Download: QUAD POWER AMPLIFIER FOR CAR RADIO

® 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 MULTIWATT15V VERY LOW STAND-BY CURRENT (1µA typ) NO SWITCH ON/OFF NOISE ORDERING NUMBER: TDA7370B PROTECTIONS: OUTPUT AC/DC SHORT CIRCUIT TO GND DESCRIPTION AND TO VS VERY INDUCTIVE LOADS The TDA7370B is a new technology class ABquad channels Audio Power Amplifier in Multiwatt OVERRATING CHIP TEMPERATURE package designed for car radio applications. LOAD DUMP VOLTAGE Thanks to the fully complementary PNP/NPN out- FORTUITOUS OPEN GND put configuration the high power performances of REVERSE BATTERY the TDA7370B are obtained without bootstrap ca- ESD pacitors. BLOCK DIAGRAM September 2003 1/17,

PIN CONNECTION (Top view) ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit VS DC Supply Voltage 28 V VOP Operating Supply Voltage 18 V VPEAK Peak Supply Voltage (t = 50ms) 50 V IO Output Peak Current (not rep. t = 100µs) 4.5 A IO Output Peak Current (rep. f > 10Hz) 3.5 A Ptot Power Dissipation (Tcase = 85°C) 36 W Tstg, Tj Storage and Junction Temperature -40 to 150 °C

THERMAL DATA

Symbol Description Value Unit Rth j-case Thermal Resistance Junction-case Max 1.8 °C/W 2/17,

ELECTRICAL CHARACTERISTICS (Refer to the test circuit; VS = 14.4V; RL = 4Ω, Tamb = 25°C,

f = 1kHz, unless otherwise specified) Symbol Parameter Test Condition Min. Typ. Max. Unit VS Supply Range 8 18 V Id Total Quiescent Drain Current RL = ∞ 150 mA PO Output Power RL = 4Ω; THD = 10% Single Ended 5.5 6.5 W Bridge 20WdDistortion RL = 4Ω; Single Ended, PO = 0.1 to 4W 0.5 % Bridge, PO = 0.1 to 10W 0.03 % CT Cross Talk f = 1kHz Bridge 65 dB f = 10kHz Bridge 55 dB f = 1kHz Single Ended 60 dB f = 10kHz Single Ended 50 dB RIN Input Impedance Single Ended 20 KΩ Bridge 15 KΩ GV Voltage Gain Single Ended 20 dB Bridge 26 dB GV Voltage Gain Match. 1 dB EIN Input Noise Voltage (*) SINGLE ENDED Non Inv. Ch., Rg = 10kΩ 3.0 µV Inv. Ch., Rg = 10kΩ 5 µV BRIDGE (Rg = 0 to 10kΩ) 3.5 µV SVR Supply Voltage Rejection Rg = 0; f = 100Hz to 10kHz 50 dB ASB Stand-by Attenuation 60 dB ISB ST-BY Current 1 µA VSB ON ST-BY On Threshold Voltage 1.5 V VSB OFF ST-BY Off Threshold Voltage 3.5 V VOS Output Offset Voltage 200 mV ICD OFF Clipping Detector "OFF" THD = 1% (**) Output Average Current 100 µA ICD ON Clipping Detector "ON" THD = 10% (**) Output Average Current 190 µA (*) Weighted A (**) Pin 10 Pulled-up to 5V with 10kΩ; 3/17, APPLICATION CIRCUIT (QUAD STEREO) QUAD STEREO P.C. BOARD AND COMPONENT LAYOUT (1:1 SCALE)

B

4/17, APPLICATION CIRCUIT (DOUBLE BRIDGE) DOUBLE BRIDGE P.C. BOARD AND COMPONENT LAYOUT (1:1 SCALE)

