VPEAK

(V)

D95AU332A

20

DEVIATION(KHz)

0.9

1.3

2.3

3.2

DETECTOR OFF (11)

32.5

45

75

OVM=10

OVM=01

OVM=00

Figure 7: Behaviour of the Deviation Dependent Threshold Adiust (Over Deviation Detector)

2.2V(00)

TRIG. THRESHOLD

0.9V

VPEAK

E’

D95AU333A

1.8V(01)

1.2V(10)

MONO

STEREO

noisy signal

good signal

ATC_SB OFF (11)

NOISE

≈3V

Figure 6: Behaviour of the Field Strength Controlled Threshold Adjustment

MUTE & PAUSE FEATURES

The TDA7340G provides three types of mute,

controlled via I2C bus (see pag.12, MUTE BYTE

register).

SOFT MUTE

Bit D0=1

→ Soft Mute ON

Bit D0=0

→Soft Mute OFF

It allows an automatic soft muting and unmuting

of the signal.

The time constant is fixed by an external capaci-

tor Csm inserted between pin Csm and ground.

Once fixed the external capacitor, two different

slopes (time constant) are selectable by program-

mation of bit D1.

Bit D1=1

→ fast slope (I=Imax)

Bit D1=0

→ slow slope (I=Imin)

The soft mute generates a gradual signal de-

creasing avoiding big click noise of an immediate

high attenuation, without necessity to program a

sequence of decreasing volume levels. A re-

sponse example is reported in Fig.12 (mute) and

Fig.13 (unmute). The final attenuation obtained

with soft mute ON is 60dB typical.

The used reference parameter is the delay time

taken to reach 20dB attenuation (no matter what

the signal level is).

Using a capacitor Csm=22nF this delay is:

d = 1. 8ms when selected Fast slope mode (bit D1=1)

d = 25 ms when selected Slow slope mode (bit D1=0)

TDA7340G

19/27