Daewoo DTK-28 Series, Service Manual, Page: 36 / 71

CP-850/F Service Manual
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4.5 TDA4470 - MULTISTANDARD VIDEO-IF AND QUASI PARALLEL SOUND PROCESSOR
4.5.1
DESCRIPTION
The TDA4470 is an integrated bipolar circuit for multi-standard video/sound IF (VIF/SIF) signal processing in TV/VCR
and multimedia applications. The circuit processes all TV video IF signals with negative modulation (e.g., B/G
standard), positive modulation (e.g., L standard) and the AM, FM/NICAM sound IF signals.
4.5.2 FEATURES
- 5 V supply voltage; low power consumption.
- Active carrier generation by FPLL principle (frequency-phase-locked-loop) for true synchronous demodulation.
- Very linear video demodulation, good pulse response and excellent intermodulation figures.
- VCO circuit operates at picture carrier frequency, the VCO frequency is switchable for L’-mode
- Alignment-free AFC without external reference circuit, polarity of the AFC curve is switchable.
- VIF-AGC for negative modulated signals (peak sync. detection) and for positive modulation (peak white/black level
detector).
- Tuner AGC with adjustable take over point.
- Alignment-free quasi parallel sound (QPS) mixer for FM/NICAM sound IF signals.
- Intercarrier output signal is gain controlled (necessary for digital sound processing).
- Complete alignment-free AM demodulator with gain controlled AF output.
- Separate SIF-AGC with average detection
- Two independent SIF inputs
- Parallel operation of the AM demodulator and QPS mixer (for NICAM-L stereo sound).
4.5.3 PINNING
Pin Symbol Function
1, 2 Vi, SIF1 SIF1 input (symmetrical)
3 VSW Input selector switch
4, 9, 16 GND Ground
5 VAGC SIF - AGC (time constant)
6, 7 Vi, VIF VIF input (symmetrical)
8 CAGC VIF - AGC (time constant)
10 RTOP Take Over Point, tuner AGC
11 Itun Tuner AGC output current
12 VO, VID Video output
13 VSW Standard switch
14 VSW L’ switch
15 Cbl Black level capacitor
17 Cref Internal reference voltage
18 LF Loop Filter
19 VSW AFC switch
20, 21 VVCO VCO circuit
22 VAFC AFC output
23 VS Supply voltage
24 VO, FM Intercarrier output
25 VO, AM AF output - AM sound
26 Rcomp Offset compensation
27, 28 Vi, SIF2 SIF2 input (symmetrical)