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PDF TDA7438 Data sheet ( Hoja de datos )
| Número de pieza | TDA7438 | |
| Descripción | THREE BANDS DIGITALLY CONTROLLED AUDIO PROCESSOR | |
| Fabricantes | ST Microelectronics | |
| Logotipo |  |
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® TDA7438
THREE BANDS
DIGITALLY CONTROLLED AUDIO PROCESSOR
INPUT MULTIPLEXER
- 3 STEREO INPUTS
- SELECTABLE INPUT GAIN FOR OPTIMAL
ADAPTATION TO DIFFERENT SOURCES
ONE STEREO OUTPUT
TREBLE, MIDDLE AND BASS CONTROL IN
2.0dB STEPS
VOLUME CONTROL IN 1.0dB STEPS
TWO SPEAKER ATTENUATORS:
- TWO INDEPENDENT SPEAKER CONTROL
IN 1.0dB STEPS FOR BALANCE FACILITY
- INDEPENDENT MUTE FUNCTION
ALL FUNCTION ARE PROGRAMMABLE VIA
SERIAL BUS
SO28
DIP28
ORDERING NUMBER: TDA7438D (SO28)
TDA7438 (DIP28)
DESCRIPTION
The TDA7438 is a volume tone (bass, middle and
treble) balance (Left/Right) processor for quality
audio applications in car-radio and Hi-Fi systems.
Selectable input gain is provided. Control of all
the functions is accomplished by serial bus.
BLOCK DIAGRAM
The AC signal setting is obtained by resistor net-
works and switches combined with operational
amplifiers.
Thanks to the used BIPOLAR/CMOS Technology,
Low Distortion, Low Noise and DC stepping are
obtained.
3
L-IN1
4
L-IN2
5
L-IN3
100K
100K
100K
MUXOUTL INL
67
TREBLE(L) MIN(L) MOUT(L) BIN(L) BOUT(L)
18 17 16 14 15
RM RB
G
VOLUME
TREBLE
MIDDLE
BASS
SPKR ATT
LEFT
27
LOUT
2
R-IN1
1
R-IN2
28
R-IN3
100K
100K
100K
0/30dB
2dB STEP
I2CBUS DECODER + LATCHES
21
SCL
22
SDA
20
DIG_GND
G
VOLUME
TREBLE
MIDDLE
BASS
SPKR ATT
RIGHT
VREF
INPUT MULTIPLEXER
+ GAIN
89
MUXOUTR INR
SUPPLY
RM RB
19 10 11 12 13 23
TREBLE(R) MIN(R) MOUT(R) BIN(R) BOUT(R) CREF
26
ROUT
24
25 VS
AGND
D96AU488A
April 1999
1/17
1 page  
TDA7438
APPLICATION SUGGESTIONS
The first and the last stages are volume control
blocks. The control range is 0 to -47dB (mute) for
the first one, 0 to -79dB (mute) for the last one.
Both of them have 1dB step resolution.
The very high resolution allows the implementation
of systems free from any noisy acoustical effect.
The TDA7438 audioprocessor provides 3 bands
tones control.
Bass, Middle Stages
The Bass and the middle cells have the same
structure.
The Bass cell has an internal resistor Ri = 44KΩ
typical.
The Middle cell has an internal resistor Ri = 25KΩ
typical.
Several filter types can be implemented, connect-
ing external components to the Bass/Middle IN
and OUT pins.
Figure 1.
Ri internal
IN OUT
C1 C2
R2
D95AU313
The fig.1 refers to basic T Type Bandpass Filter
starting from the filter component values (R1 in-
ternal and R2,C1,C2 external) the centre fre-
quency Fc, the gain Av at max. boost and the fil-
ter Q factor are computed as follows:
FC =
1
2 ⋅ π ⋅√Ri,R2, C1,C2
AV
=
R2
C2 + R2 C1 + Ri
R2 C1 + R2 C2
C1
Q
=
√RiR2+C1C2
R2 C1 + R2 C2
Viceversa, once Fc, Av, and Ri internal value are
fixed, the external components values will be:
C1
=
2
AV − 1
⋅ π ⋅ Ri ⋅
Q
C2
=
Q2 ⋅ C1
AV − 1 Q2
R2
=
2
⋅
π
⋅
AV − 1
C1 ⋅ FC
− Q2
⋅ (AV −
1)
⋅Q
Treble Stage
The treble stage is a high pass filter whose time
constant is fixed by an internal resistor (25KΩ
typical) and an external capacitor connected be-
tween treble pins and ground
Typical responses are reported in Figg. 10 to 13.
CREF
The suggested 10µF reference capacitor (CREF)
value can be reduced to 4.7µF if the application
requires faster power ON.
Figure 2: THD vs. frequency
Figure 3: THD vs. RLOAD
5/17
5 Page 
DATA BYTES (continued)
BASS SELECTION
MSB
LSB
D7 D6 D5 D4 D3 D2 D1 D0
0000
0001
0010
0011
0100
0101
0110
0111
1111
1110
1101
1100
1011
1010
1001
1000
TDA7438
BASS
2dB STEPS
-14dB
-12dB
-10dB
-8dB
-6dB
-4dB
-2dB
0dB
0dB
2dB
4dB
6dB
8dB
10dB
12dB
14dB
MIDDLE SELECTION
MSB
LSB
D7 D6 D5 D4 D3 D2 D1 D0
0000
0001
0010
0011
0100
0101
0110
0111
1111
1110
1101
1100
1011
1010
1001
1000
MIDDLE
2dB STEPS
-14dB
-12dB
-10dB
-8dB
-6dB
-4dB
-2dB
0dB
0dB
2dB
4dB
6dB
8dB
10dB
12dB
14dB
11/17
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet TDA7438.PDF ] | |
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