Datasheet

Triple Differential Receiver with
Adjustable Line Equalization
AD8123
Rev. A
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FEATURES
Compensates cables to 300 meters for wideband video
Fast rise and fall times
4.9 ns with 2 V step @ 150 meters of UTP cable
8.0 ns with 2 V step @ 300 meters of UTP cable
55 dB peak gain at 100 MHz
Two frequency response gain adjustment pins
High frequency peaking adjustment (V
PEAK
)
Broadband flat gain adjustment (V
GAIN
)
Pole location adjustment pin (V
POLE
)
Compensates for variations between cables
Can be optimized for either UTP or coaxial cable
DC output offset adjust (V
OFFSET
)
Low output offset voltage: 24 mV
Compensates both RGB and YPbPr
Two on-chip comparators with hysteresis
Can be used for common-mode sync extraction
Available in 40-lead, 6 mm × 6 mm LFCSP
APPLICATIONS
Keyboard-video-mouse (KVM)
Digital signage
RGB video over UTP cables
Professional video projection and distribution
HD video
Security video
FUNCTIONAL BLOCK DIAGRAM
OUT
R
+IN
R
–IN
R
AD8123
OUT
G
+IN
G
–IN
G
OUT
B
+IN
B
– IN
B
–IN
CMP1
+IN
CMP1
–IN
CMP2
+IN
CMP2
OUT
CMP2
OUT
CMP1
V
PEAK
V
POLE
V
OFFSET
V
GAIN
0
6814-001
Figure 1.
GENERAL DESCRIPTION
The AD8123 is a triple, high speed, differential receiver and
equalizer that compensates for the transmission losses of UTP
and coaxial cables up to 300 meters in length. Various gain
stages are summed together to best approximate the inverse
frequency response of the cable. Logic circuitry inside the AD8123
controls the gain functions of the individual stages so that the
lowest noise can be achieved at short-to-medium cable lengths.
This technique optimizes its performance for low noise, short-
to-medium range applications, while at the same time provides
the high gain bandwidth required for long cable equalization
(up to 300 meters). Each channel features a high impedance
differential input that is ideal for interfacing directly with the cable.
The AD8123 has three control pins for optimal cable
compensation, as well as an output offset adjust pin. Two
voltage-controlled pins are used to compensate for different
cable lengths; the V
PEAK
pin controls the amount of high frequency
peaking and the V
GAIN
pin adjusts the broadband flat gain,
which compensates for the low frequency flat cable loss.
For added flexibility, an optional pole adjustment pin, V
POLE
,
allows movement of the pole locations, allowing for the
compensation of different gauges and types of cable as well
as variations between different cables and/or equalizers. The
V
OFFSET
pin allows the dc voltage at the output to be adjusted,
adding flexibility for dc-coupled systems.
The AD8123 is available in a 6 mm × 6 mm, 40-lead LFCSP
and is rated to operate over the extended temperature range of
−40°C to +85°C.
06814-019
UXGA RESOLUTION IMAGE
AFTER 300 METER CAT-5 CABLE
AFTER AD8123.
UXGA RESOLUTION IMAGE
AFTER 300 METER CAT-5 CABLE
BEFORE AD8123.
Figure 2.