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| TDA7370B QUAD POWER AMPLIFIER FOR CAR RADIO MINIMUM EXTERNAL COMPONENT COUNT HIGH CURRENT CAPABILITY NO BOOTSTRAP CAPACITORS NO BOUCHEROT CELLS CLIP DETECTOR OUTPUT HIGH OUTPUT POWER HIGH APPLICATION FLEXIBILITY FIXED GAIN VERY LOW STAND-BY CURRENT (1A typ) NO SWITCH ON/OFF NOISE PROTECTIONS: OUTPUT AC/DC SHORT CIRCUIT TO GND AND TO VS VERY INDUCTIVE LOADS OVERRATING CHIP TEMPERATURE LOAD DUMP VOLTAGE FORTUITOUS OPEN GND REVERSE BATTERY ESD BLOCK DIAGRAM MULTIWATT15V ORDERING NUMBER: TDA7370B DESCRIPTION The TDA7370B is a new technology class AB quad channels Audio Power Amplifier in Multiwatt package designed for car radio applications. Thanks to the fully complementary PNP/NPN output configuration the high power performances of the TDA7370B are obtained without bootstrap capacitors. April 1995 1/17 TDA7370B PIN CONNECTION (Top view) ABSOLUTE MAXIMUM RATINGS Symbol VS VOP VPEAK IO IO Ptot Tstg, Tj DC Supply Voltage Operating Supply Voltage Peak Supply Voltage (t = 50ms) Output Peak Current (not rep. t = 100s) Output Peak Current (rep. f > 10Hz) Power Dissipation (Tcase = 85C) Storage and Junction Temperature Parameter Value 28 18 50 4.5 3.5 36 -40 to 150 Unit V V V A A W C THERMAL DATA Symbol Rth j-case Thermal Resistance Junction-case Description Max Value 1.8 Unit C/W 2/17 TDA7370B ELECTRICAL CHARACTERISTICS (Refer to the test circuit; VS = 14.4V; RL = 4, Tamb = 25C, f = 1kHz, unless otherwise specified) Symbol VS Id PO Parameter Supply Range Total Quiescent Drain Current Output Power RL = R L = 4; THD = 10% Single Ended Bridge R L = 4; Single Ended, PO = 0.1 to 4W Bridge, PO = 0.1 to 10W f f f f = 1kHz Bridge = 10kHz Bridge = 1kHz Single Ended = 10kHz Single Ended 20 15 20 26 1 SINGLE ENDED Non Inv. Ch., Rg = 10k Inv. Ch., R g = 10k BRIDGE (Rg = 0 to 10k) R g = 0; f = 100Hz to 10kHz 60 1 1.5 3.5 200 THD = 1% (**) 100 THD = 10% (**) 190 3.0 5 3.5 50 5.5 6.5 20 0.5 0.03 65 55 60 50 Test Condition Min. 8 Typ. Max. 18 150 Unit V mA W W % % dB dB dB dB K K dB dB dB V V V dB dB A V V mV A A d Distortion CT Cross Talk R IN GV GV EIN Input Impedance Voltage Gain Voltage Gain Match. Input Noise Voltage (*) Single Ended Bridge Single Ended Bridge SVR ASB ISB VSB ON VSB OFF VOS ICD OFF ICD ON Supply Voltage Rejection Stand-by Attenuation ST-BY Current ST-BY On Threshold Voltage ST-BY Off Threshold Voltage Output Offset Voltage Clipping Detector "OFF" Output Average Current Clipping Detector "ON" Output Average Current (*) Weighted A (**) Pin 10 Pulled-up to 5V with 10k; 3/17 TDA7370B APPLICATION CIRCUIT (QUAD STEREO) QUAD STEREO P.C. BOARD AND COMPONENT LAYOUT (1:1 SCALE) B 4/17 TDA7370B APPLICATION CIRCUIT (DOUBLE BRIDGE) DOUBLE BRIDGE P.C. BOARD AND COMPONENT LAYOUT (1:1 SCALE) B 5/17 TDA7370B APPLICATION CIRCUIT (STEREO/BRIDGE) Figure 1: Quiescent Drain Current vs. Supply Voltage (Bridge/Single Ended) Figure 2: Quiescent Output Voltage vs. Supply Voltage (Bridge/Single Ended) 6/17 TDA7370B Figure 3: Output Power vs. Supply Voltage (Single Ended) Figure 4: Output Power vs. Supply Voltage (Bridge) Figure 5: Distortion vs. Output Power (Single Ended) Figure 6: Distortion vs. Output Power (Bridge) Figure 7: Output Power vs. Frequency (Single Ended) Figure 8: Output Power vs. Frequency (Bridge) 7/17 TDA7370B Figure 9: Supply Voltage Rejection vs. Frequency (Single Ended) for different values of pin 6 capacitor. Figure 10: Supply Voltage Rejection vs. Frequency (Bridge) for different values of pin 6 capacitor. Rg Rg Figure 11: Cross-Talk vs. Frequency (Bridge) Figure 12: Stand-By Attenuation vs. Threshold Voltage (Single Ended/Bridge) Rg Figure 13: Clipping Detector Average Current (pin 10) vs.Distortion (Single Ended) Figure 14: En input vs. RS (Single Ended) 8/17 TDA7370B Figure 15: En input vs. RS (Single Ended) Figure 16: En input vs. RS (Bridge) Rg Rg Figure 17: Total Power Dissipation and Efficiency vs. Ouput Power (Single Ended) Figure 18: Total Power Dissipation and Efficiency vs. Ouput Power (Bridge) 9/17 TDA7370B OUTPUT STAGE The fully complementary output stage was made possible by the development of a new component: the ST exclusive power ICV PNP. A novel design based upon the connection shown in fig. 19 has then allowed the full exploitation of its possibilities. Figure 19: The new Output Stage loss on the top side of the waveform. This unbalanced saturation causes a significant power reduction. The only way to recover power consists of the addition of expensive bootstrap capacitors. 