Usb Troubleshooting - LG CU405 Service Manual

4.8 USB Troubleshooting

USB Initial sequence of CU405 is :
USB connected to CU405 power on → USB_VBUS(Q500) go to 5V → USB_D+ go to 3.3V →
48M Crystal on → USB_VP and USB_VN is triggered → USB work.
Power is on?
Cable is inserted?
Q500 4 pin is 5V?
USB_D+ is 3.3V?
48M clock is running?
Change the Main board
Copyright © 2007 LG Electronics. Inc. All right reserved.
Only for training and service purposes
Start
NO
YES
NO
YES
NO
YES
NO
YES
NO
YES
4. TROUBLE SHOOTING
Go to power on trouble shooting
Insert cable
Check Q500
Check U401
Check X200
- 91 -
LGE Internal Use Only