Dell 1909Wf Service Manual page 15

Service Manual
ZD203 Zener for ESD protection, via R210, goes into EDID EEPROM IC
U201 #5.
- CN201#15 is defined as cable detect pin, the detect pin can create a pull-low
signal send to U105#49pin via R216 to identity cable connection, if plug out
the DVI cable the U105#49pin will receive a high signal and system enter self
test mode when exit factory mode（the device must set at DVI input mode ）.
- U201 is an EEPROM IC which is memory and DVI input EDID data saved in
it ,the U201 power is supplied by PC via CN201#14 through D201, or supplied
by Monitor self via D201..
2.3.3 Buttons Control
- Button "Power" on right corner of front bezel connects to U105
(TSUM5PEHJ-LF ) #4 through CN104 #8 and R125, U105 #4 is defined as
power on/off.
- Button "+" on right corner of front bezel connects to U105 (TSUM5PEHJ-LF)
#120 through CN104 #2and R154, U105#120 is defined as "Plus".
- Button "-" on right corner of front bezel connects to U105 (TSUM5PEHJ-LF)
#121 through CN104 #3 and R155, U105 #121 is defined as "Minus".
- Button "Menu" on right corner of front bezel connects to U105
(TSUM5PEHJ-LF) #50 through CN104 #1and R153, U105 #50 is defined as
"Menu".
- Button "SELECT" on right corner of front bezel connects to U105
(TSUM5PEHJ-LF) #122 through CN104 #4, U105 #122 is defined as
"SELECT".
- LED Indicator on Front Bezel
a. When press button "power", U105 (TSUM5PEHJ-LF) #123 be send in low
Voltage, make Q107#3 sends out high Voltage to CN104#5 , and then to
keypad, LED blue on.
b. When in "Suspend" mode, U105 (TSUM5PEHJ-LF) #124 sends out a low
Voltage, make Q108#3 sends out high Voltage to CN104#7 , and then to
keypad, LED Amber on.
2.3.4 MAIN CHIP U105 (TSUM5PEHJ-LF)
- U105 (TSUM5PEHJ-LF ) #86~#77 output 8 bit even and #100~#91 output 8
bit odd LVDS digital data to panel control circuit through CN103.
- U105 (TSUM5PEHJ-LF ) #73 output PPWR "H" potential to make Q104
conducted, and then make Q101 conducted, +5V flow to CN103#1~#3 as
Panel Vdd .
- U105 (TSUM5PEHJ-LF) #109 output CCFL_ON/OFF "L" potential to control
Inverter on/off.
- U105 (TSUM5PEHJ-LF) #125 outputs Brightness "PWM" signals to control
CCFL brightness.
- TCLK by Crystal 14.318MHz input to U105 (TSUM5PEHJ-LF) #128.
- U105(TSUM5PEHJ-LF) #108 is RESET signals input pin
Please refer to TSUM5PEHJ-LF Pin Assignments table in page
2.3.5 Regulator Circuit
- +5V is from switching power supply .
- +3.3V is generated from Regulator U101 which is supplied by+5V via R101
14