TDA7374 Dual bridge audio amplifier for car radio Features ■ Minimum external component count ■ No bootstrap capacitors ■ No Boucherot cells ■ Clip detector output ■ High output power ■ Fixed gain ■ Very low stand-by current (1 µA typ) ■ No switch on/off noise Multiwatt 15 Protections ■ Output AC/DC short circuit to GND and to VS Description ■ Very inductive loads ■ Overrating chip temperature ■ Load dump voltage The TDA7374 is a class AB audio dual bridge power amplifier in Multiwatt package designed for car radio applications. ■ Fortuitous open GND ■ Reverse battery ■ ESD Table 1. June 2008 Thanks to the fully complementary PNP/NPN output configuration the high power performances of the TDA7374 are obtained without bootstrap capacitors. Device summary Order code Package Packing TDA7374BV Multiwatt 15 Tube Rev 4 1/19 www.st.com 1 Contents TDA7374 Contents 1 Block diagram and pins connections diagram . . . . . . . . . . . . . . . . . . . . 5 2 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3 2.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Electrical characteristcs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Electrical characteristics curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 3.1 Rail-to-rail output voltage swing with no need of bootstrap capacitors . . . 11 3.2 Absolute stability without any external compensation . . . . . . . . . . . . . . . 11 3.3 Other outstanding characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.4 3.3.1 Clipping detector output . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.3.2 Offset control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.3.3 Gain internally fixed to 26dB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.3.4 Silent turn on/off and muting/stand-by function . . . . . . . . . . . . . . . . . . . 12 Built-in protection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.4.1 Full protection of device and loudspeakers against AC/DC short circuits (to Gnd, to Vs, across the speakers) 13 3.4.2 Load dump voltage surge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.4.3 Polarity inversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3.4.4 Open ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.4.5 Inductive load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.4.6 DC voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.4.7 Thermal shut-down . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.4.8 Loudspeaker protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14 3.5 Clipping detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.6 What is needed for a demonstration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 3.6.1 General Information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 4 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 5 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 2/19 TDA7374 List of tables List of tables Table 1. Table 2. Table 3. Table 4. Table 5. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Electrical characteristcs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 3/19 List of figures TDA7374 List of figures Figure 1. Figure 2. Figure 3. Figure 4. Figure 5. Figure 6. Figure 7. Figure 8. Figure 9. Figure 10. Figure 11. Figure 12. Figure 13. Figure 14. Figure 15. Figure 16. Figure 17. Figure 18. Figure 19. Figure 20. Figure 21. Figure 22. Figure 23. Figure 24. 4/19 Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Pin connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Test and application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Printed board and component layout of the Figure 3.. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Quiescent drain current vs. supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Quiescent output voltage vs. supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Output power vs. supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Distortion vs. output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Output power vs. frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 Supply volt. rejection vs. frequency for a different values of C6 capacitor . . . . . . . . . . . . . . 9 Cross-talk vs. frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 En input vs. Rg . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Stand-by attenuation vs. threshold voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Stand-by attenuation vs. input voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Clipping detector average current (pin 10) vs. distortion . . . . . . . . . . . . . . . . . . . . . . . . . . 