Usb Trouble - LG CT815 Service Manual

4. TROUBLE SHOOTING

4.9 USB trouble

USB Initial sequence of CT815 is :
USB connected to CT815 → VCHG_VBUS(R409) go to 5V → USBH_SEL go to 0V(U404
Pin#10) → USBH_CS go to 1.8V (R403) → USBH_DM go to 3.3V (U404 Pin#7) →
USB_DATA is triggered → USB work
Cabl e is insert?
VCHG_VBUS i s about
USBH_DM is about to 3.3V?
USB_DATA(0) i s about to 1.8V?
Change the Main board
LGE Internal Use Only
Start
NO
YES
NO
to 5 V?
YES
NO
YES
NO
YES
- 108 -
Cable in sert
Check Z D401, U402,
FL401,R409
USB c able
Check U404
Check U403
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