7

Application suggestion

The recommended values of the external components are those shown on the application circuit of Figure 1.

Different values can be used; the following table can help the designer.

COMPONENTS

SUGGESTED

VALUE

PURPOSE

LARGER THAN

SUGGESTED

SMALLER THAN

SUGGESTED

R1 (1)

22 kΩ

INPUT RESISTANCE

INCREASE INPUT

IMPEDANCE

DECREASE INPUT

IMPEDANCE

R2

680 Ω

CLOSED LOOP GAIN SET

TO 30 dB (2)

DECREASE OF GAIN

INCREASE OF GAIN

R3 (1)

22 kΩ

INCREASE OF GAIN

DECREASE OF GAIN

R4

22 kΩ

ST-BYTIME CONSTANT

LARGERST-BY ON/OFF

TIME

SMALLER ST-BY ON/OFF

TIME; POP NOISE

R5

10 kΩ

MUTE TIME CONSTANT

LARGER MUTE ON/OFF

TIME

SMALLER MUTE ON/OFF

TIME

C1

0.47 μF

INPUT DC DECOUPLING

HIGHER LOW

FREQUENCY CUTOFF

C2

22 μF

FEEDBACK DC

DECOUPLING

HIGHER LOW

FREQUENCY CUTOFF

C3

10 μF

MUTETIME CONSTANT

LARGER MUTE ON/OFF

TIME

SMALLER MUTE ON/OFF

TIME

C4

10 μF

ST-BYTIME CONSTANT

LARGERST-BY ON/OFF

TIME

SMALLERST-BY ON/OFF

TIME; POP NOISE

C5

22 μF

BOOT STRAPPING

SIGNAL DEGRADATION AT

LOW FREQUENCY

C6, C8

1000 μF

SUPPLY VOLTAGE

BYPASS

DANGER OF

OSCILLATION

C7, C9

0.1 μF

SUPPLY VOLTAGE

BYPASS

DANGER OF

OSCILLATION

1. R1= R3 for pop optimization.

2. Closed loop gain has to be 24 dB.

TDA7294

Application suggestion

DS0013 - Rev 8

page 9/31