TEA6320 View Datasheet(PDF) - Philips Electronics

Part Name

Description

Manufacturer

TEA6320

Sound fader control circuit

Philips Electronics 

Philips Semiconductors

Sound fader control circuit

Preliminary specification

TEA6320

Loudness filter calculation example

Figure 17 shows the basic loudness circuit with an

external low-pass filter application. R1 allows an

attenuation range of 21 dB while the boost is determined

by the gain stage V2. Both result in a loudness control

range of +20 to −12 dB.

Defining fref as the frequency where the level does not

change while switching loudness on/off. The external

resistor R3 for fref → ∞ can be calculated as:

R3 = R1 -1----1–----0-1---G2--0----0--v---G2------0--v- . With Gv = −21 dB and R1 = 33 kΩ,

R3 = 3.2 kΩ is generated.

For the low-pass filter characteristic the value of the

external capacitor C1 can be determined by setting a

specific boost for a defined frequency and referring the

gain to Gv at fref as indicated above.

j---(---ω----1C-----1----)-

= --(--R-----1-----+-----R--1--3---–-)---1--×--0--1--G2------00--v----G-2-----0--v----–-----R-----3-

For example: 3 dB boost at f = 1 kHz

Gv = Gv(ref) + 3 dB = −18 dB; f = 1 kHz and C1 = 100 nF.

If a loudness characteristic with additional high frequency

boost is desired, an additional high-pass section has to be

included in the external filter circuit as indicated in the

block diagram. A filter configuration that provides

AC coupling avoids offset voltage problems.

handbook, halfpage

CKVL

8

9

C1

R3

0 dB

V1

R1

33 kΩ

V2

R2

MED437

Fig.17 Basic loudness circuit.

1995 Dec 19

29

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