TDA4474
Rev. A3, 23-Feb-01
1 (16)
Multistandard Video-IF + Quasi Parallel Sound Processing
Description
The TDA4474 is an integrated bipolar circuit for full
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.
Four IF inputs (2
VIF plus 2 SIF) and the common
pinning with TDA4471 gives flexibility to design a
universal IF module for various applications.
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 is operating on picture carrier frequency,
the VCO frequency is switchable for the 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
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 Parallel operation of the AM demodulator and QPS
mixer (for NICAM-L stereo sound)
D Four IF inputs (2 VIFin and 2 SIFin)
D Package and relevant pinning is compatible with the
TDA4471; simplifies the design of an universal IF
module
Package: SDIP30
Ordering Information
Extended Type Number
Package
Remarks
TDA4474-MSD
SDIP30
TDA4474
Rev. A3, 23-Feb-01
2 (16)
Block Diagram
AGC
(VIF)
Tuner
AGC
AGC
(SIF)
13
12
Tuner
29
30
3
1
2
5
SIF 2
SIF 1
VCO
+
phase shift
AFC
Standard
Supply
L' switch
VCO
23
22
20
Loop
filter
16
Offset
comp.
(optional)
28
FPLL
0
90
VIF amp
6
7
8
17
VIF 1
C
AGC
C
BL
Take over
point
SIF input switch
C
AGC
24
14
4,9,18
15
Standard
switch
25
V
S
19
C
Ref
Intercarrier
(FM / NICAM)
26
FM det.
AM det.
SIF amp
27
AF (AM)
AFC
Video
94 7901
Video det.
Control
and VIF input switch
21
AFC
switch
10
11
VIF 2
Figure 1. Block diagram
TDA4474
Rev. A3, 23-Feb-01
3 (16)
Pin Description
1
2
3
4
5
6
7
8
10
9
29
24
23
22
20
21
19
12
11
30
27
28
25
26
V
i,VIF1
V
i,VIF1
C
AGC
GND
V
i,VIF2
V
i,VIF2
GND
C
AGC
R
top
V
SW
V
i,SIF1
V
i,SIF1
V
S
V
AFC
V
VCO
V
VCO
V
SW
LF
V
o,AM
V
o,FM
C
Ref
R
comp
V
i,SIF2
V
i,SIF2
18
17
14
13
94 8680
I
tun
V
o,vid
GND
C
BL
16
15
V
SW
(stand.)
V
SW
(L')
Figure 2. Pinning
Pin
Symbol
Function
1, 2
V
i,SIF1
SIF1 input (symmetrical)
3
V
SW
SIF input selector switch
4
GND
Ground
5
C
AGC
SIF-AGC (time constant)
6, 7
V
i,VIF1
VIF1 input (symmetrical)
8
C
AGC
VIF-AGC (time constant)
9
GND
Ground
10, 11
V
i,VIF2
VIF2 input (symmetrical)
12
R
top
Take over point, tuner AGC
13
I
tun
Tuner AGC output current
14
V
o,vid
Video output
15
V
SW
Standard switch
16
V
SW
L'/VIF input selector switch
17
C
BL
Capacitor black level detector
18
GND
Ground
19
C
Ref
Internal reference voltage
20
LF
Loop filter
21
V
SW
AFC switch
22, 23
V
VCO
VCO circuit
24
V
AFC
AFC output
25
V
S
Supply voltage
26
V
o,FM
Intercarrier output
27
V
o,AM
AF output AM sound
28
R
comp
Offset compensation
29, 30
V
i,SIF2
SIF2 input (symmetrical)
TDA4474
Rev. A3, 23-Feb-01
4 (16)
Circuit Description
Vision IF Amplifier
The video IF signal (VIF) is fed through a external SAW
filter to one of the two VIF inputs (Pins 6-7 or 10-11). The
selection of VIF inputs is controlled by Pin 16 in
combination with the standard switch. With a minimal
external expense it is possible to switch between two
different SAW filters. Both VIF inputs features excellent
cross-talk attenuation and an input impedance which is
independent from the switching condition. The VIF
amplifier consists of three ac-coupled amplifier stages.
Each differential amplifier is gain controlled by the
automatic gain control (VIF-AGC). Output signal of the
VIF amplifier is applied to the FPLL carrier generation
and the video demodulator.
