Usb Trouble - LG L602i Service Manual

4. TROUBLE SHOOTING

4.8 USB Trouble

USB Initial sequence of L602i is :
USB connected to L602i -> USB_VBUS(Q401 Pin_4) go to 5V -> USB_D+(U400 Pin_1) go to 3.3V ->
48M Crystal on -> USB_DATA (TP_209) is triggered -> USB work.
USB_D+ is about to 3.3V?
Change the Main board
USB_DAT A
(TP209)
48MHz
(X200)
Start
NO
Cable is insert?
YES
NO
USB_VBUS is about
to 5V?
YES
NO
YES
NO
48M is run?
YES
- 96 -
Cable insert
Check Q401,USB cable
Check U400
Check X200
USB_VBU S
(Q401)
USB_D+
USB_D-