TDA7381(1999) Ver la hoja de datos (PDF) - STMicroelectronics
Número de pieza
componentes Descripción
Fabricante
TDA7381 Datasheet PDF : 10 Pages
| |||
TDA7381
Figure 7.
VREF
25
T1
T2
TTDDAA77338815
T1 << T2
VREF ≥ VREF1 >> VREF2
-
+
VREF1
-
+
VREF2
CLIP DET. (TO GAIN
COMPRESSOR/
TONE CONTROL)
FAULT, THERMAL SHUTDOWN
(TO POWER SUPPLY
SECTION, µP VOLTAGE
REGULATOR, FLASHING SYSTEM)
D95AU305
tor has to be viewed mainly as a power-depend-
ent feature rather than frequency-dependent. This
means that clipping state will be immediately sig-
naled out whenever a fixed power level is
reached, regardless of the audio frequency.
In other words, this feature offers the means to
counteract the extremely sound-damaging effects
of clipping, caused by a sudden increase of odd
order harmonics and appearance of serious inter-
modulation phenomena.
Another possible kind of distortion control could
be the setting of a maximum allowable THD limit
(e.g. 0.5 %) over the entire audio frequency
range. Besides offering no practical advantages,
this procedure cannot be much accurate, as the
non-clipping distortion is likely to vary over fre-
quency.
In case of OVERHEATING, pin 25 will signal out
the junction temperature proximity to the thermal
shut-down threshold. This will typically start about
2oC before the thermal shut-down threshold is
reached.
As various kind of diagnostics information is avail-
able at pin 25 (CLIPPING, SHORTS AND OVER-
HEATING), it may be necessary to operate some
distinctions on order to treat each event sepa-
rately. This could be achieved by taking into ac-
count the intrinsically different timing of the diag-
nostics output under each circumstance.
In fact, clipping will produce pulses normally
much shorter than those present under faulty con-
ditions. An example of circuit able to distinguish
between the two occurrences is shown by fig. 7.
STABILITY AND LAYOUT CONSIDERATIONS
If properly layouted and hooked to standard car-
radio speakers, the TDA7381 will be intrinsically
stable with no need of external compensations
such as output R-C cells. Due to the high number
of channels involved, this translates into a very
remarkable components saving if compared to
similar devices on the market.
To simplify pc-board layout designs, each ampli-
fier stage has its own power ground externally ac-
cessible (pins 2,8,18,24) and one supply voltage
pin for each couple of them.
Even more important, this makes it possible to
achieve the highest possible degree of separation
among the channels, with remarkable benefits in
terms of cross-talk and distortion features.
About the layout grounding, it is particularly im-
portant to connect the AC-GND capacitor (C5) to
the signal GND, as close as possible to the audio
inputs ground: this will guarantee high rejection of
any common mode spurious signals.
The SVR capacitor (C6) has also to be connected
to the signal GND.
Supply filtering elements (C7, C8) have naturally
to be connected to the power-ground and located
as close as possible to the Vs pins.
Pin 1, which is mechanically attached to the de-
vice’s tab, needs to be tied to the cleanest power
ground point in the pc-board, which is generally
near the supply filtering capacitors.
8/10
Share Link: 