TDA7567PD Multiple faults
Doc ID 16903 Rev 2 17/30
4 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 I
2
C 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.
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 CH3 and CH2, so = CH+, sk = CH-; in Channels CH4 and CH1, so =
CH-, sk = CH+.
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).
4.1 Faults availability
All the results coming from I
2
Cb us, 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 I
2
C reading operation. So, when the micro
reads the I
2
C, 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 I
2
C. The short to GND is still present in bytes, because it is the result of the
previous cycle. If another I
2
C reading operation occurs, the bytes do not show the short). In
general to observe a change in Diagnostic bytes, two I
2
C reading operations are necessary.
Table 5. Double fault table for turn-on diagnostic
S. GND (so) S. GND (sk) S. Vs S. Across L. Open L.
S. GND (so) S. GND S. GND
S. Vs + S.
GND
S. GND S. GND
S. GND (sk) / S. GND S. Vs S. GND Open L. (*)
S. Vs / / S. Vs S. Vs S. Vs
S. Across L. / / / S. Across L. N.A.
Open L. / / / / Open L. (*)
