ADI AD8120三路视频延迟线抖动补偿方案

ADI 公司的AD8120是三路宽带抖动补偿视频延迟线,可以进行模拟和数字控制. AD8120包括有三个延迟通路,宽带延迟高达50ns,增量0.8ns,采用64个数控点或模拟控制调整,从而在输出端最小化噪音和失调(±30 mV RTI ).AD8120的带宽从150MHz到200MHz,增益匹配在0.8%,主要用于UTP电缆传输RGB信号,专业的视频投映仪和分配,HD视频,安防视频和通用宽带延迟线与键盘视频鼠标(KVM).本文介绍了AD8120主要特性,方框图和典型应用电路.

Triple Skew-Compensating Video Delay Line with Analog and Digital Control

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 using a standard 4-wire SPI bus or a standard I2C bus, or by applying analog control voltages to the VCR, VCG, and VCB pins. 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℃ to +85℃.

AD8120主要特性:

Corrects for unshielded twisted pair (UTP) cable skew

Delay of up to 50 ns per channel

High speed

200 MHz BW @ VOUT = 1.4 V p-p and 0 ns delay

150 MHz BW @ VOUT = 1.4 V p-p and 50 ns delay

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

I2C bus

Analog voltage control

Fixed gain of 2

Low noise

High differential input impedance: 500 kΩ

32-lead, 5 mm × 5 mm LFCSP

AD8120应用:

Keyboard-video-mouse (KVM)

Digital signage

RGB video over UTP cable

Professional video projection and distribution

HD video

Security video

General broadband delay lines


图1.AD8120功能方框图


图2.AD8120典型应用电路