|ADV7177||Integrated Digital CCIR-601 to PAL/NTSC Video Encoder|
|ADV7177 Datasheet PDF : 38 Pages |
(Continued from page 1)
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 (I2C-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
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
Alternatively, each DAC can be individually powered off if not
Video output levels are illustrated in Appendix 3, Appendix 4 and
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.
PASSBAND PASSBAND STOPBAND
CUTOFF (MHz) RIPPLE (dB) CUTOFF (MHz)
Figure 5. Luminance Internal Filter Specifications
Figure 6. Chrominance Internal Filter Specifications
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