TDA7562B Datasheet, PDF (18/30 Pages) STMicroelectronics – 4 x 46 W multifunction quad power amplifier with built-in diagnostics features

Diagnostics functional description
TDA7562B
4.5
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.
Table 5. Double fault table for turn on diagnostic
-
S. GND (so) S. GND (sk)
S. Vs
S. GND (so)⁽¹⁾
S. GND (sk)⁽¹⁾
S. GND
/
S. GND
S. GND
S. Vs + S.
GND
S. Vs
S. Across L.
Open L.
S. GND
S. GND
S. GND
Open Load⁽²⁾
S. Vs
/
/
S. Vs
S. Vs
S. Vs
S. Across L.
/
/
/
S. Across L.
N.A.
Open L.
/
/
/
/
Open Load ⁽²⁾
1. 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 LR, so = CH+, sk = CH-; in channels LR and RF, so = CH-, SK = CH+.
2. In Permanent Diagnostic the table is the same, with only a difference concerning Open Load, which is not
among the recognizable 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).
4.6
Faults availability
All the results coming from I²C Bus, 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. This is true for DC diagnostic (Turn-on and Permanent), for Offset
Detector, for AC Diagnostic (the low current sensor needs to be stable to confirm the Open
tweeter).
To guarantee always resident functions, every kind of diagnostic cycles (Turn-on,
Permanent, Offset, AC) 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.
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Doc ID 17984 Rev 2