TDA7400 datasheet(13/28 Pages) STMICROELECTRONICS

13 / 28 page

til the end of demuting.

Bass

There are four parameters programmable in the

bass stage: (see figs 6, 7, 8, 9):

Attenuation

Figure 6 shows the attenuation as a function of

frequency at a center frequency at a center fre-

quency of 80Hz.

Central Frequency

Figure 7 shows the four possible center frequen-

cies 60,70,80 and 100Hz.

Quality Factors

Figure 8 shows the four possible quality factors 1,

1.25, 1.5 and 2.

DC Mode

In this mode the DC gain is increased by 5.1dB.

In addition the programmed center frequency and

quality factor is decreased by 25% which can be

used to reach alternative center frequencies or

quality factors.

TREBLE

There are two parameters programmable in the

treble stage (see figs 10, 11):

Attenuation

Figure 10 shows the attenuation as a function of

frequency at a center frequency of 17.5KHz.

Center Frequency

Figure 11 shows the four possible Center Fre-

quency (10, 12.5, 15 and 17.5kHz).

Speaker Attenuator

The speaker attenuators have exactely the same

structure and range like the Volume stage.

FUNCTIONAL DESCRIPTION OF STEREODE-

CODER

The stereodecoder part of the TDA7400D (see

Fig. 12) contains all functions necessary to de-

modulate the MPX signal like pilot tone depend-

ent

MONO/STEREO

switching

well

”stereoblend” and ”highcut” functions.

EXT.

MUTE

+SIGNAL

REF

-SIGNAL

2C BUS

OUT

Time

D97AU634

Figure 5. Softmute Timing

0.0

2.5

5.0

7.5

10.0

12.5

15.0

10.0

100.0

1.0K

10.0K

Figure 7. Bass Center @ Gain = 14dB, Q = 1

-15.0

-10.0

-5.0

0.0

5.0

10.0

15.0

10.0

100.0

1.0K

10.0K

Figure 6. Bass Control @ fc = 80Hz, Q = 1

Note: Please notice that a started Mute action is always terminated

and could not be interrupted by a change of the mute signal.

TDA7400

13/28

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