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TDA7476
CAR RADIO DIAGNOSTIC PROCESSOR
s s s s s
s
s
s s s s s s
WIDE OPERATING VOLTAGE RANGE ST-BY FUNCTION (C-MOS) LOW QUIESCENT ST-BY CURRENT CONSUMPTION I2C BUS INTERFACE WITH 2 EXTERNALLY SELECTABLE ADDRESSES UP TO 5 BTL EQUIVALENT INPUTS FOR FAULT DETECTION IN THE AUDIO CHANNELS - short to GND - short to Vs - short across the load (at turn-on) - open load (at turn-on) 2 AUX INPUTS FOR FAULT DETECTION IN THE ANTENNA AND BOOSTERS SUPPLY LINE- short to GND- open load WARNING PIN FUNCTION (interrupt facility) ACTIVATED IN THE FOLLOWING CONDITION: - audio channel shorted to VS - audio channel shorted to GND - aux input shorted to GND NOISE FREE DIAGNOSTICS OPERATION PROTECTORS LOAD DUMP VOLTAGE OPEN GND REVERSED BATTERY ESD
MULTIPOWER BCD TECHNOLOGY
SO-24 ORDERING NUMBER: TDA7476
DESCRIPTION The car radio diagnostic processor is an interface chip in BCD Technology intended for car radio applications. It is able to detect potential faults coming from any misconnection in the car radio or in the harness when installing the set. The device is able to reveal any fault in the loudspeaker lines and in the antenna and booster supply lines, providing a proper output signal (I2C bus compatible) in order to disable the ICs under fault and/or to alert the micro-controller by means of warning messages.
PIN CONNECTION (Top view)
GND SDA SCL ADD W AUX1 OUT AUX1 IN AUX2 IN AUX2 OUT 5V ST-BY VS
1 2 3 4 5 6 7 8 9 10 11 12
D97AU570A
24 23 22 21 20 19 18 17 16 15 14 13
CH5CH5+ CH4+ CH4CH3CH3+ CH2+ CH2CH1CH1+ T-CAP CSR
April 2001
1/19
TDA7476
BLOCK DIAGRAM & APPLICATION CIRCUIT
2 3 4 IC
2
SDA SCL ADD VS C3 10F R3 10K W C2 100nF
24 INTERFACE 23 22 21 20 19 CH3 CH4 CH5
12
5
DELAY CURRENT FORCING & COMPARATORS VOLTAGE REGULATOR & TEST SIGNAL GENERATOR
18 17 16 15 6 RSENS1 7 CH1 OUT AUX1 IN IN RSENS2 AUX2 OUT
D96AU499A
R4 10K ST-BY SW1 5V REF C1 10F 11 10 14 13 CT RCS
CH2
8 R5 51
DIG-GND
1
9
PIN FUNCTION
N 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15/16 17/18 19/20 21/22 23/24 Pin GND SDA SCL ADD W AUX1 OUT AUX1 IN AUX2 IN AUX2 OUT 5V ST-BY VS CSR T-CAP CH1+/CH1CH2-/CH2+ CH3+/CH3CH4-/CH4+ CH5+/CH5Ground Dta line Clock line Address select Warning AUX1 output AUX1 input AUX2 input AUX2 output 5V-Regulator Stand-by Supply Voltage Current setting resistor Timing capacitor Audio output - Channel 1 Audio output - Channel 2 Audio output - Channel 3 Audio output - Channel 4 Audio output - Channel 5 Description
2/19
TDA7476
ABSOLUTE MAXIMUM RATINGS
Symbol Vop Vs Vpeak Ptot Tstg; T`cVSB VSDA VSCL VADD VCH Operating Supply Voltage DC Supply Voltage Peak Supply Voltage t = 50ms Total Power Dissipation Tcase = 25C Storage and Junction Temperature Stand-by Pin Voltage SDA Pin Voltage SCL Pin Voltage ADD Pin Voltage CH+ or CH- Pin Voltage Parameter Value 18 28 40 1.5 -40 to 150 6 6 6 6 min (*) (VS +10, 25) Unit V V V W C V V V V
(*) Minimum value between VS+10V and 25V.
THERMAL DATA
Symbol RTh j-amb Parameter Thermal resistance junction to ambient Max. Value 85 Unit C/W
ELECTRICAL CHARACTERISTICS (Vs = 14.4V; Tamb = 25, unless otherwise specified.)
