[SOLVED]Burned TI 3.3/5V step-down controller repair

[dominicM]

So I have a laptop with localised water damage with no signs of life. It draws 5W at the wall. I tracked the issue down to
 tps51225c (datasheet: http://www.ti.com/lit/ds/symlink/tps51225c.pdf). It heats up almost instantly to too-hot-to-touch temp. There are what appears to be burn marks on the right side as pictured. After cleaning with alcohol it seems intact with all pins still soldered. The middle pin on the left is the 3.3V out and opposite side is 5V out. 3.3V out is working but 5V is shorted to ground. I can't see any other reason for it to be shorted than a damaged chip. Have I missed something? I can get a replacement chip no problem but is it likely the problem/only problem? What would a be a sensible next step in this repair and why? 

[Chalcogenide]

The first suggestion that comes to mind is to remove the chip and check whether or not the short to ground on the 5V rail remains. It could very well be an other component shorted that causes the controller to heat up that fast.

[dominicM]

That's a good suggestion, will try tomorrow to de-solder it. Assuming there is no short on the chip itself, what would you  try next?

[flolic]

Assuming there is no short on the chip itself, what would you  try next?

Connect external power supply to 5V rail, set current limiting to 2 to 3A and see what gets hot next.

[dominicM]

Thanks for all your suggestions. I only now gotten around to replacing the part, soldering was quite difficult but with some flux paste it wasn't so bad. The chip was the problem, and it all works as expected now, thanks again!

[Kjelt]

I would suggest to add a thermal two way sticker and a tiny heatsink on top of it.

[dominicM]

It does have a thermal pad which is why it was difficult to solder, is your suggestion due to possibly less than ideal soldering compared to factory?

[Kjelt]

No I was just thinking what the cause of failure was and since nothing else seems to be broken, overtemperature/overcurrent could be a viable cause.
On the other hand if it survived for >2 years already it probably is ok as is.

[dominicM]

Well it died because of water damage, it had clear burn mark as in the image.

[Kjelt]

Ah ok sorry overlooked that part of the description.