STV2246C datasheet(19/76 Pages) STMICROELECTRONICS

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STV223XD/224XC - FUNCTIONAL DESCRIPTION

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At shutdown, horizontal pulses are disabled when

VCC1 is less than 5.4 V or when VCCD is less than

3.5 V.

The horizontal output pulse may be disabled via

the bus (force a high level on HOUT).

Safety input on BCL Pin. When the BCL Pin is

switched to ground, the horizontal output pulse is

disabled and the inhibition of horizontal output

pulse is maintained until VCC1 is less than 3 V

(VCC1 power supply is switched off). The Safety

function can be disabled via the I²C bus. When

function is reset and no longer active.

The horizontal position adjustment is controlled via

the bus.

Bus-controlled DC output voltage for adjusting the

vertical amplitude. This voltage supply is used to

adjust the slope of the vertical sawtooth generated

by the external vertical booster.

Bus-controlled vertical position. The high level of

the vertical pulse is used to adjust the vertical po-

sition.

Bus-controlled 4/3-16/9 selection. 0.2 V is the low

level of the vertical pulse when 16/9 is selected

and 2 V when 4/3 is selected.

The Oversized Blanking function is controlled by

the voltage on the FBOSD pin. When the FBOSD

voltage is between the first and the second thresh-

olds, the OSD RGB signals are selected. When

the FBOSD voltage is greater than the second

threshold (4 V blanking threshold), the RGB out-

puts are blanked during the whole field, but not

during inserted cut-off lines (the cut-off loop is al-

ways active). The blanking feature, via the FBOSD

input pin, enables Vertical Oversize Blanking

when a 4/3 picture is displayed on a 16/9 screen in

Zoom mode. The picture outside the screen is

blanked by the Oversize Blanking pulse supplied

by the external vertical IC (STV9306).

Combined Flyback input and Super-Sandcastle

output: The line blanking level is clamped at 3 V,

the burst key pulse voltage is 5 V and vertical

pulse voltage is 2 V. The line pulse is extracted

with a 2.5 V slicing level used for RGB line blank-

ing and PLL2 control.

3.3 FILTERS

Integrated Trap Filter

Q = 1.5 (f-3dB = f0 (1-1/2Q)),

Center frequency:

– 4.43 MHz, 3.58 MHz for PAL and NTSC.

– 4.25 MHz, for SECAM

(-20 dB rejection between 4.1 MHz and

4.4 MHz).

The chroma trap filter is switched off in SVHS

mode, or in color standard search mode (standard

not identified). The trap filter can be switched off

via the bus.

Integrated Chroma Bandpass

Q = 3.5, Center frequency: 4.43 MHz, 3.58 MHz.

The Bus Control Frequency Shift is used to opti-

mize the chroma response for the video signal

from the IF stage.

Integrated Bell Filter for SECAM

Q = 16, Center frequency: 4.286 MHz.

The Bus Control Frequency Shift is used to opti-

mize the chroma response for the video signal

from the IF stage.

Integrated Luma Delay Line

Bandwidth: 8 MHz.

The Luma Delay Line is automatically adapted to

the chroma standard. For PAL BG and applica-

tions without group delay compensation, a Luma

Delay Shift of -140 ns can be selected via the I²C

bus.

Filter Tuning

All filters are tuned via a reference phase-locked

loop. The PLL is based on a trap filter, a phase

comparator and an internal loop filter (capacitor).

The reference signal is the continuous carrier

wave from the Chroma VCO (4.43 MHz or

3.58 MHz). The PLL adjusts the center frequency

of the trap until it equals the reference signal.The

PLL tuning voltage is used to adjust all other inte-

grated filters. The Bell filter is fine-tuned with a

second PLL during the frame retrace. The Bell fil-

ter tuning voltage is memorized on an external ca-

pacitor (BTUN Pin).

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