E-TDA7396 Datasheet, PDF (8/11 Pages) STMicroelectronics – 45W/2W BRIDGE CAR RADIO AMPLIFIER WITH DIAGNOSTIC FACILITY

TDA7396
CLIPPING DETECTION & DIAGNOSTICS
(see fig. 16)
An active pull-down circuit is provided to signal
out the occurrence of any of the conditions de-
scribed later. In order to use this function, the CD-
DIA pin (#4) has to be resistively connected to a
positive voltage reference (between 5V and Vs).
A) Clipping Detection
Current is sunk whenever the output clipping dis-
tortion level reaches a fixed 0.5% threshold; this
function allows gain compression facility when the
amplifier is overdriven.
B) Output Fault Diagnostics
Current is sunk as soon as one of the following
output faults is recognized:
- short-circuit to GND
- short-circuit to Vs
- short-circuit across the load (after turn-on)
- open load (before turn-on)
The diagnostics signal remains steadily on until
the fault is removed.
All the output fault conditions (listed above) can
be distinguished from the clipping detection (A)
because of their different time duration.
THERMAL WARNING (see fig. 17)
Thermal protection has been implemented in ac-
cordance to a new principle involving different
steps:
1) Thermal foldback (Linear Thermal Shutdown)
2) Shutdown with soft restart (Absolute Thermal
Shutdown)
As long as the junction temperature remains be-
low the preset threshold (140°C) the IC delivers
the full power. Once the threshold has been
reached, a thermal foldback starts limiting the out-
put signal level; the output power is then reduced,
thus decreasing also the temperature without out-
put signal interruption (LTS). Supposing the ther-
mal foldback does not reduce the junction tem-
perature to a safe level, a complete shutdown will
occur at 160°C (ATS).
Soft restart avoids large voltage disturbance
across the loudspeaker, due to the presence of
high input signals when the IC comes out of ther-
mal shutdown.
Current is sunk from the CD-DIA pin (#4)when the
thermal protection is acting. The voltage at pin #4
bounces back and forth (depending on the ampli-
fier input signal magnitude) during the linear ther-
mal intervention (LTS) and stays low (sinking cur-
rent) after the amplifier has been eventually
shut-down (Absolute Thermal Shutdown)
Figure 16: Clipping Detection & Diagnostics Waveforms
Vo
CLIPPING
CLIPPING
DETECTOR/
DIAGNOSTICS
OUTPUT
(pin 4)
0
NORMAL OPERATION
S/C TO GND
FAULT DIAGNOSTICS
D93AU005A
NORMAL OPERATION
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