AD8188 Просмотр технического описания (PDF) - Analog Devices
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AD8188 Datasheet PDF : 24 Pages
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AD8188/AD8189
RGB
SOURCE A
R
G
B
RGB
SOURCE B
R
G
B
5V
5V
5V
0.1µF
0.1µF 10µF
75Ω
4.99kΩ
4.99kΩ
IN0A DVCC
0.1µF
5V
75Ω
4.99kΩ
4.99kΩ
IN0B
VCC
AD8188
+
OUT0
–
0.1µF
5V
75Ω
4.99kΩ 4.99kΩ
IN1A
75Ω
4.99kΩ 0.1µF 5V
4.99kΩ
IN1B
+
OUT1
–
0.1µF
5V
75Ω
4.99kΩ
4.99kΩ
IN2A
IN2B
+
OUT2
–
TO A/D,
ETC.
0.1µF
5V
75Ω
4.99kΩ
4.99kΩ
HI = A
LO = B
SEL A/B
VREF
0.1µF
DGND VEE
OE
HI = ENABLE
LO = DISABLE
Figure 54. AD8188 AC-Coupling Using Separate Voltage Dividers
5V
5V
RGB
SOURCE A
R
G
B
RGB
SOURCE B
R
G
B
5V
100Ω
100Ω
VMID
75Ω
4.99kΩ
0.1µF VMID
75Ω
4.99kΩ
0.1µF VMID
75Ω
4.99kΩ
75Ω 0.1µF VMID
4.99kΩ
75Ω 0.1µF VMID
4.99kΩ
0.1µF VMID
75Ω
4.99kΩ
0.1µF
VMID
0.1µF 10µF
0.1µF
0.1µF 10µF
IN0A DVCC
IN0B
VCC
AD8188
+
OUT0
–
IN1A
IN1B
+
OUT1
–
TO A/D,
ETC.
IN2A
IN2B
HI = A
LO = B
SEL A/B
VREF
DGND
VEE
+
OUT2
–
OE
HI = ENABLE
LO = DISABLE
Figure 55. AD8188 AC-Coupling Using a Single VMID Reference
The circuit in Figure 55 can increase the crosstalk between
inputs, because each input signal creates a small signal on VMID
due to its nonzero impedance. There are several means to
minimize this. First, make the impedance of the VMID divider
small. Small resistor values lower the dc resistance, and good
bypassing to ground minimizes the ac impedance. It is also
possible to use a voltage regulator or another system supply
voltage if it is the correct value. It should be close to the mid-
supply voltage of the AD8188.
The second technique for minimizing crosstalk is to use large
resistor values to connect from the inputs to VMID. The major factor
limiting the value of these resistors is offset caused by the input
bias current (IB) that must flow through these resistors to the
AD8188 inputs. The typical IB for an AD8188 input is 1.5 μA,
which causes an offset voltage of 1.5 mV per 1 kΩ of resistance.
Rev. 0 | Page 18 of 24
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