TDA7437 Datasheet, PDF (15/23 Pages) STMicroelectronics – DIGITALLY CONTROLLED AUDIO PROCESSOR

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 I²C bus the Transmitted Byte, bit P
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)
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)
The TDA7437 allows the reading of four info bits.
The type (Stereo/Mono) of received broadcasting
signal is easily checked and displayed by using
TDA7437
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 I²C BUS PROTOCOL
The protocol is standard I²C, 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).
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