TDA7403 datasheet(7/26 Pages) STMICROELECTRONICS

7 / 26 page

Input stages

The input circuits are the same as in preceeding

ST audioprocessors with exception of the CD in-

puts (see figure 1).

The typical input impedance is 100k

Ω.

AutoZero

In order to reduce the number of pins there is no

AC coupling between the In-Gain and the follow-

ing stage, so that any offset generated by or be-

fore the In-Gain stage would be transferred or

even amplified to the output.

To avoid that effect a special offset cancellation

stage called AutoZero is implemented.

To avoid audible clicks the audioprocessor is

muted before the loudness stage during this time.

In some cases, for example if the

µP is executing

a refresh cycle of the I

2C bus programming, it is

not useful to start a new AutoZero action because

no new source is selected and an undesired mute

would appear at the outputs. For such applica-

tions the TDA7403 could be switched in the ”Auto

Zero Remain” mode (Bit 6 of the subaddress

byte). If this bit is set to high, the DATABYTE 0

could be loaded without invoking the AutoZero

and the old adjustment value remains.

Mixing Stage

This stage offers the possibility to mix the internal

beep or the phone signal to any other source.

Due to the fact that the mixing stage is also lo-

cated behind the In-Gain stage fine adjustments

of the main source level can be done in this way.

Loudness

There are four parameters programmable in the

loudness stage (see fig. 2, 3, 4):

- Attenuation

- Center Frequency

- Loudness Q

- Flat Mode: in this mode the loudness stage works

as a 0 - 15dB attenuator.

D98AU951

100K

STEREODECODER

IN GAIN

CASSETTE

MPX

Figure 1. Input stages

-20.0

-15.0

-10.0

-5.0

0.0

10.0

100.0

1.0K

10.0K

Figure 2. Loudness Attenuation @ fc = 400Hz

(second order)

-20.0

-15.0

-10.0

-5.0

0.0

10.0

100.0

1.0K

10.0K

Figure 3. Loudness Center frequency @ Attn.

= 15dB (second order)

DESCRIPTION OF THE AUDIOPROCESSOR

TDA7403

7/26

TDA7403 数据表(PDF) 7 Page - STMicroelectronics

TDA7403 数据表(HTML) 7 Page - STMicroelectronics

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

数据表下载