TDA8190 Datasheet, PDF (8/11 Pages) STMicroelectronics – TV SOUND CHANNEL WITH DC CONTROLS

TDA8190
The ratio of these frequenciesdefines the peak-to-
peak separation of the ”S” curve :
f2
f₁
=
√1 +_CC⁹⁸
A differential peak detector detects the audio fre-
quency signal that amplified, reaches the deem-
phasis network R0 ; C11.
The AF amplifier can be muted (see turn-on and
turn-off switch and VCR facility).
- Pin 7 is the output of the low-pass filter and one
input of the differential peak detector
- Pin 8 is the other input of the differential peak
detector
- Pin 9 is used to provide the required deemphasis
time constant by grounding it with C11. At this pin,
the internal impedance of which is typically of
1.1K, is available the recovered audio signal as
auxiliary output.
DC Tone Control
The same signal available or applied to pin 10, after
a voltage to current converter, reaches, the DC
Tone Control block. It operates, inside the 10KHz
bandwidth, by cutting the high audio frequencies
with a variable slope of an RC network, by means
of P1.
The maximum slope of the RC network is of 20dB
per decade and its pole is defined by :
X_C11 = 6.8K, typically.
Pin 11 - At this pin is tied the tone capacitor.
Pin 12 - Is the DC Tone Control input.
DC Volume Control
After tone control regulation, the AF current signal
reaches the DC volume control block that controls
its intensity. The normal control, for which the block
has been designed for a narrow spread, is pro-
duced by P2 ; however, without P2, a voltage
control can be operated by forcing a voltage at pin
13 through R8.
- Pin 12, already seen as a DCTC input, is the
reference voltage for the DCVC. Because of this,
a small interface between tone and volume regu-
lation can be expected.
- Pin 13 is the DC volume control input.
- Pin 14 after a current to voltage converter, the
audio frequency signal comes out at this pin.
Audio Frequency Power Amplifier and Ther-
mal Protection
Through C12 the signal reaches the amplifier non-
inverting input. The closed loop gain is defined by
the feedback at pin 19 (inverting input) or by the
ratio :
G_V
=
20
Log
R5 + R4
R5
(dB)
The amplifier, thermally protected, can supply 4W
of power into a 16 load with 24V of supply voltage.
The power output stage is a class B type.
- Pin 20 is the non-inverting input
- Pin 19 is the inverting input
- Pin 17 is the output of the AFPA.
Turn-on And Turn-off Switch
This block has been mainly designed to avoid,
turning on the TV set, that transients, produced by
the vision output, can reach the speaker.
Moreover this block, together an optimized rise
time and full time of the supply voltage Vs, can avoid
any pop generally producedduring the turn-on and
the turn-off transients.
Turninig on, pin 1 follows the supply voltage V_s by
means of C7 ; a threshold is reached and the
muting of the AFPA output (pin 17) is suddenly
produced.
When Vs reaches it stop, C7 charges itself through
the input impedance of pin 1 and the muting is
removed with a time constant depending on the C7
value.
Turning off, the Vs trend, in series to the voltage Vs
V1 and which C7 is charged, drives pin 1 at a low
level threshold and a sudden muting is produced
again.
Since the turn-off can be operated with high output
power, if the muting operates when the current
through the inductance of the speaker is different
from zero, a flyback is generated and then a small
pop can be produced.
The flyback is clipped by integrated diodes.
The thresholds that produce the muting have been
chosen in the way that 1 Vpp of ripple on the supply
voltage does not produce any switching..
- Pin 1 is the turn-on and turn-off muting input.
Supply
An integratedvoltage regulator with different output
levels, supplies all the blocks operating with small
signal.
- Pin 18 is the main supply of the device.
- Pin 5 ; pin 6 ; pin 15 and pin 16 are the ground of
the supply. These pins are used to drain out from
the device the heat produced by the dissipated
power.
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