TDA7432 Datasheet, PDF (8/10 Pages) STMicroelectronics – BASIC FUNCTION AUDIO PROCESSOR

TDA7432
Loudness
MSB
LSB
D₇
D₆
D₅
D₄
D₃
D₂
D₁
D₀
LOUDNESS
X
X
X
0
0
0
0
0 0dB
X
X
X
0
0
0
0
1 -1dB
X
X
X
0
0
0
1
0 -2dB :
X
X
X
0
0
0
1
1 -3dB
X
X
X
0
0
1
0
0 -4dB
X
X
X
0
0
1
0
1 -5dB
X
X
X
0
0
1
1
0 -6dB
X
X
X
0
0
1
1
1 -7dB
X
X
X
0
1
0
0
0 -8dB
X
X
X
0
1
0
0
1 -9dB
X
X
X
0
1
0
1
0 -10dB
X
X
X
0
1
0
1
1 -11dB
X
X
X
0
1
1
0
0 -12dB
X
X
X
0
1
1
0
1 -13dB
X
X
X
0
1
1
1
0 -14dB
X
X
X
0
1
1
1
1 -15dB
X
X
X
1
D3 D2 D1 D0 Loudness flat (Note 3)
For example to select -14dB Loudness the Data Byte is : X X X 0 1 1 1 0.
Note3:
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 1 stereo inputs
and 1 mono input (AM). The inputs are DC biased
with 100kΩ resistors to the internal reference volt-
age of 3V. The AM input can be use additionally
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 20kΩ 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 50KΩ 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 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 3kΩ.
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