TDA935x Philips, TDA935x Datasheet - Page 63

• Manufacturer Part Number: TDA935x
• Description: TV Signal Processor-Teletext Decoder with Embedded u-Controller
• Manufacturer: Philips

Philips Semiconductors
Synchronisation circuit
The IC contains separator circuits for the horizontal and
vertical sync pulses and a data-slicing circuit which
extracts the digital teletext data from the analog signal.
The horizontal drive signal is obtained from an internal
VCO which is running at a frequency of 25 MHz. This
oscillator is stabilised to this frequency by using a 12 MHz
signal coming from the reference oscillator of the
The horizontal drive is switched on and off via the soft
start/stop procedure. This function is realised by means of
variation of the T
addition the horizontal drive circuit has a ‘low-power
start-up’ function.
The vertical synchronisation is realised by means of a
divider circuit. The vertical ramp generator needs an
external resistor and capacitor. For the vertical drive a
differential output current is available. The outputs must be
DC coupled to the vertical output stage.
In the types which are intended for 90 picture tubes the
following geometry parameters can be adjusted:
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.
2001 Jan 18
-Controller.
Horizontal shift
Vertical amplitude
Vertical slope
S-correction
Vertical shift
EW width
EW parabola width
EW upper and lower corner parabola correction
EW trapezium correction
Vertical zoom
horizontal parallelogram and bow correction.
TV signal processor-Teletext decoder with
embedded -Controller
ON
of the horizontal drive pulses. In
63
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:
Peaking control circuit. The ratio of the positive and
negative overshoots of the peaking can be adjusted by
means of the bits RPO1/RPO0 in subaddress 2EH.
Black stretch. This function corrects the black level for
incoming signals which have a difference between the
black level and the blanking level.
TDA935X/6X/8X PS/N2 series
Tentative Device Specification