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TDA7294
100V - 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY
VERY HIGH OPERATING VOLTAGE RANGE (40V) DMOS POWER STAGE HIGH OUTPUT POWER (UP TO 100W MUSIC POWER) MUTING/STAND-BY FUNCTIONS NO SWITCH ON/OFF NOISE NO BOUCHEROT CELLS VERY LOW DISTORTION VERY LOW NOISE SHORT CIRCUIT PROTECTION THERMAL SHUTDOWN DESCRIPTION The TDA7294 is a monolithic integrated circuit in Multiwatt15 package, intended for use as audio class AB amplifier in Hi-Fi field applications (Home Stereo, self powered loudspeakers, Topclass TV). Thanks to the wide voltage range and Figure 1: Typical Application and Test Circuit MULTIPOWER BCD TECHNOLOGY
Multiwatt15 ORDERING NUMBER: TDA7294V
to the high out current capability it is able to supply the highest power into both 4 and 8 loads even in presence of poor supply regulation, with high Supply Voltage Rejection. The built in muting function with turn on delay simplifies the remote operation avoiding switching on-off noises.
C7 100nF R3 22K C2 22F +Vs R2 680 C1 470nF R1 22K IN+MUTE R5 10K MUTE STBY R4 22K C3 10F C4 10F 4 10 9 IN2
+Vs
C6 1000F
+PWVs 13 14 OUT C5 22F 6 BOOTSTRAP
TDA7294
-
7
IN+
3
+
VM VSTBY
MUTE STBY 1 STBY-GND 8
THERMAL SHUTDOWN
S/C PROTECTION 15 -PWVs C8 1000F
D93AU011
-Vs C9 100nF -Vs
February 1996
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TDA7294
PIN CONNECTION (Top view)
TAB connected to -VS
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS
Symbol VS IO Ptot Top Tstg, Tj 2/16 Output Peak Current Power Dissipation Tcase = 70C Operating Ambient Temperature Range Storage and Junction Temperature Parameter Supply Voltage (No Signal) Value 50 10 50 0 to 70 150 Unit V A W C C
TDA7294
THERMAL DATA
Symbol R th j-case Description Thermal Resistance Junction-case Max Value 1.5 Unit C/W
ELECTRICAL CHARACTERISTICS (Refer to the Test Circuit VS = 35V, RL = 8, GV = 30dB; Rg = 50 ; Tamb = 25C, f = 1 kHz; unless otherwise specified.
Symbol VS Iq Ib VOS IOS PO Parameter Supply Range Quiescent Current Input Bias Current Input Offset Voltage Input Offset Current RMS Continuous Output Power d = 0.5%: VS = 35V, RL = 8 VS = 31V, RL = 6 VS = 27V, RL = 4 d = 10% RL = 8 ; VS = 38V RL = 6 ; VS = 33V RL = 4 ; VS = 29V (***) PO = 5W; f = 1kHz PO = 0.1 to 50W; f = 20Hz to 20kHz VS = 27V, RL = 4: PO = 5W; f = 1kHz PO = 0.1 to 50W; f = 20Hz to 20kHz SR GV GV eN fL, fH Ri SVR TS VST on VST off ATT st-by Iq st-by VMon VMoff ATTmute Slew Rate Open Loop Voltage Gain Closed Loop Voltage Gain Total Input Noise Frequency Response (-3dB) Input Resistance Supply Voltage Rejection Thermal Shutdown f = 100Hz; Vripple = 0.5Vrms A = curve f = 20Hz to 20kHz PO = 1W 100 60 75 145 24 7 60 60 60 70 70 70 100 100 100 0.005 0.1 0.01 0.1 10 80 30 1 2 40 5 Test Condition Min. 10 20 30 Typ. Max. 40 60 500 +10 +100 Unit V mA nA mV nA W W W W W W % % % % V/s dB dB V V k dB C 1.5 3.5 70 90 1 3 1.5 3.5 60 80 V V dB mA V V dB
Music Power (RMS) IEC268.3 RULES - t = 1s (*)
d
Total Harmonic Distortion (**)
20Hz to 20kHz
STAND-BY FUNCTION (Ref: -VS or GND) Stand-by on Threshold Stand-by off Threshold Stand-by Attenuation Quiescent Current @ Stand-by Mute on Threshold Mute off Threshold Mute AttenuatIon
MUTE FUNCTION (Ref: -VS or GND)
Note (*): MUSIC POWER CONCEPT MUSIC POWER is the maximal power which the amplifier is capable of producing across the rated load resistance (regardless of non linearity) 1 sec after the application of a sinusoidal input signal of frequency 1KHz. Note (**): Tested with optimized Application Board (see fig. 2) Note (***): Limited by the max. allowable current.