Symbol VSBIN Parameter Stand-By IN Threshold 3.5 Stand-By Voltage Pin = 1.5V Total quiescent Current with TDA7476 not addressed 5 100 Test Condition Min. Typ. Max. 1.5 Unit V V A mA
VSBOUT Stand-By OUT Threshold ISB Iq Stand-By Current Consumption Total Quiescent Current
AUDIO INPUTS CH1, CH2, CH3, CH4, CH5 - TURN ON DIAGNOSTIC Pgnd Short to GND det. (below this limit, the Audio Output is considerd in Short Circuit to GND) Short to Vs det. (above this limit, the Audio Output is considered in Short Circuit to Vs) Normal operation thresholds. (Within these limits, the Audio Output is considered without faults) Power amplifier in st-by condition 0.8 V
Pvs
Vs-0.6
V
Pnop
1.2
Vs-1.2
V
3/19
TDA7476
ELECTRICAL CHARACTERISTICS (continued) (Vs = 14.4V; Tamb = 25, unless otherwise specified.)
Symbol Lsc Parameter Shorted Load det. (voltage across the Audio Outputs). Below this limit the load is considered shorted. Open Load det. (voltage across the Audio Outputs). Above this limit the load is considered open. Normal load det. (Voltage across the Audio Output). Within these limits the load resistance is considered normal. Test Condition Power amplifier in st-by condition Min. Typ. Max. 5 Unit mV
Lop
550
mV
Lnop
22
220
mV
AUX INPUTS AUX1, AUX2 - TURN ON DIAGNOSTIC Agnd Short to GND det. (voltage across the sensing resistor). Above this limit the AUX pin is considered in Short Circuit to GND. Open load det. (voltage across the sensing resistor). Below this limit the Aux pin is considered in Open Load condition. Normal Operation det. (Voltage across the sensing resistor). Within these limits the load resistance connected to the Aux pin is considered correct. 0.125 High side driver ON 0.85 V
Aol
0.085
V
Anop
0.5
V
AUDIO INPUTS - PERMANENT DIAGNOSTIC Pgnd Short to GND det. (below this limit, the Audio Output is considered in Short Circuit to Vs) This condition must be true for a time higher than Tdel Short to Vs det. (above this limit the Audio Output is considered in Short Circuit to Vs) This condition must be true for a time higher than Tdel Normal operation thresholds. (Within these limits, the Audio Output is considered without faults) Power amplifier ON 0.8 V
Pvs
Vs-0.6
V
Pnop
1.2
Vs-1.2
V
AUX INPUTS - PERMANENT DIAGNOSTIC Agnd Short to GND det. (above this limit, the Audio Output is considered in Short Circuit to Vs) This condition must be true for a time higher than Tdel High side driver ON 0.85 V
4/19
TDA7476
ELECTRICAL CHARACTERISTICS (continued) (Vs = 14.4V; Tamb = 25, unless otherwise specified.)
Symbol Aol Parameter Open load det. (voltage across the sensing resistor. Below this limit the Aux pin is considered in Open Load condition)This condition must be true for a time higher than Tdel Normal Operation det. (Voltage across the sensing resistor. Within these limits the load resistance connected to the Aux pin is considered correct) Test Condition High side driver ON Min. Typ. Max. 0.085 Unit V
Anop
0.125
0.5
V
PERMANENT DIAGNOSTIC - ACQUISITION TIME DELAY Tdel Acquisition time delay - The fault is considered true if the fault condition are present for more than Tdel without interruption 2 s
PERMANENT DIAGNOSTIC - WARNING PIN Vsat Saturation voltage on pin 5 Sink Current at Pin 5 = 1mA 1 V
ADDRESS SELECT VADD Voltage on pin 4 Address 0100010X Address 0100011X I2C BUS INTERFACE fSCL VIL VIH VSAT Clock Frequency Input Low Voltage Input High Voltage Sat Voltage at pin 2 Sink Current at Pin 2 = 5mA 3 1.5 400 1.5 KHz V V V 3 1.5 5 V V
WORKING PRINCIPLES Turn-on diagnostic - CH1, CH2, CH3, CH4, CH5 Shorted load/open load detection s To detect a short across the load or an open load, a subsonic current pulse is generated. The information related to the status of the outputs is measured and memorized at the top of the current pulse (tm in fig.1). The current is sourced by the positive pins (CH1+,...CH5+) and it is sunk by the corresponding negative pins (CH1-,...CH5-).
