a
Low Cost RGB to NTSC/PAL Encoder
with Luma Trap Port
AD725
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A.
Tel: 781/329-4700 World Wide Web Site: http://www.analog.com
Fax: 781/326-8703 © Analog Devices, Inc., 1997
FEATURES
Composite Video Output: Both NTSC and PAL
Chrominance and Luminance (S-Video) Outputs
Luma Trap Port to Eliminate Cross Color Artifacts
TTL Logic Levels
Integrated Delay Line and Auto-Tuned Filters
Drives 75 V Reverse-Terminated Loads
Low Power +5 V Operation
Power-Down to <1 mA
Very Low Cost
APPLICATIONS
RGB/VGA to NTSC/PAL Encoding
Personal Computers/Network Computers
Video Games
Video Conference Cameras
Digital Still Cameras
PRODUCT DESCRIPTION
The AD725 is a very low cost general purpose RGB to NTSC/
PAL encoder that converts red, green and blue color compo-
nent signals into their corresponding luminance (baseband
amplitude) and chrominance (subcarrier amplitude and phase)
signals in accordance with either NTSC or PAL standards.
These two outputs are also combined on-chip to provide a
composite video output. All three outputs are available sepa-
rately at voltages of twice the standard signal levels as re-
quired for driving 75 Ω, reverse-terminated cables.
The AD725 features a luminance trap (YTRAP) pin that pro-
vides a means of reducing cross color generated by subcarrier
frequency components found in the luminance signal. For por-
table or other power-sensitive applications, the device can be
powered down to less than 1 µA of current consumption. All
logic levels are TTL compatible thus supporting the logic re-
quirements of 3 V CMOS systems.
The AD725 is packaged in a low cost 16-lead SOIC and oper-
ates from a +5 V supply.
FUNCTIONAL BLOCK DIAGRAM
4FSC
NTSC/PAL
HSYNC
VSYNC
BURST
NTSC/PAL
FSC 90
8
C
FSC 0
8
C
4FSC
FSC 90
8
C/270
8
C
CSYNC
CSYNC
RED
GREEN
BLUE
CSYNC
Y
U
V
BALANCED
MODULATORS
NTSC/PAL
X2
X2
X2
LUMINANCE
OUTPUT
COMPOSITE
OUTPUT
CHROMINANCE
OUTPUT
CLOCK
AT 8FSC
SYNC
SEPARATOR
QUADRATURE
+4
DECODER
BURST
3-POLE
LP PRE-
FILTER
4-POLE
LPF
4-POLE
LPF
6
180
8
C
(PAL ONLY)
RGB-TO-YUV
ENCODING
MATRIX
SAMPLED-
DATA
DELAY LINE
4-POLE
LPF
2-POLE
LP POST-
FILTER
LUMINANCE
TRAP
4FSC CLOCK
V
CLAMP
U
CLAMP
DC
CLAMP
DC
CLAMP
DC
CLAMP
XNOR
S
REV. 0
Information furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assumed by Analog Devices for its
use, nor for any infringements of patents or other rights of third parties
which may result from its use. No license is granted by implication or
otherwise under any patent or patent rights of Analog Devices.
