Functional Description

The input selector is able to select 2 stereo inputs

and 1 mono input (AM). The inputs are DC biased

with 100k

Ω resistors to the internal reference volt-

age of 3V. The mono input can be used addition-

ally as hardware mute pin. If this pin is pulled to

ground by an external transistor and AM is not se-

lected, the input selector mutes the input (refer-

ence voltage selected). The AM part is consid-

ered to be switched OFF. If the output of the AM

part is not high ohmic in this condition, a series

resistor of about 20k

Ω has to be foreseen.

The volume control can be programmed from a

gain of +32dB to an attenuation of -79dB in 1dB

steps. The maximum gain should be kept as low

as possible for system performance reason. It has

to be limited by software to the absolute neces-

sary system gain, depending on the signal source

level and the power amplifier gain.

The bass control acts in a range from +18dB to -

18dB in 2dB steps. The filter response is deter-

mined by the external filter components. An ex-

tensive simulation software is available in order to

support the design of the bass filter response with

different filter configurations.

The extended bass boost range of +18dB allows

the implementation of the software loudness func-

tion by additional bass and treble boost.

The treble control acts in a range of

±14dB in 2dB

steps. The external capacitor determines with the

internal resistor of 50K

Ω the corner frequency of

the treble response.

The four speaker attenuators can be controlled in-

dependently from 0 to -37.5dB, which allows the

implementation of balance and fader a the four

speaker system. The attenuation steps size is 1

db from 0 to -24dB and increases non linearly up

to the maximum attenuation of 37.5dB. A special

mute bit forces the speaker attenuator into the

mute position.

All 4 outputs are low distortion push pull outputs,

able to drive a load of 3k

Ω.

TDA7433

8/10