TDA7476 Datasheet, PDF (7/15 Pages) STMicroelectronics – CAR RADIO DIAGNOSTIC PROCESSOR

TURN-ON DIAGNOSTIC - THRESHOLDS
CH1, CH2, CH3, CH4, CH5
Output voltage during test. (The power amplifier must be in ST-BY mode).
S.C. to GND x Normal Operation x
S.C. to Vs
TDA7476
0V
0.8V 1.2V
V_S-1.3 V_S-0.7V
V_S
D96AU502A
Voltage across the load during test. (The power amplifier must be in ST-BY mode).
S.C. across Load x Normal Operation x
Open Load
0V
5mV 22mV
220mV 550mV
V_S
D97AU631A
Note: some faults can mask others if they are present at the same moment on the same channel:
- If there is a short to GND and an open load on the same channel, the TDA7476 gives information
only about one of them, depending on the wire on which the short circuit is present.
- The short circuit to GND masks any short circuit across the load.
- The short circuit to Vs masks any short or open load.
AUX1 - AUX2
Voltage across the sensing resistors.
S.C. to GND x Normal Operation x Open Load
V_S
0.75V 0.5V
125mV 85mV
0V
D97AU572
The minimum voltage of the AUX IN pin to sense the open load condition is 2V.
The minimum voltage of the AUX IN pin to detect the short circuit to GND, by sensing the drop on the
resistors is 4.5V. If this voltage falls below 2V, the AUX in is considered short circuited to GND. From
2V to 4.5V the sensing circuit can detect a short circuit in both ways (by sensing across the resistor or
through the voltage between the AUX IN pin and GND).
PERMANENT DIAGNOSTIC - THRESHOLDS
CH1, CH2, CH3, CH4, CH5
The circuit will recognize as a fault condition any situation where the following short circuit voltages
last more than 2 sec (typ).
Output voltage
S.C. to GND x Normal Operation x
S.C. to Vs
0V
0.8V 1.2V
V_S-1.3 V_S-0.7V
V_S
D97AU573A
AUX1 - AUX2
The voltage across the resistors Rsens1 or Rsens2 is sensed. The circuit will recognize as a fault con-
dition any situation where the following voltages last more than 2sec (typ) in the region ”S.C.to GND”
or ”open load”.
S.C. to GND x Normal Operation x
Open Load
V_S
0.75V 0.5V
125mV 85mV
0V
D97AU574
The minimum voltage of the AUX IN pins to sense the open load condition is 2V.
The minimum voltage of the AUX IN pin to detect the short circuit to GND by sensing drop on the re-
sistor is 4.5V. If this voltage is below 2V, the AUX line is considered short circuited to GND. From 2V
to 4.5V the sensing circuit can detect a short circuit in both ways (by sensing across the resistor or
through the voltage between the AUX IN pin and GND).
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