ISL59311 Datasheet, PDF (10/14 Pages) Intersil Corporation – Differential Video Amplifier with Common Mode Sync Encoder and Serial Digital Interface

ISL59311
Typical Performance Curves (Continued)
JEDEC JESD51-7 HIGH EFFECTIVE THERMAL
CONDUCTIVITY TEST BOARD - QFN EXPOSED
DIEPAD SOLDERED TO PCB PER JESD51-5
3
2.857W
2.5
2
1.5
1
0.5
0
0
25 50 75 85 100 125 150
AMBIENT TEMPERATURE (°C)
FIGURE 17. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
JEDEC JESD51-3 AND SEMI G42-88
(SINGLE LAYER) TEST BOARD
0.8
0.7 _758mW
0.6
0.5
0.4
0.3
0.2
0.1
0
0
25 50 75 85 100 125 150
AMBIENT TEMPERATURE (°C)
FIGURE 18. PACKAGE POWER DISSIPATION vs AMBIENT
TEMPERATURE
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
schemes. Horizontal and Vertical sync signals (H_SYNC and
V_SYNC) 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 V_REF pin is used to control the common mode level
of the differential output; in the case of the ISL59311 the
V_REF of each of the three internal amplifier channels
receives a signal from the Logic Encoding Block with
encoded H_SYNC and V_SYNC 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. H_SYNC and V_SYNC can easily be
separated from the differential output signals, decoded and
transmitted along with the RGB video signals to the video
monitor.
Sync Transmission
The ISL59311 encodes H_SYNC and V_SYNC signals on the
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.
Extract Common Mode Sync and Decode H_SYNC
and V_SYNC
H_SYNC and V_SYNC can be regenerated from the Common
Mode sync output voltages. The relationships between
H_SYNC, V_SYNC and the 3 common mode levels are given by
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.
HSYNC
Low
Low
High
High
TABLE 1. SYNC SIGNAL ENCODING
VSYNC
COMMON
MODE A
(RED)
COMMON
MODE B
(GREEN)
COMMON
MODE C
(BLUE)
High
3.0
2.0
2.5
Low
2.5
3.0
2.0
Low
2.0
3.0
2.5
High
2.5
2.0
3.0
10
FN6372.2
April 4, 2007