AD724

Features:

Low Cost, Integrated Solution
+5 V Operation
Accepts FSC Clock or Crystal, or 4FSC Clock
Composite Video and Separate Y/C (S-Video) Outputs
Luma and Chroma Outputs Are Time Aligned
Minimal External Components:
No External Filters or Delay Lines Required
Onboard DC Clamp
Accepts Either HSYNC and VSYNC or CSYNC
Phase Lock to External Subcarrier
Drives 75 V Reverse-Terminated Loads
Logic Selectable NTSC or PAL Encoding Modes
Compact 16-Lead SOIC




Application

RGB to NTSC or PAL Encoding




Pinout








Specifications

Supply Voltage, APOS to AGND . . . . . . . . . . . . . . . . . . +6 V
Supply Voltage, DPOS to DGND . . . . . . . . . . . . . . . . . . +6 V
AGND to DGND . . . . . . . . . . . . . . . . . . . . . 0.3 V to +0.3 V
Inputs . . . . . . . . . . . . . . . . . DGND 0.3 V to DPOS + 0.3 V
Internal Power Dissipation . . . . . . . . . . . . . . . . . . 800 mW
Operating Temperature Range . . . . . . . . . . . 0°C to +70°C
Storage Temperature Range . . . . . . . . . .65°C to +125°C
Lead Temperature Range (Soldering 30 sec) . . . . . +230°C






Description

The AD724 is a low cost RGB to NTSC/PAL Encoder that converts red, green and blue color component 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 to provide composite video output. All three outputs can simultaneously drive 75 Ω, reverse-terminated cables. All logical inputs are TTL, 3 V and 5 V CMOS compatible.

The AD724 accepts either FSC or 4FSC clock. When a clock is not available, a low cost parallel-resonant crystal (3.58 MHz (NTSC) or 4.43 MHz (PAL)) and the AD724's on-chip oscillator generate the necessary subcarrier clock. The AD724 also accepts the subcarrier clock from an external video source. The interface to graphics controllers is simple: an on-chip logic "XNOR" accepts the available vertical (VSYNC) and horizontal sync (HSYNC) signals and creates the composite sync (CSYNC) signal on-chip. If available, the AD724 will also accept a standard CSYNC signal by connecting VSYNC to Logic HI and applying CSYNC to the HSYNC pin. The AD724 contains decoding logic to identify valid horizontal sync pulses for correct burst insertion.