STV2236 datasheet(22/86 Pages) STMICROELECTRONICS

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STV224XH/228XH/223XH - FUNCTIONAL DESCRIPTION

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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).

3.2.7 Vertical Output

The Vertical output pulse is locked on a pulse that

is twice the horizontal frequency to ensure perfect

interlacing.

The Vertical output pulse duration is 10.5 lines.

Horizontal output pulse is a 28 µs line pulse on an

open collector output.

3.2.8 Vertical Control

Bus-controlled DC output voltage for adjusting the

vertical amplitude (pin VAMP). This voltage supply

is used to adjust the slope of the vertical sawtooth

generated by the external vertical booster.

Bus-controlled vertical position (pin VERT). The

high level of the vertical pulse is used to adjust the

vertical position.

The bus-controlled vertical output (pin VERT) low

level voltage can be either 0.2 V or 2.0 V.

3.2.9 Horizontal Output

Start-up circuit: the horizontal output is at high lev-

el (disabled) when VCC1 increases from 0 to 6.0 V

and when VCCD has not reached 4 V.

Soft mode circuit: it provides a softer operating

horizontal output with a 75% duty cycle [tHIGH /

(tHIGH +tLOW)]. This results in a smaller conducting

time (16 µs instead of 28 µs).

This mode is active at start-up until two frames af-

ter the VCC2 reaches 75% of the VCC1. It is also

active at shutdown when the VCC1 floats between

6 V and 5.4 V. And finally, this mode is used if the

VCC2 drops below 75% of the VCC1.

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).

The horizontal position adjustment is controlled via

the bus.

3.2.10 Horizontal Control

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.

3.2.11

Combined

Line

Flyback

Super-

Sandcastle

Combined Line Flyback input and Super-Sandcas-

tle 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.

3.2.12 Line Blanking

Line blanking at RGB outputs is logical OR of line

flyback pulse and internal line blanking pulse with

a 12 µs width.

In Wide Line Blanking mode, line blanking at RGB

outputs is logical OR of line flyback pulse and in-

ternal line blanking pulse with a 15.8 µs width.

Wide line blanking is recommended when display-

ing a 4:3 image on a 16:9 screen (horizontal scan-

ning reduction).

3.2.13 Copy Protection Mode

This mode is used to improve the display of copy-

protected video signals.

3.3 FILTERS

3.3.1 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). In external YCrCb mode, the trap

and luma delay can be switched off via the I²C bus.

3.3.2 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.

3.3.3 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.

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