TDA7437 datasheet(16/23 Pages) STMICROELECTRONICS

16 / 23 page

WARNING

The TDA7437 always needs to receive a STOP

condition, before beginning a new START condi-

tion. The device doesn’t recognize a START con-

dition if a previously active communication was

not ended by a STOP condition.

2C BUS READ MODE

The TDA7437 gives to the master a 1 byte

”TRANSMITTED INFO” via I2C bus in read

mode. The read mode is Master activated by

sending the chip address with LSB set to 1, fol-

lowed by acknowledge bit.

The TDA7437 recognizes the request. At the fol-

lowing

master

generated

clocks

bits,

the

TDA7437 issues the TRANSMITTED INFO byte

on the SDA data bus line (MSB transmitted first).

At the nineth clock bit the MCU master can:

- acknowledge the reception, starting in this

way the transmission of another byte from

the TDA7437.

- no acknowledge, stopping the read mode

communication.

LOUDNESS STAGE

The previous SGS-THOMSON audioprocessors

were implementing a fixed loudness response,

only ON/OFF sw programmable.

No possibility to change the loud boost rate at a

certain volume level.

The TDA7437 implements a fully programmable

loudness control in 20 steps of 1dB.

It allows a customized loudness response for

each application.

The external network connected to the loudness

pins LOUD_L and LOUD_R fixes the type of loud-

ness response

1) Simple Capacitor

The loudness effect is only a boost of low fre-

quencies. (see Fig.20)

2)Second order Loudness (boost of low and

high frequencies).

3)Second order decreased type Loudness

(lower boost of low and high frequencies).

4)Second order modified type Loudness (higher

boost of low and high frequencies).

BASS & MID FILTERS

Several bass filter types can be implemented.

Normally it is used the basic T-type Bandpass Filter.

Starting from the filter component values (R1 in-

ternal and R2, C1, C2 external), the centre fre-

quency Fc, the gain Av at max bass boost and

the filter Q factor are computed as follows:

Fc =

⋅ Π ⋅√

(R1 ⋅ R2 ⋅ C1 ⋅ C2)

⋅ C2 + R2 ⋅ C1 + R1 ⋅ C1

⋅ C1 + R2 ⋅ C2

√

(R1 ⋅ R2 ⋅ C1 ⋅ C2)

⋅ C1 + R2 ⋅ C2

Viceversa fixed Fc, Av, and R1 (internal typ.+/-

30%), the external component values are:

− 1

⋅ Π ⋅ R1 ⋅ Q

⋅ Q ⋅ C1

− 1 − Q ⋅ Q

Av − 1 − Q ⋅ Q

⋅ Π ⋅ C1 ⋅ Fc ⋅ (Av − 1) ⋅ Q

TREBLE STAGE

The Treble stage is a simple high pass filter which

time constant is fixed by internal resistor (50Kohm

typ) and an external capacitor connected between

pins TREB_R/TREB_L and Ground.

IN-OUT PINS

The multiplexer output is available at OUT_R and

OUT_L pins for optional connection of external

graphic equalizer (TDA7316/TDA7317), surround

chip (TDA7346) etc. The signal is fed in again at

pins IN_L and IN-R. In case of application without

external devices the pins OUT_L/OUT_R and

IN_L/IN_R can be left unconnected if bit D3 byte

input selector is forced = 0 (DC connect) instead if

bit D3 is kept = 1 an external decoupling capacitor

must be

provided between OUTR/INR and

OUTL/INR necessary to avoid signal DC jumps,

generating ”Clicking” output noise.

The input impedance of the next volume stage is

44Kohm typical (minimum 31Kohm). A capacitor

no lower than 1

µF should be used.

INPUT SELECTOR

The multiplexer selector can choose one of the

following inputs:

- a differential CD stereo input.

- a mono input.

- four stereo input

The signal fed to the input pins must be decou-

pled via series capacitors. The minimum allowed

value depends on the correspondent input imped-

ance. For the CD diff input (Zi=10Kohm worst

case ) a Cin=4.7uF is recommended.

TDA7437

16/23

TDA7437 датащи(PDF) 16 Page - STMicroelectronics

TDA7437 датащи(HTML) 16 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

датащи скачать

ссылки URL