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

Figure 1: Microprocessor Application

ELECTRICAL CHARACTERISTICS (Continued)

Symbol

Parameter

Test Condition

Min.

Typ.

Max.

Unit

Mute Threshold

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 Noise Voltage

A curve

f = 20Hz to 20kHz

150

220

500

µV

µV

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 guaran-

tee the right St-by and mute signals sequence.

It is quite simple to obtain this function using a mi-

croprocessor (Fig. 1 and 2).

At first St-by signal (from mP) goes high and the

voltage across the St-by terminal (Pin 7) starts to

increase exponentially. 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.

TDA7297

3/9