TDA7437N_06 Datasheet, PDF (23/34 Pages) STMicroelectronics – Digitally controlled audio processor

TDA7437N
Mute and pause features
5.3
Speakers mute
An additional direct mute function is included in the speakers attenuators stage.
The four output LF, RF, LR, RR can be separately muted by setting the speaker attenuator
byte to the value 01111111 binary.
Typical attenuation level 100dB. This mute is useful for fader and balance functions. It
should not be applied for system mute/unmute, because it can generate noise due to the
offset of previous stages (bass / treble).
5.4
Zero crossing mute
bit D2 = 1 D4 = 0 zero crossing mute ON
bit D2 = 0 D4 = 0 zero crossing mute OFF
The mute activation/deactivation is delayed until the signal waveform crosses the DC zero
level (Vref level).
The detection works separately for left and right channels (see Figure 13 and Figure 14).
Four different window thresholds are software selectable by two dedicated bits.
bit D6 bit D5 Window
0 0 Vref DC +/-280mV
0 1 Vref DC +/-140mV
1 0 Vref DC +/-70mV
1 1 Vref DC +/-35mV
The zero crossing mute activation/deactivation starts when the AC signal level falls inside
the selected window (internal comparator).
The zero crossing mute (and pause) detector is always active. It can be disabled, if the
feature is not used, by forcing the bit D4 = 1 Zero crossing and pause detector reset.
In this way the internal comparator logic is stopped, eliminating its switching noise.
The zero cross mute status is detected reading the transmitted byte bit ZM.
bit ZM = 1 zero cross mute status ON
bit ZM = 0 zero cross mute status OFF
5.5
Pause function
On chip is implemented by a pause detector block.
It uses the same 4 windows threshold selectable for the zero crossing mute, bit D6,D5 byte
MUTE (see above). The detector can be put into OFF by forcing bit D4 = 1, otherwise it is
active.
Pause detector information is available at the PAUSE pin. A capacitor must be connected
between the PAUSE pin and ground.
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