Vostro 3668

The smoke come out when I power on 

i still need help plz help on this 

While it might be possible to replace that chip, it may not be possible for a user to do it himself/herself. It likely is not user-replaceable, as it may be soldered to the motherboard and require specialized tools and skills to remove and replace. Plus, you'd need to find a source for a replacement chip.

If that chip was smoking, I'd suspect that that may not be the only damage. So, even if you could replace that chip, the system might still not work and the motherboard might need to be replaced.

Do you know why the chip was smoking? Did you change any components? Did you change the power supply?

Also, Vostro 3668 is a desktop computer, but you posted in the Laptop area. Did you make a mistake with the name/model of the computer? Do you have a laptop or a desktop?

Look on EBay -- boards for this desktop system run $100-150.  You won't be able to repair the system yourself, even if you can find a schematic for purchase due to the limited to no availability of repair parts.  

Before you replace the board, you may want to consider replacing the power supply as well (or test it if you can find a power supply tester that will work with your power supply).  The failed component may have died due to a power issue (or conversely may have damaged the power supply itself).