Daewoo DTC-14D9T Service Manual page 33

IC DESCRIPTION
TV signal processor-Teletext decoder with embedded -Controller
TDA9345 PS-N3; TDA9346 PS-N3
GENERAL DESCRIPTION
The TDA9345 and TDA9346 PS-N3 combine the functions
of a video processor together with a m-Controller a Teletext
decoder and US Closed Caption decoder. The teletext
decoder has an internal RAM memory for 1 page
(TDA9345) or 10 page (TDA9346) text.The ICs are
intended to be used in economy television receivers with
picture tubes up to 100¡.
The ICs have supply voltages of 8 V and 3.3 V and they
are mounted in an SDIP-64 envelope.
The features are given in the following feature list.
FEATURES
TV processor
¥ Multi-standard vision IF circuit with alignment-free PLL
demodulator
¥ Internal (switchable) time-constant for the IF-AGC circuit
¥ The mono intercarrier sound circuit has a selective FM-
PLL demodulator which can be switched to the different
FM sound frequencies (4.5/5.5/6.0/6.5 MHz).
The quality of this system is such that the external band-
pass filters can be omitted.
¥ Source selection between the internal CVBS and an
external CVBS or Y/C signal
¥ Integrated chrominance trap circuit
¥ Integrated luminance delay line with adjustable delay
time
¥ Picture improvement features with peaking (with
switchable centre frequency, depeaking, variable
positive/negative overshoot ratio and coring) and black
stretching. These features are available for CVBS and
Y/C signals. The black stretch feature is also available for
external YPB PR signals.
¥ Integrated chroma band-pass filter with switchable centre
frequency
¥ Only one reference (12 MHz) crystal required for the m-
Controller and the colour decoder
¥ Multi-standard colour decoder with automatic search
system
¥ Internal base-band delay line
¥ Indication of the Signal-to-Noise ratio of the incoming
CVBS signal
¥ A linear RGB/YPB PR input with fast blanking for
external RGB/YPB PR sources. The synchronisation
circuit can be connected to the incoming Y signal. The
OSD signals are internally supplied from the m-
Controller.
¥ RGB control circuit with Continuous Cathode
Calibration , white point and black level off-set adjustment
so that the colour temperature of the dark and the light
parts of the screen can be chosen independently.
¥ OSD/Text gain reduction control
¥ Horizontal synchronization with two control loops and
alignment-free horizontal oscillator
¥ Vertical count-down circuit
¥ Vertical driver optimized for DC-coupled vertical output
stages
¥ Low-power start-up of the horizontal drive circuit
¥ Macrovision keying possibility for horizontal
synchronisation.
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APPENDIX