3/11

TDA7297SA

APPLICATION SUGGESTION

STAND-BY AND MUTE FUNCTIONS

(A) Microprocessor Application

In order to avoid annoying "Pop-Noise" during Turn-On/Off transients, it is necessary to guarantee the right St-

by and mute signals sequence. It is quite simple to obtain this function using a microprocessor (Fig. 1 and 2).

At first St-by signal (from

µP) goes high and the voltage across the St-by terminal (Pin 7) starts to increase ex-

ponentially. The external RC network is intended to turn-on slowly the biasing circuits of the amplifier, this to

avoid "POP" and "CLICK" on the outputs.

When this voltage reaches the St-by threshold level, the amplifier is switched-on and the external capacitors in

series to the input terminals (C3, C5) start to charge.

It's necessary to mantain the mute signal low until the capacitors are fully charged, this to avoid that the device

goes in play mode causing a loud "Pop Noise" on the speakers.

A delay of 100-200ms between St-by and mute signals is suitable for a proper operation.

Figure 1. Microprocessor Application

Input Resistance

25

30

K

Ω

Mute Threshold

Vo = -30dB

2.3

2.9

4.1

V

St-by Threshold

0.8

1.3

1.8

V

St-by Current V6 = GND

100

µA

Total Output Voltage

A Curve;

f = 20Hz to 20KHz

150

220

500

µV

µV

ELECTRICAL CHARACTERISTCS (continued)

Symbol

Parameter

Test Condition

Min.

Typ.

Max.

Unit

1

2

4

Vref

ST-BY

7

IN1

C1 0.22

µF

VCC

13

3

D95AU258A

+

-

-

+

OUT1+

OUT1-

15

14

12

MUTE

6

IN2

C3 0.22

µF

+

-

-

+

OUT2+

OUT2-

8

9

S-GND

PW-GND

C5

470

µF

C6

100nF

R1 10K

C2

10

µF

µP

R2 10K

C4

1

µF