STV224X datasheet(24/86 Pages) STMICROELECTRONICS

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STV224XH/228XH/223XH - FUNCTIONAL DESCRIPTION

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green DC levels for black point adjustment takes

place via the bus.

3.4.9 Bus-controlled Contrast & Saturation

The Contrast Control regulates internal RGB, ex-

ternal RGB and OSD RGB inputs. The maximum

attenuation on internal and external RGB inputs is

-24 dB and is limited to -12 dB for OSD RGB in-

puts. The bus-controlled saturation range is 50 dB.

3.4.10 Bus-controlled Brightness & Sharpness

The total brightness range is 60% of the black-to-

white amplitude at maximum contrast. The bright-

ness control regulates all RGB sources (internal,

external and OSD). Bus-controlled Sharpness

(peaking)

provided

PAL/SECAM/NTSC

standards.

3.4.11 Bus-controlled Coring on Sharpness

When

the

Coring-on-sharpness

function

switched ON, the peaking function is not active on

low amplitude signals (below 10 IRE).

3.4.12 Black Stretch

The Black Stretch circuit can be disabled via the

bus. Two modes are provided, one to be used

when the video signal is transmitted with a set-up

(7.5IRE set-up in NTSC), the other to be used

when the video signal is transmitted without a set-

up (PAL/SECAM).

3.4.13 Bus-controlled Blue Screen

The bus-controlled Blue Screen feature is used to

insert a blue background on the screen when no

video is available. The RGB OSD can be dis-

played when the blue screen is active.

3.4.14 White Insertion

This function is used to force a full white screen at

RGB output via the I²C bus or during Soft mode at

Powerdown.

3.4.15 Automatic RGB Peak Regulation (APR)

The APR function is used to take advantage of the

total RGB output range. APR circuits detect the

peak level of the RGB outputs (before OSD inser-

tion) and regulate the RGB gain (contrast) so that

signals above the APR threshold are limited. For

example, at maximum drive and contrast levels

with the APR function switched OFF, the 100 IRE

input signal gives 3 V(B/W) to the RGB outputs.

With APR ON and the APR threshold at 70 IRE,

the 70 IRE input signal gives 3 V (B/W) at RGB

outputs. For input signals above 70 IRE, the APR

will decrease the RGB gain so that amplitude at

the RGB output is always 3 V (B/W). The APR

gain control voltage is memorized on an external

capacitor where the gain decrease is very fast and

the gain increase is very slow (several frames).

The APR function can be enabled or disabled via

the I²C bus.

APR ON when register 10 hex d0 = 1 and register

07 hex d6 = 0.

3.4.16 RGB Peak Limitation

The APR function can be switched into an RGB

Peak Limitation function via the I²C bus: register

07 hex, data d6 = 1 and register 10 hex d0 = 1.

For this purpose, the APR threshold, tracked with

the contrast for the APR function, is changed in a

fixed threshold that is independent of the contrast.

In this case, the APR threshold I²C control should

be set to its maximum value.

3.5 CHROMA CIRCUIT

3.5.1 PAL/SECAM/NTSC Decoders

SVHS Chroma input; bus-controlled SVHS mode.

– 30 dB Automatic Color Control (ACC) range.

The ACC function is an automatic gain control of

the color amplifier.

– Integrated chroma base band delay line and ON/

OFF bus control.

– Automatic standard identification, with possibility

of forcing the standard via the bus.

– 3-crystal application capability for the South

American market:

The first crystal on Pin XTAL1 (3.5X MHz only),

the second crystal on Pin XTAL2 (3.5X MHz on-

ly), and the third crystal on Pin XTAL3/BTUN

(3.5X MHz only, used for PAL/NTSC application

only).

3.5.2 PAL/NTSC Decoder

ACC carried out by peak detector on synchronous

demodulation of the burst.

Fully-integrated killer function.

VCO using two standard crystals: 4.43 MHz and

3.58 MHz. One crystal is internally selected de-

pending on the standard selection. A third crystal

can be used in PAL/NTSC applications only.

VCO reference signal is available on Pin X1.

– 4.433619 MHz Crystal specification.

Mode of operation: serial resonance (without

load capacity),

Motional capacitance: CM = 13fF ±3fF,

Shunt capacitance: CP < 7pF,

Serial resistance: RS < 70W.

– 3.579545 MHz Crystal specification (NTSC M).

Mode of operation: serial resonance (without

load capacity),

Motional capacitance: CM = 11fF ±3fF,

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