TDA7449

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3

APLICATION 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 TDA7449 audioprocessor

provides 2 bands tones control.

3.1 Bass, Stages

The Bass cell has an internal resistor Ri = 25K

Ω typical. Several filter types can be implemented, connect-

ing external components to the Bass IN and OUT pins. The fig.6 refers to basic T Type Bandpass Filter

starting from the filter component values (R1 internal Fc, the gain Av at max. boost and the filter Q factor

are computed as follows:

Figure 6.

Viceversa, once Fc, Av, and Ri internal value are fixed, the external components values will be:

3.2 Treble Stage

The treble stage is a high pass filter whose time constant is fixed by an internal resistor (25K

Ω typical) and

an external capacitor connected between treble pins and ground Typical responses are reported in Figg.

10 to 13.

3.3 CREF

The suggested 10

µF reference capacitor (CREF) value can be reduced to 4.7µF if the application requires

faster power ON.

Ri internal

OUT

IN

D95AU313

F

C

1

2

π

R1 R2 C 1 C2

⋅⋅

⋅

⋅⋅

-----------------------------------------------------------------

=

A

V

R2C 2

R2C1

RiC1

++

R2 C1

R2C2

+

------------------------------------------------------------

=

Q

R 1 R2 C1 C2

⋅⋅

⋅

R 2C1

R2C2

+

--------------------------------------------------

=

C1

A

V

1

–

2

π Fc Ri Q

⋅⋅

⋅

⋅

------------------------------------------

C2

Q

2

C1

⋅

A

V

1

–

Q

2

–

------------------------------

=

=

R2

A

V

1

–

Q

2

–

2

π C1 Fc A

V

1

–

() Q

⋅⋅

⋅⋅

⋅

----------------------------------------------------------------------

=