.If you're having issues using your iPhone, iPad, or iPod touch with iTunes, the USB communication to your device might not be working properly. Use the steps in this article if your device disconnects during syncing or you see one of these alert messages:
"iPhone has timed out" when syncing
An unknown error occurred when syncing
The USB device can't operate because it needs more power
"This device can perform faster" if you use a higher speed USB port
iTunes error 9 or error 2001–2011 while updating or restoring