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Details, datasheet, quote on part number:TDA4472-MSD
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Datasheet text preview:
TDA4472
Video-IF and Quasi Parallel Sound Processing
Description
The TDA4472 is an integrated bipolar circuit for 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), and the FM/NICAM sound IF signals.
Features
D 5 V supply voltage; low power consumption D Active carrier generation by FPLL principle (frequency-phase-locked-loop) for true synchronous demodulation D Very linear video demodulation, good pulse response and excellent intermodulation figures D VCO circuit operates at picture carrier frequency D Alignment-free AFC without external reference circuit, polarity of the AFC curve is switchable D VIF-AGC with peak sync. detection D Tuner AGC with adjustable take over point Package: SDIP28, SO28 D Alignment-free quasi parallel sound (QPS) mixer for FM/NICAM sound IF signals D Intercarrier output signal is gain controlled (necessary for digital sound processing) D Separate SIF-AGC with average detection D Two independent SIF inputs D Package and relevant pinning is compatible with the multistandard version TDA4470, which simplifies the design of an universal IF module
Ordering Information
Extended Type Number TDA4472-MSD TDA4472-MFLG3 Package SDIP28 SO28 Remarks Delivery in taped form
Rev. A3, 23FEb01
1 (14)
Preliminary Information
TDA4472
Block Diagram
Offset comp. (optional) Loop filter VCO
FPL L
90°
AFC
6 VIF
VIF amp
Video det.
7
CAGC
8
AGC (VIF)
11
10
Tuner AGC FM det.
Supply
Take over point
27 28
SIF 2
SIF amp
Input switch
3
1
SIF 1
2
AGC (SIF)
5
CAGC
94 8719
Figure 1. Block diagram
2 (14)
Preliminary Information
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Tuner
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0°
VCO + phase shift
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26
18
20
21
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AFC switch
19
22
AFC
12
Video
4,9,16
23 VS 17
CRef
24
Intercarrier (FM / NICAM)
Rev. A3, 23FEb01
TDA4472
Circuit Description
Vision IF Amplifier
The video IF signal (VIF) is fed through a SAW filter to the differential input (Pin 6-7) of the VIF amplifier. This amplifier consists of three AC-coupled amplifier stages. Each differential amplifier is gain controlled by the automatic gain control (VIF-AGC). The output signal of the VIF amplifier is applied to the FPLL carrier generation and the video demodulator. designed for low distortion and large bandwidth. The demodulator output signal passes an integrated low pass filter for attenuation of the residual vision carrier and is fed to the video amplifier. The video amplifier is realized by an operational amplifier with internal feedback and 8 MHz bandwidth (3 dB). An additional noise clipping is provided. The video signal is fed to VIF-AGC and to the video output buffer. This amplifier with a 6 dB gain offers easy adaption of the sound trap. For nominal video IF modulation the video output signal at Pin 12 is 2 Vpp.
Tuner-and VIF-AGC
At Pin 8, the VIF-AGC charges/discharges the AGC capacitor to generate a control voltage for setting the gain of the VIF amplifier and tuner in order to keep the video output signal at a constant level. Therefore, in the case of all negative modulated signals (e.g., B/G standard) the sync. level of the demodulated video signal is the criterion for a fast charge/discharge of the AGC capacitor. The control voltage (AGC voltage at Pin 8) is transferred to an internal control signal, and is fed to the tuner AGC to generate the tuner AGC current at Pin 11 (open collector output). The take over point of the tuner AGC can be adjusted at Pin 10 by a potentiometer or an external dc voltage (from interface circuit or microprocessor).
Sound IF Amplifier and SIF-AGC
The SIF amplifier is nearly identical with the 3-stage VIF amplifier . Only the first amplifier stage exists twice and is switchable by a control voltage at Pin 3. Therefore with a minimal external expense it is possible to switch between two different SAW filters. Both SIF inputs features excellent cross-talk attenuation and an input impedance which is independent from the switching condition. The SIF-AGC is related to the average level of FM-carrier and controls the SIF amplifier to provide a constant SIF signal to the QPS mixer.
FPLL, VCO and AFC
The FPLL circuit (frequency phase locked loop) consists of a frequency and phase detector to generate the control voltage for the VCO tuning. In the locked mode, the VCO is controlled by the phase detector and in unlocked mode, the frequency detector is superimposed. The VCO operates with an external resonance circuit (L and C parallel) and is controlled by internal varicaps. The VCO control voltage is also converted to a current and represents the AFC output signal at Pin 22. A practicable VCO alignment of the external coil is the adjustment to zero AFC output current at Pin 22. At center frequency the AFC output current is equal to zero. The optional potentiometer at Pin 26 allows an offset compensation of the VCO phase for improved sound quality (fine adjustment). Without a potentiometer (open circuit at Pin 26), this offset compensation is not active. The oscillator signal passes a phase shifter and supplies the in-phase signal (0°) and the quadrature signal (90°)of the generated picture carrier.
Quasi-Parallel-Sound (QPS) Mixer
The QPS mixer is realized by a multiplier. The SIF signal (FM or NICAM carrier) is converted to the intercarrier frequency by the regenerated picture carrier (quadrature signal) which is provided from the VCO. The intercarrier signal is fed via an output amplifier to Pin 24.
AFC Switch
The AFC output signal at Pin 22 can be controlled by a switching voltage at Pin 19. It is possible to switch off the AFC.
VCR Mode
For the VCR mode in a TV set (external video source selected), it is recommendable to switch off the IF circuit. With an external switching voltage at Pin 6 or 7, the IF amplifiers are switched off and all signal output levels at Pins 12 and 24 are according to the internal dc voltage.
Internal Voltage Stabilizer
The internal bandgap reference ensures constant performance independent of supply voltage and temperature.
Video Demodulation and Amplifier
The video IF signal, which is applied from the gain controlled IF amplifier, is multiplied with the inphase component of the VCO signal. The video demodulator is
Rev. A3, 23FEb01
3 (14)
Preliminary Information
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