10 Total power dissipation and efficiency vs. output power. . . . . . . . . . . . . . . . . . . . . . . . . . . 10 The new output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 Clipping detection waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 A suggested LC network. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Voltage pulse train on pins 3 and 13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 Maximum allowable power dissipation vs. ambient temperature . . . . . . . . . . . . . . . . . . . . 14 Clipping detector control routine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 Application with TDA7302 + TDA7374 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16 Multiwatt 15 mechanical data and package dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . . 17 TDA7374 1 Block diagram and pins connections diagram Block diagram and pins connections diagram Figure 1. Block diagram Figure 2. Pin connection (top view) 5/19 Electrical specifications TDA7374 2 Electrical specifications 2.1 Absolute maximum ratings Table 2. Absolute maximum ratings Symbol Unit DC supply voltage 28 V VOP Operating supply voltage 18 V Peak supply voltage (t = 50 ms) 50 V IO Output peak current (not rep. t = 100 µs) 4.5 A IO Output peak current (rep. f > 10 Hz) 3.5 A Ptot Power dissipation (Tcase = 85 °C) 36 W Tstg, Tj Storage and junction temperature -40 to 150 °C Thermal data Table 3. Symbol Rth j-case 6/19 Value VS VPEAK 2.2 Parameter Thermal data Parameter Thermal resistance junction to case max. Value Unit 1.8 °C/W TDA7374 Electrical specifications 2.3 Electrical characteristcs Table 4. Electrical characteristcs (Refer to the test circuit; VS = 14.4 V; RL = 4 Ω, Tamb = 25 °C, f = 1 kHz, unless otherwise specified) Symbol VS Id Parameter Test condition Supply range Typ. 8 Total quiescent drain current Output power RL = 4 Ω; THD = 10 % d Distortion RL = 4 Ω; PO = 0.1 to 10 W CT Cross talk PO Min. 17 Max. Unit 18 V 150 mA 21 W 0.5 % f = 1 kHz; Rg = 0 65 dB f = 10 kHz; Rg = 0 55 dB RIN Input impedance 10 GV Voltage gain 26 dB GV Voltage gain match. 1 dB Rg = 0 to 10 kΩ; Weight A EIN SVR Input noise voltage Supply voltage rejection Rg = 0 to 10 kΩ; 22 Hz to 22 kHz Rg = 0; f = 100 Hz Stand-by attenuation ISB Stand-by current consumption VSB ON Stand-by IN Threshold Voltage VSB OFF Stand-by OUT threshold voltage VOS μV 3.5 10 48 Rg = 0; f = 10 kHz ASB KΩ μV dB 55 dB 60 dB μA 1 1.5 3.5 V V Output offset voltage 200 mV ICD OFF Clipping detector "OFF" output average current THD = 1 % (1) 100 μA ICD ON Clipping detector "ON" output average current THD = 10 % (1) 190 μA 1. Pin 10 pulled-up to 5V with 10kΩ; RL = 4Ω 7/19 Electrical specifications 8/19 Figure 3. Test and application circuit Figure 4. Printed board and component layout of the Figure 3. TDA7374 TDA7374 Electrical specifications 2.4 Electrical characteristics curves Figure 5. Quiescent drain current vs. supply voltage Figure 6. Quiescent output voltage vs. supply voltage Figure 7. Output power vs. supply voltage Figure 8. Distortion vs. output power Figure 9. Output power vs. frequency Figure 10. Supply volt. rejection vs. frequency for a different values of C6 capacitor 9/19 Electrical specifications TDA7374 Figure 11. Cross-talk vs. frequency Figure 12. En input vs. Rg Figure 13. Stand-by attenuation vs. threshold voltage Figure 14. Stand-by attenuation vs. input voltage Figure 15. Clipping detector average current (pin 10) vs. distortion Figure 16. Total power dissipation and efficiency vs. output power 10/19 TDA7374 3 Output stage 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 Figure 17 has then allowed the full exploitation of its possibilities. Figure 17. The new output stage The clear advantages this new approach has over classical output stages are as follows: 3.1 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 Ω each. Classical solutions adopting composite PNP-NPN for the upper output stage have higher saturation 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. 3.2 Absolute stability without any external compensation Referring to the circuit of Figure 17 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 * β) to less than unity at frequency for which the phase shift is 180°C. 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. 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. 11/19 Output stage TDA7374 3.3 Other outstanding characteristics 3.3.1 Clipping detector output The TDA7374 is equipped with an internal circuit able to detect the output stage saturation providing a proper 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. Figure 18. Clipping detection waveforms 3.3.2 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 riduce the voltage drop across the input resistors, which appears amplified at the outputs. 