STV5730A datasheet(14/20 Pages) STMICROELECTRONICS

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VIDEO OUT1

VIDEO OUT2

disa ble

S TV5730A

Figure 4 :

The Translucent Mixed Mode Output

Configuration

FUNCTIONAL DESCRIPTION (continued)

5.1 - Internal Bias Mode

This mode is intended for minimal cost applica-

tions. C10 must be cleared.

The luma levels of the OSD output signal are as

follows :

- LEBLACK : black level

nominal value : 1.25V

- LESYNC : sync level

nominal value : LEBLACK - 300mV

- LESCREEN : page background level

nominal value : LEBLACK + 150mV

- LECHAR : character level

nominal value : LEBLACK + 650mV

LEBLACK is also used to clamp the VIDEO IN

signal and to create the character border.

5.2 - External Bias Mode

This mode is intended to give more flexibility to the

user. C10 must be set.

The LESCREEN and LECHAR levels may be user

defined relatively to the internal LEBLACK level.

The final luma amplitude should not be greater than

the peak white level.

These levels may be static or dynamic.

Dynamic levels can be easily generated by analog

sum of the R/G/B and CO STV5730A outputs (a

few resistors are necessary) to give grey scale

character shading in the mixed mode.

C0 is useful to control the character foreground

luma level.

6 - THE CHROMA GENERATOR

The STV5730Aencoder operates in full page mode

only. It may perform PAL or NTSC encodingaccord-

ing to the C8 control bit.

A 4*fsc chroma quartz crystal is necessary

(fsc = 4.43MHz for PAL, 3.58MHz for NTSC).

The encoder can be turned off by the M6 mode bit

for black & white or for SECAM applications.

The character encoding is controlled by the C9

control bit.

The chroma signal is output on the COUT pin for

external filtering and for attenuation if necessary. It

is then re-entered on the CIN pin and added to the

YIN pin signal to create the final CVBS output

signal.

The chroma saturation is controlled by the

STV5730A :

- burst nominal amplitude : 320mVPP

- blue or yellow colors nominal amplitude :

420mVPP

- red, magenta, green or cyan colors nominal am-

plitude : 580mVPP

7 - THE MARKERS

The STV5730A can generate 3 different markers

that can be activated simultaneously (i.e. on the

same page).

The following marker features are performed :

- Blinking character, character background off.

The character foreground blinks (BK = 1, BE = 0

or C1 = 1).

- Not blinking character, character background on

(C1 = 0, BE = 1).

- Blinking character, character background on.

The character foreground blinks and the charac-

ter background remains (BK = 1, BE = 1, C1 = 0).

8 - THE TRANSLUCENT MIXED MODE

The VIDEO OUT1 and VIDEO OUT2 outputs may

be summed via two external resistors to create a

translucent text (mixed mode). In this case, the

background picture is still visible behind the text.

The background picture visibility (or level of trans-

lucence is controlled by the resistor ratio.

Another benefit from this function is to allow

PAL/SECAM/NTSC multistandard applications to

be built with no SECAM chroma re-insertion filter

and no additional control switches.

The sum may be cancelled by setting the M8 mode

bit. In this case, the VIDEO OUT2 pin is in high

impedance state and the resistor network delivers

VIDEO OUT1 only.

When using the resistor network, please set M8 in

the following cases :

- in full page mode

- when OSD in not displayed

- to select opaque text. This allows the viewer to

select by software the preferred display mode.

The DC levels of the VIDEO OUT1, VIDEO OUT2

and the sum signals are high enough to directly

drive a NPN emitter follower driver (see Table 1).

STV5730A

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