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AD8192

Rev. 0 | Page 21 of 28

CABLE LENGTHS AND EQUALIZATION

The AD8192 offers two levels of programmable equalization

for the high speed inputs: 6 dB and 12 dB. The equalizer of

the AD8192 supports video data rates of up to 2.25 Gbps and

can equalize more than 20 meters of 24 AWG HDMI cable at

2.25 Gbps, which corresponds to the video format 1080p with

12-bit deep color. The length of cable that can be used in a

typical HDMI/DVI application depends on a large number

of factors including

•

Cable quality: the quality of the cable in terms of conductor

wire gauge and shielding. Thicker conductors have lower

signal degradation per unit length.

•

Data rate: the data rate being sent over the cable. The signal

degradation of HDMI cables increases with data rate.

•

Edge rates: the edge rates of the source input. Slower input

edges result in more significant data eye closure at the end

of a cable.

•

Receiver sensitivity: the sensitivity of the terminating

receiver.

As such, specific cable types and lengths are not recommended

for use with a particular equalizer setting. In nearly all applica-

tions, the AD8192 equalization level can be set to high, or 12 dB,

for all input cable configurations at all data rates, without degrading

the signal integrity.

TMDS OUTPUT RISE/FALL TIMES

The TMDS outputs of the AD8192 are designed for optimal

performance even when external components are connected

such as external ESD protection, common-mode filters, and

the HDMI connector. In applications where the output of the

AD8192 is connected to an HDMI output connector, additional

ESD protection is recommended. The capacitance of the additional

ESD protection circuits for the TMDS outputs should be as low

as possible. In a typical application, the output rise/fall times are

compliant with the HDMI 1.3a specification at the output of the

HDMI connector.

FRONT PANEL BUFFER FOR ADVANCED TV

A front panel input provides easy access to an HDMI connector

for connecting an HD camcorder or video game console to an

HDTV. In designs where the main PCB is not near the side or

front of the HDTV, a front panel buffer must be connected to

the main board by a cable. The AD8192 enables the implemen-

tation of a front or side panel HDMI input for an HDTV by

buffering the HDMI signals and compensating for the cable

interconnect to the main board.

HDMI RX

AD8192

MAIN PCB

CABLE

HDTV SET

Figure 31. AD8192 as a Front Panel Buffer for an HDTV

HDMI SWITCHER

In home theatre applications where more HDMI inputs are

needed, a multiple input HDMI switcher can be used to extend

the number of available HDMI inputs. This switch can be con-

tained within an audio/video receiver (AVR) or as a standalone

unit. The AD8192 can be cascaded to create larger arrays as

shown in Figure 32.

AD8192

Figure 32. AD8192 Cascaded as a 4:1 HDMI Switcher

CASCADING MULTIPLE DEVICES

Unlike traditional I2C bidirectional buffers, the DDC/CEC

buffers in the AD8192 can be cascaded to create larger arrays

such as those shown in Figure 32. The TMDS signals can also

be cascaded, although it is important to use caution because

cascading high gain equalizers can increase the output jitter

beyond acceptable limits. In such cases, set the programmable

equalizer in the AD8192 to low (6 dB).

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