BenQ G2220HD - 21.5" LCD Monitor, Service Manual, Page: 40 / 47

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- LED Indicator on Front Bezel
a. When press button “power”, U108 #48 sends out a low potential, via R169, flow to CN104 #7 on
keypad, LED Green ON.
b. When in “Suspend” mode, U108 #1 sends out a low potential, via R166, flows to CN104 #5 on
keypad, LED Amber ON.
5.6.5 REALTEK CHIP U105 (scaler)
- U105 (RTD2555L) #21~#38 output 8 bit LVDS digital data to panel control circuit through CN103.
- U105 (RTD2555L) #44 outputs Brightness “PWM” signals to control CCFL brightness.
- U105 (RTD2555L ) #39 output PANEL_ENABLE to make Q104 conducted, and then make Q101
conducted, +5V flow to CN103#1~#3 as Panel VDD .
- U105 (RTD2555L) #20 output CCFL_ON/OFF ”H” and “L” potential to control Inverter on/off.
Please refer to RTD2555L Pin Assignments table in page
5.6.6 Regulator Circuit
- +5V is from switching mode power supply for Panel used.
- +3.3V generates from +5V through C101 filtering and U101 which is 3.3V LDO for
U102 ,U105 and U108 used.
- +1.8V generates from +3.3V through C102 filtering and U102 which is 1.8V LDO.