TDA7437N datasheet(23/34 Pages) STMICROELECTRONICS

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TDA7437N

Mute and pause features

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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

Vref DC +/-280mV

Vref DC +/-140mV

Vref DC +/-70mV

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.

TDA7437N Datasheet(PDF) 23 Page - STMicroelectronics