Download: TDA7294 100V - 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY

TDA7294

100V - 100W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY VERY HIGH OPERATING VOLTAGE RANGE (±40V) MULTIPOWER BCD TECHNOLOGY DMOS POWER STAGE HIGH OUTPUT POWER (UP TO 100W MU- SIC POWER) MUTING/STAND-BY FUNCTIONS NO SWITCH ON/OFF NOISE NO BOUCHEROT CELLS VERY LOW DISTORTION Multiwatt15 VERY LOW NOISE ORDERING NUMBER: TDA7294V SHORT CIRCUIT PROTECTION THERMAL SHUTDOWN to the high out current capability it is able to sup- DESCRIPTION ply the highest power into both 4Ω and 8Ω loads even in presence of poor supply regulation, with The TDA7294 is a monolithic integrated circuit in high Supply Voltage Rejection. Multiwatt15 package, intended for use as audio class AB amplifier in Hi-Fi field applications The built in muting function with turn on delay (Home Stereo, self powered loudspeakers, Top- simplifies the remote operation avoiding switching class TV). Thanks to the wide voltage range and on-off noises. Figure 1: Typical Application and Test Circuit C7 100nF +Vs C6 1000µF R3 22K +Vs +PWVs C2 µ R2 22 F TDA7294 7 13680Ω IN- 2 - 14 OUT C1 470nF IN+ 3 + C5 R1 22K 22µF IN+MUTE 4 BOOTSTRAP R5 10K MUTE 10 VM MUTE STBY 9 THERMAL S/C VSTBY STBY SHUTDOWN PROTECTION R4 22K1815 STBY-GND -Vs -PWVs C3 10µF C4 10µF C9 100nF C8 1000µF D93AU011 -Vs February 1996 1/16,

PIN CONNECTION (Top view)

TAB connected to -VS

BLOCK DIAGRAM ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit VS Supply Voltage (No Signal) ±50 V IO Output Peak Current 10 A Ptot Power Dissipation Tcase = 70°C 50 W Top Operating Ambient Temperature Range 0 to 70 °C Tstg, Tj Storage and Junction Temperature 150 °C 2/16,

THERMAL DATA

Symbol Description Value Unit Rth j-case Thermal Resistance Junction-case Max 1.5 °C/W

ELECTRICAL CHARACTERISTICS (Refer to the Test Circuit VS = ±35V, RL = 8Ω, GV = 30dB; Rg = 50 Ω; Tamb = 25°C, f = 1 kHz; unless otherwise specified.

Symbol Parameter Test Condition Min. Typ. Max. Unit VS Supply Range ±10 ±40 V Iq Quiescent Current 20 30 60 mA Ib Input Bias Current 500 nA VOS Input Offset Voltage +10 mV IOS Input Offset Current +100 nA PO RMS Continuous Output Power d = 0.5%: VS = ± 35V, RL = 8Ω 60 70 W VS = ± 31V, RL = 6Ω 60 70 W VS = ± 27V, RL = 4Ω 60 70 W Music Power (RMS) d = 10% IEC268.3 RULES - ∆t = 1s (*) RL = 8Ω ; VS = ±38V 100 W RL = 6Ω ; VS = ±33V 100 W RL = 4Ω ; VS = ±29V (***) 100WdTotal Harmonic Distortion (**) PO = 5W; f = 1kHz 0.005 % PO = 0.1 to 50W; f = 20Hz to 20kHz 0.1 % VS = ±27V, RL = 4Ω: PO = 5W; f = 1kHz 0.01 % PO = 0.1 to 50W; f = 20Hz to 20kHz 0.1 % SR Slew Rate 7 10 V/µs GV Open Loop Voltage Gain 80 dB GV Closed Loop Voltage Gain 24 30 40 dB eN Total Input Noise A = curve 1 µV f = 20Hz to 20kHz25µV fL, fH Frequency Response (-3dB) PO = 1W 20Hz to 20kHz Ri Input Resistance 100 kΩ SVR Supply Voltage Rejection f = 100Hz; Vripple = 0.5Vrms 60 75 dB TS Thermal Shutdown 145 °C STAND-BY FUNCTION (Ref: -VS or GND) VST on Stand-by on Threshold 1.5 V VST off Stand-by off Threshold 3.5 V ATTst-by Stand-by Attenuation 70 90 dB Iq st-by Quiescent Current @ Stand-by13mA MUTE FUNCTION (Ref: -VS or GND) VMon Mute on Threshold 1.5 V VMoff Mute off Threshold 3.5 V ATTmute Mute AttenuatIon 60 80 dB 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. 3/16,

