Usb Troubleshooting - LG KS20 Operating Instructions Manual

4.12 USB Troubleshooting

USB Initial sequence of KS20 is :
USB connected to KS20 power on → VBUS_5.0V(Q400) go to 5V → MSM7200 48M PLL work →
USB_DAT is triggered → USB_CTL_N go to 0V → USB work.
Power is on?
Cable is inserted?
C314 is 5V?
USB_CTL_N is 0V?
Check an U100 SMT status
by X-ray
Exchange U304 or
Change the Main board
And Retest
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NO
YES
NO
YES
NO
YES
NO
YES
4. TROUBLE SHOOTING
Go to power on trouble shooting
Insert cable
Check C314, CN300#16
Check U300 (pin 7)
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