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Details, datasheet, quote on part number:TDA4470-MSD
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TDA4470
Multistandard Video-IF + Quasi Parallel Sound Processing
Description
The TDA4470 is an integrated bipolar circuit for multistandard 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.
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, the VCO frequency is switchable for L'-mode D Alignment-free AFC without external reference circuit, polarity of the AFC curve is switchable D VIF-AGC for negative modulated signals (peak sync. detection) and for positive modulation (peak white/ black level detector) D Tuner AGC with adjustable take over point D Alignment-free quasi parallel sound (QPS) mixer for FM/NICAM sound IF signals Package: SDIP28, SO28, SSO28 D Intercarrier output signal is gain controlled (necessary for digital sound processing) D Complete alignment-free AM demodulator with gain controlled AF output D Separate SIF-AGC with average detection D Two independent SIF inputs D Parallel operation of the AM demodulator and QPS mixer (for NICAM-L stereo sound) D Package and relevant pinning is compatible with the single standard version TDA4472, which simplifies the design of an universal IF module
Ordering Information
Extended Type Number TDA4470-MSD TDA4470-MFLG3 TDA4470-MFS TDA4470-MFSG3 Package SDIP28 SO28 SSO28 SSO28 Remarks Delivery in taped form Delivery in tubes Delivery in taped form
Rev. A4, 23-Feb-01
1 (17)
TDA4470
Offset comp. (optional) Loop filter
VCO
26
18
20
21
FPLL
0° 90°
VCO + phase shift
Control
AFC VIF amp
6 VIF CAGC 7
8 15
Video det. AGC (VIF)
CBL Tuner
10 Take over point SIF 2 SIF input switch
Tuner AGC FM det.
Supply
27 28
SIF amp
3
1 2
SIF 1
AGC (SIF) AM det.
5 CAGC
95 10851
Figure 1. Block diagram
2 (17)
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Standard
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14
Block Diagram
L' switch
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19 AFC switch AFC 22 12 Video 13 Standard switch 23 VS 17 CRef 24 Intercarrier (FM / NICAM) 25 AF (AM) 4,9,16 Rev. A4, 23-Feb-01
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TDA4470
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. The oscillator signal passes a phase shifter and supplies the in-phase signal (0°) and the quadrature signal (90°)of the generated picture carrier.
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 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). A standard dependent dc level shift in this stage delivers the same sync. level for positive and negative modulation. 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. For positive modulation (e.g., L standard) the peak white level of video signal controls the charge current. In order to reduce reaction time for positive modulation, where a large time constant is needed, an additional black level detector controls the discharge current in the event of decreasing VIF input signal. 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 AM- or FM-carrier and controls the SIF amplifier to provide a constant SIF signal to the AM demodulator and 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. At the AFC switch (Pin 19) three operating conditions of the AFC are possible: AFC curve "rising" or "falling" and AFC "off". 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. Furthermore, at Pin 14, the VCO center frequency can be switched for setting to the required L' value (L' standard). 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.
AM Demodulator
The alignment-free AM demodulator is realized by a synchronous detector. The modulated SIF signal from the SIF amplifier output is multiplied in phase with the limited SIF signal (AM is removed). The AF signal of the demodulator output is fed to the output amplifier and to the SIF-AGC. For all TV standards with negative video modulation (e.g., B/G standard), the AF output signal (Pin 25) is switched off by the standard switch.
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.
Rev. A4, 23-Feb-01
3 (17)
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