TDA7476 CAR RADIO DIAGNOSTIC PROCESSOR PRELIMINARY DATA 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 PROTETCTORS LOAD DUMP VOLTAGE MULTIPOWER BCD TECHNOLOGY SO24 OPEN GND REVERSED BATTERY ESD 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 µcontroller by means of warning messages. PIN CONNECTION (Top view) GND 1 24 CH5- SDA 2 23 CH5+ SCL 3 22 CH4+ ADD 4 21 CH4- W 5 20 CH3- AUX1 OUT 6 19 CH3+ AUX1 IN 7 18 CH2+ AUX2 IN 8 17 CH2- AUX2 OUT 9 16 CH1- 5V 10 15 CH1+ ST-BY 11 14 T-CAP VS 12 13 CURR. SET. RES. D97AU570 December 1999 1/15 This is preliminary information on a new product now in development or undergoing evaluation. Details are subject to change without notice. TDA7476 BLOCK DIAGRAM 2 SDA 24 3 SCL ADD 23 I2C 4 CH5 INTERFACE 22 21 CH4 12 VS C3 10µF R3 10KΩ 20 C2 100nF 19 5 W CH3 18 DELAY 17 R4 10KΩ CURRENT FORCING & COMPARATORS 11 ST-BY SW1 10 14 5V REF 13 CH2 16 15 CH1 6 VOLTAGE REGULATOR & TEST SIGNAL GENERATOR OUT RSENS1 AUX1 7 C1 10∝F CT IN RCS 8 IN RSENS2 R5 51Ω 1 DIG-GND AUX2 9 OUT D96AU499A ABSOLUTE MAXIMUM RATINGS Symbol Value Unit Vop Operating Supply Voltage 18 V Vs DC Supply Voltage 28 V Peak Supply Voltage t = 50ms 40 V Total Power Dissipation Tcase = 25°C 1.5 W -40 to 150 °C Vpeak Ptot Tstg; Tj Parameter Storage and Junction Temperature VSB Stand-by Pin Voltage 6 V VSDA SDA Pin Voltage 6 V VSCL SCL Pin Voltage 6 V V ADD ADD Pin Voltage 6 V THERMAL DATA Symbol RTh j-amb Parameter Thermal resistance junction to ambient Max. Value Unit 85 °C/W ELECTRICAL CHARACTERISTICS (Vs = 14.4V; Tamb = 25°; RL = 4Ω, unless otherwise specified.) Symbol VSBIN VSBOUT 2/15 Parameter Test Condition Min. Typ. Stand-By IN Threshold Stand-By OUT Threshold Max. Unit 1.5 V 100 µA 3.5 ISB Stand-By Current Consumption Stand-By Voltage Pin = 1.5V Iq Total Quiescent Current Total quiescent Current with TDA7476 not addressed V 5 mA TDA7476 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Test Condition AUDIO INPUTS CH1, CH2, CH3, CH4, CH5 - TURN ON DIAGNOSTIC Power amplifier in st-by Pgnd Short to GND det. (below this condition limit, the Audio Output is considerd in Short Circuit to GND) Pvs Short to Vs det. (above this limit, the Audio Output is considered in Short Circuit to Vs) Pnop Normal operation thresholds. (Within these limits, the Audio Output is considered without faults) Lsc Shorted Load det. (voltage across the Audio Outputs). Below this limit the load is considered shorted. Lop Open Load det. (voltage across the Audio Outputs). Above this limit the load is considered open. Lnop Normal load det. (Voltage across the Audio Output). Within these limits the load resistance is considered normal. AUX INPUTS AUX1, AUX2 - TURN ON DIAGNOSTIC High side driver ON Agnd Short to GND det. (voltage across the sensing resistor). Above this limit the AUX pin is considered in Short Circuit to GND. Aol Open load det. (voltage across the sensing resistor). Below this limit the Aux pin is considered in Open Load condition. Anop Normal Operation det. (Voltage across the sensing resistor). Within these limits the load resistance connected to the Aux pin is considered correct. AUDIO INPUTS - PERMANENT DIAGNOSTIC Power amplifier ON 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 Pvs 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 Pnop Normal operation thresholds. (Within these limits, the Audio Output is considered without faults) Min. Typ. Max. Unit 0.8 V Vs-0.7 1.2 V Vs-1.3 V 5 mV 550 22 mV 220 0.75 0.125 V 0.085 V 0.5 V 0.8 V Vs-0.7 1.2 mV V Vs-1.3 V 3/15 TDA7476 ELECTRICAL CHARACTERISTICS (continued) Symbol Parameter Test Condition AUX INPUTS - PERMANENT DIAGNOSTIC High side driver ON 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 Aol 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 Anop Normal Operation det. (Voltage across the sensing resistor. Within these limits the load resistance connected to the Aux pin is considered correct) 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 PERMANENT DIAGNOSTIC - WARNING PIN Vsat Saturation voltage on pin 5 Sink Current at Pin 5 = 1mA ADDRESS SELECT VADD Voltage on pin 4 Address 0100010X Address 0100011X I2C BUS INTERFACE fSCL Clock Frequency V IL Input Low Voltage VIH InputHigh Voltage VSAT Sat Voltage at pin 2 Sink Current at Pin 2 = 5mA Min. Typ. Max. 0.75 V 0.125 0.085 V 0.5 V 2 3 Unit s 1 V 1.5 5 V V 400 1.5 KHz V V V 3 1.5 WORKING PRINCIPLES Turn-on diagnostic - CH1, CH2, CH3, CH4, CH5 - Shorted load/open load detection 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 are 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) I