SGS Thomson Microelectronics TDA7438D, TDA7438 Datasheet
DIGITALLY CONTROLLED AUDIO PROCESSOR
INPUTMULTIPLEXER
- 3 STEREO INPUTS
- SELECTABLEINPUT GAIN FOR OPTIMAL
ADAPTATIONTO DIFFERENT SOURCES
ONE STEREO OUTPUT
TREBLE, MIDDLE AND BASS CONTROL IN
2.0dB STEPS
VOLUMECONTROL IN 1.0dB STEPS
TWOSPEAKERATTENUATORS:
- TWOINDEPENDENTSPEAKERCONTROL
IN 1.0dBSTEPSFOR BALANCE FACILITY
- INDEPENDENTMUTE FUNCTION
ALL FUNCTION ARE PROGRAMMABLE VIA
SERIALBUS
TDA7438
THREE BANDS
SO28
ORDERING NUMBER: TDA7438D (SO28)
TDA7438 (DIP28)
DIP28
DESCRIPTION
The TDA7438 is a volume tone (bass, middle and
treble) balance (Left/Right) processor for quality
audio applicationsin car-radio and Hi-Fi systems.
Selectable input gain is provided. Control of all
the functions is accomplishedby serialbus.
BLOCK DIAGRAM
MUXOUTL INL
6 7 18 17 16 14 15
G
0/30dB
2dB STEP
G
8 9 19 10 11 12 13 23
MUXOUTR INR TREBLE(R)
VOLUME
VOLUME
L-IN1
L-IN2
L-IN3
R-IN1
R-IN2
R-IN3
3
100K
4
100K
5
100K
2
100K
1
100K
28
100K
INPUT
MULTIPLEXER
+ GAIN
The AC signal setting is obtained by resistor networks and switches combined with operational
amplifiers.
Thanks to the used BIPOLAR/CMOSTechnology,
Low Distortion, Low Noise and DC stepping are
obtained.
TREBLE(L)
MIN(L)
TREBLE
TREBLE
MIDDLE
I2CBUS DECODER + LATCHES
MIDDLE
MIN(R) MOUT(R) BOUT(R)BIN(R)
MOUT(L)
R
M
R
M
BIN(L)
BASS
BASS
R
B
R
B
BOUT(L)
SPKR ATT
LEFT
SPKR ATT
RIGHT
V
REF
SUPPLY
CREF
27
21
22
20
26
24
25
D96AU488A
LOUT
SCL
SDA
DIG_GND
ROUT
V
S
AGND
April 1999
1/17
TDA7438
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
S
T
amb
T
stg
PIN CONNECTION
Operating Supply Voltage 10.5 V
Operating Ambient Temperature -10 to 85 °C
Storage Temperature Range -55 to 150 °C
R_IN2
R_IN1
L_IN1
L_IN2
L_IN3 V
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
22
21
20
19
18
17
16
15
R_IN3
LOUT
ROUT
AGND
S
CREF23
SDA
SCL
DIG-GND
TREBLE(R)
TREBLE(L)
MIN(L)
MOUT(L)
BOUT(L)
THERMAL DATA
Symbol Parameter Value Unit
R
thj-pin
Thermal ResistanceJunction-pins 85 °C/W
QUICK REFERENCE DATA
Symbol Parameter Min. Typ. Max. Unit
V
S
V
CL
THD Total Harmonic Distortion V = 1Vrms f = 1KHz 0.01 0.1 %
S/N Signal to Noise Ratio V
S
C
(*) Even applied to Speaker AttenuatorLeft, Speaker Attenuator Right, Volume Control stand alone or to the combination, if any.
2/17
Supply Voltage 6 9 10.2 V
Max. input signal handling 2 Vrms
= 1Vrms (mode = OFF) 106 dB
out
Channel Separation f = 1KHz 90 dB
Input Gain in (2dBstep) 0 30 dB
Volume Control (1dB step) -47 0 dB
Treble Control (2dB step) -14 +14 dB
Middle Control (2dB step) -14 +14 dB
Bass Control (2dB step) -14 +14 dB
Balance Control 1dB step -79 0 dB
Mute Attenuation (*) 80 100 dB
TDA7438
ELECTRICALCHARACTERISTICS
R
= 600Ω, all controlsflat (G = 0dB), unless otherwisespecified)
G
(refer to the test circuit T
=25°C,VS= 9V,RL= 10KΩ,
amb
Symbol Parameter Test Condition Min. Typ. Max. Unit
SUPPLY
V
S
I
S
SVR Ripple Rejection 60 90 dB
Supply Voltage 6 9 10.2 V
Supply Current 7 mA
INPUT STAGE
G
G
R
V
S
inman
G
IN
CL
IN
inmin
step
Input Resistance 100 KΩ
Clipping Level THD = 0.3% 2 2.5 Vrms
Input Separation The selected input is grounded
80 100 dB
through a 2.2µ capacitor
Minimum Input Gain -1 0 1 dB
Maximum Input Gain 30 dB
Step Resolution 2 dB
VOLUMECONTROL
R
C
RANGE
A
VMAX
A
STEP
E
A
E
V
DC
A
mute
BASS CONTROL
Gb Control Range Max. Boost/cut +12.0 +14.0 +16.0 dB
B
STEP
R
TREBLECONTROL
Gt Control Range Max. Boost/cut +13.0 +14.0 +15.0 dB
T
STEP
MIDDLE CONTROL
Gm Control Range Max. Boost/cut +12.0 +14.0 +16.0 dB
M
STEP
R
M
Input Resistance 20 33 50 KΩ
i
Control Range 45 47 49 dB
Max. Attenuation 45 47 49 dB
Step Resolution 0.5 1 1.5 dB
Attenuation Set Error AV= 0 to-24dB -1.0 0 1.0 dB
A
= -24 to -47dB -1.5 0 1.5 dB
V
Tracking Error AV= 0 to-24dB 0 1 dB
T
A
= -24 to -47dB 0 2 dB
V
DC Step adjacent attenuation steps
from 0dB to A
V
max
0
0.5
Mute Attenuation 80 100 dB
(The center frequency and the response quality can be chosen by the ext. circuitry)
Step Resolution 1 2 3 dB
Internal FeedbackResistance 33 44 55 KΩ
B
(The centerfrequency and the response quality can be chosen by the ext.circuitry)
Step Resolution 1 2 3 dB
(The centerfrequency and the response quality can be chosen by the ext. circuitry)
Step Resolution 1 2 3 dB
Internal FeedbackResistance 18.75 25 31.25 K
3mV
SPEAKERATTENUATORS
C
RANGE
S
V
A
STEP
E
A
E
DC
mute
Control Range 76 dB
Step Resolution 0.5 1 1.5 dB
Attenuation Set Error AV= 0 to-20dB -1.5 0 1.5 dB
A
= -20 to -56dB -2 0 2 dB
V
Tracking Error AV= 0 to-24dB 0 1 dB
T
A
= -24 to -47dB 0 2 dB
V
DC Step adjacent attenuation steps 0 3 mV
Mute Attenuation 80 100 dB
mV
Ω
3/17
TDA7438
ELECTRICALCHARACTERISTICS
(continued.)
Symbol Parameter Test Condition Min. Typ. Max. Unit
AUDIOOUTPUTS
VCLIP ClippingLevel d = 0.3% 2.1 2.6 VRMS
R
L
R
O
DC DC Voltage Level 3.8 V
V
GENERAL
E
NO
Output Load Resistance 2 KΩ
Output Impedance 10 40 70
(Gain, Bass, Treble, Middle Controls Flat)
Output Noise All gains = 0dB;
515µV
BW = 20Hz to 20KHz flat
E
t
S/N Signal to Noise Ratio All gains 0dB; V
S
C
d Distortion A
Total Tracking Error
(Volume + SpeakerAttenuator)
AV= 0to -24dB 0 1 dB
A
= -24to -47dB 0 2 dB
V
A
= -47to -79dB 0 3 dB
V
O =1VRMS ; 90 106 dB
Channel Separation Left/Right 80 100 dB
=0;VI=1V
V
; 0.01 0.08 %
RMS
BUS INPUT
V
IL
V
IH
I
IN
Input Low Voltage 1V
Input High Voltage 3 V
Input Current VIN= 0.4V -5 5
Ω
A
µ
TEST CIRCUIT
L-IN1
0.47µF
L-IN2
0.47µF
L-IN3
0.47µF
R-IN1
0.47µF
R-IN2
0.47µF
R-IN3
0.47µF
5.6nF
2.2µF
3
100K
4
100K
5
100K
2
100K
1
100K
28
100K
INPUT MULTIPLEXER
MUXOUTL INL
G
0/30dB
2dB STEP
G
+ GAIN
MUXOUTR INR TREBLE(R)
TREBLE(L)
6 7 18 17 16 14 15
VOLUME
VOLUME
8 9 19 10 11 12 13 23
2.2µF
5.6nF
2.7K 5.6K
18nF 22nF 100nF 100nF
MIN(L)
MOUT(L)
R
M
TREBLE
TREBLE
MIDDLE
I2CBUS DECODER + LATCHES
MIDDLE
R
M
MOUT(R) BOUT(R)BIN(R)
MIN(R)
18nF 22nF 100nF 100nF
2.7K 5.6K
BIN(L)
BASS
BASS
BOUT(L)
R
B
SPKR ATT
LEFT
SPKR ATT
RIGHT
V
REF
R
SUPPLY
B
CREF
10µF
27
21
22
20
26
24
25
LOUT
SCL
SDA
DIGGND
ROUT
V
S
AGND
D96AU490A
4/17
TDA7438
APPLICATIONSUGGESTIONS
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 resolutionallows the implementation
of systemsfreefromanynoisyacousticaleffect.
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 internalresistor Ri = 25KΩ
typical.
Several filter types can be implemented, connecting external components to the Bass/Middle IN
and OUTpins.
Figure 1.
Ri internal
OUTIN
C
1
R
2
D95AU313
C
2
The fig.1 refers to basic T Type Bandpass Filter
starting from the filter component values (R1 internal and R2,C1,C2 external) the centre frequency Fc, the gain Av at max. boost and the filter Q factorare computedas follows:
=
F
C
1
2 ⋅ π ⋅√Ri, R2, C1, C2
R2 C2+R2 C1+Ri C1
A
=
V
R2 C1 + R2 C2
√Ri R2 + C1 C2
=
Q
R2 C1+R2 C2
Viceversa, once Fc, Av, and Ri internal value are
fixed, the external componentsvalues will be:
2
V
Q
A
V
−1) ⋅
2
−
⋅
C1
1Q
Q
2
C1 =
2 ⋅ π ⋅ R
=
R2
− 1
A
V
⋅ π ⋅C1⋅
2
− 1 − Q
V
F
C
C2 =
⋅ (
A
⋅ Q
i
A
TrebleStage
The treble stage is a high pass filter whose time
constant is fixed by an internal resistor (25KΩ
typical) and an external capacitor connected between treble pins andground
Typical responsesare reported in Figg. 10 to 13.
CREF
The suggested 10µF reference capacitor (CREF)
value can be reduced to 4.7µF if the application
requiresfasterpower ON.
Figure 2:
THD vs. frequency
Figure3:
THDvs. R
LOAD
5/17
TDA7438
Figure 4:
Channelseparationvs. frequency
Figure 6: Middleresponse
=25kΩ
R
i
C9= 15nF (MIN)
C6- 22nF (MOUT)
R1 = 2.7kΩ
Figure5:
Bassresponse
Figure7: Trebleresponse
Ri= 44kΩ
C9 = C10 = 100nF (Bout,Bin)
R3 = 5.6kΩ
Figure 8:
6/17
Typicaltoneresponse
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