E-TDA7476013TR Datasheet E-TDA7476, TDA7476, TDA7476013TR | P7-P9

7/19

TDA7476

1) The amplifier can drain current in the resistive path of the short circuit, hence this current and consequently

the short circuit resistor cannot be determined with a sufficient level of accuracy.

2) The voltage difference between the car radio ground (reference) and the position of the chassis of the car

where the loudspeaker line is connected (due to an accidental short circuit) can be up to some hundreds of

mV. This does not permit a correct measure of the short circuit resistor.

Turn-on diagnostic - AUX1, AUX2

To detect if there is a short circuit to GND or an open load involving to the AUX output of the car radio, the volt-

age across a sensing resistor Rsens is detected.These output voltages (for example for the active antenna and

for the booster) are usually generated by high side drivers, but also voltage regulators with Vout >5V are admis-

sible. The detection ranges can be set by adjusting the sensing resistors Rsens1 or Rsens2 as following:

Where A

, Anop, Agnd are as specified in the ELECTRICAL CHARACTERISTICS.

For example, if Rsens = 5 Ohm, the following detection table will be operative :

Permanent diagnostic - CH1, CH2, CH3, CH4, CH5 - Short to GND and Vs

During the CAR-RADIO normal operation, to detect a short circuit to GND (or to Vs), the output voltages are

sensed. If one or more outputs stay at any voltage below 0.8V or over Vs-0.6V for more than 2 sec. (typ), the

warning pin is pulled down.The

P can address the TDA7476 to know the status.The subsonic current pulse is

activated also in this case. The fault is correctly detected if it remains until the memorization (tm in fig.1).In this

phase, faults regarding shorts across the load and open loads cannot be detected.

S.C. to GND x Open Load

xNormal Operation

D01AU1258

OL,ma

sens

--------------------

nop,min

sens

----------------------=

nop,max

sens

------------------------=

gnd,min

sens

----------------------=

Open Load

S.C. to GND

100mA 25mA

xNormal Operation

170mA 17mA

D96AU50

TDA7476

8/19

Permanent diagnostic - AUX1, AUX2 - Short circuit to GND and open load

■ The detection mode of the auxiliary inputs is equal to what is in place during turn-on, but the fault must

be lasting without interruption for more than 2 seconds.The warning pin is pulled down only in case of

short to GND. This is to avoid that this pin remains permanently to 0 level if one or both AUX outputs of

the car radio are unused.

Timing

■ From the byte "ADD1" to the byte "ADD2" the mP must wait a period Twait1(see Software Specification)

that is depending on the timing capacitor CT according to the following table (Twait1> tm, max):

Note: any (positive) spread of the capacitor value must be added. The relation to be used to determine Twait1

from the value of CT according to the following:

Twait1 > tm, max = (130 · CT/10

F)ms

■ After the byte "ADD2" the power amplifier can be switched-on. In some cases, the µP has to wait until

the current pulse is finished (Twait2). This time (ts in fig.1) is given by:

Twait2 > ts, max = (140 · CT/10

F)ms

For bridge or bridge equivalent devices (figg.5,6), Ct = 10

F will be enough.

TURN-ON DIAGNOSTIC - THRESHOLDS

CH1, CH2, CH3, CH4, CH5

■ Output voltage during test. (The power amplifier must be in ST-BY mode).

■ Voltage across the load during test. (The power amplifier must be in ST-BY mode).

■ 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.

CT (µF) tm max (ms)

3.3 45

4.7 65

10 130

22 290

47 620

100 1300

D96AU502B

S.C. to GND x S.C. to Vs

0V 1.2V V

-1.2 V

xNormal Operation

0.8V V

-0.6V

S.C. across Load x Open Load

0V 22mV 220mV V

xNormal Operation

5mV

550mV

D97AU631A

9/19

TDA7476

The following table shows the result pointed out by TDA7476 when multiple misconnections are present:

(*) CH means CH+ or CH-

AUX1 - AUX2

■ Voltage across the sensing resistors

■ 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

AUX1 - AUX2

■ The voltage across the resistors Rsens1 or Rsens2 is sensed. The circuit will recognize as a fault

condition any situation where the following voltages last more than 2sec (typ) in the region "S.C.to GND"

or "open load".

ACTUAL FAULTS POINTED OUT FAULT

S.C. CH+ to GND + OPEN LOAD S.C. to GND

S.C. CH(*) to GND + S.C. ACROSS LOAD S.C. to GND

S.C. CH- to GND + OPEN LOAD OPEN LOAD

S.C. CH(*) to V

+ OPEN LOAD S.C. to V

S.C. CH(*) to V

+ S.C. ACROSS LOAD S.C. to V

S.C. CH+ to V

+ S.C. CH- to GND S.C. to V

S.C. CH- to V

+ S.C. CH+ to GND S.C. to GND + S.C. to V

S.C. to GND x Open Load

0.5V 125mV 0V

xNormal Operation

0.85V

85mV

D97AU572A

S.C. to GND x S.C. to Vs

0V 1.2V V

-1.2 V

xNormal Operation

0.8V

-0.6V

D97AU573B

S.C. to GND x Open Load

0.5V 125mV 0V

xNormal Operation

0.85V

85mV

D97AU574A

P1-P3 P4-P6 P7-P9 P10-P12 P13-P15 P16-P18 P19-P19

E-TDA7476013TR

Mfr. #:

Buy E-TDA7476013TR

Manufacturer:

STMicroelectronics

Description:

Audio DSPs CAR RADIO DIAG PROCESSOR

Lifecycle:

New from this manufacturer.

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E-TDA7476013TR

E-TDA7476013TR

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