Figure 1.
I(mA)
ISOURCE
ISINK
tm
D97AU571
ts
t(ms)
5/19
TDA7476
s
Isink and Isource are depending on the external resistor Rcs. The minimum allowed value for Rcs is 1.65KOhm. The relationship among Isink, Isource and Rcs is the following: Isink = (3.3/Rcs) * 11 Isource = 1.5 * Isink On bridge (or bridge equivalent) devices if there is no short circuit to GND or to Vs, Isource goes into saturation mode (for Vout > 3V), and in the load flows Isink. As the turn-on diagnostic thresholds are fixed, it is possible to calculate the ranges of loudspeaker resistance in which short circuit (S.C.), normal operation and open load are detected as following:
S.C. across Load x Normal Load x Open Load
s
0
R1
R2
R3
R4
infinite
D01AU1256
L sc ,max Ls c,max R1 = ------------------ = ------------------ R cs 36.3 I sin k L nop ,min L no p,min R2 = --------------------- = --------------------- R c s 36.3 I sin k L no p,max Lno p,max R3 = ---------------------- = ---------------------- R c s 36.3 I sin k L op, min L op ,max R3 = ------------------- = ------------------- R cs 36.3 I sin k where Lsc, Lnop, Lop as specified in the ELCTRICAL CHARACTERISTICS. For example, here below are two cases, with Rcs = 3.3KOhm and Rcs = 1.8KOhm..
S.C. across Load x Normal Operation x Open Load
0
0.45
2
20
50
infinite
S.C. across Load
x
Normal Operation
x
Open Load
0
0.24
1.1
11
27
D96AU500A
infinite
The exact values of the above mentioned resistive ranges may vary a little, depending on the power amplifier used. Turn-on diagnostic - CH1, CH2, CH3, CH4, CH5 - Short to GND and Vs. To detect if there is short circuit to GND or Vs, the subsonic current pulse is exploited. The information related to the status of the outputs are measured and memorized at the top of the current pulse (tm in fig.1). If no faults are present, the pins connected to the audio outputs (CH1,..CH5) will reach about 3V.If one or more outputs are shorted to GND, these voltages become lower than 3V.If one or more outputs are shorted to Vs, the output voltage increases over 3V.The fault status can be know by sensing the output voltages. The reason way voltage threshold has been preferred instead of a current threshold to declare short circuit resistor ranges is two fold:
6/19
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 voltage 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 admissible. The detection ranges can be set by adjusting the sensing resistors Rsens1 or Rsens2 as following:
S.C. to GND x Normal Operation x Open Load
I1
I2
I3
I4
D01AU1258
A O L,max I 4 = --------------------R s en s A nop ,min I 3 = --------------------R s ens A n op,max I 2 = ----------------------R s en s A gn d,min I 1 = --------------------R sen s Where AOL, Anop, Agnd are as specified in the ELECTRICAL CHARACTERISTICS. For example, if Rsens = 5 Ohm, the following detection table will be operative :
S.C. to GND x Normal Operation x Open Load
170mA 100mA
25mA 17mA
D96AU503
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.
7/19
TDA7476
Permanent diagnostic - AUX1, AUX2 - Short circuit to GND and open load s 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 s 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):
CT (F) 3.3 4.7 10 22 47 100 tm max (ms) 45 65 130 290 620 1300
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/10F)ms
s
After the byte "ADD2" the power amplifier can be switched-on. In some cases, the P has to wait until the current pulse is finished (Twait2). This time (ts in fig.1) is given by: Twait2 > ts, max = (140 * CT/10F)ms
For bridge or bridge equivalent devices (figg.5,6), Ct = 10F will be enough. TURN-ON DIAGNOSTIC - THRESHOLDS CH1, CH2, CH3, CH4, CH5 s 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
0V
s
0.8V
1.2V
VS-1.2
VS-0.6V
D96AU502B
VS
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
s
5mV
22mV
220mV
550mV
D97AU631A
VS
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.
