TDA4481 Datasheet, PDF (2/10 Pages) TEMIC Semiconductors – Multistandard quasi parallel-sound processor for Mono-TV-Sets

TDA4481-D
TELEFUNKEN Semiconductors
Pin Configuration
Pin
Function
1–2 Picture-IF-carrier input
3
SCART-switch
4
AGC storage capacitor
5
SCART-AF input
6
Standard switch
7
AF output (controlled)
8
Volume control voltage
9
SCART-AF output
10
VC0 tank circuit
Pin
11
12–13
14
15
16
17
18–19
20
Function
Ground
FM demod. circuit 5.5 MHz
FM deemphasis capacitor
Intercarrier output 5.5 MHz
Supply voltage
Intercarrier input 5.5 MHz
and muting
Sound-IF-carrier input
not connected
Description
This circuit configuration permits high-quality processing
of audio carriers for all standards, providing separate inputs
for the video and audio carriers. The audio carrier signal
(FM or AM) is passed to two multiplying mixer
arrangements via a 3-stage variable wide-band amplifier
with levelled output signals. One mixer demodulates AM
and generates the gain control signal. The second mixer
operates as an intercarrier demodulator and supplies the
intermediate AF carrier.
The video carrier signal required to form the intercarrier is
decoupled in a prelimited and selected form from the
demodulator tank of the intermediate video frequency
circuit (TDA 4453 or TDA 4439) and led to the intercarrier
mixer via a limiting amplifier. By virtue of the system, the
Nyquist range of the IF input filter in the video channel
affects the attainable AF signal-to-noise ratio.
The audio FM IF carrier reaches a quadrature demodulator
via an interconnected IF-filter and subsequent limiting
amplifier. The resulting AF signal is led via a low-pass
amplifier with increased level and the AF standard switch
to the SCART switch. It is available at both AF outputs,
regulated (pin 7) and unregulated (pin 9).
Pin 14 is provided to connect a de-emphasis capacitor
(10 nF for 50 ms). The de-emphasis is effective for both AF
outputs during FM operation, but deactivated for AM
operation.
A frequency converter is inserted to mix the different
possible sound frequency standards (4.5, 6.0, 6.5 MHz)
into a uniform intermediate audio frequency, e.g. 5.5 MHz.
The VCO frequency (pin 10) can be controlled from the
unlevelled AF output at pin 9 or the de-emphasis
connection at pin 14.
The intercarrier and converter circuits as well as the FM
demodulator are deactivated during AM modulation. FM
muting is also possible if a switching voltage is applied to
pin 17.
All switching functions (standard, SCART, mute) can take
place with TTL-equivalent level.
2 (10)
Rev. A1: 23.02.1995