E-TDA7476013TR Datasheet E-TDA7476, TDA7476, TDA7476013TR | P13-P15

13/19

TDA7476

READ BYTE 1

READ BYTE 2

READ BYTE 3

Repetitive turn-on diagnostic

During the turn-on diagnostic, the TDA7476 can reveal false "short circuit across load" and/or false "open load"

due to noise sources such as door slams.

This problem can be solved doing more than one turn-on diagnostic routine. If the

P asks for N times the state

of the audio system, it has to consider a fault as really present only if it is detected in all the N turn-on diagnos-

tic.As above explained, the first time the TDA7476 receivers the byte ADD1, it does the turn-on diagnostic; then

each time it is addessed with ADD1, it does the permanent diagnostic. This is not true if, when the

P sends for

the first time the byte ADD2, it does not send to the TDA7476 the acknowledge after it has received the byte

BYTE3. In this case, the TDA7476 does not switch from turn-on to permanent diagnostic mode so if it receives

again the byte ADD1 it works as it was the first time that it does the turn-on diagnostic. In order to do repetitive

turn-on diagnostic, the mP has to be programmed as following:

■ Step 1: the µP sends ADD1

■ Step 2: the µP waits Twait1 seconds

■ Step 3: the µP sends ADD2, receives BYTE1, BYTE2, BYTE3, does not send the acknowlegde after

BYTE3

MSB LSB

STAT US

D7 D6 D5 D4 D3 D2 D1 D0

0 0 X X 1 1 X 0 CH1 short circuit to Vs

0 0 X X 1 1 0 X CH1 short circuit to GND

00XX1111

0 0 X 0 1 1 X X CH2 short circuit to Vs

0 0 0 X 1 1 X X CH2 short circuit to GND

001111XX

1 1 X X 1 1 X 0 CH3 short circuit to Vs

1 1 X X 1 1 0 X CH3 short circuit to GND

11XX1111

1 1 X 0 1 1 X X CH4 short circuit to Vs

1 1 0 X 1 1 X X CH4 short circuit to GND

111111XX

1 1 X X X X 1 0 AUX1 short circuit to GND

1 1 X X X X 0 1 AUX1 open load

1 1 X X 1 0 X X AUX2 short circuit to GND

1 1 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

1111XXXX

START ADD1 ACK

ACK

TDA7476

14/19

■ Step 4: repeat Step1, Step2, Step3 while the second, third, fourth, ...turn-on diagnostic has to be done.

During the last turn-on diagnostic the µP sends ADD2, receives BYTE1

, BYTE2, BYTE3, and sends

the acknowlegde after BYTE3

In this way only after that the TDA7476 has done for N times the turn-on diagnostic, it switches from turn-on to

permanent diagnostic mode.From now the TDA7476 always does the permanent diagnostic.To save time when

the audio system is switched on, it is possible to do the repetitive turn-on diagnostic when the car-radio is turned

off. In this case the steps to follow to do the repetitive turn-on diagnostic are the following:

1- to switch off the TDA7476 connecting STBY pin to ground;

2- to wait T

seconds (time necessary for the discharge of the capacitor). If C

= 10

F then T

= 20ms typ;

3- to switch on the TDA7476

4- to do the repetitive turn-on diagnostic as above described;

5- to turn off the TDA7476.

WARNING PIN

■ This is an open drain output pin that is activated when a fault condition is present for more than 2 sec

(TYP). The fault conditions related to the warning pin are as follows:

- AUX1, AUX2

Short to GND

- CH1, CH2, CH3, CH4, CH5:

Short Circuit to GND

Short Circuit to Vs

■ The purpose of this pin is to alert the µP and start with the permanent diagnostic routine only if faults

are present, thus avoiding CPU's waste of time.

START ADD2 ACK BYTE1 ACK BYTE2 ACK BYTE3 STOP

START ADD2 ACK

BYTE1 ACK BYTE2 ACK BYTE3 ACK STOP

15/19

TDA7476

APPLICATION NOTES

■ When single-ended devices are used and the application circuit is as shown in fig. 7,8, it is necessary

to use:

a greater timing capacitor so that the time tm is high and the outputs of the amplifiers are able to rise over 1V

;

- a resistor R

1.5 times higher than that used for the bridge amplifiers.

In this case, the loudspeaker resistance ranges in which short circuit, normal operation and open load

are detected will be as follows:

For example, here below are two cases, with R

= 4.7kOhm and R

= 2.7kOhm.

The exact values of the above mentioned resistive ranges may vary a little, depending on the power amplifier

used

In Permanent mode for single-ended devices as in fig. 7, 8 a short citcuit to ground is detected both when a

short to ground is really present and when the load is missing.

On single-ended devices as in figure 6, 8 if the loads are present then both in turn-on and in permanent diag-

nostic the fault present on one channel is pointed out for all the loads connected together.For example:

- see fig.8 if CH1+ is shorted to ground, the TDA7476 reveals a short to ground both for CH2 and for CH1.

- see fig.6 if CH1+ is shorted to ground, the TDA7476 detects a short circuit to ground for CH1, CH2, CH3, CH4.

About timing for the TDA7375, connected as in fig.7, Ct = 47

F if Cout = 1000

F, and Ct = 100

F if Cout =

2200

If the circuit is as shown by fig. 8, the suggested values of Ct are as follows: Ct = 22

F if Cout = 1000

Ct = 47

F if Cout = 2200

S.C. across Load x Open Load

2,SE

3,SE

xNormal Operation

1,SE

4,SE

D01AU1257

R1,SE

SC,max

source

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

SC,max

54.45

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

⋅==

R2,SE

SC,min

source

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

nop,min

54.45

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

⋅==

R3,SE

nop,max

source

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

nop,max

54.45

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

⋅==

R4,SE

op,min

source

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

op,min

54.45

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

⋅==

S.C. across Load x Open Load

0Ω 1.9Ω 19Ω infinite

xNormal Operation

0.43Ω 47Ω

D96AU501A

S.C. across Load x Open Load

0Ω 1.1Ω 11Ω infinite

xNormal Operation

0.24Ω 27Ω

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.

Delivery:

DHL FedEx Ups TNT EMS

Payment:

T/T Paypal Visa MoneyGram Western Union

E-TDA7476013TR

E-TDA7476013TR

Products related to this Datasheet