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TEA6323

Sound fader control circuit

Philips Electronics 

Philips Semiconductors

Sound fader control circuit

Preliminary specification

TEA6323T

handbook, halfpage

SDA 1

40 SCL

MUTE 2

DGND 3

AGND 4

39 n.c.

38 VCC

37 n.c.

OUTLR 5

36 OUTRR

OUTLF 6

35 OUTRF

TL 7

34 TR

B2L 8

33 B2R

B1L 9

32 B1R

OVL 10

31 OVR

TEA6323T

IVL 11

30 IVR

ILL 12

29 ILR

QSL 13

28 QSR

IDL 14

i.c. 15

ICL 16

27 IDR

26 Vref

25 ICR

COM 17

24 CAP

IBL 18

23 IBR

i.c. 19

22 i.c.

IAL 20

21 IAR

MHA257

Fig.2 Pin configuration.

FUNCTIONAL DESCRIPTION

The source selector allows either the source selection

between the differential stereo input (IAL, IAR and COM)

and three stereo inputs, or selection of four stereo inputs

and the mono input (COM). The maximum input signal

voltage is Vi(rms) = 2 V. The outputs of the source selector

and the inputs of the following volume control parts are

available at pins 13 and 11 for the left channel and pins 28

and 30 for the right channel. This offers the possibility of

interfacing a noise reduction system.

The volume control part is following the source selector.

The signal phase from input volume control part to all

outputs is 180°.

The volume control function is split into two sections:

volume I control block and volume II control block.

The control range of volume I is between +20 dB and

−31 dB in steps of 1 dB. The volume II control range is

between 0 dB and −55 dB in steps of 1 dB. Although the

theoretical possible control range is 106 dB

(+20 to −86 dB), in practice a range of 86 dB

(+20 to −66 dB) is recommended. The gain/attenuation

setting of the volume I control block is common for both

channels.

The volume I control block operates in combination with

the loudness control. The filter is linear when the maximum

gain for the volume I control (+20 dB) is selected. The filter

characteristic increases automatically over a range of

32 dB down to a setting of −12 dB. That means the

maximum filter characteristic is obtained at −12 dB setting

of volume I. Further reduction of the volume does not

further influence the filter characteristic (see Fig.5). The

maximum selected filter characteristic is determined by

external components. The proposed application gives a

maximum boost of 17 dB for bass and 4.5 dB for treble.

The loudness may be switched on or off via I2C-bus control

(see Table 7).

The volume I control block has an output pin and is

followed by the bass control block. An external filter for

each channel in combination with internal resistors,

provides the frequency response of the bass control (see

Fig.3). The adjustable range is between −18 and +18 dB in

steps of 1.8 dB at 46 Hz.

Both, loudness and bass control result in a maximum bass

boost of 35 dB for low volume settings.

The treble control block offers a control range between

−12 and +12 dB in steps of 1.5 dB at 15 kHz. The filter

characteristic is determined by a single capacitor of 5.6 nF

for each channel in combination with internal resistors

(see Fig.4).

The basic step width of treble control is 3 dB. The

intermediate steps are obtained by switching 1.5 dB boost

and 1.5 dB attenuation steps.

The bass and treble control functions can be switched off

via I2C-bus. In this event the internal signal flow is

disconnected. The connections B2L and B2R are outputs

and TL and TR are inputs for inserting an external

equalizer.

1995 Dec 20

5

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