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. 4/16,

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 Fig-

ure 1. Different values can be used; the following table can help the designer. COMPONENTS SUGGESTED VALUE PURPOSE LARGER THAN SMALLER THANSUGGESTED SUGGESTED R1 (*) 22k INPUT RESISTANCE INCREASE INPUT DECREASE INPUT IMPRDANCE IMPEDANCE R2 680Ω CLOSED LOOP GAIN DECREASE OF GAIN INCREASE OF GAIN SET TO 30dB (**) R3 (*) 22k INCREASE OF GAIN DECREASE OF GAIN R4 22k ST-BY TIME LARGER ST-BY SMALLER ST-BY CONSTANT ON/OFF TIME ON/OFF TIME; POP NOISE R5 10k MUTE TIME LARGER MUTE SMALLER MUTE CONSTANT ON/OFF TIME ON/OFF TIME C1 0.47µF INPUT DC HIGHER LOW DECOUPLING FREQUENCY

CUTOFF

C2 22µF FEEDBACK DC HIGHER LOW DECOUPLING FREQUENCY

CUTOFF

C3 10µF MUTE TIME LARGER MUTE SMALLER MUTE CONSTANT ON/OFF TIME ON/OFF TIME C4 10µF ST-BY TIME LARGER ST-BY SMALLER ST-BY CONSTANT ON/OFF TIME ON/OFF TIME; POP NOISE C5 22µF BOOTSTRAPPING SIGNAL DEGRADATION AT LOW FREQUENCY C6, C8 1000µF SUPPLY VOLTAGE DANGER OF BYPASS OSCILLATION C7, C9 0.1µF SUPPLY VOLTAGE DANGER OF BYPASS OSCILLATION (*) R1 = R3 FOR POP OPTIMIZATION (**) CLOSED LOOP GAIN HAS TO BE ≥ 24dB 5/16, 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 6/16, TYPICAL CHARACTERISTICS (continued) Figure 9: Quiescent Current vs. Supply Voltage Figure10: SupplyVoltage Rejection vs. Frequency Figure 11: Mute Attenuationvs. Vpin10 Figure 12: St-by Attenuationvs. Vpin9 Figure 13: Power Dissipation vs. Output Power Figure 14: PowerDissipation vs. Output Power 7/16, INTRODUCTION monic distortion and good behaviour over fre- quency response; moreover, an accurate control In consumer electronics, an increasing demand of quiescent current is required. has arisen for very high power monolithic audio amplifiers able to match, with a low cost the per- A local linearizing feedback, provided by differen- formance obtained from the best discrete de- tial amplifier A, is used to fullfil the above require- signs. ments, allowing a simple and effective quiescent current setting. The task of realizing this linear integrated circuit in conventional bipolar technology is made ex- Proper biasing of the power output transistors tremely difficult by the occurence of 2nd break- alone is however not enough to guarantee the ab- down phenomenon. It limits the safe operating sence of crossover distortion. area (SOA) of the power devices, and as a con- While a linearization of the DC transfer charac- sequence, the maximum attainable output power, teristic of the stage is obtained, the dynamic be- especially in presence of highly reactive loads. haviour of the system must be taken into account. Moreover, full exploitation of the SOA translates A significant aid in keeping the distortion contrib- into a substantial increase in circuit and layout uted by the final stage as low as possible is pro- complexity due to the need for sophisticated pro- vided by the compensation scheme, which ex- tection circuits. ploits the direct connection of the Miller capacitor To overcome these substantial drawbacks, the at the amplifier’s output to introduce a local AC use of power MOS devices, which are immune feedback path enclosing the output stage itself. from secondary breakdown is highly desirable. The device described has therefore been devel- 2) Protections oped in a mixed bipolar-MOS high voltage tech- In designing a power IC, particular attention must nology called BCD 100. be reserved to the circuits devoted to protection of the device from short circuit or overload condi- 1) Output Stage tions. The main design task one is confrontedwith while Due to the absence of the 2nd breakdown phe- developing an integrated circuit as a power op- nomenon, the SOA of the power DMOS transis- erational amplifier, independently of the technol- tors is delimited only by a maximum dissipation ogy used, is that of realizing the output stage. curve dependent on the duration of the applied stimulus. The solution shown as a principle shematic by Fig 15 represents the DMOS unity-gain output buffer In order to fully exploit the capabilities of the of the TDA7294. power transistors, the protection scheme imple- mented in this device combines a conventional This large-signal, high-power buffer must be ca- SOA protection circuit with a novel local tempera- pable of handling extremely high current and volt- ture sensing technique which ” dynamically” con- age levels while maintaining acceptably low har- trols the maximum dissipation. Figure 15: Principle Schematic of a DMOS unity-gain buffer. 8/16, Figure 16: Turn ON/OFF Suggested Sequence +Vs (V) +35 -35 -Vs

