only reason these chips fail and overheat is because their I2C interface was broken from the factory and I shouldn't be afraid of buying new ones and continue with my projects? If this was somehow caused by me, I really need to figure out what I did because I have all my TQFP projects on a stall now just because of this

 

[jayanth.devarayanadurga]

If you make a pin low and connect it to +Ve then you are shorting. You have to use resistors as you use for reset pin.