AD8197 Analog Devices, AD8197 Datasheet - Page 25

• Manufacturer Part Number: AD8197
• Description: 4:1 HDMI/DVI Switch with Equalization
• Manufacturer: Analog Devices

Preliminary Data Sheet
APPLICATION INFORMATION
The AD8197 is an HDMI/DVI switch featuring equalized
TMDS inputs and pre-emphasized TMDS outputs. It is in-
tended for use as a 4:1 switch in systems with long cable runs
on both the input and/or the output, and is fully HDMI 1.3
receive-compliant.
PINOUT
The AD8197 is designed for an HDMI/DVI receiver pinout
at its input and a transmitter pinout at its output. This makes
the AD8197 ideal for use in AVR-type applications where the
designer routes both the inputs and the outputs directly to
HDMI/DVI connectors. This type of layout is used on the
AD8197 evaluation board, as shown in Figure 31. When the
AD8197 is used in receiver type applications, it is necessary to
change the ordering of the output pins on the PCB to match up
with the on-board receiver.
One advantage of the AD8197 in an AVR-type application is
that all of the high speed signals can be routed on one side (the
topside) of the board, as shown in Figure 31. In addition to
12 dB of input equalization, the AD8197 provides up to 6 dB of
output pre-emphasis that boosts the output TMDS signals and
allows the AD8197 to precompensate when driving long PCB
traces or output cables. The net effect of the input equalization
Figure 31. Layout of the TMDS Traces on the AD8197 Evaluation Board (Only Top Signal Routing Layer is Shown)
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and output pre-emphasis of the AD8197 is that the AD8197 can
compensate for the signal degradation of both input and output
cables; it acts to reopen a closed input data eye and transmit a
full-swing HDMI signal to an end receiver. More information
on the specific performance metrics of the AD8197 can be
found in the Typical Performance Characteristics section.
The AD8197 also provides a distinct advantage in receive-type
applications because it is a fully buffered HDMI/DVI switch.
Although inverting the output pin order of the AD8197 on the
PCB requires a designer to place vias in the high speed signal
path, the AD8197 fully buffers and electrically decouples the
outputs from the inputs. Consequently, the effects of the vias
placed on the output signal lines are not seen at the input of the
AD8197. The programmable output terminations also improve
signal quality at the output of the AD8197. Therefore, the PCB
designer has significantly improved flexibility in the placement
and routing of the output signal path with the AD8197 over
other solutions.
CABLE LENGTHS AND EQUALIZATION
The AD8197 offers two levels of programmable equalization
for the high speed inputs: 6 dB and 12 dB. The equalizer of
the AD8197 supports video data rates of up to 2.25 Gbps. It can
equalize more than 20 meters of 24 AWG HDMI cable at 2.25
AD8197