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

Reverse-Terminated Loads

Low Power +5 V Operation

Power-Down to <1

A

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 C

FSC 0 C

4FSC

FSC 90 C/270 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

180 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

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.