Usb Troubleshooting - LG CU720 Service Manual

4. TROUBLE SHOOTING

4.12 USB Troubleshooting

USB Initial sequence of CU720 is :
USB connected to CU720 power on → USB_VBUS(U401) go to 5V → USB_D+ go to 3.3V →
USB_VP and → USB_VN is triggered → USB work.
Start
Power is on?
Cable is inserted?
U401 2pin is 5V?
USB_D+ is 3.3V?
Change the Main board
LGE Internal Use Only
NO
Go to power on trouble shooting
YES
NO
YES
NO
YES
NO
YES
[ USB Troubleshooting Flow ]
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Insert cable
Check U401 2Pin
Check U402
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