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TDA7294
Figure 2: P.C.B. and components layout of the circuit of figure 1. (1:1 scale)
Note: The Stand-by and Mute functions can be referred either to GND or -VS. On the P.C.B. is possible to set both the configuration through the jumper J1.
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TDA7294
APPLICATION SUGGESTIONS (see Test and Application Circuits of the Fig. 1) The recommended values of the external components are those shown on the application circuit of Figure 1. Different values can be used; the following table can help the designer.
COMPONENTS R1 (*) R2 R3 (*) R4 SUGGESTED VALUE 22k 680 22k 22k PURPOSE INPUT RESISTANCE LARGER THAN SUGGESTED INCREASE INPUT IMPRDANCE SMALLER THAN SUGGESTED DECREASE INPUT IMPEDANCE
CLOSED LOOP GAIN DECREASE OF GAIN INCREASE OF GAIN SET TO 30dB (**) INCREASE OF GAIN DECREASE OF GAIN ST-BY TIME CONSTANT MUTE TIME CONSTANT INPUT DC DECOUPLING FEEDBACK DC DECOUPLING MUTE TIME CONSTANT ST-BY TIME CONSTANT BOOTSTRAPPING LARGER MUTE ON/OFF TIME LARGER ST-BY ON/OFF TIME LARGER ST-BY ON/OFF TIME LARGER MUTE ON/OFF TIME SMALLER ST-BY ON/OFF TIME; POP NOISE SMALLER MUTE ON/OFF TIME HIGHER LOW FREQUENCY CUTOFF HIGHER LOW FREQUENCY CUTOFF SMALLER MUTE ON/OFF TIME SMALLER ST-BY ON/OFF TIME; POP NOISE SIGNAL DEGRADATION AT LOW FREQUENCY DANGER OF OSCILLATION DANGER OF OSCILLATION
R5 C1
10k 0.47F
C2
22F
C3 C4
10F 10F
C5
22F
C6, C8 C7, C9
1000F 0.1F
SUPPLY VOLTAGE BYPASS SUPPLY VOLTAGE BYPASS
(*) R1 = R3 FOR POP OPTIMIZATION (**) CLOSED LOOP GAIN HAS TO BE 24dB
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TDA7294
TYPICAL CHARACTERISTICS (Application Circuit of fig 1 unless otherwise specified) Figure 3: Output Power vs. Supply Voltage. Figure 4: Distortion vs. Output Power
Figure 5: Output Power vs. Supply Voltage
Figure 6: Distortion vs. Output Power
Figure 7: Distortion vs. Frequency
Figure 8: Distortion vs. Frequency
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TDA7294
TYPICAL CHARACTERISTICS (continued) Figure 9: Quiescent Current vs. Supply Voltage Figure 10: SupplyVoltage Rejection vs. Frequency
Figure 11: Mute Attenuation vs. Vpin10
Figure 12: St-by Attenuation vs. Vpin9
Figure 13: Power Dissipation vs. Output Power
Figure 14: Power Dissipation vs. Output Power
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TDA7294
INTRODUCTION In consumer electronics, an increasing demand has arisen for very high power monolithic audio amplifiers able to match, with a low cost the performance obtained from the best discrete designs. The task of realizing this linear integrated circuit in conventional bipolar technology is made extremely difficult by the occurence of 2nd breakdown phenomenon. It limits the safe operating area (SOA) of the power devices, and as a consequence, the maximum attainable output power, especially in presence of highly reactive loads. Moreover, full exploitation of the SOA translates into a substantial increase in circuit and layout complexity due to the need for sophisticated protection circuits. To overcome these substantial drawbacks, the use of power MOS devices, which are immune from secondary breakdown is highly desirable. The device described has therefore been developed in a mixed bipolar-MOS high voltage technology called BCD 100. 1) Output Stage The main design task one is confronted with while developing an integrated circuit as a power operational amplifier, independently of the technology used, is that of realizing the output stage. The solution shown as a principle shematic by Fig 15 represents the DMOS unity-gain output buffer of the TDA7294. This large-signal, high-power buffer must be capable of handling extremely high current and voltage levels while maintaining acceptably low harmonic distortion and good behaviour over frequency response; moreover, an accurate control of quiescent current is required. A local linearizing feedback, provided by differential amplifier A, is used to fullfil the above requirements, allowing a simple and effective quiescent current setting. Proper biasing of the power output transistors alone is however not enough to guarantee the absence of crossover distortion. While a linearization of the DC transfer characteristic of the stage is obtained, the dynamic behaviour of the system must be taken into account. A significant aid in keeping the distortion contributed by the final stage as low as possible is provided by the compensation scheme, which exploits the direct connection of the Miller capacitor at the amplifier's output to introduce a local AC feedback path enclosing the output stage itself. 2) Protections In designing a power IC, particular attention must be reserved to the circuits devoted to protection of the device from short circuit or overload conditions. Due to the absence of the 2nd breakdown phenomenon, the SOA of the power DMOS transistors is delimited only by a maximum dissipation curve dependent on the duration of the applied stimulus. In order to fully exploit the capabilities of the power transistors, the protection scheme implemented in this device combines a conventional SOA protection circuit with a novel local temperature sensing technique which " dynamically" controls the maximum dissipation.
