ADV453KN40 Analog Devices Inc, ADV453KN40 Datasheet - Page 8

• Manufacturer Part Number: ADV453KN40
• Manufacturer: Analog Devices Inc

Specifications of ADV453KN40

• Lead Free Status / Rohs Status: Not Compliant

ADV453
Frame Buffer Interface
The P0–P7, OL0 and OL1 inputs are used to address the color
palette RAM and overlay registers, as shown in Table IV. These
inputs are latched on the rising edge of CLOCK and address
any of the 256 locations in the color palette RAM or the three
overlay registers. The addressed location contains 24 bits of
color (8 bits of red, 8 bits of green and 8 bits of blue) informa-
tion. This data is transferred to the three DACs and is then con-
verted to an analog output (IOR, IOG and IOB), these outputs
then control the red, green and blue electron guns in the monitor.
The SYNC and BLANK inputs are also latched on the rising
edge of CLOCK. This is to maintain synchronization with the
color data.
OL1
0
0
•
•
0
0
1
1
Analog Interface
The ADV453 has three analog outputs, corresponding to the
red, green and blue video signals. A fourth analog output
(I
zation information onto the green signal. In this case, I
connected to IOG as shown in Figure 3. If it is not required to
encode sync information onto the green signal (as would be the
case if a separate synchronization circuit was used), I
should be connected to GND and the digital SYNC input pin
should be tied low.
SYNC
) can be used if it is required to encode video synchroni-
Table IV. Pixel and Overlay Control Truth Table
OL0
0
0
•
•
0
1
0
1
Figure 3. Encoding SYNC onto Green Signal
P0–P7
00H
01H
•
•
FFH
XXH
XXH
XXH
Addressed by Frame Buffer
Color Palette RAM Location 00H
Color Palette RAM Location 01H
Color Palette RAM Location FFH
Overlay Color 1
Overlay Color 2
Overlay Color 3
•
•
SYNC
SYNC
is
–8–
The red, green and blue analog outputs of the ADV453 are high
impedance current sources. Each one of these three RGB cur-
rent outputs is capable of directly driving a 37.5
a doubly-terminated 75
quired configuration for each of the three RGB outputs con-
nected into a doubly-terminated 75
will develop RS-343A video output voltage levels across a 75
monitor. A simple method of driving RS-170 video levels into a
75
of the DACs remain unchanged, but the source termination re-
sistance, Z
to 150 .
More detailed information regarding load terminations for vari-
ous output configurations, including RS-343A and RS-170, is
available in an application note entitled “Video Formats &
Required Load Terminations,” available from Analog Devices.
Figure 5 shows the video waveforms associated with the three
RGB outputs, driving the doubly terminated 75
ure 4a. As well as the gray scale levels, black level to white level,
the diagram also shows the contributions of SYNC and BLANK.
These control inputs add appropriately weighted currents to the
analog outputs producing the specific output level requirements
for video applications. Table V details how the SYNC and
BLANK inputs modify the output levels.
Figure 4a. Recommended Analog Output Termination
for RS-343A
Figure 4b. Recommended Analog Output Termination
for RS-170
monitor is shown in Figure 4b. The output current levels
S
, on each of the three DACs is increased from 75
coaxial cable. Figure 4a shows the re-
load. This arrangement
load of Fig-
load, such as
REV. B