TDA7372A Datasheet, PDF (8/10 Pages) STMicroelectronics – 4 x 6W POWER AMPLIFIER FOR CAR RADIO

TDA7372A
FUNCTIONAL DESCRIPTION
Function
GENERAL
OUTPUT STAGE
ST-BY
MUTE
THERMAL
PROTE CTION
BUILT-IN SHORT
CIRCUIT
PROTE CTION
Description
The TDA7372A is a quad channel single package audio power amplifier intended to reduce the
mismatch in the electrical characteristics among the four different channels and to consistently
drop the external component count. It contains four non inverting stages capable to operate
down to 20dB gain so minimizing the output noise and optimizing SVR and distortion.
The output stage is a single ended type suitable to drive 4Ω loads. It consists of a class AB fully
complementary PNP/NPN stages short circuit protected.
A rail to rail output swing is achieved without need of boostrap capacitors. Moreover, the
external compensation is not necessary.
The device features a St-BY function which shuts down the internal bias generators when the
ST-BY input is low. In ST-BY mode the amplifier sinks a small current (in the range of few µAs).
When the St-BY pin is high the IC becomes fully operational.
A mute function is also provided. This reduces the gain of the input stage to a level effectively
eliminating any audio input influence on the output stage when the mute line is low. When the
mute line is high the normal input path is restored.
The device goes automatically into mute state when the supply voltage goes below the
minimum allowable value. This prevents pop noises whenever the battery voltage drops below
a fixed threshold. When the supply voltage rises to it nominal value the device recovers the play
condition with a delay fixed by the C_SVR capacitor.
The Thermal protection principle involves two different steps
a) Soft thermal limitation
b) Shutdown
As long as the junction temperature remains below a preset threshold, the I.C. will deliver the
full power. Once the threshold has been reached, the device automatically goes into mute
status. The play to mute transition is internally controlled so producing a soft muting without
unpleasant effect. Supposing the junction temperature does not reduce to safe levels, a
complete shutdown will occur.
A built-in protection circuit assures reliable and safe operation in presence of:
- AC short circuit to GND
- DC short circuit to GND and to VS during power-on phase
The DC short protector acts in a way to avoid that the device is being turned on (by ST-BY)
when a DC short is present from OUT to GND or OUT to VS. Due to this reason it is necessary
to introduce a proper delay on the st-by pin (expecially when it is driven by V_S.)
Moreover, as the involved circuitry is normally disabled when a current higher than 5mA is fed
into the st-by pin, it is important, in order not to disable it, to have the external current source
driving the pin itself limited to 5mA. (figure 1 is shows the relevant waveforms).
Figure 15: Fault (DC short) waveforms
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