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2003 Feb 12 8
Philips Semiconductors Preliminary specification
70 W high efficiency power amplifier
with diagnostic facility
TDA1562Q; TDA1562ST;
TDA1562SD
Diagnostic output (pin DIAG)
DYNAMIC DISTORTION DETECTOR (DDD)
At the onset of clipping of the output stages, the DDD
becomes active. This information can be used to drive a
sound processor or DC-volume control to attenuate the
input signal and so limit the distortion.
SHORT-CIRCUIT PROTECTION
When a short-circuit occurs at the outputs to ground or to
the supply voltage, the output stages are switched off.
They will be switched on again approximately 20 ms after
removing the short-circuit. During this short-circuit
condition the diagnostic output is continuously LOW.
When a short-circuit occurs across the load, the output
stages are switched off during approximately 20 ms. After
that time is checked during approximately 50 µs whether
the short-circuit is still present. During this short-circuit
condition the diagnostic output is LOW for 20 ms and
HIGH for 50 µs. The power dissipation in any short-circuit
condition is very low.
TEMPERATURE DETECTION
Just before the temperature protection becomes active the
diagnostic output becomes continuously LOW.
LOAD DETECTION
Directly after the circuit is switched from standby to mute
or on, a built-in detection circuit checks whether a load is
present. The results of this check can be detected at the
diagnostic output, by switching the mode select input in the
mute mode.
Since the diagnostic output is an open-collector output,
more devices can be connected.
Fig.4 Diagnostic information.
handbook, full pagewidth
HIGH
MID
LOW
mode select
input
diagnostic
output
output voltage
across load
0
HIGH
LOW
no load
clipping signal
short-circuit to
supply or ground
short-circuit
across load
t
MGL265