E-TDA7294V - STMicroelectronics, Inc.

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 MU-

SIC POWER)

MUTI N G/STAND-BY FUNC TION S

NO SWITCH ON/OFF NOISE

NO BOU CHER OT CELLS

VERY LOW DISTORTION

VERY LOW NOISE

SHORT CIR C U IT PROTECTION

THERMA L SHUTDOW N

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, Top-

class TV). Thanks to the wide voltage range and

to t he high out current capability it is able to sup-

ply the highest power into both 4Ω and 8Ω 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.

April 2003

IN- 2

680Ω

22µF

C1 470nF IN+

R1 22K

2.7Ω

C10

100nF

R3 22K

MUTE

STBY

VSTBY

IN+MUTE

MUTE

STBY

R4 22K

THERMAL

SHUTDOWN S/C

PROTECTION

R5 10K

C3 10µF C4 10µF

STBY-GND

22µF

713

158

-Vs -PWVs

BOOT-

STRAP

OUT

+PWVs+Vs

C9 100nF C8 1000µF

-Vs

D93AU011

+VsC7 100nF C6 1000µF

Note: The Boucherot cell R6, C10, normally not necessary for a stable operation it could

be needed in presence of particular load impedances at V

<±25V.

Figure 1: Typical Application and Test Circuit

MULTIPOWER BCD TECHNOLOGY

Multiwatt15V Multiwatt15H

ORDERING NUMBERS:

TDA7294V TDA7294HS

1/17

BLOCK DIAGRAM

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

VSSupply Voltage (No Signal) ±50 V

IOOutput Peak Current 10 A

Ptot Power Dissipation Tcase = 70°C50W

op Operating Ambient Temperature Range 0 to 70 °C

Tstg, TjStorage and Junction Temperature 150 °C

TAB connected to -VS

PIN C ONNECTION (Top view)

TDA7294

2/17

THERMAL DATA

Symbol Description Value Unit

Rth j-case Thermal Resistance Junction-case Max 1.5 °C/W

ELECTRICA L CHARACTERI STICS (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

VSSupply Range ±10 ±40 V

IqQuiescent Current 20 30 65 mA

IbInput Bias Current 500 nA

VOS Input Offset Voltage +10 mV

IOS Input Offset Current +100 nA

PORMS Continuous Output Power d = 0.5%:

VS = ± 35V, RL = 8Ω

VS = ± 31V, RL = 6Ω

VS = ± 27V, RL = 4Ω

Music Power (RMS)

IEC268.3 RULES - ∆t = 1s (*) d = 10%

RL = 8Ω ; VS = ±38V

RL = 6Ω ; VS = ±33V

RL = 4Ω ; VS = ±29V (***)

100

d Total Harmonic Distortion (**) PO = 5W; f = 1kHz

PO = 0.1 to 50W; f = 20Hz to 20kHz 0.005 0.1 %

VS = ±27V, RL = 4Ω:

PO = 5W; f = 1kHz

PO = 0.1 to 50W; f = 20Hz to 20kHz 0.01 0.1 %

SR Slew Rate 7 10 V/µs

GVOpen Loop Voltage Gain 80 dB

GVClosed Loop Voltage Gain 24 30 40 dB

eNTotal Input Noise A = curve

f = 20Hz to 20kHz 1

, fHFrequency Response (-3dB) PO = 1W 20Hz to 20kHz

RiInput Resistance 100 kΩ

SVR Supply Voltage Rejection f = 100Hz; Vripple = 0.5Vrms 60 75 dB

TSThermal 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-by 1 3 mA

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

No te (* ):

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 i nput signal of frequ ency 1KHz .

No te (* *) : Tested with optimized Application Board (see fig. 2)

No te (* **) : Limited by the max. allowable current.

TDA7294

3/17

Figure 2: P.C.B. and components layout of the circuit of figure 1. (1:1 scale)

Note:

Th e 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 jum per J1.

TDA7294

4/17

APPLICATION SUGGES TION S (see Test and Application Circuits of the Fig. 1)

The rec ommended values of the external components ar e those s hown on t he application circuit of Fig-

ure 1. Different values can be used; the following table can help the designer.

COMPONENTS SUGGESTED VALUE PURPOSE LARGER THAN

SUGGESTED SMALLER THAN

SUGGESTED

R1 (*) 22k INPUT RESISTANCE INCREASE INPUT

IMPRDANCE DECREASE INPUT

IMPEDANCE

R2 680ΩCLOSED LOOP GAIN

SET TO 30dB (**) DECREASE OF GAIN INCREASE OF GAIN

R3 (*) 22k INCREASE OF GAIN DECREASE OF GAIN

R4 22k ST-BY TIME

CONSTANT LARGER ST-BY

ON/OFF TIME SMALLER ST-BY

ON/OFF TIME;

POP NOISE

R5 10k MUTE TIME

CONSTANT LARGER MUTE

ON/OFF TIME SMALLER MUTE

ON/OFF TIME

C1 0.47µF INPUT DC

DECOUPLING HIGHER LOW

FREQUENCY

CUTOFF

C2 22µF FEEDBACK DC

DECOUPLING HIGHER LOW

FREQUENCY

CUTOFF

C3 10µF MUTE TIME

CONSTANT LARGER MUTE

ON/OFF TIME SMALLER MUTE

ON/OFF TIME

C4 10µF ST-BY TIME

CONSTANT LARGER ST-BY

ON/OFF TIME SMALLER ST-BY

ON/OFF TIME;

