Usb Trouble - LG KU950 Service Manual

4. TROUBLE SHOOTING

4.9 USB trouble

USB Initial sequence of KU950 is :
USB connected to KU950 → USB_VBUS(D501 Pin_4) go to 5V → USB_D+(D501 Pin_1) go to
3.3V → 48M Crystal on → USB_DATA is triggered → USB work.
Cable is insert?
USB_VBUS is about
USB_D+ is about to 3.3V?
48MHz is run?
Change the Main board
D501
USB_VBUS
Start
NO
YES
NO
to 5V?
YES
NO
YES
NO
YES
USB_D+
USB_D-
- 110 -
Cable insert
Check D501,Q600,D601,
USB cable
Check D501
Check X300
X300 (48MHz)