ADV7401
DETAILED DESCRIPTION
ANALOG FRONT END
The SDP has an IF filter block that compensates for attenuation
in the high frequency luma spectrum due to tuner SAW filter.
The ADV7401 analog front end comprises four 10-bit ADCs
that digitize the analog video signal before applying it to the
SDP or CP (see Table 8 for sampling rates). The analog front
end uses differential channels to each ADC to ensure high
performance in a mixed-signal application.
The SDP has specific luminance and chrominance parameter
control for brightness, contrast, saturation, and hue.
The ADV7401 implements a patented adaptive-digital-line-
length-tracking (ADLLT) algorithm to track varying video
line lengths from sources such as a VCR. ADLLT enables the
ADV7401 to track and decode poor quality video sources
such as VCRs, noisy sources from tuner outputs, VCD players,
and camcorders. The SDP also contains a chroma transient
improvement (CTI) processor. This processor increases the
edge rate on chroma transitions, resulting in a sharper
video image.
The front end also includes a 12-channel input mux that enables
multiple video signals to be applied to the ADV7401. Current
and voltage clamps are positioned in front of each ADC to
ensure that the video signal remains within the range of the
converter. Fine clamping of the video signals is performed
downstream by digital fine clamping in either the CP or SDP.
Optional antialiasing filters are positioned in front of each
ADC. These filters can be used to band-limit standard
definition video signals, removing spurious, out-of-band noise.
The SDP can process a variety of VBI data services, such as
TeleText, closed captioning (CC), wide screen signaling (WSS),
video programming system (VPS), vertical interval time codes
(VITC), copy generation management system (CGMS),
Gemstar 1×/2×, and extended data service (XDS). The
ADV7401 SDP section has a Macrovision 7.1 detection circuit
that allows it to detect Types I, II, and III protection levels. The
decoder is also fully robust to all Macrovision signal inputs.
The ADCs are configured to run in 4× oversampling mode
when decoding composite and S-video inputs; 2× oversampling
is performed for component 525i, 625i, 525p, and 625p sources.
All other video standards are 1× oversampled. Oversampling
the video signals reduces the cost and complexity of external
anti-aliasing filters with the benefit of an increased signal-to-
noise ratio (SNR).
COMPONENT PROCESSOR
The ADV7401 can support simultaneous processing of CVBS
and RGB standard definition signals to enable SCART compat-
ibility and overlay functionality. A combination of CVBS and
RGB inputs can be mixed and output under control of I2C
registers and the fast blank pin.
The CP section is capable of decoding/digitizing a wide range of
component video formats in any color space. Component video
standards supported by the CP are 525i, 625i, 525p, 625p, 720p,
1080i, 1250i, VGA up to SXGA @ 75 Hz (ADV7401KSTZ-140
only), and many other standards not listed here.
Table 8. Maximum ADC Sampling Rates
The CP section of the ADV7401 contains an AGC block.
When no embedded sync is present, the video gain can be set
manually. The AGC section is followed by a digital clamp
circuit that ensures the video signal is clamped to the correct
blanking level. Automatic adjustments within the CP include
gain (contrast) and offset (brightness); manual adjustment
controls are also supported.
Model
Maximum ADC Sampling Rate
ADV7401BSTZ-80
ADV7401BSTZ-110
ADV7401WBSTZ-110
ADV7401KSTZ-140
80 MHz
110 MHz
110 MHz
140 MHz
STANDARD DEFINITION PROCESSOR (SDP)
A fully programmable, any-to-any, 3 × 3 color space conversion
matrix is placed between the analog front end and the CP
section. This enables YPrPb-to-RGB and RGB-to-YCrCb
conversions. Many other standards of color space can be
implemented using the color space converter.
The SDP section is capable of decoding a large selection of
baseband video signals in composite S-video and YUV formats.
The video standards supported by the SDP include PAL
B/D/I/G/H, PAL60, PAL M, PAL N, NTSC M/J, NTSC 4.43, and
SECAM B/D/G/K/L. The ADV7401 can automatically detect
the video standard and process it accordingly.
The SDP has a 5-line superadaptive 2D comb filter that gives
superior chrominance and luminance separation when decod-
ing a composite video signal. This highly adaptive filter auto-
matically adjusts its processing mode according to video
standard and signal quality with no user intervention required.
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