Features
•
5-V Supply Voltage
•
Gain-controlled 3-stage Wide-band IF Amplifier
•
Active Carrier Generation by FPLL Principle (Frequency-Phase-Locked-Loop) for True
Quadrature Demodulation
•
Complete Alignment-free AM Demodulator
•
Switchable Amplitude Detector for Gain Control, which Operates as a Peak Detector for
FM Sound and as a Mean Level Detector for AM Sound
Description
The U4468B is an integrated bipolar circuit for full multistandard sound IF signal pro-
cessing in TV/VTR and multimedia applications. It supplies AM signals as well as
FM/NICAM sound IF signals and thus allows the design of a universal sound IF mod-
ule for various applications.
Quasi-split
Sound Circuit
and AM
Demodulator IC
U4468B
Figure 1.
Block Diagram
V
S
4
14
REF
IF-amp
Loop
filter
5
FPLL
05
905
VCO
8
9
VCO
IF
FM
2
1
IF
AM
12
Intercarrier
(FM)
Mean
3
AGC
Peak
level
13
IF AGC
Mean/peak
7
S
1
Mute
AM-det
10
S
2
6
AF (AM)
Rev. 4777A–TVVCR–01/04
Circuit Description
IF Amplifier and AGC
The symmetrical IF input signal from the external SAW filter is fed to the pins 1 and 2. In
case of FM/NICAM applications, a SAW filter with double band-pass characteristic is
required for the vision and sound carrier. In case of the L-standard, a band-pass filter
with the center frequency at the L-sound carrier is used.
The amplifier consists of three AC-coupled wide-band IF stages. Each differential ampli-
fier stage is gain controlled by the AGC (Automatic Gain Control) voltage, available at
pin 3. The output signal of the IF amplifier is then applied to the FPLL carrier generation,
to the mixer for FM/NICAM signals and to the AM demodulator.
The IF-AGC is derived from the average level of the AM carrier (L-standard) or from the
peak value of the FM carrier (e.g., B/G standard). It controls the three-stage wide-band
amplifier to provide a constant SIF signal to the AM demodulator or to the QSS (quasi-
split sound) mixer.
Standard Switch
If the standard switch (pin 7) is in position “low” (for AM sound), the AGC is operating as
an average level detector. In position “open” or “high” (for FM/NICAM sound), the AGC
acts as a peak value detector.
The internal band gap reference voltage (4.25 V at pin 4) ensures constant perfor-
mance, independent of supply voltage and temperature.
The FPLL (frequency-phase-locked loop) circuit consists of a frequency detector and a
phase detector to generate a control voltage for the VCO tuning. In locked mode, the
VCO is controlled by the phase detector while in unlocked mode, the frequency detector
is superimposed. The VCO operates with an external resonance circuit (L and C paral-
lel) and is controlled by integrated varicaps.
A practicable VCO alignment of the external coil is the adjustment of the loop filter volt-
age (pin 5) to 2.3 V. At this value, the capture and hold range are centered.
Internal Voltage
Stabilizer
FPLL, VCO
AM Demodulator
The alignment-free AM demodulator is realized by a synchronous detector. The modu-
lated IF signal from the wide-band IF amplifier output is multiplied in phase with the
limited SIF signal to remove the AM. Then, the resulting AF signal of the demodulator
output is fed to the output amplifier and to the AGC stage.
Quasi-Split-Sound (QSS)
The QSS mixer is realized by a multiplier circuit. The IF signal (FM/NICAM) is converted
to the intercarrier frequency by means of a quadrature signal from the generated picture
Mixer
carrier provided by the PLL. The intercarrier signal is fed via an output amplifier to
pin 12.
Mute Switch
The AM sound output (pin 6) can be muted by switching the pulling mute switch (pin 10)
to “low”.
2
U4468B
4777A–TVVCR–01/04
Absolute Maximum Ratings
Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating
only and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of this
specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
Reference point pin 13, unless otherwise specified.
