TDA7454 Datasheet, PDF (9/13 Pages) STMicroelectronics – 4 x 35W HIGH EFFICIENCY QUAD BRIDGE CAR RADIO AMPLIFIER

Table 1: MODE SELECTION TABLE OPERATION OF THE DEVICE
1) STD/HI-EFF (pin 16 = OPEN)
STANDARD QUAD
BRIDGE MODE
HIGH-EFF QUAD
BRIDGE MODE
100
STANDARD QUAD
SINGLE-ENDED MODE
ST-BY MODE
150
17 0
2) STD/HI-EFF (pin 16 = GND)
HIGH-EFF QUAD BRIDGE MODE
STANDARD QUAD
SINGLE-ENDED MODE
ST-BY MODE
150
170
3) STD/HI-EFF (pin 16 connected as shown in the figure below.
STANDARD QUAD
BRIDGE MODE OR
HIGH-EFF MODE
(Theatsink dependent)
HIGH-EFF QUAD
BRIDGE MODE
100
STANDARD QUAD
SINGLE-ENDED MODE
ST-BY MODE
150
17 0
STD/HI-EFF (pin 16)
Vref
NTC t(Theatsink)
TDA7454
Tchip (deg)
Tchip (deg)
Tchip (deg)
OUTPUT STAGE STABILITY
The TDA7454’s is intrinsically stable and will
properly drive any kind of conventional car-radio
speakers without the need of supplementary out-
put compensation (e.g. Boucherot cells), thus al-
lowing a drastic reduction of the external parts
whose number, abated to the essentials, reflects
that of traditional amplifiers. In this respect, per-
fect pin-to-pin compatibility with the entire Sgs-
Thomson’s 4-BTL family (TDA738X) exists.
STANDARD / HIGH-EFFICIENCY OPERATION
(pin 16)
The TDA7454’s operating mode can be selected
by changing the connection of pin 16, according
to table 1.
At low battery levels (<10 V), the device will auto-
matically turn into STANDARD BRIDGE mode, in-
dependently from the status of pin 16.
Condition # 3 in table 1 is particularly useful when
the TDA7454’s operation has to be conditioned
by the temperature in other more heat-sensitive
devices in the same environment. The NTC resis-
tor is a temperature sensor, to be situated near
the critical part(s), will appropriately drive pin 16
through a low-power transitor. Initially the
D94AU174A
TDA7454 can be set to operate as a STANDARD
BRIDGE, turning into HIGH EFFICIENCY mode
only if overheating is recognised in the critical
spot, thus reducing the overall temperature in the
circuit.
CLIPPING DETECTOR / DIAGNOSTIC (pin 25)
The TDA7454 is equipped with a diagnostic func-
tion whose output is available at pin 25. This pin
requires a pull-up resistor (10 KOhm min.) to a
DC source that may range from 5 V to Vcc. The
following events will be recognized and signaled
out:
Clipping
A train of negative-going pulses will appear, each
of them syncronized with every single clipping
event taking place in ant of the outputs.
A possible application consists of filtering / inte-
grating the pulses and implement a routine for
automatically reducing / restoring the volume us-
ing microprocessor - driven audioprocessors, to
counteract the clipping sound-damagingeffects.
Overheating
Chip temperatures above 150 oC will be signaled
out at pin 25 in the form of longer-lasting pulses,
as the stepping back into the operating tempera-
ture requires some time.
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