TDA4433 Datasheet, PDF (4/5 Pages) STMicroelectronics – TV SIGNAL IDENTIFICATION CIRCUIT AND AFC INTERFACE

TDA4433
TEST CIRCUIT
0 or 3V (DC)
Hor. Flyback in
6
A
S1a ₁₂
B
0 or 3V (DC)
Pos. Video in
5.6kΩ
47nF
S1 A : Statictests
B : Functional tests
150pF
S1b ₁₃
3
S1c
S2 A : DC or pulses width
B : Functional tests
P1 Digital AFC perfect tuning
P2 Sensitivity control
82kΩ
P1
47kΩ
22kΩ
0.1µF
11kΩ
14
1
2
TDA4433
10
4
S1d
11
S1e
5
S2
AB
11kΩ
11kΩ
3.3kΩ
10kΩ
56kΩ
6.2kΩ ^P2
100kΩ
5kΩ
22nF
Digital AFC L
out TDA4433 H
+V_S = 12V
H
out B
out A
L
(no ident.)
H
Identif. out
L
(ident.)
APPLICATION INFORMATION
(refer to the block diagram)
TV Signal Identification Circuit
The circuit recognizes only TV signals by checking
logically during one line the coincidence between
the horizontal flyback pulse and the pulse detected
by a sync. separator.
The signal identification is carried out by charging
the capacitor connected to pin 5 ; when the capaci-
tor voltage overcomes a fixed threshold voltage, a
Schmitt trigger switches and enables the AFC con-
trol. If a TV signal is recognized, the capacitor is
slightly charged every line and its voltage reaches
the thresholdafter a number of line which is defined
by the value of the capacitor itself. The sensitivity
of the identification circuit, hence the number of
lines required to charge the capacitor, can be ad-
justed by means of the resistor connected between
pin 11 and ground.
When the identification has been made, a signal
(level L) is available at pin 10.
Threshold Circuit
The circuit detects 3 ranges of AFC voltage and in
combination with the TV signal identification circuit
drives the electronic switches.
With a correct TV signal, the output levels corre-
sponding to the 3 ranges are :
fo – δf
f_o
f_o + δf
(V2)
High Level
Low Level
Low Level
(V6)
Low Level
Low Level
High Level
The TDA4433 has two separate outputs which can
have only two states, high (H) or low (L). The
outputs at pin 2 and at pin 6 remain at a low level
with no video signal input or with a video signal not
identified as a true TV signal. Both pin 2 and pin 6
are open collector outputs and must be pulled-up
to the positive supply voltage by external resistors.
Voltage Regulator
The circuit can deliver 1 mA and it can be used as
D/A converter reference to supply fine tuning volt-
age.
EPM SYSTEM CONFIGURATIONS
With microprocessor
TDA4433
µP
µP interface M206
4/5