Tuner and VIF-AGC
At Pin 8 the VIF-AGC charges/discharges the AGC
capacitor to generate a control voltage for setting gain of
VIF amplifier and tuner in order to keep the video output
signal at a constant level. Therefore in case of 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
very large time constant is needed, an additional black
level detector (Pin 17) controls the discharge current in
the event of decreasing VIF input signal. The AGC volt-
age is transferred to an internal control signal and fed to
the tuner AGC to generate the tuner AGC current at
Pin 13 (open collector output).
Take over point of the tuner AGC can be adjusted at
Pin 12 by a potentiometer or an external dc voltage (from
interface circuit or microprocessor).
FPLL, VCO and AFC
The FPLL circuit (frequency phase locked loop) consists
of a frequency and phase detector to generate 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 24. With the AFC
switch (Pin 21) 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 24. At center
frequency the AFC output current is equal to zero.
Furthermore, at Pin 16, the VCO center frequency can be
switched for setting to the required L' value This function
is active when "L mode" is selected by the standard
switch.
The optional potentiometer at Pin 28 allows an offset
compensation of the VCO phase for improved sound
quality (fine adjustment). Without a potentiometer (open
circuit at Pin 28) 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.
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 6 dB gain offers
easy adaption of the sound trap. For nominal video IF
modulation the video output signal at Pin 14 is 2 V (peak-
to-peak value).
Sound IF Amplifier and SIF-AGC
The SIF amplifier is nearly identical with the 3-stage VIF
amplifier. 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. Each differential amplifier is controlled by the
automatic gain control for the sound IF path (SIF-AGC).
Output signal of the SIF amplifier is applied to the mixer
for FM/NICAM signals and the demodulator for AM
sound signals.
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.
TDA4474
Rev. A3, 23-Feb-01
5 (16)
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 27) 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 26.
Standard Switch
To have equal polarity of the video output signal the
polarity can be switched in the demodulation stage in
accordance with the TV standard. Additional a standard
dependent dc level shift in the video amplifier delievers
the same sync. level. Parallel the correct VIF-AGC is
selected for positive or negative modulated VIF signals.
In case of negative modulation (e.g., B/G standard) the
AM output signal is switched off. If the standard for
positive modulation (L standard) is selected the AM
demodulator and QPS mixer is active. This condition
allows a parallel operation of the AM sound signal and the
NICAM-L stereo sound.
L' Switch and VIF Input Selection
For positive modulated signals (L/L' standard) Pin 16
works as L' switch. With a control voltage the VCO
frequency can be switched for setting to the required
L' value (L' standard). Also a fine adjustment of the
L'-VCO center frequency is possible by a potentiometer.
The L' switch is only active for positive modulated video
IF signals (standard switch in L mode). In this mode the
video IF input 2 (VIF2) is forced by the standard switch.
The possibility to select VIF1 input is given by
connecting VIF2 input (Pin 10 or 11) via 10 k
W resistor
to ground.
If negative modulation (B/G mode) is selected Pin 16
operates as an input selection switch for the two VIF
inputs.
AFC Switch
The AFC output signal at Pin 24 can be controlled by a
switching voltage at Pin 21. It is possible to select an AFC
output signal with rising- or falling AFC curve and to
switch off the AFC.
Internal Voltage Stabilizer
The internal bandgap reference ensures constant
performance independant of supply voltage and
temperature.
Absolute Maximum Ratings
Reference point Pin 4 (9, 18), unless otherwise specified
Parameters
Symbol
Value
Unit
Supply voltage
Pin 25
V
s
9.0
V
Supply current
Pin 25
I
s
93
mA
Power dissipation, V
s
= + 9 V
P
840
mW
Output currents
Pin 14, 26, 27
I
out
5
mA
External voltages
Pins 1, 2, 58, 1012, 14, 16, 19, 20, 2630
+ 4.5
V
Pins 17, 22, 23
V
ext
+ 3.5
V
Pin 13
+ 13.5
V
Pins 3, 15, 21, 24
V
s
V
Junction temperature
T
j
+125
C
Storage temperature
T
stg
25 to +125
C
Electrostatic handling *)
all pins
V
ESD
"300
V
*) Equivalent to discharging a 200 pF capacitor through a 0
W resistor
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