TDA7372B Datasheet, PDF (8/10 Pages) STMicroelectronics – 4 x 6W POWER AMPLIFIER FOR CAR RADIO

TDA7372B
FUNCTIONAL DESCRIPTION
Function
GENERAL
OUTPUT STAGE
ST-BY
MUTE
THERMAL
PROTE CTION
BUILT-IN SHORT
CIRCUIT
PROTE CTION
Description
The TDA7372B 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 whose gain is
internally fixed to 40dB.
The output stage is a single ended type suitable to drine 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 supplies 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 is mute status when the supply voltage goes below the minimum
allowed value. This prevents pop noises whenever the battery voltage drops below a fixed
threshold. When the supply voltage rises to its 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
Until the juntion 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 unpleasent
effect. Supposing the junction temperature does not reduce to safe levels a complete shutdown
will occur.
Reliable and safe operation in presence of:
- AC short circuit to GND
- DC short circuit to GND and to VS during power-on phase
is assured by a built-in protection circuitry.
the DC short protector acts in such a way to avoid the device is turned on (by ST-BY) when a
DC short is present between out to GND or out to V_S. 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.)
More over, as the involved circuitry is normally disabled when a current higher than 5mA is
flowing into the st-by pin, it is important, in order not to disable it, to have the external current
source driving the pin it self limited to 5mA. (figure 1 is showing relevant waveforms).
Figure 15: Fault (DC short) waveforms
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