VDP313XY datasheet(9/76 Pages) MICRONAS

9 / 76 page

ADVANCE INFORMATION

VDP 313xY

Micronas

2.4. Color Decoder

In this block, the standard luminance/chrominance

(luma/chroma) separation and multistandard color

demodulation is carried out. The color demodulation

uses an asynchronous clock, thus allowing a unified

architecture for all color standards.

A block diagram of the color decoder is shown in

Fig. 2–3. The luminance as well as the chrominance

processing, is shown here. The color decoder provides

also some special modes, e.g. wide band chrominance

format which is intended for S-VHS wide bandwidth

chrominance.

If the adaptive comb filter is used for luminance/

chrominance separation, the color decoder uses the

S-VHS mode processing. The output of the color

decoder is YCRCB in a 4:2:2 format.

2.4.1. IF-Compensation

With off-air or mistuned reception, any attenuation at

higher frequencies or asymmetry around the color

subcarrier is compensated. Four different settings of

the IF-compensation are possible:

– flat (no compensation)

– 6dB/octave

– 12 dB/octave

– 10 dB/MHz

The last setting gives a very large boost to high fre-

quencies. It is provided for SECAM signals that are

decoded using a SAW filter specified originally for the

PAL standard.

Fig. 2–2: Frequency response of chrominance IF-com-

pensation

Fig. 2–3: Color decoder

ColorPLL/ColorACC

1 H Delay

CrossSwitch

Notch

Filter

Luma / CVBS

Luma

Chroma

Mixer

Lowpass Filter

Phase/Freq

Demodulator

ACC

Chroma

IF Compensation

DC-Reject

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