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AD720

Analog Devices
Part Number AD720
Manufacturer Analog Devices
Description RGB to NTSC/PAL Encoders
Published Mar 23, 2005
Detailed Description a FEATURES Composite Video Output Chrominance and Luminance (S-Video) Outputs No External Filters or Delay Lines Require...
Datasheet PDF File AD720 PDF File

AD720
AD720

Overview
a FEATURES Composite Video Output Chrominance and Luminance (S-Video) Outputs No External Filters or Delay Lines Required Drives 75 Ω Reverse-Terminated Loads Compact 28-Pin PLCC Logic Selectable NTSC or PAL Encoding Modes Automatically Selects Proper Chrominance Filter Cutoff Frequency for Encoding Standard Logic Selectable Encode or Power-Down Mode (AD720 Only) Logic Selectable Encode or Bypass Mode (AD721 Only) Low Power: 200 mW typical APPLICATIONS RGB to NTSC or PAL Encoding Drive RGB Signals into 75 Ω Load (AD721 Only) PRODUCT DESCRIPTION RGB to NTSC/PAL Encoders AD720/AD721 (subcarrier amplitude and phase) signals in accordance with either NTSC or PAL standards.
These two outputs are also combined to provide a composite video output.
All three outputs are available separately at voltages of twice the standard signal levels as required for driving 75 Ω reverse terminated cables.
The AD721 also features a bypass mode, in which the RGB inputs may bypass the encoder section of the IC via three gain-of-two amplifiers suitable for driving 75 Ω reverse terminated cables.
The AD720 and AD721 provide a complete, fully calibrated function, requiring only termination resistors, bypass capacitors, a clock input at four times the subcarrier frequency, and a composite sync pulse.
There are two control inputs: one input selects the TV standard (NTSC/PAL) and the other (ENCD) powers down most sections of the chip when the encoding function is not in use (AD720) or activates the triple bypass buffer to drive the RGB signals when RGB encoding is not required (AD721).
All logical inputs are CMOS compatible.
The chip operates from ± 5 V supplies.
(continued on page 5) The AD720 and AD721 RGB to NTSC/PAL Encoders convert red, green and blue color component signals into their corresponding luminance (baseband amplitude) and chrominance FUNCTIONAL BLOCK DIAGRAM NTSC/ PAL ASNC C-SYNC SYNC DECODER C-SYNC DELAY BURST ±180° (PAL ONLY) SC 90 °/270 ° NTSC/ PAL CLOCK AT 8FSC DELAYED C-...


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