TDA7437 datasheet(15/23 Pages) STMICROELECTRONICS

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a)by reading directly the Pause pin level.

The ON/OFF voltage threshold is 3.0V typical.

Pause OFF = level low (< 3.0V)

Pause ON = level high ( ; 3.0V)

b)by reading via I

2C bus theTransmittedByte, bitP

P= 0 pause active.

P= 1 no pause detected.

The external capacitor value fixes the time con-

stant.

The pull up current is 25uV typical

With input signal

Vin = 1Vrm --; Vdc pin pause = 15mV

Vin = 0Vrms --; Vdc pin pause = 5.62V

For example choosing Cpause = 100nF the

charge up constant is about 22ms. Instead with

Cpause = 15nF the charge up constant is about

360us.

The Pause detection is useful in applications like

RDS, to perform noiseless tuning frequeny jumps

avoiding to mute the signal.

NO SYMMETRICAL BASS CUT RESPONSE

bit D7=0 No symmetrical

bit D7=1 Symmetrical

The Bass stage has the option to generate an

unsymmetrical response, for cut mode settings

(bass level from -2db to - 14dB)

For example using a T-type band pass externa

The feature is useful for human ear equalization

in noisy enviroments like cars etc.

See examples in Fig. 18 (symmetrical response)

and Fig. 19 (unsymmetrical response).

TRANSMITTED DATA (SEND MODE)

The TDA7437 allows the reading of four info bits.

The type (Stereo/Mono) of received broadcasting

signal is easily checked and displayed by using

the ST bit.

The P bit check is useful in tuning jumps without

signal muting.

The SM soft mute status becomes active immedi-

ately, when bit D0 is set to 1 (soft mute ON,

MUTE byte) and not when the signal level has

reached the 60 dB final attenuation.

TDA7437 I

2C BUS PROTOCOL

The protocol is standard I

2C, using subaddress

byte plus data bytes (see pagg.8 to 13).

The optional Autoincrement mode allows to re-

fresh all the bytes registers with transmission of a

single subaddress, reducing drastically the total

transmission time.

Without autoincrement, subaddress bit I= 0, to

refresh all the bytes registers (10), it is necessary

to transmit 10 times the chip address, the subad-

dress and the data byte.

Working with a 100Kb/s clock speed the total time

would be :

[(9*3+2)*10]bits*10us=2.9ms

Instead using autoincrement mode, subaddress

bit I=1, the total time will be:

(9*12+2)*10us=1.1ms.

The autoincrement mode is useful also to refresh

partially the data. For example to refresh the 4

speakers attenuators it is possible to program the

subaddress Spkr LF (code XX010100), followed

by the data byte of SPKR LF, LR, RF, RR in se-

quence.

Note:

that the autoincrement mode has a module 16

counter, whereas the total used register bytes are

10.

It is not correct to refresh all the 10 bytes starting

from a subaddress different than XX010000.

For example using subaddress XX010010 (vol-

ume) the registers

from Volume to Mute (see

pag. 8) are correctly updated but the next two

transmitted bytes instead to refer to the wanted

Input selector and Loudness are discharged. (the

solution in this case is to send two separated pat-

tern in autoinc mode, the first composed by ad-

dress, subaddress XX010010, 8 data bytes, and

the second composed by address, subaddress

XX010000, 2 data bytes).

With autoincrement disabled, the protocol allows

the transmission in sequence of N data bytes of a

specific register, without necessity to resend each

time the address and subaddress bytes.

This feature can be implemented, for example, if

a gradual Volume change has to be performed

(the MCU has not to send the STOP condition,

keeping active the TDA7437 communication).

bit P= 0

Pause active

bit P= 1

No pause detected

bit ZM = 1

Zero cross mute ON

bit ZM = 0

Zero cross mute OFF

bit SM = 1

Soft mute ON

bit SM = 0

Soft mute OFF

bit ST = 1

Stereo signal detected (input MPX)

bit ST = 0

Mono signal detected (input MPX)

TDA7437

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