Triple Skew-Compensating Video Delay

Line with Analog and Digital Control

AD8120

Rev. 0

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FEATURES

Corrects for unshielded twisted pair (UTP) cable skew

Delay of up to 50 ns per channel

High speed

Excellent channel-to-channel matching

30 mV offset matching RTI

0.8% gain matching

Low output offset

±30 mV RTI

No external circuitry required to correct for offsets

Independent red, green, and blue delay controls

Drives 4 double-terminated video loads

Digital and analog delay control

6-bit SPI bus

Analog voltage control

Fixed gain of 2

Low noise

High differential input impedance: 500 kΩ

32-lead, 5 mm × 5 mm LFCSP

APPLICATIONS

Keyboard-video-mouse (KVM)

Digital signage

RGB video over UTP cable

Professional video projection and distribution

HD video

Security video

General broadband delay lines

GENERAL DESCRIPTION

The AD8120 is a triple broadband skew-compensating delay line

that corrects for time mismatch between video signals incurred

by transmission in unshielded twisted pairs of Category 5 and

Category 6 type cables. Skew between the individual pairs exists

in most types of multipair UTP cables due to the different twist

rates that are used for each pair to minimize crosstalk between

pairs. For this reason, some pairs are longer than others, and in

long cables, the difference in propagation time between two pairs

can be well into the tens of nanoseconds.

The AD8120 contains three delay paths that provide broadband

delays up to 50 ns, in 0.8 ns increments, using 64 digital control

steps or analog control adjustment. The delay technique used in

the AD8120 minimizes noise and offset at the outputs.

The bandwidth of the AD8120 ranges from 150 MHz to 200 MHz,

depending on the delay setting. This wide bandwidth makes the

AD8120 ideal for use in applications that receive high resolution

video over UTP cables.

The logic circuitry of the AD8120 provides individual delay con-

trols for each channel. The delay times are set independently

Analog control offers a simple solution for systems that do not

have digital control available.

The AD8120 is designed to be used with the AD8123 triple

UTP equalizer in video over UTP applications, but it can

also be used in other applications where similar controllable

broadband delays are required.

The AD8120 is available in a 5 mm × 5 mm, 32-lead LFCSP

and is rated to operate over the industrial temperature range

of −40°C to +85°C.

FUNCTIONAL BLOCK DIAGRAM

R

d

G

B

d

d

Figure 1.