ViewSonic VS11354 Service Manual page 20

2V to pin10 of IC501 enables the IC and activates the striking timer. The SSTCMP pin of IC501 performs the soft
function, the C511 set the time of SST. The operation frequency determined by external capacitor C512, C521 and
resistor R508 connected at CT pin of IC501. C515 connect the TIMER pin of IC501, the capacitor to set striking
time and shunt down delay time. DRV!, DRV2 output for power MOSFET U501, U502.
2.OZ9938 provides two drive signals forU501, U502, and they work in push pull topology driving, two
transformers are connected in parallel with each transformer driving two lamps in series.Turningeach N-Channel
MOSFET "on/off＂ complementarily, produces an alternating current through thetransformer primary and
secondary. The "on＂ duration of the switches determines the amount of energy delivered to the CCFLs. R504,
C504, R505, C505, R532, C529, R530, C522 are snubber networks, they suppress Voltage transient spike in drain
of power MOSFET.
3. R506, R510, C509, C513, C514, R525, R531, C528, C525, and C527 are connected betweenhigh voltage
output connector and ground, the divided AC voltage is inverted DC voltage through D502, D503, D508, and
D509.The sense voltage feedback to VSEN (pin 6 of IC501) for an over voltage/over current condition during
normal operation. R528, R533 are current sense resistor, current sense signal feed back to Isense (pin 5 of IC501)
for lamp "ON＂ detection.
4.3 I/F Board Circuit
4.2.1 Power Input
+5V is from the power board and supply for U101(LD1117AL-3.3V)､U105(TSUM56AL-1) and panel.
+3.3V output is generated from +5V through C101 and C103 filtering, and U101 outputs. +3.3V is used
for U105 (MCU & Scaler: TSUM16AL). +1.8V output is generated from +3.3V through U102 outputs.
+1.8V is only used for U105.
4.2.2 MCU & Scaler(TSUM16AL)
The frequency of XTAL1 is 14.318MHz. U105 # 48 is defined as panel-enable. When the I/O port is
high, Q101 and Q103 are conducted. And then after C108 and C109 filtering, obtain the voltage of VLCD,
which will be connected to CN104. U105 # 85 is defined as CCFL-enable. When the I/O port is low, Q106
is pulled up and the backlights are on; When the I/O port is high, Q106 is conducted and the backlights
are off. U105 # 35 is defined as DET-VGA, connected with CN103 #5. U105 # 84 is a pin of hardware
reset. U105 # 54-# 55,# 58-# 65, # 67-# 74, # 77-# 78 output LVDS digital data of 8 bit to panel control
circuit through CN104. U105 # 86 generates a PWM waveform by regulating the duty to control the
brightness of the backlights.
U103 is EEPROM used for saving EDID data, which is connected by SCL and SDA pins with # 31 and
# 30 of TSUM56AL-1.
U106 is a flash memory, U106 # 2, # 1, # 6, # 5 are the communications with U105 # 37-# 40.
U108 is EEPROM used for saving user's OSD setting. U108 is connected by SCL and SDA pin with # 44
and # 43 of TSUM16AL.
4.2.3 VGA Input
Signal R, G, B input through CN103 #1, #2, #3, and C112, C113 and C114 filtering the high frequency
noise. Signal HSYNC and VSYNC input through CN103 #13 and #14, and C125, R137, C126, R136
filtering. Then the analog signal enters U105, and then U104 deals with it internally. In addition, TVS101,
TVS102, TVS103, TVS104 (the four are BAV99), ZD101, ZD105, ZD106, ZD107, ZD108(they are
constant voltage diode of 5V6) are ESD protector. Signal DDC-SCL inputs via CN103 #15, and then
passes through ZD101 for ESD protection, goes into EDID EEPROM IC U103. Signal DDC-SDA inputs
via CN103 #12, and then passes through ZD107 for ESD protection, goes into EDID EEPROM IC U103.
CN103 #5 is defined as cable detect pin, this detector realizes via R124 and U105 # 35,The PC-5V of
U103 is supplied by PC via CN103 #9 with D103 for ESD protection, or supplied by Monitor self via
D103.U103 is an EEPROM IC, which is a kind of memory and used for saving EDID data.
4.2.4 Button Control
Button "Key-Power" is defined as power on/off, which is connected to U105 # 90 through CN105 # 6.
Button "Key-2" is defined as two functions of selecting and adjustment, which is connected to U105 #94
through CN105 # 5.
Button "Key-Up" is defined as plus, which is connected to U105 # 95 through CN105 # 8.
Button "Key-Down" is defined as minus, which is connected to U105 # 99 through CN105 # 7.
Button "Key-1" is defined as two functions of menu and exit, which is connected to U105 # 89 through
CN105 # 4.
LED indicator on the front bezel is defined as follows:
a. When press button "Key-Power", U105 # 91 is pulled down and U105 # 92 is pulled high, so Q102 is
conducted and the LED indicator is green.
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