AD8123ACPZ-R7 Analog Devices Inc, AD8123ACPZ-R7 Datasheet - Page 15

• Manufacturer Part Number: AD8123ACPZ-R7
• Description: IC,LINE RECEIVER,TRIPLE,DIFFERENTIAL,LLCC,40PIN,PLASTIC
• Manufacturer: Analog Devices Inc
• Type: Receiverr

Specifications of AD8123ACPZ-R7

• Number Of Drivers/receivers: 0/3
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 40-LFCSP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Protocol: -
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: AD8123ACPZ-R7TR

INPUT COMMON-MODE RANGE
Most applications that use the AD8123 as a receiver use a driver
(such as one from the
AD8133, or the AD8134) powered from ±5 V supplies. This
places the common-mode voltage on the line nominally at 0 V
relative to the ground potential at the driver and provides optimum
immunity from any common-mode anomalies picked up along
the cable (including ground shifts between the driver and receiver
ends). In many of these applications, the AD8123 input voltage
range of typically ±3.0 V is sufficient. If wider input range is
required, the
range equals ±10.5 V on ±12 V supplies) may be placed in front of
the AD8123. Figure 32 illustrates how this is done for one channel.
The Schottky diodes are required to protect the AD8123 from
any
The 49.9 Ω resistor limits the fault current and produces a pole
at approximately 800 MHz with the effective diode capacitance of
3 pF and the AD8123 input capacitance of 1 pF. The pole drops
the response by only 0.07 dB at 100 MHz and therefore has a
negligible effect on the signal.
When using a single 5 V supply on the driver side, the common-
mode voltage at the driver is typically midsupply, or V
The largest received differential video signal is approximately
700 mV p-p, and this therefore adds 175 mV
mode voltage, resulting in a worst-case peak voltage of 2.675 V
on an AD8123 input (presuming there is no ground shift between
driver and receiver). This is within the AD8123 input voltage
swing limits, and such a system works well as long as the difference
in ground potential between driver and receiver does not cause
the input voltage swing to exceed its specified limits.
AD8143
RECEIVED
SIGNAL
Figure 32. Optional Use of AD8143 in Front of AD8123 for
outputs that may exceed the AD8123 input limits.
AD8143
100Ω
POWER SUPPLIES = ±12V
Wide Input Common-Mode Range
ONE AD8143 CHANNE L
AD8146/AD8147/AD8148
triple receiver (input common-mode
49.9Ω
HBAT-540C
PEAK
1
2
to the common-
3
ONE AD8123
family, the
CM
INPUT
+5V
–5V
= 2.5 V.
Rev. A | Page 15 of 16
When used, common-mode sync signals are generally applied
with a peak deviation of 500 mV and thereby increase the
common-mode level from 2.675 V to 3.175 V. This common-
mode level exceeds the specified input voltage swing limits of
±3.0 V; therefore, the AD8123 cannot be used with a system
that uses common-mode sync encoding with 500 mV sync peak
deviation and 2.5 V common-mode line level. While it is possible
to operate a driver powered from a single 5 V supply at a common-
mode voltage of <2.5 V to obtain a received voltage swing that is
within the specified limits, there is not much margin for other
shifts in the common-mode level due to interference pickup and
differing ground potentials. There are two ways to increase the
common-mode range of the overall system. One is to power the
driver from ±5 V supplies, and the other is to place an
in front of the AD8123, as shown in Figure 32. These techniques
may be combined or applied separately.
SMALL SIGNAL FREQUENCY RESPONSE
Though the AD8123 large signal frequency response
(V
interested in the small signal frequency response. The AD8123
frequency response for V
for 200 meter and 300 meter cable lengths.
POWER-DOWN
The power-down feature is intended to be used to reduce power
consumption when a particular device is not in use and does
not place the output in a high-Z state when asserted. The input
logic levels and supply current in power-down mode are presented
in the Power Supply section of Table 1.
O
Figure 33. Small Signal Frequency Response for Various Cable Lengths
= 1 V p-p) is of most concern, occasionally designers are
–10
–11
–12
–1
–2
–3
–4
–5
–6
–7
–8
–9
3
2
1
0
0.01
V
O
= 300mV p-p
0.1
O
FREQUENCY (MHz)
= 300 m V p-p is shown in Figure 33
1
300 METERS
10
200 METERS
100
AD8123
AD8143