AD724

a 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 ⍀ Reverse-Terminated Loads Logic Selectable NTSC or PAL Encoding Modes Compact 16-Lead SOIC APPLICATIONS RGB to NTSC or PAL Encoding PRODUCT DESCRIPTION RGB to NTSC/PAL Encoder AD724 operates from a single +5 V supply. No external delay lines or filters are required. The AD724 may be powered down when not in use. 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. Delays in the U and V chroma filters are matched by an on-chip sampled-data de...