VIN

(mV) VST-BY PIN #9 5V (V) VMUTE 5V PIN #10 (V)

IP

(mA)

VOUT

(V)

OFF

ST-BY PLAY ST-BY OFF MUTE MUTE D93AU013 In addition to the overload protection described Tj = 150 oC). above, the device features a thermal shutdown Full protection against electrostatic discharges on circuit which initially puts the device into a muting every pin is included. state (@ Tj = 145 oC) and then into stand-by (@ Figure 17: Single Signal ST-BY/MUTE Control 3) Other Features Circuit 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 MUTE STBY avoid any kind of uncontrolled audible transient at MUTE/ 20K the output. ST-BY The sequence that we recommend during the 10K 30K ON/OFF transients is shown by Figure 16. 10µF 10µF The application of figure 17 shows the possibility 1N4148 of using only one command for both st-by and D93AU014 mute functions. On both the pins, the maximum applicable range corresponds to the operating supply voltage. 9/16, APPLICATION INFORMATION From fig. 20, where the maximum power is HIGH-EFFICIENCY around 200 W, we get an average of 20 W, in this condition, for a class AB amplifier the average Constraints of implementing high power solutions power dissipation is equal to 65 W. are the power dissipation and the size of the power supply. These are both due to the low effi- The typical junction-to-case thermal resistance ofo o ciency of conventional AB class amplifier ap- the TDA7294 is 1 C/W (max= 1.5 C/W). To proaches. avoid that, in worst case conditions, the chip tem- perature exceedes 150 oC, the thermal resistance Here below (figure 18) is described a circuit pro- of the heatsink must be 0.038 oC/W (@ max am- posal for a high efficiency amplifier which can be bient temperature of 50 oC). adopted for both HI-FI and CAR-RADIO applica- tions. As the above value is pratically unreachable; a high efficiency system is needed in those cases The TDA7294 is a monolithic MOS power ampli- where the continuous RMS output power is higher fier which can be operated at 80V supply voltage than 50-60 W. (100V with no signal applied) while delivering out- put currents up to ±10 A. The TDA7294 was designed to work also in higher efficiency way. This allows the use of this device as a very high power amplifier (up to 180W as peak power with For this reason there are four power supply pins: T.H.D.=10 % and Rl = 4 Ohm); the only drawback two intended for the signal part and two for the is the power dissipation, hardly manageable in power part. the above power range. T1 and T2 are two power transistors that only op- Figure 20 shows the power dissipation versus erate when the output power reaches a certain output power curve for a class AB amplifier, com- threshold (e.g. 20 W). If the output power in- pared with a high efficiency one. creases, these transistors are switched on during the portion of the signal where more output volt- In order to dimension the heatsink (and the power age swing is needed, thus ”bootstrapping” the supply), a generally used average output power power supply pins (#13 and #15). value is one tenth of the maximum output power at T.H.D.=10 %. The current generators formed by T4, T7, zener Figure 18: High Efficiency Application Circuit +40V T3 BC394 T1 R4 R5 BDX53A 270 270 D1 BYW98100 T4 T5 +20V 270 BC393 BC393 L1 1µH D3 1N4148 R6 20K C11 330nF Z1 3.9V C1 C3 C5 C7 C93713IN C11 22µF 1000µF 100nF 1000µF 100nF 330nF R3 680 R16 2 R7 C16 R1 13K 3.3K 1.8nFR16 L3 5µH24TDA7294 13K PLAY C13 10µF 14 OUT