8/19
TDA7476
The following table shows the result pointed out by TDA7476 when multiple misconnections are present:
ACTUAL FAULTS S.C. CH+ to GND + OPEN LOAD S.C. CH(*) to GND + S.C. ACROSS LOAD S.C. CH- to GND + OPEN LOAD S.C. CH(*) to VS + OPEN LOAD S.C. CH(*) to VS + S.C. ACROSS LOAD S.C. CH+ to VS + S.C. CH- to GND S.C. CH- to VS + S.C. CH+ to GND
(*) CH means CH+ or CH-
POINTED OUT FAULT S.C. to GND S.C. to GND OPEN LOAD S.C. to VS S.C. to VS S.C. to VS S.C. to GND + S.C. to VS
AUX1 - AUX2 s Voltage across the sensing resistors
S.C. to GND
x
Normal Operation
x
Open Load
VS
s s
0.85V
0.5V
125mV
85mV
D97AU572A
0V
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 s The circuit will recognize as a fault condition any situation where the following short circuit voltages last more than 2 sec (typ).
s
Output voltage
S.C. to GND
x
Normal Operation
x
S.C. to Vs
0V
0.8V
1.2V
VS-1.2
VS-0.6V
D97AU573B
VS
AUX1 - AUX2 s 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".
S.C. to GND
x
Normal Operation
x
Open Load
VS
0.85V
0.5V
125mV
85mV
D97AU574A
0V
9/19
TDA7476
s s
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 resistor 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).
I2C BUS INTERFACE Data transmission from microprocessor to the TDA7476 and viceversa takes place through the 2 wires I2C BUS interface, consisting of the two lines SDA and SCL (pull-up resistors to positive supply voltage must be connected). Data Validity As shown by fig. 2, the data on the SDA line must be stable during the high period of the clock. The HIGH and LOW state of the data line can only change when the clock signal on the SCL line is LOW. Start and Stop Conditions As shown by fig. 3 a start condition is a HIGH to LOW transition of the SDA line while SCL is HIGH. The stop condition is a LOW to HIGH transition of the SDA line while SCL is HIGH. Byte Format Every byte transferred to the SDA line must contain 8 bits. Each byte must be followed by an acknowledge bit. The MSB is transferred first. Acknowledge The transmitter* puts a resistive HIGH level on the SDA line during the acknowledge clock pulse (see fig.4). The receiver** the acknowledges has to pull-down (LOW) the SDA line during the acknowledge clock pulse, so that the SDAline is stable LOW during this clock pulse. * Transmitter = master (P) when it writes an address to the TDA7476 = slave (TDA7476) when the P reads a data byte from TDA7476 ** Receiver = slave (TDA7476) when the P writes an address to the TDA7476 = master (P) when it reads a data byte from TDA7476 Figure 2. Data Validity on the I2CBUS
SDA
SCL DATA LINE STABLE, DATA VALID CHANGE DATA ALLOWED
D99AU1031
10/19
TDA7476
Figure 3. Timing Diagram on the I2CBUS
SCL I2CBUS SDA
D99AU1032
START
STOP
Figure 4. Acknowledge on the I2CBUS
SCL 1 2 3 7 8 9
SDA MSB START
D99AU1033
ACKNOWLEDGMENT FROM RECEIVER
SOFTWARE SPECIFICATIONS The TDA7476 is activated by turning-on the ST-BY pin (CMOS compatible). In this condition it waits for the I2CBus addressing byte ADD1 (WRITE to TDA7476)
ADD1 S 010001A 0 ACK STOP
This sequence (where the bit 0 of ADD1 is at 0 level) enables the acquisition routine and starts the single pulse (containing infrasonic harmonics) for the test. During this period the data regarding all the outputs are memorized.After a period Twait1 that depends on the value of the timing capacitor (see Timing) the P redirects the TDA7476 by the byte ADD2.