Parameters
Supply voltage range
Supply current
Power dissipation (V
S
= 9 V)
Output currents
External voltages
Junction temperature
Operating temperature range
Storage temperature
Electrostatic handling
(1)
Note:
All
6, 12
1 - 4, 6, 12
5, 8, 9
7, 10
T
j
T
amb
T
stg
V
ESD
V
ext
Pin
14
14
Symbol
V
s
I
s
P
I
out
Value
4.5 to 9.0
55
500
5
+4.5
+3.5
V
s
+125
0 to +85
-25 to +125
±300
Unit
V
mA
mW
mA
V
V
V
°C
°C
°C
V
1. Equivalent to discharging a 200-pF capacitor through a 0-W resistor
Thermal Resistance
Parameters
Junction ambient when soldered to PCB
Symbol
R
thJA
Value
60
Unit
K/W
4
U4468B
4777A–TVVCR–01/04
U4468B
Electrical Characteristics
V
S
= +5 V, T
amb
= +25°C; reference point pin 13, unless otherwise specified.
Parameters
DC Supply (Pin 14)
Supply voltage
Supply current
IF Input (Pins 1, 2)
Minimum IF input signal
Maximum IF input signal
Input impedance
Input capacitance
SIF-AGC (Pin 3)
IF gain control range
AGC capacitor
FPLL and VCO (Pins 5, 8, and 9)
Maximum oscillator frequency
Vision carrier capture range
Oscillator drift (free running) as
function of temperature
Standard Switch (Pin 7)
Switching voltage for mode 1:
FM/NICAM sound
Switching voltage for mode 2:
AM sound
Switching current
AM Mute Switch (Pin 10)
Switching voltage
Switching voltage
Switching current
Intercarrier Output (Pin 12)
(4)
DC output voltage
Output resistance
Intercarrier output signal
Intercarrier bandwidth
Notes:
1.
2.
3.
4.
(1)
Test Conditions
Symbol
V
S
Min.
4.5
Typ.
5.0
40
50
Max.
9.0
Unit
V
mA
µV
rms
mV
rms
kW
pF
dB
µF
MHz
V
in
=10 mV or V
3
= 2 V
Output signal: -3 dB
Output signal: +1 dB
(1)
(1)
I
S
v
in
v
in
R
in
C
in
G
v
C
AGC
60
70
100
1.2
2
65
4.7
For carrier generation
f
VCO
= 38.9 MHz
C
VCO
= 6.2 pF
DT
amb
= 55°C,
f
VCO
= 38.9 MHz
C
VCO
= 6.2 pF
(2)
f
VCO
Df
cap
Df/DT
70
±1.5
±2
MHz
-0.3
%
Peak value control
(3)
Average level control
V
sw1
V
sw2
I
sw
2.0
0
±100
open
0
-100
2
V
S
1.5
V
V
µA
AM output active
AM output switched off
V
mute1
V
mute2
I
mute
V
DC
R
out
V
out
B
100
1.5
V
µA
V
200
150
TBD
TBD
W
mV
rms
MHz
MHz
v
in
= 10 mV
5.5 MHz output signal
-1 dB
-3 dB
This parameter is given as an application information and is not tested during production.
The oscillator drift is related to the picture carrier frequency, with an external temperature-compensated LC circuit.
Without external control voltage (pin 7 open), the IC automatically operates in mode 1.
Picture carrier PC = 38.9 MHz; sound carrier SC
1
= 33.4 MHz, SC
2
= 33.16 MHz;
PC/SC
1
=13 dB; PC/SC
2
= 20 dB; PC unmodulated (equivalent to sync peak level).
5. Sound carrier SC = 32.4 MHz, modulated with f
mod
= 1 kHz, m = 54%; v
in
= 10 mV.
5
4777A–TVVCR–01/04
51mcu
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