Dell 2000FP Service Manual page 29

Dell 2000FP LCD Monitor Service Guide
DDC IC for both D-SUB and DVI
24C02 is used to support DDC2B function in both D-SUB and DVI ports. EDID data used for D-SUB and DVI
are stored in different 24C02's respectively.
EEPROM
A 24C16 (2048 bytes) is used to store user settings, such as user timing settings, brightness/contrast, color
temperature, etc.
DC-DC converter
Buck Converter
+
R731
Fig.1 shows a typical Buck converter circuit. Q705 is a switching device. Q703, Q704 are a totem pole which
gets enough ability to drive P-MOS. When pin4 of Q705 is low, Q750 turns on. At high level, Q750 turns off.
So, pulse waveform will appear at D-terminal of Q705. L701,C711,C712,C713 and D701,D703 will transfer the
pulse to stable DC level.
PWM IC (TL1451)
Q703
2N3904
R737
R714
20K
3.3K
R715
22
Q704
2N3906
R733
2.7K
GND
R732
0
Q705
SI4431DY
1 8
S D
2 7
S D
3 6
S D
4 5
G D
D701
RB060L-40 RB060L-40
Fig.1
4
Confidential
Circuit Operation Theory
L701
68U
L703
OPEN
+ +
C713 C712 C711
100U 100U 100U
16V 16V 16V
D703
R719
1.1K
(1%)
+