ADD1 S 010001A 0 ACK BYTE1 ACK BYTE2 ACK BYTE3 ACK STOP
The byte ADD2 contains the bit 0 at 1 level. This enables the reading mode, TDA7476's. The 3 bytes with the diagnostic information BYTE1, BYTE2, BYTE3 (READ FROM TDA7476) are now transmitted to the P. The address of TDA7476 is selected using pin ADD (pin 4) . If ADD is connected to ground, then A = 0 and the TDA7476 address is 0100010X. If ADD is connected to 5V, than A = 1 and the TDA7476 address is 0100011X s The TDA7476 provides two types of diagnostic information: A) TURN-ON DIAGNOSTIC - The first time that the TDA7476 is addressed by I2CBus, the more complete set of diagnostic information is activated: - CH1, CH2, CH3, CH4, CH5 Short Circuit to GND Short Circuit to Vs Open Load (*) Short Circuit across the load (*) (*) Detected if the power amplifiers are in ST-BY condition. - AUX1, AUX2 Short Circuit to GND (*) Open Load (*) (*) Detected if the high side drivers attached to the Aux outputs are ON. Here following the turn-on diagnostic output bytes
11/19
TDA7476
READ BYTE 1
MSB D7 X X X X 1 1 1 0 D6 X X X X 1 1 0 1 D5 X X X X X 0 1 1 D4 X X X X 0 X 1 1 D3 1 1 1 0 X X X X D2 1 1 0 1 X X X X D1 X 0 1 1 X X X X LSB D0 0 X 1 1 X X X X STATUS CH1 short circuit to Vs CH1 short circuit to GND CH1 open load CH1 short circuit across the load CH2 short circuit to Vs CH2 short circuit to GND CH2 open load CH2 short circuit across the load
READ BYTE 2
X X X X 1 1 1 0 X X X X 1 1 0 1 X X X X X 0 1 1 X X X X 0 X 1 1 1 1 1 0 X X X X 1 1 0 1 X X X X X 0 1 1 X X X X 0 X 1 1 X X X X CH3 short circuit to Vs CH3 short circuit to GND CH3 open load CH3 short circuit across the load CH4 short circuit to Vs CH4 short circuit to GND CH4 open load CH4 short circuit across the load
READ BYTE 3
X X X X 1 1 1 0 X X X X 1 1 0 1 X X X X X 0 1 1 X X X X 0 X 1 1 X X 1 0 X X X X X X 0 1 X X X X 1 0 X X X X X X 0 1 X X X X X X AUX1 short circuit to GND AUX1 open load AUX2 short circuit to GND AUX2 open load CH5 short circuit to Vs CH5 short circuit to GND CH5 open load CH5 short circuit across the load
When the P reads correctly all the 3 bytes containing the mentioned information and gives the last acknowledge, 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 before. 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 P 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
TDA7476
READ BYTE 1
MSB D7 0 0 0 0 0 0 0 0 D6 0 0 0 0 0 0 0 0 D5 X X X X X 0 1 1 D4 X X X X 0 X 1 1 D3 1 1 1 1 1 1 1 1 D2 1 1 1 1 1 1 1 1 D1 X 0 1 1 X X X X LSB D0 0 X 1 1 X X X X CH2 short circuit to Vs CH2 short circuit to GND STATUS CH1 short circuit to Vs CH1 short circuit to GND
READ BYTE 2
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 X X X X X 0 1 1 X X X X 0 X 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 X 0 1 1 X X X X 0 X 1 1 X X X X CH4 short circuit to Vs CH4 short circuit to GND CH3 short circuit to Vs CH3 short circuit to GND
READ BYTE 3
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 X X X X X 0 1 1 X X X X 0 X 1 1 X X 1 0 X X X X X X 0 1 X X X X 1 0 X X X X X X 0 1 X X X X X X AUX1 short circuit to GND AUX1 open load AUX2 short circuit to GND AUX2 open load CH5 short circuit to Vs CH5 short circuit to GND
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 diagnostic.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: s Step 1: the P sends ADD1
START
s s
ADD1
ACK
ACK
Step 2: the P waits Twait1 seconds Step 3: the P sends ADD2, receives BYTE1, BYTE2, BYTE3, does not send the acknowlegde after BYTE3
13/19
TDA7476
START
s
ADD2
ACK
BYTE1
ACK
BYTE2
ACK
BYTE3
STOP
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 P sends ADD2, receives BYTE1, BYTE2, BYTE3, and sends the acknowlegde after BYTE3
START ADD2 ACK BYTE1 ACK BYTE2 ACK BYTE3 ACK STOP
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 T5V seconds (time necessary for the discharge of the capacitor). If C5V = 10F then T5V = 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 s 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
s
The purpose of this pin is to alert the P and start with the permanent diagnostic routine only if faults are present, thus avoiding CPU's waste of time.
