TDA7438
THREE BANDS
DIGITALLY CONTROLLED AUDIO PROCESSOR
1
■
FEATURES
INPUT MULTIPLEXER
– 3 STEREO INPUTS
– SELECTABLE INPUT GAIN FOR OPTIMAL
ADAPTATION TO DIFFERENT SOURCES
Figure 1. Package
SO28
DIP28
■
■
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
Table 1. Order Codes
Part Number
TDA7438
TDA7438D
TDA7438D013TR
■
■
■
ALL FUNCTION ARE PROGRAMMABLE VIA
SERIAL BUS
Selectable input gain is provided. Control of all the
functions is accomplished by serial bus.
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.
2
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.
Figure 2. Block Diagram
3
L-IN1
L-IN2
4
O
so
b
te
le
L-IN3
R-IN1
R-IN2
R-IN3
5
ro
P
100K
100K
100K
100K
uc
d
G
0/30dB
2dB STEP
s)
t(
MUXOUTL
6
INL
so
b
-O
TREBLE(L)
18
17
R
M
P
te
le
od
r
Tape & Reel
s)
t(
uc
DIP28
SO28
Package
MIN(L) MOUT(L) BIN(L)
16
14
R
B
BOUT(L)
15
7
VOLUME
TREBLE
MIDDLE
BASS
SPKR ATT
LEFT
27
LOUT
21
I
2
CBUS DECODER + LATCHES
22
20
SCL
SDA
DIG_GND
2
1
100K
28
V
REF
100K
24
INPUT MULTIPLEXER
+ GAIN
8
MUXOUTR
INR
9
19
TREBLE(R)
SUPPLY
R
M
10
11
12
R
B
13
23
D96AU488A
G
VOLUME
TREBLE
MIDDLE
BASS
SPKR ATT
RIGHT
26
ROUT
25
V
S
AGND
MIN(R) MOUT(R) BIN(R)
BOUT(R) CREF
June 2004
REV. 7
1/19
TDA7438
Table 2. Absolute Maximum Ratings
Symbol
V
S
T
amb
T
stg
Operating Supply Voltage
Operating Ambient Temperature
Storage Temperature Range
Parameter
Value
10.5
0 to 70
-55 to 150
Unit
V
°C
°C
Figure 3. Pin Connection
R_IN2
R_IN1
L_IN1
L_IN2
L_IN3
MUXOUTL
INL
MUXOUTR
INR
MIN(R)
MOUT(R)
BIN(R)
BOUT(R)
BIN(L)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
D96AU489A
28
27
26
25
24
23
22
21
20
19
18
17
16
15
R_IN3
LOUT
ROUT
AGND
V
S
CREF
SDA
SCL
DIG-GND
TREBLE(R)
TREBLE(L)
MIN(L)
MOUT(L)
BOUT(L)
Table 3. Thermal Data
Symbol
R
th j-pins
Parameter
Thermal Resistance Junction-pins
Table 4. Quick Reference Data
Symbol
V
S
V
CL
THD
S/N
S
C
Supply Voltage
b
O
so
te
le
Max. input signal handling
Total Harmonic Distortion V = 1Vrms f = 1KHz
Signal to Noise Ratio V
out
= 1Vrms (mode = OFF)
Channel Separation f = 1KHz
Input Gain in (2db step)
Volume Control (1db step)
Treble Control (2db step)
Middle Control (2db step)
Bass Control (2dB step)
Balance Control 1dB step
Mute Attenuation (*)
ro
P
uc
d
s)
t(
so
b
-O
P
te
le
Max.
od
r
Value
85
s)
t(
uc
Unit
°C/W
Parameter
Min.
6
2
Typ.
9
0.01
106
90
Max.
10.2
0.1
Unit
V
Vrms
%
dB
dB
0
-47
-14
-14
-14
-79
80
100
30
0
+14
+14
+14
0
dB
dB
dB
dB
dB
dB
dB
(*) Even applied to Speaker Attenuator Left, Speaker Attenuator Right, Volume Control stand alone or to the combination, if any.
2/19
TDA7438
Table 5. Electrical Characteristcs:
(refer to the test circuit Tamb = 25°C, VS = 9V, RL= 10KΩ,
RG = 600Ω, all controls flat (G = 0dB), unless otherwise specified
)
Symbol
SUPPLY
V
S
I
S
Parameter
Test Condition
Min.
Typ.
Max.