SOURCE ISINK tm D97AU571 ts t (ms) 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) x 11 Isource = 1.5 x Isink 4/15 TDA7476 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, normal operation and open load are detected. For example, here below are two cases, with Rcs = 3.3KOhm and Rcs = 1.8KOhm. (RL = Vthr*/Isink). S.C. across Load Rcs = 3.3kΩ 0Ω x Normal Operation 0.5Ω 2Ω S.C. across Load x x 20Ω Normal Operation Open Load 50Ω x infinite Open Load Rcs = 1.8kΩ 0Ω 0.27Ω 1.1Ω 11Ω 27Ω infinite D96AU500 The exact values of the above mentioned resistive ranges may vary a little, depending on the power amplifier used. These values for the various possible ST power amplifiers will be communicated later. When single-ended devices are used and the application circuit is as shown in fig. 5,6, it is necessary to use: - a greater timing capacitor so that the time t m 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 with Rcs = 4.7KOhm and Rcs = 2.7KOhm (RL = Vthr/Isource) Rcs = 4.7kΩ S.C. across Load 0Ω Rcs = 2.7kΩ 0.47Ω S.C. across Load 0Ω x 0.27Ω Normal Operation 1.9Ω x 19Ω Normal Operation 1.1Ω x 11Ω Open Load 47Ω x infinite Open Load 27Ω infinite D96AU501 The exact values of the above mentioned resistive ranges may vary a little, depending on the power amplifier used. These values will be communicated later. 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: 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. (*) Vthr is the threshold described in the table on page 3/14 - 4/14 (for example Pgnd-min, Pvs - max, Pnop - min, Pnop - max etc..) 5/15 TDA7476 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. For example, if Rsens = 5Ohm, the following detection table will be operative (I = Vthr/Rsens): S.C. to GND x Normal Operation 150mA 100mA x Open Load 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-0.8V for more than 2 sec. (typ), the warning pin is pulled down. The µP 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. For single-ended devices as in fig. 5, 6 a short citcuit to ground is detected both when a short to ground is really present and when the load is missing. 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 µP 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 (µF) tm max (ms) 3.3 45 4.7 65 10 130 22 290 47 620 100 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 x CT/10µF)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 x CT/10µF)ms For bridge or bridge equivalent devices (figg.7,8), Cs = 10µF will be enough. For the TDA7375, connected as in fig.5, Cs = 47µF if Cout = 1000µF, and Cs = 100µF if Cout = 2200µF. If the circuit is as shown by fig. 6, the suggested values of Cs are as follows: Cs = 22µF if Cout = 1000µF, Cs = 47µF if Cout = 2200µF. 6/15 TDA7476 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 0V x Normal Operation 0.8V 1.2V x VS-1.3 S.C. to Vs VS-0.7V D96AU502A VS Voltage across the load during test. (The power amplifier must be in ST-BY mode). S.C. across Load 0V x 5mV Normal Operation 22mV x 220mV Open Load 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. AUX1 - AUX2 Voltage across the sensing resistors. S.C. to GND VS x 0.75V Normal Operation 0.5V Open Load x 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 0V x 0.8V Normal Operation 1.2V x VS-1.3 S.C. to Vs VS-0.7V D97AU573A VS 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”. S.C. to GND VS 0.75V x Normal Operation 0.5V 125mV x Open Load 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 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). 7/15 TDA7476 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. Figure 2: Data Validity on the I2CBUS Figure 3: Timing Diagram on the I2CBUS Figure 4: Acknowledge on the I2CBUS 8/15 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 pulldown (LOW) the SDA line during the acknowledge clock pulse, so that the SDAline is stable LOW during this clock pulse. * Transmitter = master (µP) when it writes an address to the TDA7476 = slave (TDA7476) when the µP reads a data byte from TDA7476 ** Receiver = slave (TDA7476) when the µP writes an address to the TDA7476 = master (µP) when it reads a data byte from TDA7476 TDA7476 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 P 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 µP redirects the TDA7476 by the byte ADD2. ADD2 S 010001A 1 ACK BYTE 1 ACK BYTE 2 ACK BYTE 3 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 µP. 