AD721

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-SYNC NTSC/ PAL POWER AND GROUNDS +5V +5V –5V AGND DGND LOGIC ANALOG ANALOG ONLY ANALOG LOGIC SC 90 ° 4FSC ENCD QUADRATURE DECODER BURST Y SC 0 ° RED 5MHz 4-POLE LP PRE-FILTER 1.2MHz 4-POLE LPF 1.2MHz 4-POLE LPF SAMPLEDDATA DELAY LINE DC RESTORE AND C-SYNC INSERTION NTSC/ PAL 5MHz 2-POLE LP POSTFILTER LUMINANCE OUTPUT* X2 –0.572V TO 1.43V NTSC –0.6V TO 1.4V PAL GREEN RGB-TO-YUV ENCODING MATRIX U ∑ COMPOSITE OUTPUT* X2 –0.572V TO 2V NTSC –0.6V TO 2V PAL V BLUE BALANCED MODULATORS ∑ 3.6MHz (NTSC) 4.4MHz (PAL) 3-POLE LPF X2 CHROMINANCE OUTPUT* 572mVp-p NTSC 600mVp-p PAL X2 ROUT 1.5Vp-p AD721 (ONLY) X2 GOUT 1.5Vp-p *NOTE: THE LUMINANCE, COMPOSITE, AND CHROMINANCE OUTPUTS ARE AT TWICE NORMAL LEVELS FOR DRIVING 75Ω REVERSE-TERMINATED LINES. X2 BOUT 1.5Vp-p 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. One Technology Way, P.O. Box 9106, Norwood. MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703 AD720/AD721–SPECIFICATIONS Parameter SIGNAL INPUTS (RDIN, GRIN, BLIN) Input Amplitude Input Resistances1 RDIN with Respect to AGND GRIN with Respect to AGND BLIN with Respect to AGND Input Capacitance LOGIC INPUTS (C-SYNC, 4FSC, ENCD, NTSC) Logic LO Input Voltage Logic HI Input Voltage Logic LO Input Current (DC) Logic HI Input Current (DC) BYPASS AMPLIFIERS (AD721 Only) Gain Error Small Signal –3 dB Bandwidth Output Offset Voltage (Active State) Output Voltage (Inactive State) VIDEO OUTPUTS3 (LUMA, CRMA, CMPS) Luminance (LUMA) Output Bandwidth Gain Error Linearity Sync Level Chrominance (CRMA) Output Bandwidth Color Burst Amplitude Absolute Gain Error Absolute Phase Error Chroma/Luma Time Alignment4 Composite Output Absolute Gain Error Differential Gain Differential Phase Output Offset Voltage Chroma Feedthrough POWER SUPPLIES (APOS, DPOS, VNEG) Recommended Supply Range Full Output Current5 Zero Signal Quiescent Current Bypass Mode Quiescent Current (AD721 Only) NTSC PAL (TA = +25°C and supplies = ± 5 V unless otherwise noted) Min Typ 714 700 2.3 4.2 4.2 5 1 4