Usb Trouble Shooting - LG -P990 Service Manual

4.11 USB Trouble shooting

The sequence of LGP990USB is,
USB connected to LGP990
USB work
Block Diagram of USB & UART connection is shown below
START
Start
Cable is inserted?
Cable is inserted?
Yes
YES
C647 is 5V?
C647 is 5V?
YES
Yes
Lower FPCB
Lower FPCB
NO
No
USB_D+ is 3.3V?
USB_D+is 3.3V?
YES
Yes
Change the Main
Change the main
LGE Internal Use Only
USB_OUT_5V(C647) goes to 5V
NO
No
Insert
NO
Check Lower FPCB
No
Check Lower FPCB connector
connector
YES
Change Lower
Yes
NO
Check
No
- 111 -
USB_D+ go to 3.3V
General Path
Insert
Change Lower
Check
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4. TROUBLE SHOOTING
USB_DATA is triggered
Only for training and service purposes