TDA9550 PHILIPS [NXP Semiconductors], TDA9550 Datasheet - Page 65

• Manufacturer Part Number: TDA9550
• Description: TV signal processor-Teletext decoder with embedded m-Controller
• Manufacturer: PHILIPS [NXP Semiconductors]

Philips Semiconductors
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:
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:
2000 Jun 22
EW width
EW parabola width
EW upper and lower corner parabola correction
EW trapezium correction
Vertical zoom
horizontal parallelogram and bow correction.
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.
TV signal processor-Teletext decoder with
embedded -Controller
65
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
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 -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.
-Controller/Teletext decoder.
TDA955X/6X/8X PS/N1 series
Tentative Device Specification