2 - Absolute Stability Without Any External Compensation. Referring to the circuit of Fig. 19 the gain VOUT/VIN is greater than unity, approximately 1 + R2/R1. The DC output (VCC/2) is fixed by an auxiliary amplifier common to all the channels). By controlling the amount of this local feedback it is possible to force the loop gain (A * ) to less than unity at frequency for which the phase shift is 180 Deg. This means that the output buffer is intrinsically stable and not prone to oscillation. Most remarkably, the above feature has been achieved in spite of the very low closed loop gain of the amplifier (20 dB). In contrast, with the classical PNP-NPN stage, the solution adopted for reducing the gain at high frequencies makes use of external RC networks, namely the Boucherot cells. The clear advantages this new approach has over classical output stages are as follows: 1 - Rail-to-Rail Output Voltage Swing With No Need Of Bootstrap Capacitors. The output swing is limited only by the Vcesat of the output transistors, which are in the range of 0.6 Ohm (Rsat) each. Classical solutions adopting composite PNP-NPN for the upper output stage have higher saturation Figure 20: Clipping Detection Waveforms OTHER OUTSTANDING CHARACTERISTICS: Clipping Detector Output The TDA7370B is equipped with an internal circuit able to detect the output stage saturation providing a current sinking into a open collector output (pin 10) when a certain distortion level is reached at each output. This particular function allows gain compression facility whenever the amplifier is overdriven, thus obtaining high quality sound at all listening levels. 10/17 TDA7370B Offset Control The quiescent output voltage must be as close as possible to its nominal value, so that less undistorted power would be available. For this reason an input bias current compensation is implemented to reduce the voltage drop across the input resistors, which appears amplified at the outputs. Gain Internally Fixed to 20dB in Single Ended, 26dB in Bridge Advantages of this design choice are in terms of: components and space saving output noise, supply voltage rejection and distortion optimization. Silent Turn On/Off and Muting/Stand-by Function The stand-by can be easily activated by means of a CMOS level applied to pin 7 through a RC filter. Under stand-by condition the device is turned off completely (supply current= 1 A TYP ; output attenuation= 90 dB TYP). Every ON/OFF operation is virtually pop free. Furthermore, at turn-on the device stays in muting condition for a time determined by the value assigned to the SVR capacitor (T= Csvr * 7,000). While in muting the device outputs becomes insensitive to any kinds of signal that may be present at the input terminals. In other words every transient coming from previous stages produces no unpleasantacoustic effect to the speakers. Another situation under which the device is totally muted is whenever the supply voltage drops lower than 7V. This is helpful to pop suppression during the turn-off by battery switch. Easy Single Ended to Bridge Transition. The change from single ended to bridge configurations is made simply by means of a short circuit across the inputs, that is no need of further external components. High Application Flexibility The availability of 4 independent channels makes it possible to accomplish several kinds of applications ranging from 4 speakers stereo (F/R) to 2 speakers bridge solutions. In case of working in single ended conditions the polarity of the speakers driven by the inverting amplifier must be reversed respect to those driven by non inverting channels. This is to avoid phase inconveniences causing sound alterations especially during the reproduction of low frequencies. BUILT-IN PROTECTION SYSTEMS Full Protection of Device and Loudspeakers Against AC/DC Short Circuits (to Gnd, to Vs, across the Speakers). Reliable and safe operation in presence of all kinds of short circuit involving the outputs is assured by a built-in protection system that operates in the following way: In case of overload, a SCR is activated as soon as the current flowing through the output transistors overcomes a preset threshold value depending on the chip temperature. The SCR causes an interruption of the supply current of the power transistor. The normal working is restored by a restart circuit going into action as soon as the short circuit is removed. Load Dump Voltage Surge The TDA7370B has a circuit which enables it to withstand a voltage pulse train on pins 3 and 13, of the type shown in fig. 22. If the supply voltage peaks to more than 50V, then an LC filter must be inserted between the supply and pins 3 and 13, in order to assure that the pulses at pins 3 and 13 will be held within the limits shown. A suggested LC network is shown in fig. 21. With this network, a train of pulses with amplitude up to 120V and width of 2ms can be applied at point A. This type of protection is ON when the supply voltage (pulse or DC) exceeds 18V. For this reason the maximum operating supply voltage is 18V. Figure 21 Figure 22 11/17 TDA7370B Polarity Inversion High current (up to 10A) can be handled by the device with no damage for a longer period than the blow-out time of a quick 2A fuse (normally connected