ViewSonic VG920-1 Service Manual page 71

10. Schematic Diagram
+5V
C701
NC
+12V
C706 C707
GND
+
0.1uF GND
100uF/25V +12V
GND
+5V
+5V
3,4 +5V
GND
C710
C709
+
0.1uF 100uF/25V
R706 NC
Adj_BACKLIGHT
R707
4.7K
+3V3
R716 R717
10K
10K 1/16W
NC
R725
4 on_Panel
4.7K 1/16W
C718
0.1uF
ViewSonic Corporation
SOT-223
U701
+3V3
NC/LT1117-18
3 2
VI VO +3V3
4
VO
C703 C704
+
100uF/25V NC
BL_ADJ(DC) R31 C51 R32 R29 R33 Q4
0V ~ 3.3V 4.7K 1UF 0 X X X
0V ~ 5V 4.7K 1UF X 1K 4.7K MMBT3904
BL_ADJ R31 C32
P W M 47 N.C
D C 4K7 1uF
+5V
R708
+12V 4
CN701
10K 1/16W
1 2 BL_ON R710 NC
3 4 BL_ADJ
5 6 +12V
GND
7 8 C711
+5V
9 10 R712 4.7K 1/16W
11 12 GND 0.1uF
Q703
PMBS3904
CONN
VCC5V
R701
1K 1/16W
R705 4.7K
1/16W
Q701 C708
PMBS3904 1uF
1/16W
P.S: The 1N4148 Vf=0.7V~1V can't meet
LDO spec. The BAT42, Vf is OK but the
If=200mA(forward current) can not
meet current spec.
For RSDS and Panel VCC=12V
+3V3
+5V
VLCD
VLCD 5
+5V +3V3
R714 R715
1/16W NC
R721 R722
Q704
R723 51K 1/16W AO3401L 0 1 / 16W NC
Q706
C715
4 on_Panel_12V
PMBS3904
0.1uF C717 R727
+
10uF/16V 10K 1/16W
Confidential - Do Not Copy
68
H1 H2 H3
9 5 9 5 9 5
9 5 9 5 9 5
4 4 4
4 4 4
TP TP TP
+5V
R711
10K 1/16W
on_BACKLIGHT 4 3,4 +5V
3,4 +5V
D704(SSM12L) Vf=0.38V and If=1A.
D704
So when system power on, the
SMAL140
system loading is about 400mA
(3.3V is about 200mA and 1.8V is
about 200mA), So D35 changed
from 1N4148(or BAT42) to
SSM12L(schottky diode).
+5V
+5V +12V VLCD_12V
VLCD_12V
R718 R729 R719
NC/10K NC/10K NC/10K
Q705
R724 51K AO3401L
R726 NC/4K7 C716
Q707
0.1uF
PMBS3904
C720 C719 R728
+
NC/0.1uF NC/10uF/16V NC/4K7
VG920-1
VCTRL
R702
51 1/16W
VCC1.8
C702
+
4.7uF/16V
D701
1N4148
B R703
Q702
2K 1/16W
D702 CHT2907
1N4148
C705
1uF/16V R704
100 1/16W VCC3.3
+5V PC5V
Recommond to used "Blue" parts circuit
for VCC1.8V if you want to suppoert DDC
PC5V 3
function when system power off
R732 R709
+5V 10 1/16W 0 1 / 16W
D703
TO-263
BAT54C
U702
3 2
VIN VOUT
4
VOUT
1
ADJ
R713 C712
C713 AIC1084-33PM C714
+
NC
0.1uF 100uF/25V 0.1uF
R720 0 1/16W
12/21 MODIFY
+5V +12V
5
R730
R731
0 1/16W NC
Model
Title
Date
4
VCC1.8 4
VCC3.3 4
VCC3.3
VCC3.3 4
ViewSonic Corporation
POWER
Rev: