5/19

TDA7438

Figure 4. Test Circuit

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 = 44K

Ω typical.

The Middle cell has an internal resistor Ri = 25K

Ω typical.

Several filter types can be implemented, connecting external components to the Bass/Middle IN and OUT

pins.

Figure 5.

0/30dB

2dB STEP

MUXOUTL

INL

VOLUME

VOLUME

TREBLE

TREBLE

TREBLE(L)

MIDDLE

MIDDLE

MUXOUTR

INR

TREBLE(R)

BOUT(L)

SPKR ATT

LEFT

LOUT

SCL

SDA

DIGGND

ROUT

D96AU490A

I

5.6nF

2.2

µF

100K

100K

100K

G

L-IN1

L-IN2

L-IN3

0.47

µF

0.47

µF

0.47

µF

100K

100K

100K

R-IN1

R-IN2

R-IN3

0.47

µF

0.47

µF

0.47

µF

G

INPUT MULTIPLEXER

+ GAIN

MOUT(L)

BASS

BIN(L)

18nF

22nF

100nF

100nF

2.7K

5.6K

BASS

SPKR ATT

RIGHT

MOUT(R)

BOUT(R)

BIN(R)

5.6nF

18nF

22nF

100nF

100nF

2.7K

5.6K

SUPPLY

10

µF

CREF

AGND

27

3

4

5

2

1

28

21

22

20

26

24

25

8

9

19

10

11

12

13

23

6

7

18

17

16

14

15

2.2

µF

Ri internal

OUT

IN

D95AU313