TDA7476_01 Datasheet, PDF (12/19 Pages) STMicroelectronics – CAR RADIO DIAGNOSTIC PROCESSOR

TDA7476
READ BYTE 1
MSB
LSB
D7
D6
D5
D4
D3
D2
D1
D0
STATUS
X
X
X
X
1
1
X
0 CH1 short circuit to Vs
X
X
X
X
1
1
0
X CH1 short circuit to GND
X
X
X
X
1
0
1
1 CH1 open load
X
X
X
X
0
1
1
1 CH1 short circuit across the load
1
1
X
0
X
X
X
X CH2 short circuit to Vs
1
1
0
X
X
X
X
X CH2 short circuit to GND
1
0
1
1
X
X
X
X CH2 open load
0
1
1
1
X
X
X
X CH2 short circuit across the load
READ BYTE 2
X
X
X
X
1
1
X
0 CH3 short circuit to Vs
X
X
X
X
1
1
0
X CH3 short circuit to GND
X
X
X
X
1
0
1
1 CH3 open load
X
X
X
X
0
1
1
1 CH3 short circuit across the load
1
1
X
0
X
X
X
X CH4 short circuit to Vs
1
1
0
X
X
X
X
X CH4 short circuit to GND
1
0
1
1
X
X
X
X CH4 open load
0
1
1
1
X
X
X
X CH4 short circuit across the load
READ BYTE 3
X
X
X
X
X
X
1
0 AUX1 short circuit to GND
X
X
X
X
X
X
0
1 AUX1 open load
X
X
X
X
1
0
X
X AUX2 short circuit to GND
X
X
X
X
0
1
X
X AUX2 open load
1
1
X
0
X
X
X
X CH5 short circuit to Vs
1
1
0
X
X
X
X
X CH5 short circuit to GND
1
0
1
1
X
X
X
X CH5 open load
0
1
1
1
X
X
X
X CH5 short circuit across the load
When the µP reads correctly all the 3 bytes containing the mentioned information and gives the last acknowl-
edge, the TDA7476 switches to the "permanent diagnostic operation"
B) PERMANENT DIAGNOSTIC
It can sense the following diagnostic information:
CH1, CH2, CH3, CH4, CH5
- Short Circuit to GND
- Short Circuit to Vs
Aux1, Aux2
- Short Circuit to GND (*)
- Open Load (*)
(*) Detected if the high side drivers attached to the Aux outputs are ON.
In this case the above conditions are not detected while the single infrasonic current pulse is present but be-
fore. The fault condition must be present for more than 2sec. (typ) and must be also true during the pulse,
where the data are memorized and then transmitted.The bytes from/to µP and TDA7476 are the same as
those in case of turn-on diagnostic (see above).
Here following is the permanent diagnostic output Data Bytes. The bits D7 and D6 of the first byte both stand at
0 level. This condition, although not possible during the turn-on diagnostic, can be useful to confirm that the
bytes are referred to the permanent diagnostic.
12/19