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ADV7177KS Fiches technique(PDF) 11 Page - Analog Devices |
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ADV7177KS Fiches technique(HTML) 11 Page - Analog Devices |
11 / 38 page ADV7177/ADV7178 –11– REV. 0 compatible with worldwide standards. The 4:2:2 YUV video data is interpolated to two times the pixel rate. The color- difference components (UV) are quadrature modulated using a subcarrier frequency generated by an on-chip 32-bit digital synthesizer (also running at two times the pixel rate). The two times pixel rate sampling allows for better signal-to-noise ratio. A 32-bit DDS with a 9-bit look-up table produces a superior subcarrier in terms of both frequency and phase. In addition to the composite output signal, there is the facility to output S-Video (Y/C) video, YUV or RGB video. Each analog output is capable of driving the full video-level (34.7 mA) signal into an unbuffered, doubly terminated 75 Ω load. With external buffering, the user has the additional option to scale back the DAC output current to 5 mA min, thereby signifi- cantly reducing the power dissipation of the device. The ADV7177/ADV7178 also supports both PAL and NTSC square pixel operation. The output video frames are synchronized with the incoming data timing reference codes. Optionally, the encoder accepts (and can generate) HSYNC, VSYNC and FIELD timing signals. These timing signals can be adjusted to change pulsewidth and position while the part is in the master mode. The encoder requires a single two times pixel rate (27 MHz) clock for standard operation. Alternatively, the encoder requires a 24.54 MHz clock for NTSC or 29.5 MHz clock for PAL square pixel mode operation. All internal timing is generated on-chip. The ADV7177/ADV7178 modes are set up over a two-wire serial bidirectional port (I 2C-Compatible) with two slave addresses. Functionally the ADV7178 and ADV7177 are the same with the exception that the ADV7178 can output the Macrovision anticopy algorithm, and OSD is only supported on the ADV7177. The ADV7177/ADV7178 is packaged in a 44-lead thermally enhanced PQFP package. DATA PATH DESCRIPTION For PAL B, D, G, H, I, M, N and NTSC M, N modes, YCrCb 4:2:2 data is input via the CCIR-656 compatible pixel port at a 27 MHz data rate. The pixel data is demultiplexed to from three data paths. Y typically has a range of 16 to 235, Cr and Cb typically have a range of 128 ± 112; however, it is possible to input data from 1 to 254 on both Y, Cb and Cr. The ADV7177/ADV7178 supports PAL (B, D, G, H, I, N, M) and NTSC (with and without Pedestal) standards. The appropri- ate SYNC, BLANK and Burst levels are added to the YCrCb data. Macrovision antitaping (ADV7178 only), closed captioning, OSD (ADV7177 only), and teletext levels are also added to Y, and the resultant data is interpolated to a rate of 27 MHz. The interpolated data is filtered and scaled by three digital FIR filters. The U and V signals are modulated by the appropriate subcarrier sine/cosine phases and added together to make up the chromi- nance signal. The luma (Y) signal can be delayed 1–3 luma cycles (each cycle is 74 ns) with respect to the chroma signal. The luma and chroma signals are then added together to make up the composite video signal. All edges are slew rate limited. The YCrCb data is also used to generate RGB data with appropriate SYNC and BLANK levels. The RGB data is in synchronization with the composite video output. Alternatively analog YUV data can be generated instead of RGB. The three 9-bit DACs can be used to output: 1. RGB Video. 2. YUV Video 3. One Composite Video Signal + LUMA and CHROMA 3. (S-Video). Alternatively, each DAC can be individually powered off if not required. Video output levels are illustrated in Appendix 3, Appendix 4 and Appendix 5. INTERNAL FILTER RESPONSE The Y filter supports several different frequency responses, including two 4.5 MHz/5.0 MHz low-pass responses, PAL/ NTSC subcarrier notch responses and a PAL/NTSC extended response. The U and V filters have a 2/2.4 MHz low-pass response for NTSC/PAL. These filter characteristics are illus- trated in Figures 7 to 13. (Continued from page 1) MR04 MR03 NTSC 0 0 2.3 0.026 7.0 >54 4.2 PAL 0 0 3.4 0.098 7.3 >50 5.0 NTSC 0 1 1.0 0.085 3.57 >27.6 2.1 PAL 0 1 1.4 0.107 4.43 >29.3 2.7 NTSC/PAL 1 0 4.0 0.150 7.5 >40 5.35 NTSC 1 1 2.3 0.054 7.0 >54 4.2 PAL 1 1 3.4 0.106 7.3 >50.3 5.0 FILTER SELECTION F3 dB PASSBAND CUTOFF (MHz) STOPBAND CUTOFF (MHz) PASSBAND RIPPLE (dB) STOPBAND ATTENUATION (dB) Figure 5. Luminance Internal Filter Specifications NTSC 1.0 0.085 3.2 >40 0.3 2.05 PAL 1.3 0.04 4.0 >40 0.02 2.45 FILTER SELECTION F3 dB PASSBAND CUTOFF (MHz) STOPBAND CUTOFF (MHz) PASSBAND RIPPLE (dB) STOPBAND ATTENUATION (dB) ATTENUATION @ 1.3MHz (dB) Figure 6. Chrominance Internal Filter Specifications |
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