TDA7563 Datasheet, PDF (12/20 Pages) STMicroelectronics – MULTIFUNCTION QUAD POWER AMPLIFIER WITH BUILT-IN DIAGNOSTICS FEATURES

TDA7563
– STOP = Actual reading operation
Excess offset is signalled out if persistent throughout the assigned testing time. This feature is disabled if any
overloads leading to activation of the short-circuit protection occurs in the process.
MULTIPLE FAULTS
When more misconnections are simultaneously in place at the audio outputs, it is guaranteed that at least one
of them is initially read out. The others are notified after successive cycles of I²C reading and faults removal,
provided that the diagnostic is enabled. This is true for both kinds of diagnostic (Turn on and Permanent).
The table below shows all the couples of double-fault possible. It should be taken into account that a short circuit
with the 4 ohm speaker unconnected is considered as double fault.
Double fault table for Turn On Diagnostic
S. GND (so)
S. GND (sk)
S. GND (so)
S. GND
S. GND
S. GND (sk)
/
S. GND
S. Vs
/
/
S. Across L.
/
/
Open L.
/
/
S. Vs
S. Vs + S. GND
S. Vs
S. Vs
/
/
S. Across L.
S. GND
S. GND
S. Vs
S. Across L.
/
Open L.
S. GND
Open L. (*)
S. Vs
N.A.
Open L. (*)
S. GND (so) / S. GND (sk) in the above table make a distinction according to which of the 2 outputs is shorted
to ground (test-current source side= so, test-current sink side = sk). More precisely, in Channels LF and RR, so
= CH+, sk = CH-; in Channels LR and RF, so = CH-, sk = CH+ .
In Permanent Diagnostic the table is the same, with only a difference concerning Open Load(*) , which is not
among the recognisable faults. Should an Open Load be present during the device's normal working, it would
be detected at a subsequent Turn on Diagnostic cycle (i.e. at the successive Car Radio Turn on).
FAULTS AVAILABILITY
All the results coming from I²Cbus, by read operations, are the consequence of measurements inside a defined
period of time. If the fault is stable throughout the whole period, it will be sent out.
To guarantee always resident functions, every kind of diagnostic cycles (Turn on, Permanent, Offset) will be
reactivate after any I²C reading operation. So, when the micro reads the I²C, a new cycle will be able to start,
but the read data will come from the previous diag. cycle (i.e. The device is in Turn On state, with a short to Gnd,
then the short is removed and micro reads I²C. The short to Gnd is still present in bytes, because it is the result
of the previous cycle. If another I²C reading operation occurs, the bytes do not show the short). In general to
observe a change in Diagnostic bytes, two I²C reading operations are necessary.
THERMAL PROTECTION
Thermal protection is implemented through thermal foldback (fig. 21). Thermal foldback begins limiting the audio
input to the amplifier stage as the junction temperatures rise above the normal operating range. This effectively
limits the output power capability of the device thus reducing the temperature to acceptable levels without totally
interrupting the operation of the device. The output power will decrease to the point at which thermal equilibrium
is reached. Thermal equilibrium will be reached when the reduction in output power reduces the dissipated pow-
er such that the die temperature falls below the thermal foldback threshold. Should the device cool, the audio
level will increase until a new thermal equilibrium is reached or the amplifier reaches full power. Thermal fold-
back will reduce the audio output level in a linear manner.
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