Figure 15: Principle Schematic of a DMOS unity-gain buffer.
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TDA7294
Figure 16: Turn ON/OFF Suggested Sequence
+Vs (V) +35
-35
-Vs VIN (mV)
VST-BY PIN #9 (V)
5V
VMUTE PIN #10 (V)
5V
IP (mA)
VOUT (V)
OFF ST-BY PLAY MUTE MUTE
D93AU013
ST-BY
OFF
In addition to the overload protection described above, the device features a thermal shutdown circuit which initially puts the device into a muting state (@ Tj = 145 oC) and then into stand-by (@ Figure 17: Single Signal ST-BY/MUTE Control Circuit
Tj = 150 oC). Full protection against electrostatic discharges on every pin is included. 3) Other Features The device is provided with both stand-by and mute functions, independently driven by two CMOS logic compatible input pins. The circuits dedicated to the switching on and off of the amplifier have been carefully optimized to avoid any kind of uncontrolled audible transient at the output. The sequence that we recommend during the ON/OFF transients is shown by Figure 16. The application of figure 17 shows the possibility of using only one command for both st-by and mute functions. On both the pins, the maximum applicable range corresponds to the operating supply voltage.
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MUTE MUTE/ ST-BY
20K 10K 30K
STBY
1N4148
10F
10F
D93AU014
TDA7294
APPLICATION INFORMATION HIGH-EFFICIENCY Constraints of implementing high power solutions are the power dissipation and the size of the power supply. These are both due to the low efficiency of conventional AB class amplifier approaches. Here below (figure 18) is described a circuit proposal for a high efficiency amplifier which can be adopted for both HI-FI and CAR-RADIO applications. The TDA7294 is a monolithic MOS power amplifier which can be operated at 80V supply voltage (100V with no signal applied) while delivering output currents up to 10 A. This allows the use of this device as a very high power amplifier (up to 180W as peak power with T.H.D.=10 % and Rl = 4 Ohm); the only drawback is the power dissipation, hardly manageable in the above power range. Figure 20 shows the power dissipation versus output power curve for a class AB amplifier, compared with a high efficiency one. In order to dimension the heatsink (and the power supply), a generally used average output power value is one tenth of the maximum output power at T.H.D.=10 %. Figure 18: High Efficiency Application Circuit From fig. 20, where the maximum power is around 200 W, we get an average of 20 W, in this condition, for a class AB amplifier the average power dissipation is equal to 65 W. The typical junction-to-case thermal resistance of the TDA7294 is 1 oC/W (max= 1.5 oC/W). To avoid that, in worst case conditions, the chip temperature exceedes 150 oC, the thermal resistance of the heatsink must be 0.038 oC/W (@ max ambient temperature of 50 oC). As the above value is pratically unreachable; a high efficiency system is needed in those cases where the continuous RMS output power is higher than 50-60 W. The TDA7294 was designed to work also in higher efficiency way. For this reason there are four power supply pins: two intended for the signal part and two for the power part. T1 and T2 are two power transistors that only operate when the output power reaches a certain threshold (e.g. 20 W). If the output power increases, these transistors are switched on during the portion of the signal where more output voltage swing is needed, thus "bootstrapping" the power supply pins (#13 and #15). The current generators formed by T4, T7, zener
+40V T1 BDX53A +20V D1 BYW98100 270 L1 1H C11 330nF C1 1000F C3 100nF C5 1000F C7 100nF C9 330nF R1 2 GND PLAY ST-BY R2 2 C10 330nF D5 1N4148 IN R16 13K 4 C13 10F 9 R13 20K R14 30K R15 10K 10 C14 10F 8 15 6 1 3 7 13 2
T3 BC394
R4 270 T4 BC393
R5 270 T5 BC393 R6 20K