B

5/17, APPLICATION CIRCUIT (STEREO/BRIDGE) Figure 1: Quiescent Drain Current vs. Supply Figure 2: Quiescent Output Voltage vs. Supply Voltage (Bridge/Single Ended) Voltage (Bridge/Single Ended) 6/17, Figure 3: Output Power vs. Supply Voltage Figure 4: Output Power vs. Supply Voltage (Single Ended) (Bridge) Figure 5: Distortion vs. Output Power (Single Figure 6: Distortion vs. Output Power (Bridge) Ended) Figure 7: Output Power vs. Frequency (Single Figure 8: Output Power vs. Frequency (Bridge) Ended) 7/17, Figure 9: Supply Voltage Rejection vs. Figure 10: Supply Voltage Rejection vs. Frequency (Single Ended) for different Frequency (Bridge) for different values of pin 6 capacitor. 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 Figure 14: En input vs. RS (Single Ended) (pin 10) vs.Distortion (Single Ended) 8/17, Figure 15: En input vs. RS (Single Ended) Figure 16: En input vs. RS (Bridge) Rg Rg Figure 17: Total Power Dissipation and Figure 18: Total Power Dissipation and Efficiency vs. Ouput Power (Single Efficiency vs. Ouput Power (Bridge) Ended) 9/17, OUTPUT STAGE loss on the top side of the waveform. This unbal- anced saturation causes a significant power re- The fully complementary output stage was made duction. The only way to recover power consists possible by the development of a new compo- of the addition of expensive bootstrap capacitors. nent: the ST exclusive power ICV PNP. A novel design based upon the connection shown in fig. 19 has then allowed the full exploitation of 2 - Absolute Stability Without Any External its possibilities. Compensation. Referring to the circuit of Fig. 19 the gain Figure 19: The new Output Stage VOUT/VIN is greater than unity, approximately 1 + R2/R1. The DC output (VCC/2) is fixed by an aux- iliary amplifier common to all the channels). By controlling the amount of this local feedback it is possible to force the loop gain (A * β) 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 OTHER OUTSTANDING CHARACTERISTICS: classical output stages are as follows: Clipping Detector Output The TDA7370B is equipped with an internal cir- 1 - Rail-to-Rail Output Voltage Swing With No cuit able to detect the output stage saturation pro- Need Of Bootstrap Capacitors. viding a current sinking into a open collector out- put (pin 10) when a certain distortion level is The output swing is limited only by the Vcesat of reached at each output. the output transistors, which are in the range of 0.6 Ohm (R ) each. This particular function allows gain compressionsat facility whenever the amplifier is overdriven, thus Classical solutions adopting composite PNP-NPN obtaining high quality sound at all listening levels. for the upper output stage have higher saturation Figure 20: Clipping Detection Waveforms 10/17, Offset Control BUILT-IN PROTECTION SYSTEMS The quiescent output voltage must be as close as Full Protection of Device and Loudspeakers possible to its nominal value, so that less undis- Against AC/DC Short Circuits (to Gnd, to Vs, torted power would be available. across the Speakers). For this reason an input bias current compensa- Reliable and safe operation in presence of all tion is implemented to reduce the voltage drop kinds of short circuit involving the outputs is as- across the input resistors, which appears ampli- sured by a built-in protection system that operates fied at the outputs. in the following way: In case of overload, a SCR is activated as soon Gain Internally Fixed to 20dB in Single Ended, as the current flowing through the output transis- 26dB in Bridge tors overcomes a preset threshold value depend- ing on the chip temperature. The SCR causes an Advantages of this design choice are in terms of: interruption of the supply current of the power components and space saving transistor. The normal working is restored by a re- output noise, supply voltage rejection and dis- start circuit going into action as soon as the short tortion optimization. circuit is removed. Silent Turn On/Off and Muting/Stand-by Func- Load Dump Voltage Surge tion The TDA7370B has a circuit which enables it to The stand-by can be easily activated by means of withstand a voltage pulse train on pins 3 and 13, a CMOS level applied to pin 7 through a RC filter. of the type shown in fig. 22. Under stand-by condition the device is turned off If the supply voltage peaks to more than 50V, completely (supply current= 1 µA TYP ; output at- then an LC filter must be inserted between the tenuation= 90 dB TYP). supply and pins 3 and 13, in order to assure that Every ON/OFF operation is virtually pop free. the pulses at pins 3 and 13 will be held within the limits shown. Furthermore, at turn-on the device stays in muting condition for a time determined by the value as- A suggested LC network is shown in fig. 21. signed to the SVR capacitor (T= Csvr 7,000). With this network, a train of pulses with amplitude* While in muting the device outputs becomes in- up to 120V and width of 2ms can be applied at sensitive to any kinds of signal that may be pre- point A. This type of protection is ON when the sent at the input terminals. In other words every supply voltage (pulse or DC) exceeds 18V. For transient coming from previous stages produces this reason the maximum operating supply volt- no unpleasant acoustic effect to the speakers. age is 18V. Another situation under which the device is totally Figure 21 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 configu- rations is made simply by means of a short circuit Figure 22 across the inputs, that is no need of further exter- nal components. High Application Flexibility The availability of 4 independent channels makes it possible to accomplish several kinds of applica- tions 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 reproduc- tion of low frequencies. 