14/19
TDA7476
APPLICATION NOTES s 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 RCS 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:
S.C. across Load
x
Normal Operation
x
Open Load
R1,SE
R2,SE
R3,SE
R4,SE
D01AU1257
L SC,max L S C,max R1 ,SE = -------------------- = -------------------- R CS 54.45 I s ourc e L no p,min LS C,min R2 ,SE = ------------------- = --------------------- R CS 54.45 I s ou rce L n op,max L n op ,max R3 ,SE = ---------------------- = ---------------------- R CS 54.45 I s ourc e L op,min L o p,min R4 ,SE = ------------------ = ------------------ R CS 54.45 I so urce For example, here below are two cases, with RCS = 4.7kOhm and RCS = 2.7kOhm.
S.C. across Load
x
Normal Operation
x
Open Load
0
0.43
1.9
19
47
infinite
S.C. across Load
x
Normal Operation
x
Open Load
0
0.24
1.1
11
27
D96AU501A
infinite
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 diagnostic 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 = 47F if Cout = 1000F, and Ct = 100F if Cout = 2200F. If the circuit is as shown by fig. 8, the suggested values of Ct are as follows: Ct = 22F if Cout = 1000F, Ct = 47F if Cout = 2200F.
15/19
TDA7476
s
To use the TDA7476 with a car-radio system which has less than five audio channel and less than two auxiliary loads, it is necessary to take some cares: - each pin CH not used has to be fixed to 5V - each pin AUX1IN, AUX1OUT, AUXIN2, AUX2OUT not used has to be fixed to a voltage equal or greater than 5V The 5V voltage reference available on the chip (pin 10) is very useful to fix both CH and AUX pins to 5V.
APPLICATION EXAMPLES WITH ST AUDIO POWER ICs Figure 5. Quad Bridge Amplifiers
TDA7384, TDA7385, TDA7386, TDA7454
+
-
-
+
+
-
R CH1+ CH2+ CH3+ CH4+ CH5+
+
CH5-
CH4-
CH3-
CH2-
CH1-
TDA7476
D97AU578A
Figure 6. TDA7451
TDA7451
+
-
-
+
+
-
R CH1+ CH2+ CH3+ CH4+ CH5+
+
CH5-
CH4-
CH3-
CH2-
CH1-
TDA7476
D97AU577A
16/19
TDA7476
Figure 7. TDA7375 in S.E. mode with 4 output capacitors
TDA7375
+ -
COUT1
COUT2 + COUT3 + COUT4 R CH1+ CH2+ CH3+ CH4+ CH5+ CH5CH4CH3CH2CH1+
TDA7476
D97AU575A
Figure 8. TDA7375 in S.E. mode with 2 output capacitors
TDA7375
+ -
COUT1
-
+
+
COUT2
R CH1+ CH2+ CH3+ CH4+ CH5+
+
CH5-
CH4-
CH3-
CH2-
CH1-
TDA7476
D97AU576A
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TDA7476
DIM. MIN. A A1 A2 B C D E e H h k L 0.40 10.0 0.25 0.33 0.23 15.20 7.40 2.35 0.10
mm TYP. MAX. 2.65 0.30 2.55 0.51 0.32 15.60 7.60 1.27 10.65 0.75 0.394 0.010 0.013 0.009 0.598 0.291 MIN. 0.093 0.004
inch TYP. MAX. 0.104 0.012 0.100 0.0200 0.013 0.614 0.299 0,050 0.419 0.030
OUTLINE AND MECHANICAL DATA
0 (min.), 8 (max.)
SO24
1.27 0.016 0.050
h x 45
A2
A1
A
0.10mm .004 Seating Plane
B
e
K L H
A1
C
D
24
13
1
12
SO24
18/19
E
TDA7476
Information furnished is believed to be accurate and reliable. However, STMicroelectronics assumes no responsibility for the consequences of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics. The ST logo is a registered trademark of STMicroelectronics 2001 STMicroelectronics - All Rights Reserved STMicroelectronics GROUP OF COMPANIES Australia - Brazil - China - Finland - France - Germany - Hong Kong - India - Italy - Japan - Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - U.S.A. http://www.st.com
(R)
19/19

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