Loudness

MSB

LSB

LOUDNESS

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

0

1

0

0

0

0

0

0

0

0

1

1

1

1

1

1

1

1

0

0

0

0

1

1

1

1

0

0

0

0

1

1

1

1

0

0

1

1

0

0

1

1

0

0

1

1

0

0

1

1

D1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

0

1

D0

0dB

-1dB

-2dB

:

-3dB

-4dB

-5dB

-6dB

-7dB

-8dB

-9dB

-10dB

-11dB

-12dB

-13dB

-14dB

-15dB

Loudness flat (Note 3)

For example to select -14dB Loudness the Data Byte is : X X X 01110.

Note 3:

FIat attenuation, according to the selected byte. The loudness can be completely disabled by setting bit D7 in the volume byte to ”0”. In this

case the attenuation is 0dB independent from the loudness settings.

Functional Description

The input selector is able to select 2 stereo inputs

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

with a 100k

Ω resistors to the internal reference

voltage of 3V. The AM input can be used addi-

tionally as hardware mute pin. If this pin is pulled

to ground by an external transistors and AM is not

selected, 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 for a four

speaker system. The attenuation steps size is 1

db from 0 to -24dB and increases nonlinearly 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.

TDA7434

8/10