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 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 9/15 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 CH1 short CH1 short CH1 open CH1 short CH2 short CH2 short CH2 open CH2 short circuit to Vs circuit to GND load circuit across the load circuit to Vs circuit to GND load circuit across the load 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 CH3 short CH3 open CH3 short CH4 short CH4 short CH4 open CH4 short circuit to Vs circuit to GND load circuit across the load circuit to Vs circuit to GND load circuit across the load 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 STATUS READ BYTE 2 X X X X 1 1 1 0 X X X X 1 1 0 1 READ BYTE 3 X X X X 1 1 1 0 X X X X 1 1 0 1 When the µP 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 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. 10/15 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 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 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 STATUS CH1 short circuit to Vs CH1 short circuit to GND CH2 short circuit to Vs CH2 short circuit to GND READ BYTE 2 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 CH3 short circuit to Vs CH3 short circuit to GND CH4 short circuit to Vs CH4 short circuit to GND READ BYTE 3 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 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 µP 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 timeit is addessed with ADD1, it does the permanent diagnostic. This is not true if, when the µP sends for the forst 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 µP has to be programmed as following: Step 1: the µP sends ADD1 START ADD1 ACK STOP Step 2: the µP waits Twait1 seconds Step 3: the µP sends ADD2, receives BYTE1, BYTE2, BYTE3, does not send the acknowlegde after BYTE3 START 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 µP sends ADD2, receives BYTE1, BYTE2, BYTE3, and sends the acknowlegde after BYTE3 START ADD2 ACK BYTE1 ACK BYTE2 ACK BYTE3 ACK STOP 11/15 TDA7476 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 necessaryfor the discharge of the capacitor). If C5V = 10µF 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 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. APPLICATION NOTES On single-ended devices as in figure 6, 7 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.6 if CH1+ is shorted to ground, the TDA7476 reveals a short to groundboth for CH2 and for CH1. - seefig.7 if CH1+ is shortedto ground, theTDA7476detectsa short circuit to groundfor CH1, CH2, CH3, CH4. 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: - If the loads are 4Ω speakers (Rcs= 3.3 KΩ), R ≅ 10Ω has to be connected between CH+ and CH- of each channel (see figg. 5,6,7,8 concerning CH5). R ≅ 5Ω has to be used if loads are 2Ω speakers (Rcs= 1.8 KΩ). - If AUX1/AUX2 are unused, Rsens1/Rsens2 will not be needed. The AUX-IN pin(s) can be tied to the 5 internal regulator (pin 10) while setting the AUX-OUT pin(s) about 250mV lower than AUX-IN’s (admissible range = 125mV to 500mV). This can easily be obtained by means of a voltage divider. If both the AUX channelsare unused, pins 7-8 (AUX-INs) and pins 6-9 (AUX-OUTs) can be respectively connectedtogether, so that a single voltage divider could be used. The above actions will prevent any ”warning” activation which might cause unwanted microprocessor’s interrupt. 12/15 TDA7476 APPLICATION EXAMPLES WITH ST AUDIO POWER ICs Figure 5: TDA7375 in S.E. mode with 4 output capacitors TDA7375 COUT1 + - - + + - - + COUT2 COUT3 COUT4 R CH1+ CH2+ CH3+ CH4+ CH5+ CH5- CH4- CH3- CH2- CH1- TDA7476 D97AU575A Figure 6: 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 Figure 7: TDA7451 TDA7451 + - - + + - - + R CH1+ CH2+ CH3+ CH4+ CH5+ CH5- CH4- CH3- CH2- CH1- TDA7476 D97AU577A Figure 8: Quad Bridge Amplifiers TDA7384, TDA7385, TDA7386, TDA7454 + - - + + - - + R CH1+ CH2+ CH3+ CH4+ CH5+ CH5- CH4- CH3- CH2- CH1- TDA7476 D97AU578A 13/15 TDA7476 mm DIM. MIN. TYP. inch MAX. MIN. TYP. MAX. A 2.35 2.65 0.093 0.104 A1 0.10 0.30 0.004 0.012 A2 2.55 0.100 B 0.33 0.51 0.013 0.0200 C 0.23 0.32 0.009 0.013 D 15.20 15.60 0.598 0.614 E 7.40 7.60 0.291 0.299 e 1.27 0,050 H 10.0 10.65 0.394 0.419 h 0.25 0.75 0.010 0.030 k OUTLINE AND MECHANICAL DATA 0° (min.), 8° (max.) L 0.40 1.27 0.016 SO24 0.050 0.10mm B e A A2 h x 45° A1 K A1 L .004 H Seating Plane D 13 1 12 E 24 SO24 14/15 C 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. Specification 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 1999 STMicroelectronics – Printed in Italy – 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 15/15