The ratio of these frequenciesdefines the peak-to-

peak separation of the ”S” curve :

=

√

1

+

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

The maximum slope of the RC network is of 20dB

per decade and its pole is defined by :

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 :

= 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

any pop generally produced during the turn-on and

the turn-off transients.

means of C7 ; a threshold is reached and the

muting of the AFPA output (pin 17) is suddenly

produced.

the input impedance of pin 1 and the muting is

removed with a time constant depending on the C7

value.

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.

TDA8190

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