DocID006317 Rev 5

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TDA7449

Application recommendations

21

3

Application recommendations

The first and the last stages are volume control blocks. The control range is 0 to -47 dB

(mute) for the first one and 0 to -79 dB (mute) for the last one. Both of them have 1 dB step

resolution. The very high resolution allows the implementation of systems free from any

noisy acoustical effect. The TDA7449 audio processor provides dual-band tone control.

Typical responses are shown in Figure 5 through 9.

3.1

Bass stage

The bass cell has an internal resistor Ri = 25 k

 typical. Several filter types can be

implemented, connecting external components to the bass IN and OUT pins. Figure 4 refers

to a basic T-type bandpass filter. The filter component values R1 internal FC, the gain AV at

max. boost and the filter Q factor are calculated as given below.

Figure 4. T bandpass filter

Once the FC, AV, and Ri internal values are fixed, the external component values will be:

3.2

Treble stage

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

(25 k

 typical) and an external capacitor connected between the treble pins and ground.

3.3

CREF

The recommended 10 μF reference capacitor (CREF) value can be reduced to 4.7 μF if the

application requires faster power ON.

Ri internal

C2

OUT

IN

C1

R2

D95AU313

FC

1

2



R1 R2 C1 C2





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

=

AV

R2C2 R2C1 RiC1

++

R2C1 R2C2

+

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

=

Q

R1 R2 C1 C2



R2C1 R2C2

+

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

=

C1

AV 1

–

2

 Fc Ri Q







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

C2

Q

2 C1



AV 1

–

Q

2

–

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

=

=

R2

AV 1

–

Q

2

–

2

 C1 Fc A

V

1

–

 Q







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

=

Obsolete

Product(s)

- Obsolete

Product(s)