10

FN6372.2

April 4, 2007

Operational Description and Application

Information

Introduction

The ISL59311 is designed to differentially drive composite

RGB video signals onto twisted pair lines, while

simultaneously encoding horizontal and vertical sync signals

as common mode output. The entire video signal plus sync

can therefore be transmitted on 3 twisted pairs of wire. When

utilizing CAT-5 cable, the 4th available twisted pair can be

used for transmission of audio, data or control information.

The distribution of composite video over standard CAT-5

cable enables enormous cost and labor savings compared

with traditional coaxial cable, when considering both the

relative low price and ease of pulling CAT-5 cable.

The digital block of the chip is a data transceiver which is

intended to drive one twisted pair line. The maximum

baudrate for this block is 50Mbps.

Functional Description

The ISL59311 provides three fully differential high-speed

amplifiers, suitable for driving high-resolution composite

video signals onto twisted pair or standard coaxial cable.

The input common-mode range extends to the negative rail,

allowing simple ground-referenced input termination to be

used with a single supply. The amplifiers provide a fixed gain

of +2 to compensate for standard video cable termination

encode the sync information as three discrete signals of

different voltage levels. Generally, in differential amplifiers an

of the differential output; in the case of the ISL59311 the

receives a signal from the Logic Encoding Block with

consists of three fully differential video signals, with sync

encoded on the common mode of each of the three RGB

separated from the differential output signals, decoded and

transmitted along with the RGB video signals to the video

monitor.

Sync Transmission

common mode output of the differential video signals; Red,

Green and Blue respectively. Data Sheet Table 1 shows the

common mode levels for the different SYNC input

combinations. Note that the sum of the common mode

voltages results in a fixed average DC level with no AC

content. This dramatically reduces EMI radiation into any

common mode signal along the twisted pairs of CAT 5 cable.

Mode sync output voltages. The relationships between

Table 1. The common mode levels are easily separated from

the differential outputs of the ISL59311 using this simple

resistor network at the cable receiver input of each

differential channel; see Figure 20.

FIGURE 17. PACKAGE POWER DISSIPATION vs AMBIENT

TEMPERATURE

FIGURE 18. PACKAGE POWER DISSIPATION vs AMBIENT

TEMPERATURE

JEDEC JESD51-7 HIGH EFFECTIVE THERMAL

CONDUCTIVITY TEST BOARD - QFN EXPOSED

DIEPAD SOLDERED TO PCB PER JESD51-5

3

2.5

2

1.5

1

0.5

0

0

255075

100

150

AMBIENT TEMPERATURE (°C)

2.857W

125

85

JEDEC JESD51-3 AND SEMI G42-88

(SINGLE LAYER) TEST BOARD

0.8

0.7

0.5

0.3

0.2

0.1

0

0

255075

100

150

AMBIENT TEMPERATURE (°C)

125

85

0.6

0.4

758mW

TABLE 1. SYNC SIGNAL ENCODING

HSYNC

VSYNC

COMMON

MODE A

(RED)

COMMON

MODE B

(GREEN)

COMMON

MODE C

(BLUE)

Low

High

3.0

2.0

2.5

Low

Low

2.5

3.0

2.0

High

Low

2.0

3.0

2.5

High

High

2.5

2.0

3.0

ISL59311