Unit
Supply Voltage
Supply Current
Ripple Rejection
6
9
7
10.2
V
mA
dB
SVR
60
90
INPUT STAGE
R
IN
V
CL
S
IN
G
inmin
Input Resistance
Clipping Level
Input Separation
Minimum Input Gain
Maximum Input Gain
Step Resolution
THD = 0.3%
The selected input is grounded
through a 2.2µ capacitor
2
80
-1
100
2.5
100
0
30
2
1
KΩ
Vrms
dB
dB
G
inman
G
step
VOLUME CONTROL
R
i
Input Resistance
Control Range
Max. Attenuation
Step Resolution
Attenuation Set Error
20
C
RANGE
A
VMAX
A
STEP
E
A
A
V
= 0 to -24dB
A
V
= -24 to -47dB
E
T
Tracking Error
V
DC
A
DC Step
Mute Attenuation
mute
BASS CONTROL
(The center frequency and the response quality can be chosen by the ext. circuitry)
Gb
B
STEP
R
B
Control Range
b
O
TREBLE CONTROL
(The center frequency and the response quality can be chosen by the ext. circuitry)
Gt
Control Range
Step Resolution
Max. Boost/cut
+13.0
1
+14.0
2
+15.0
3
dB
dB
so
Step Resolution
Internal Feedback Resistance
te
le
ro
P
uc
d
s)
t(
A
V
= 0 to -24dB
A
V
= -24 to -47dB
so
b
-O
P
te
le
45
45
0.5
-1.0
-1.5
od
r
33
47
47
1
0
0
0
0
0
0.5
s)
t(
uc
50
49
49
1.5
1.0
1.5
1
2
3
dB
dB
KΩ
dB
dB
dB
dB
dB
dB
dB
adjacent attenuation steps from
0dB to A
V
max
80
mV
mV
dB
100
Max. Boost/cut
+12.0
1
33
+14.0
2
44
+16.0
3
55
dB
dB
KΩ
T
STEP
MIDDLE CONTROL
(The center frequency and the response quality can be chosen by the ext. circuitry
)
Gm
M
STEP
R
M
Control Range
Step Resolution
Internal Feedback Resistance
Max. Boost/cut
+12.0
1
18.75
+14.0
2
25
+16.0
3
31.25
dB
dB
KΩ
3/19
TDA7438
Table 5
(continued)
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
SPEAKER ATTENUATORS
C
RANGE
Control Range
S
STEP
E
A
Step Resolution
Attenuation Set Error
A
V
= 0 to -20dB
A
V
= -20 to -56dB
E
T
Tracking Error
A
V
= 0 to -24dB
A
V
= -24 to -47dB
V
DC
A
mute
DC Step
Mute Attenuation
adjacent attenuation steps
80
0.5
-1.5
-2
76
1
0
0
0
0
0
100
1.5
1.5
2
1
2
3
dB
dB
dB
dB
dB
dB
mV
dB
AUDIO OUTPUTS
V
CLIP
R
L
R
O
V
DC
Clipping Level
Output Load Resistance
Output Impedance
DC Voltage Level
d = 0.3%
2.1
2
10
2.6
GENERAL
(Gain, Bass, Treble, Middle Controls Flat)
E
NO
E
t
Output Noise
Total Tracking Error
(Volume + Speaker Attenuator)
All gains = 0dB;
BW = 20Hz to 20KHz flat
A
V
= 0 to -24dB
A
V
= -24 to -47dB
A
V
= -47 to -79dB
S/N
S
C
d
Signal to Noise Ratio
Channel Separation Left/Right
Distortion
BUS INPUT
V
IL
V
IH
I
IN
Input Low Voltage
Input High Voltage
Input Current
O
so
b
et
l
P
e
ro
uc
d
s)
t(
All gains 0dB; VO = 1V
RMS
;
so
b
-O
te
le
r
P
90
80
od
3.8
5
0
0
0
106
100
0.01
40
s)
t(
uc
70
V
15
1
2
3
V
RMS
KΩ
W
µV
dB
dB
dB
dB
dB
A
V
= 0; VI = 1V
RMS
;
0.08
%
1
3
V
IN
= 0.4V
-5
5
V
V
µA
4/19
TDA7438
Figure 4. Test Circuit
5.6nF
2.2µF
2.7K
18nF
MIN(L)
5.6K
22nF 100nF
100nF
MUXOUTL
L-IN1
0.47µF
L-IN2
0.47µF
L-IN3
0.47µF
5
100K
4
100K
G
3
100K
6
INL
TREBLE(L)
7
18
MOUT(L)
17
R
M
16
BIN(L)
14
R
B
BOUT(L)
15
VOLUME
TREBLE
MIDDLE
BASS
SPKR ATT
LEFT
27
LOUT
R-IN1
0.47µF
R-IN2
0.47µF
R-IN3
0.47µF
2
100K
1
100K
28
100K
0/30dB
2dB STEP
21
I CBUS DECODER + LATCHES
2
22
20
SCL
SDA
DIGGND
G
VOLUME
TREBLE
MIDDLE
BASS
SPKR ATT
RIGHT
V
REF
26
ROUT
24
INPUT MULTIPLEXER
+ GAIN
8
MUXOUTR
INR
9
TREBLE(R)
19
MIN(R)
10
R
M
11
12
BIN(R)
R
B
13
BOUT(R)
SUPPLY
25
V
S
23
MOUT(R)
2.2µF
5.6nF
18nF
2.7K
22nF 100nF
3
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.
3.1 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, connecting external components to the Bass/Middle IN and OUT
pins.
Figure 5.
O
so
b
te
le
ro
P
uc
d
s)
t(
so
b
-O
P
te
le
100nF
5.6K
od
r
CREF
10µF
AGND
s)
t(
uc
D96AU490A
Ri internal
IN
C
1
R
2
D95AU313
OUT
C
2
5/19
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