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4543ILZ

Triple Differential Twisted-Pair Driver with Common-Mode Sync Encoding

Renesas Electronics 

EL4543

Typical Performance Curves (Continued)

JEDEC JESD51-7 HIGH EFFECTIVE THERMAL

CONDUCTIVITY TEST BOARD - QFN EXPOSED

DIEPAD SOLDERED TO PCB PER JESD51-5

3

2.500W

2.5

2

1.5

JA(4=m4m0°QCx/FW4Nm2m0 )

1

0.5

0

0

25

50

75 85 100 125 150

AMBIENT TEMPERATURE (°C)

FIGURE 37. PACKAGE POWER DISSIPATION vs AMBIENT TEMPERATURE

Operational Description and Application

Information

Introduction

The EL4543 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 CAT5 cable, the 4th available twisted pair can be

used for transmission of audio, data or control information.

The distribution of composite video over standard CAT5

cable enables enormous cost and labor savings compared

with traditional coaxial cable, when considering both the

relative low price and ease of pulling CAT5 cable.

Functional Description

The EL4543 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

schemes. Horizontal and Vertical sync signals (HSYNC and

VSYNC) are passed to an internal Logic Encoding Block to

encode the sync information as three discrete signals of

different voltage levels. Generally, in differential amplifiers an

external VREF pin is used to control the common mode level

of the differential output; in the case of the EL4543 the VREF

of each of the three internal amplifier channels receives a

signal from the Logic Encoding Block with encoded HSYNC

and VSYNC information. The final output consists of three

fully differential video signals, with sync encoded on the

common mode of each of the three RGB differential signals.

HSYNC and VSYNC can easily be separated from the

differential output signals, decoded and transmitted along

with the RGB video signals to the video monitor.

EN

+

INA-

+

-

+

O- UTA

VREF

VSYNC

HSYNC

EN

LOGIC

DECODING

RCM

GCM

BCM

EN

+

INB-

+

-

+

O- UTB

VREF

EN

+

INC-

+

-

+

O- UTC

VREF

FIGURE 38. BLOCK DIAGRAM EL4543

Sync Transmission

The EL4543 encodes HSYNC and VSYNC signals on the

common mode output of the differential video signals; Red,

Green and Blue respectively. Data Sheet Figures 16, 17 and

18 clearly illustrate that the sum of the common mode

voltages results in a fixed average DC level with no AC

content and illustrates the logic levels. This eliminates EMI

radiation into any common mode signal along the twisted

pairs of CAT5 cable.

FN7325 Rev 11.00

September 13, 2007

Page 11 of 18

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