3.3.3 Gain internally fixed to 26 dB Advantages of this design choice are in terms of: 3.3.4 ● 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 µA 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 unpleasant acoustic 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. 12/19 TDA7374 Output stage 3.4 Built-in protection systems 3.4.1 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. 3.4.2 Load dump voltage surge The TDA7374 has a circuit which enables it to withstand a voltage pulse train on pins 3 and 13, of the type shown in Figure 20. 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 Figure 19. With this network, a train of pulses with amplitude up to 120 V and width of 2ms can be applied at point A. This type of protection is ON when the supply voltage (pulse or DC) exceeds 18 V. For this reason the maximum operating supply voltage is 18 V. Figure 19. A suggested LC network Figure 20. Voltage pulse train on pins 3 and 13 3.4.3 Polarity inversion High current (up to 10 A) can be handled by the device with no damage for a longer period than the blow-out time of a quick 2 A 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. 13/19 Output stage 3.4.4 TDA7374 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 TDA7374 protection diodes are included to avoid any damage. 3.4.5 Inductive load A protection diode is provided to allow use of the TDA7374 with inductive loads. 3.4.6 DC voltage The maximum operating DC voltage for the TDA7374 is 18 V. However the device can withstand a DC voltage up to 28 V with no damage. This could occur during winter if two batteries are series connected to crank the engine. 3.4.7 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 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); Figure 21 shows the dissipable power as a function of ambient temperature for different thermal resistance. Figure 21. Maximum allowable power dissipation vs. ambient temperature 3.4.8 Loudspeaker protection The TDA7374 guarantees safe operations even for the loudspeaker in 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. 14/19 TDA7374 3.5 Output stage Clipping detector Figure 23 shows an application using the TDA7374 in combination with the STM 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 Figure 22. 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 step 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 22. Clipping detector control routine 3.6 What is needed for a demonstration ● IBM compatible PC with parallel port ● STM audioprocessor application disk ● TDA7302 + TDA7374 board ● Connector from audioprocessor board to PC parallel port 15/19 Output stage 3.6.1 TDA7374 General Information In the application shown in Figure 23 the TDA7302 audioprocessor works on PC 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. Figure 23. Application with TDA7302 + TDA7374 16/19 TDA7374 4 Package information Package information In order to meet environmental requirements, ST (also) offers these devices in ECOPACK® packages. ECOPACK® packages are lead-free. The category of second Level Interconnect is marked on the package and on the inner box label, in compliance with JEDEC Standard JESD97. The maximum ratings related to soldering conditions are also marked on the inner box label. ECOPACK is an ST trademark. ECOPACK specifications are available at: www.st.com. Figure 24. Multiwatt 15 mechanical data and package dimensions DIM. mm MIN. TYP. inch MAX. MIN. TYP. A5 MAX. 0.197 B 2.65 C 1.6 D OUTLINE AND MECHANICAL DATA 0.104 0.063 1 0.039 E 0.49 0.55 0.019 F 0.66 0.75 0.026 0.022 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 0.030 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 0.87 0.886 L2 17.65 18.1 0.695 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 0.191 0.713 L7 2.65 2.9 0.104 M 4.25 4.55 4.85 0.167 0.179 0.114 M1 4.73 5.08 5.43 0.186 0.200 S 1.9 2.6 0.075 0.102 S1 1.9 2.6 0.075 0.102 Dia1 3.65 3.85 0.144 0.152 0.214 Multiwatt15 (Vertical) 0016036 J 17/19 Revision history 5 TDA7374 Revision history Table 5. 18/19 Document revision history Date Revision Changes 12-Oct-1999 3 Initial release. 30-Jun-2008 4 Document reformatted. Added Table 1: Device summary. Added ECOPACK description in Section 4: Package information. TDA7374 Please Read Carefully: Information in this document is provided solely in connection with ST products. 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