TDA7454
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
STANDARD QUAD
SINGLE-ENDED MODE
ST-BY MODE
Tchip (deg)
100
150
17 0
2) STD/HI-EFF (pin 16 = GND)
STANDARD QUAD
SINGLE-ENDED MODE
HIGH-EFF QUAD BRIDGE MODE
ST-BY MODE
Tchip (deg)
150
170
3) STD/HI-EFF (pin 16 connected as shown in the figure below.
STANDARD QUAD
BRIDGE MODE OR
HIGH-EFF MODE
HIGH-EFF QUAD
BRIDGE MODE
STANDARD QUAD
SINGLE-ENDED MODE
ST-BY MODE
(Theatsink dependent)
Tchip (deg)
100
150
17 0
Vref
STD/HI-EFF (pin 16)
NTC t(Theatsink)
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.
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.
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:
STANDARD / HIGH-EFFICIENCY OPERATION
(pin 16)
Clipping
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.
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.
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
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.
through a low-power transitor.
Initially the
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STMICROELECTRONICS [ ST ]
