MAX9526 datasheet(13/38 Pages) MAXIM

13 / 38 page

standards automatically. See the

Standard Select,

Shutdown, and Control Register section for manual pro-

gramming.

The sync processor block also detects analog copy

protection. Extracted copy protection information is

available in Status register 0x01.

Composite Automatic Gain Control (AGC)

In addition to the analog AGC that optimizes the ADC

full-scale range, a digital AGC is used to more accu-

rately set the video amplitude. The Composite AGC

uses the amplitude of the sync signal to set the gain.

Adaptive Comb Filter

The MAX9526 uses a 5-line adaptive comb filter to sep-

arate luminance and chrominance components from a

single composite channel. The adaptation algorithm

does not require configuration. The adaptive comb filter

adjusts based on the relationship and content of video

data between neighboring lines. The filter automatically

adapts the comb filter structure between a 5-line filter

and a notch filter.

Chrominance Signal Demodulator

After luminance (Y) and chrominance (C) components

are separated, the Y component passes through a

delay line to compensate for the C component delay

through the demodulator. The chrominance signal path

contains an AGC before the signal demodulator. The

chrominance AGC uses the color burst amplitude to set

the gain. The chrominance is demodulated using a

subcarrier signal locked to the burst. The demodulated

chrominance signals, Cb and Cr, are lowpass filtered to

eliminate unwanted products of demodulation.

Output Formatting

Figure 4 shows the output formatting section of the

MAX9526.

Image Enhancement and Color Correction

The MAX9526 provides contrast, brightness, hue, and

saturation manual control in registers 0x05 to 0x08.

Time Base Correction

The MAX9526 provides time base correction (TBC) to

allow the decoder to properly process unstable and

nonstandard video from sources such as a VCR. The

time base correction minimizes the effect of sampling

jitter to ensure that there are a correct number of pixels

per active line.

Test Pattern Insertion

The MAX9526 automatically outputs a black screen

when there is no video at the inputs. The test pattern

can also be configured to provide a blue screen, 75%

color bars, or 100% color bars through register 0x0C.

Timing Reference Signal Insertion

and ITU-R BT.656 Encoding

The MAX9526 multiplexes the Y, Cr, and Cb signals

with an embedded timing reference signal conforming

to the ITU-R BT.656 standard.

SAV and EAV sequences are inserted into the data

stream to indicate the active video time in ITU-R BT.656

format. The output timing insertion is illustrated in

Figure 5. The SAV and EAV sequences are shown in

Table 2.

Output Timing

The output setup and hold diagram is shown in Figure 6.

Low-Power, High-Performance

NTSC/PAL Video Decoder

______________________________________________________________________________________

SYNC-LEVEL

CORRECTION

AND

SYNC EXTRACTION

SYNC PROCESSOR

AND ANALOG COPY

PROTECTION DETECT

COMPOSITE

AGC

ADAPTIVE

COMB

FILTER

LINE

DELAYS

Y-DELAY

CHROMINANCE

DEMODULATOR

Y/Cb/Cr

FILTERS

LPF

CHROMA

AGC

FROM

ANALOG

FRONT-END

NTSC/PAL

TIMING

INFO

HORZ, VERT, FRAME

NONSTD

VIDEO

NONSTD VIDEO

Figure 3. Digital Composite Decoding Functional Diagram

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