D3 1N4148 Z1 3.9V R3 680 R16 13K C11 22F
L3 5H
R7 3.3K
C16 1.8nF OUT
TDA7294
14 C15 22F 270 R8 3.3K Z2 3.9V
C17 1.8nF
C2 1000F
C4 100nF
C6 1000F
C8 100nF
L2 1H
D4 1N4148 T7 BC394 R9 270 R10 270 T8 BC394 R11 29K
D2 BYW98100 -20V
270 T2 BDX54A
T6 BC393
-40V
D93AU016
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TDA7294
Figure 19: P.C.B. and Components Layout of the Circuit of figure 18 (1:1 scale)
diodes Z1,Z2 and resistors R7,R8 define the minimum drop across the power MOS transistors of the TDA7294. L1, L2, L3 and the snubbers C9, R1 and C10, R2 stabilize the loops formed by the "bootstrap" circuits and the output stage of the TDA7294. In figures 21,22 the performances of the system in terms of distortion and output power at various frequencies (measured on PCB shown in fig. 19) are displayed. The output power that the TDA7294 in highef ficien cy application is able to supply at Vs = +40V/+20V/-20V/ -40V; f =1 KHz is: - Pout = 150 W @ T.H.D.=10 % with Rl= 4 Ohm - Pout = 120 W @ " = 1% " " " - Pout = 100 W @ " =10 % with Rl= 8 Ohm - Pout = 80 W @ " = 1% " " "
Results from efficiency measurements (4 and 8 Ohm loads, Vs = 40V) are shown by figures 23 and 24. We have 3 curves: total power dissipation, power dissipation of the TDA7294 and power dissipation of the darlingtons. By considering again a maximum average output power (music signal) of 20W, in case of the high efficiency application, the thermal resistance value needed from the heatsink is 2.2oC/W (Vs =40 V and Rl= 4 Ohm). All components (TDA7294 and power transistors T1 and T2) can be placed on a 1.5oC/W heatsink, with the power darlingtons electrically insulated from the heatsink. Since the total power dissipation is less than that of a usual class AB amplifier, additional cost savings can be obtained while optimizing the power supply, even with a high headroom.
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TDA7294
Figure 20: Power Dissipation vs. Output Power Figure 21: Distortion vs. Output Power
HIGH-EFFICIENCY
Figure 22: Distortion vs. Output Power
Figure 23: Power Dissipation vs. Output Power
Figure 24: Power Dissipation vs. Output Power
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TDA7294
BRIDGE APPLICATION Another application suggestion is the BRIDGE configuration, where two TDA7294 are used, as shown by the schematic diagram of figure 25. In this application, the value of the load must not be lower than 8 Ohm for dissipation and current capability reasons. A suitable field of application includes HI-FI/TV subwoofers realizations. The main advantages offered by this solution are: - High power performances with limited supply voltage level. - Considerably high output power even with high load values (i.e. 16 Ohm). The characteristics shown by figures 27 and 28, measured with loads respectively 8 Ohm and 16 Ohm. With Rl= 8 Ohm, Vs = 25V the maximum output power obtainable is 150 W, while with Rl=16 Ohm, Vs = 35V the maximum Pout is 170 W.
Figure 25: Bridge Application Circuit
+Vs 0.22F 2200F 7 Vi 0.56F 22K 1 4 ST-BY/MUTE 20K 22F 1N4148 10 10K 30K 22F 3 0.56F 22K 1 4 7 13 9 15 8 6 14 22F 22K 2200F 22K -Vs 0.22F 10 3 + 2 13 6 14 22F 22K
TDA7294
9 15 8
680
TDA7294
+ -
2
680
D93AU015A
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TDA7294
Figure 26: Frequency Response of the Bridge Application Figure 27: Distortion vs. Output Power
Figure 28: Distortion vs. Output Power
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TDA7294
MULTIWATT15 PACKAGE MECHANICAL DATA (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
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TDA7294
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) 1996 SGS-THOMSON Microelectronics All Rights Reserved 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.
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