GND

9 C15 ST-BY R13 20K 22µF 6 R8 C17 R2 R14 30K 3.3K 1.8nF 2 D5 1N4148 R15 10K 1 C2 C4 C6 C8 C10 10 8 15 1000µF 100nF 1000µF 100nF 330nF Z2 3.9V C14 10µF L2 1µH D4 1N4148 T7 T8 D2 BYW98100 BC394 BC394270 -20V T2 R9 R10 R11 BDX54A T6 270 270 29K BC393 -40V D93AU016 10/16, Figure 19: P.C.B. and ComponentsLayout of the Circuit of figure 18 (1:1 scale) diodes Z1,Z2 and resistors R7,R8 define the mini- Results from efficiency measurements (4 and 8 mum drop across the power MOS transistors of Ohm loads, Vs = ±40V) are shown by figures 23 the TDA7294. L1, L2, L3 and the snubbers C9, and 24. We have 3 curves: total power dissipa- R1 and C10, R2 stabilize the loops formed by the tion, power dissipation of the TDA7294 and ”bootstrap” circuits and the output stage of the power dissipation of the darlingtons. TDA7294. By considering again a maximum average In figures 21,22 the performances of the system output power (music signal) of 20W, in case in terms of distortion and output power at various of the high efficiency application, the thermal frequencies (measured on PCB shown in fig. 19) resistance value needed from the heatsink is are displayed. 2.2oC/W (Vs =±40 V and Rl= 4 Ohm). The output power that the TDA7294 in high- All components (TDA7294 and power transistors ef ficiency application is able to supply at T1 and T2) can be placed on a 1.5oC/W heatsink, Vs = +40V/+20V/-20V/-40V; f =1 KHz is: with the power darlingtons electrically insulated - Pout = 150 W @ T.H.D.=10 % with Rl= 4 Ohm from the heatsink. - Pout = 120 W @ ” = 1 % ” ” ” Since the total power dissipation is less than that - Pout = 100 W @ ” =10 % with Rl= 8 Ohm of a usual class AB amplifier, additional cost sav- ings can be obtained while optimizing the power - Pout = 80 W @ ” = 1 % ” ” ” supply, even with a high headroom. 11/16, Figure 21: Distortion vs. Output Power Figure 20: Power Dissipation vs. Output Power HIGH-EFFICIENCY Figure 22: Distortion vs. Output Power Figure 23: PowerDissipation vs. Output Power Figure 24: Power Dissipation vs. Output Power 12/16, BRIDGE APPLICATION - High power performances with limited supply Another application suggestion is the BRIDGE voltage level. configuration, where two TDA7294 are used, as - Considerably high output power even with high shown by the schematic diagram of figure 25. load values (i.e. 16 Ohm). In this application, the value of the load must not The characteristics shown by figures 27 and 28, be lower than 8 Ohm for dissipation and current measured with loads respectively 8 Ohm and 16 capability reasons. Ohm. A suitable field of application includes HI-FI/TV With Rl= 8 Ohm, Vs = ±25V the maximum output subwoofers realizations. power obtainable is 150 W, while with Rl=16 The main advantagesoffered by this solution are: Ohm, Vs = ±35V the maximum Pout is 170 W. Figure 25: Bridge Application Circuit +Vs 0.22µF 2200µF 7 13 Vi + 14 22µF 0.56µF 22K - 22K12

TDA7294 680

ST-BY/MUTE 10 9 15 8 20K 22µF 22K -Vs 1N4148 2200µF 0.22µF 9 15 8 10K 30K 22µF TDA7294 + 14 22µF 0.56µF 22K - 22K12713 680 D93AU015A 13/16, Figure 26: Frequency Response of the Bridge Figure 27: Distortion vs. Output Power Application Figure 28: Distortion vs. Output Power 14/16,

MULTIWATT15 PACKAGE MECHANICAL DATA (Vertical)

mm inch DIM. MIN. TYP. MAX. MIN. TYP. MAX. A 5 0.197 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 1.14 1.27 1.4 0.045 0.050 0.055 G1 17.57 17.78 17.91 0.692 0.700 0.705 H1 19.6 0.772 H2 20.2 0.795 L 22.1 22.6 0.870 0.890 L1 22 22.5 0.866 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 4.2 4.3 4.6 0.165 0.169 0.181 M1 4.5 5.08 5.3 0.177 0.200 0.209 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 15/16, 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 men- tioned 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 ex- press written approval of SGS-THOMSON Microelectronics. 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. 16/16]

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