Usb Trouble - LG U8290 Service Manual

4.11 USB Trouble

USB Initial sequence of U8290 is :
USB connected to U8290 → USB_VBUS(D520) go to 5V → USB_D+ go to 3.3V → 48M Crystal on →
USB_VP and USB_VN is triggered → USB work.
Cable is insert?
USB_VBUS is about
USB_D+ is about to 3.3V?
48M is run?
Change the Main board
Start
NO
YES
NO
to 5V?
YES
NO
YES
NO
YES
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4. TROUBLE SHOOTING
Cable insert
Check U404,D520,USB
cable
Check U404
Check X100