TDA9554PS datasheet(65/125 Pages) PHILIPS

65 / 125 page

2000 Jun 22

Philips Semiconductors

Tentative Device Speciﬁcation

TV signal processor-Teletext decoder with

embedded

µ-Controller

TDA955X/6X/8X PS/N1 series

The types which are intended to be used in combination

with 110

° picture tubes have an East-West control circuit

in stead of the AVL function. The additional controls for

these types are:

• EW width

• EW parabola width

• EW upper and lower corner parabola correction

• EW trapezium correction

• Vertical zoom

• horizontal parallelogram and bow correction.

When the vertical amplitude is compressed (zoom

factor <1) it is still possible to display the black current

measuring lines in the overscan. This function is activated

by means of the bit OSVE in subaddress 26H.

Chroma, luminance and feature processing

The chroma band-pass and trap circuits (including the

SECAM cloche filter) are realised by means of gyrators

and are tuned to the right frequency by comparing the

tuning frequency with the reference frequency of the

colour decoder. The luminance delay line and the delay

cells for the peaking circuit are also realised with gyrators.

The circuit contains the following picture improvement

features:

• Video dependent coring in the peaking circuit. The

coring can be activated only in the low-light parts of the

screen. This effectively reduces noise while having

maximum peaking in the bright parts of the picture.

• Black stretch. This function corrects the black level for

incoming signals which have a difference between the

black level and the blanking level.

• Blue-stretch. This circuit is intended to shift colour near

‘white’ with sufficient contrast values towards more blue

to obtain a brighter impression of the picture.

• Dynamic skin tone (flesh) control. This function is

realised in the YUV domain by detecting the colours

near to the skin tone.

Colour decoder

The ICs can decode PAL, NTSC and SECAM signals. The

PAL/NTSC decoder does not need external reference

crystals but has an internal clock generator which is

stabilised to the required frequency by using the 12 MHz

clock signal from the reference oscillator of the

µ-Controller/Teletext decoder.

Under bad-signal conditions (e.g. VCR-playback in feature

mode), it may occur that the colour killer is activated

although the colour PLL is still in lock. When this killing

action is not wanted it is possible to overrule the colour

killer by forcing the colour decoder to the required standard

and to activate the FCO-bit (Forced Colour On) in

subaddress 21H.

The Automatic Colour Limiting (ACL) circuit (switchable

via the ACL bit in subaddress 20H) prevents that

oversaturation occurs when signals with a high

chroma-to-burst ratio are received. The ACL circuit is

designed such that it only reduces the chroma signal and

not the burst signal. This has the advantage that the colour

sensitivity is not affected by this function.

The SECAM decoder contains an auto-calibrating PLL

demodulator which has two references, viz: the divided 12

MHz reference frequency (obtained from the

µ-Controller)

which is used to tune the PLL to the desired free-running

frequency and the bandgap reference to obtain the correct

absolute value of the output signal. The VCO of the PLL is

calibrated during each vertical blanking period, when the

IC is in search or SECAM mode.

The base-band delay line (TDA 4665 function) is

integrated. This delay line is also active during NTSC to

obtain a good suppression of cross colour effects. The

demodulated colour difference signals are internally

supplied to the delay line.

TDA9554PS Datasheet(PDF) 65 Page - NXP Semiconductors

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