Usb Trouble - LG U880 Service Manual

4. TROUBLE SHOOTING

4.9 USB Trouble

USB Initial sequence of U880 is :
USB connected to U880 -> USB_VBUS(U401 Pin_4) go to 5V -> USB_D+(U401 Pin_1) go to 3.3V ->
48M Crystal on -> USB_DATA(TP_200) is triggered -> USB work.
USB_D+ is about to 3.3V?
Change the Main board
USB_DATA
(TP200)
USB_D-
USB_D+
USB_VBUS
Start
Cable is insert?
YES
USB_VBUS is about
to 5V?
YES
YES
48M is run?
YES
NO
Cable insert
NO
Check U401,D401,USB
cable
NO
Check U401
NO
Check X200
- 100 -
X200(48MHz)