11/17, Polarity Inversion safety compared with that of a conventional circuit. There is no device damage in case of High current (up to 10A) can be handled by the excessive junction temperature: all happens device with no damage for a longer period than is that Po (and therefore Ptot) and Id are re- the blow-out time of a quick 2A fuse (normally duced. connected in series with the supply). This fea- tures is added to avoid destruction, if during fitting The maximum allowable power dissipation de- to the car, a mistake on the connection of the pends upon the size of the external heatsink (i.e. supply is made. its thermal resistance); Fig. 23 shows the dissi- pable power as a function of ambient temperature for different thermal resistance. Open Ground When the radio is in the ON condition and the Figure 23: Maximum Allowable Power ground is accidentally opened, a standard audio Dissipation vs. Ambient Temperature amplifier will be damaged. On the TDA7370B pro- tection 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 dur- ing winter if two batteries are series connected to crank the engine. Thermal Shut-down Loudspeaker Protection The presence of a thermal limiting circuit offers the following advantages: The TDA7370B guarantees safe operations even for 1)an overload on the output (even if it is perma- the loudspeaker in case of accidental shortcircuit. nent), or an excessive ambient temperature Whenever a single OUT to GND, OUT to VS short can be easily withstood. circuit occurs both the outputs are switched OFF so limiting dangerous DC current flowing through 2)the heatsink can have a smaller factor of the loudspeaker. 12/17, CLIPPING DETECTOR WHAT IS NEEDED FOR A DEMONSTRATION Figures 25 and 26 show an application using the TDA7370B in combination with the SGS-THOM- - a XT or AT IBM compatible PC, supplied with SON audioprocessor TDA7302. EGA card - a SGS-THOMSON audioprocessor application disk The output clipping is recognized by the microproc- - a TDA 7302 + TDA7370B board essor (in this application it is simulated by a PC). - a connector from audioprocessor board to PC The detailed way to operate of the system is rep- parallel port resented by the flow-chart of fig.24 The controller detects when the clipping is active GENERAL INFORMATION (minimun detection width fixed by a C29 = 12 nF external capacitor), and reduces the volume (or In the application shown in figures 25 and 26 the bass ) by steps of 2 dB (with a programmable TDA7302 audioprocessor works on PC XT or AT waiting time), until no more clipping is detected. IBM compatible. Then the controller waits for a programmable time Control is accomplished by serial bus ( S-bus or2 before increasing the volume again by step of2IC-bus or SPI bus) sent to the test board through dB until clipping is again detected or the panel se- the PC parallel port. lected volume is reached. The PC simulates the behaviour of the microproc- Practical advantages of this application is a better essor in a real application (for example in a car sound quality deriving from operation under no radio) and the buffer is necessary only in this ap- clipping conditions, which also means the avail- plication for protecting the PC. ability of higher undistorted power. Figure 24: Clipping Detector Control Routine 13/17, Figure 25: Application with TDA7302 + TDA7370B (QUAD STEREO) 14/17 TDA7370B, Figure 26: Application wiyh TDA7302 + TDA7370B (DOUBLE BRIDGE) 15/17 TDA7370B, mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. OUTLINE ANDA50.197 MECHANICAL DATA B 2.65 0.104 C 1.6 0.063D10.039 E 0.49 0.55 0.019 0.022 F 0.66 0.75 0.026 0.030 G 1.02 1.27 1.52 0.040 0.050 0.060 G1 17.53 17.78 18.03 0.690 0.700 0.710 H1 19.6 0.772 H2 20.2 0.795 L 21.9 22.2 22.5 0.862 0.874 0.886 L1 21.7 22.1 22.5 0.854 0.870 0.886 L2 17.65 18.1 0.695 0.713 L3 17.25 17.5 17.75 0.679 0.689 0.699 L4 10.3 10.7 10.9 0.406 0.421 0.429 L7 2.65 2.9 0.104 0.114 M 4.25 4.55 4.85 0.167 0.179 0.191 M1 4.63 5.08 5.53 0.182 0.200 0.218 S 1.9 2.6 0.075 0.102 S1 1.9 2.6 0.075 0.102 Multiwatt15 V Dia1 3.65 3.85 0.144 0.152 16/17, 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. All other names are the property of their respective owners © 2003 STMicroelectronics - All rights reserved STMicroelectronics GROUP OF COMPANIES Australia – Belgium - Brazil - Canada - China – Czech Republic - Finland - France - Germany - Hong Kong - India - Israel - Italy - Japan - Malaysia - Malta - Morocco - Singapore - Spain - Sweden - Switzerland - United Kingdom - United States www.st.com 17/17]

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