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1.2.2 Schematic Guidelines
Each RGB output (RED, GREEN, and BLUE) is terminated with one 150-Ω resistor near
the chipset from the DAC output to the board ground. A second 150Ω resistor should
be placed close to the CRT connector. Additionally, one 75-Ω termination resistor
exists within the display. The equivalent DC resistance at the output of each DAC is
37.5 Ω. The current output from each DAC flows into this equivalent resistive load to
produce a video voltage without the need for external buffering. There is also a
pi-filter on each channel that is used to reduce high-frequency noise and to reduce
EMI. In order to maximize the performance, the filter impedance, cable impedance,
and load impedance should be matched.
The host VGA controller in CPU board is weak device without strong ESD protection,
and therefore ESD and EMI solutions close to connector are must for VGA port.
CPU
CN
Board
VGA_R
VGA_G
VGA_B
VGA_DDC_DAT
VGA_HS
VGA_VS
VGA_DDC_CLK
Figure 1.2.1-1 Demonstration for VGA Application
D1
1
6
VGA_z_B
VGA_z_R
2
5
3
4
VGA_z_G
AZC099-04S.R7G
5.5A
GND_Chasis
SOT-23-6
I/O Board
RA1
RA2
RA3
150
150
150
1%
1%
1%
0402
0402
0402
PS1
SPR-P150
+V5_VGA
1.5A
0805
B5
600_100MHz
0402
0.3A
R1
0402
R2
0402
B6
600_100MHz
0402
0.3A
VGA_y _HS
+V3.3
GND_Chasis
VGA_y _DDAT
M1
0.1uF
16V
0402
B2
47_100MHz
0.3A
B3
47_100MHz
0.3A
B1
47_100MHz
0.3A
C1
C2
C3
10pF
10pF
10pF
50V
50V
50V
0402
0402
0402
B4
120_100MHz
0603
2A
VGA_y _DDAT
VGA_y _HS
0 5%
VGA_y _VS
0 5%
VGA_y _DCLK
C7
C8
C9
100pF
10pF
10pF
50V
50V
50V
0402
0402
0402
10
D2
1
6
VGA_y _VS
2
5
3
4
VGA_y _DCLK
AZC099-04S.R7G
5.5A
SOT-23-6
VGA_z_R
VGA_z_G
VGA_z_B
C4
C5
C6
10pF
10pF
10pF
50V
50V
50V
0402
0402
0402
D3
MBRX120-TP
1
2
1A
SOD-123
C10
100pF
50V
0402
+V5_VGA
M2
0.1uF
16V
0402
CN1
6
1
7
2
8
3
9
4
10
5
16
17
11
12
13
14
GND_Chasis
15
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