in series with the supply). This features is added to avoid destruction, if during fitting to the car, a mistake on the connection of the supply is made. Open Ground When the radio is in the ON condition and the ground is accidentally opened, a standard audio amplifier will be damaged. On the TDA7370B protection diodes are included to avoid any damage. Inductive Load A protection diode is provided to allow use of the TDA7370B with inductive loads. DC Voltage The maximum operating DC voltage for the TDA7370B is 18V. However the device can withstand a DC voltage up to 28V with no damage. This could occur during winter if two batteries are series connected to crank the engine. Thermal Shut-down The presence of a thermal limiting circuit offers the following advantages: 1)an overload on the output (even if it is permanent), or an excessive ambient temperature can be easily withstood. 2)the heatsink can have a smaller factor of Loudspeaker Protection The TDA7370B guarantees safe operations even for the loudspeakerin case of accidental shortcircuit. Whenever a single OUT to GND, OUT to VS short circuit occurs both the outputs are switched OFF so limiting dangerous DC current flowing through the loudspeaker. safety compared with that of a conventional circuit. There is no device damage in case of excessive junction temperature: all happens is that Po (and therefore Ptot) and Id are reduced. The maximum allowable power dissipation depends upon the size of the external heatsink (i.e. its thermal resistance); Fig. 23 shows the dissipable power as a function of ambient temperature for different thermal resistance. Figure 23: Maximum Allowable Power Dissipation vs. Ambient Temperature 12/17 TDA7370B CLIPPING DETECTOR Figures 25 and 26 show an application using the TDA7370B in combination with the SGS-THOMSON audioprocessor TDA7302. The output clipping is recognized by the microprocessor (in this application it is simulated by a PC). The detailed way to operate of the system is represented by the flow-chart of fig.24 The controller detects when the clipping is active (minimun detection width fixed by a C29 = 12 nF external capacitor), and reduces the volume (or bass ) by steps of 2 dB (with a programmable waiting time), until no more clipping is detected. Then the controller waits for a programmable time before increasing the volume again by step of 2 dB until clipping is again detected or the panel selected volume is reached. Practical advantages of this application is a better sound quality deriving from operation under no clipping conditions, which also means the availability of higher undistorted power. Figure 24: Clipping Detector Control Routine WHAT IS NEEDED FOR A DEMONSTRATION - a XT or AT IBM compatible PC, supplied with EGA card - a SGS-THOMSON audioprocessor application disk - a TDA 7302 + TDA7370B board - a connector from audioprocessor board to PC parallel port GENERAL INFORMATION In the application shown in figures 25 and 26 the TDA7302 audioprocessor works on PC XT or AT IBM compatible. Control is accomplished by serial bus ( S-bus or I2C-bus or SPI bus) sent to the test board through the PC parallel port. The PC simulates the behaviour of the microprocessor in a real application (for example in a car radio) and the buffer is necessary only in this application for protecting the PC. 13/17 TDA7370B Figure 25: Application with TDA7302 + TDA7370B (QUAD STEREO) 14/17 TDA7370B TDA7370B Figure 26: Application wiyh TDA7302 + TDA7370B (DOUBLE BRIDGE) TDA7370B 15/17 TDA7370B MECHANICAL DATA AND DIMENSIONS OF THE MULTIWATT15 (Vertical) DIM. MIN. A B C D E F G G1 H1 H2 L L1 L2 L3 L4 L7 M M1 S S1 Dia1 22.1 22 17.65 17.25 10.3 2.65 4.2 4.5 1.9 1.9 3.65 4.3 5.08 17.5 10.7 0.49 0.66 1.14 17.57 19.6 20.2 22.6 22.5 18.1 17.75 10.9 2.9 4.6 5.3 2.6 2.6 3.85 0.870 0.866 0.695 0.679 0.406 0.104 0.165 0.177 0.075 0.075 0.144 0.169 0.200 0.689 0.421 1.27 17.78 1 0.55 0.75 1.4 17.91 0.019 0.026 0.045 0.692 0.772 0.795 0.890 0.886 0.713 0.699 0.429 0.114 0.181 0.209 0.102 0.102 0.152 0.050 0.700 mm TYP. MAX. 5 2.65 1.6 0.039 0.022 0.030 0.055 0.705 MIN. inch TYP. MAX. 0.197 0.104 0.063 16/17 TDA7370B Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics 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 SGS-THOMSON Microelectronics. Specifications mentioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied. SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without express written approval of SGS-THOMSON Microelectronics. (c) 1995 SGS-THOMSON Microelectronics - All Rights Reserved MULTIWATT (R) is a Registered Trademark of the SGS-THOMSON Microelectronics SGS-THOMSON Microelectronics GROUP OF COMPANIES Australia - Brazil - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands - Singapore Spain - Sweden - Switzerland - Taiwan - Thaliand - United Kingdom - U.S.A. 17/17 |
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