POP NOISE

C5 22µF BOOTSTRAPPING SIGNAL

DEGRADATION AT

LOW FREQUENCY

C6, C8 1000µF SUPPLY VOLTAGE

BYPASS DANGER OF

OSCILLATION

C7, C9 0.1µF SUPPLY VOLTAGE

BYPASS DANGER OF

OSCILLATION

(*) R1 = R3 FOR POP OPTI MIZATI O N

(**) CLOSED LOOP GAIN HAS TO BE ≥ 24dB

TDA7294

5/17

Figure 3: Output Power vs. Supply Voltage.

Figure 5: Output Power vs. Supply Voltage

Figure 4: Distortion vs. Output Power

Figure 8: Distortion vs. Frequency

TYPICAL CHARAC TERISTI CS

(Application Circuit of fig 1 unless otherwise specified)

Figure 6: Distortion vs. Output Power

Figure 7: Distortion vs. Frequency

TDA7294

6/17

Figure 14: Power Dissipation vs. Output Power

Figure 13: Power Dissipation vs. Output Power

Figure 11: Mute Attenuation vs. Vpin10 Figure 12: St-by Attenuation vs. Vpin9

Figure 10: Supply Voltage Rejection vs. Frequency

TYPICAL CHARAC TERISTI CS (continued)

Figure 9: Quiescent Current vs. Supply Voltage

TDA7294

7/17

INTRODUCTION

In consumer electronics, an increasing demand

has arisen for very high power monolithic audio

amplifiers able to match, with a low cost the per-

formance obtained from the best discrete de-

signs.

The task of realizing this linear integrated circuit

in conventional bipolar technology is made ex-

tremely difficult by the occurence of 2nd break-

down phenomenon. It limits the safe operating

area (SOA) of the power devices, and as a con-

sequence, 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 pro-

tection 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 devel-

oped in a mixed bipolar-MOS high voltage tech-

nology called BCD 100.

1) Output Stage

The main d esign task one is confronted with while

developing an integrated circuit as a power op-

erational amplifier, independently of the technol-

ogy 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 ca-

pable of handling extrem ely high current and volt-

age levels while maintaining acceptably low har-

monic distortion and good behaviour over fre-

quency response; moreover, an accurate control

of quiescent current is required.

A local linearizing feedback, provided by differen-

tial amplifier A, is used to fullf il the above require-

ments, allowing a simple and effective quiescent

current setting.

Proper biasing of the power output transistors

alone is however not eno ugh to guarantee the ab-

sence of crossover distortion.

While a linearization of the DC transfer charac-

teristic of the stage is obtained, the dynamic be-

haviour of the system must be taken into account.

A significant aid in keeping the distortion contrib-

uted by the final stage as low as possible is pro-

vided by the compensation scheme, which ex-

ploits 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 condi-

tions.

Due to the absence of the 2nd breakdown phe-

nomenon, the SOA of the power DMOS transis-

tors 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 imple-

mented in this device combines a conventional

SOA protection circuit with a novel local tempera-

ture sensing technique which " dynamically" con-

trols the maximum dissipation.

Figure 15: Principle Schematic of a DMOS unity-gain buffer.

TDA7294

8/17

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 (@

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 t o 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.

1N4148

10K 30K

20K

10µF10µF

MUTE STBY

D93AU014

MUTE/

ST-BY

Figure 17: Single Signal ST-BY/MUTE Control

Circuit

PLAY

OFF

ST-BY

MUTE MUTE

ST-BY OFF

D93AU013

+Vs

(V)

+35

-35

VMUTE

PIN #10

(V)

VST-BY

PIN #9

(V)

-Vs

VIN

(mV)

(mA)

VOUT

(V)

Figure 16: Turn ON/OFF Suggested Sequence

TDA7294

9/17

TDA7294

137

815

R3 680 C11 22µF

L3 5µH

270

R16

13K

C15

22µF

R16

13K

C13 10µF

R13 20K

C11 330nF

R15 10K

C14

10µF

R14 30K

1N4148

PLAY

ST-BY

270

L1 1µH

BDX53A

BC394

D3 1N4148

270 R5

270

BC393 T5

BC393

20K

3.3K C16

1.8nF

3.3K C17

1.8nF

Z2 3.9V

Z1 3.9V

L2 1µH

270

D4 1N4148

D2 BYW98100

330nF

C10

330nF

BDX54A T6

BC393

BC394 T8

BC394

270 R10

270 R11

29K

OUT

INC7

100nF

1000µF

100nF

1000µF

100nF

+40V

+20V D1 BYW98100

GND

-20V

-40V

D93AU016

Figure 18: High Ef ficiency Application Circuit

APPLICATION IN FOR MATION

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 effi-

ciency of conventional AB class amplifier ap-

proaches.

Here below (figure 18) is described a circuit pro-

posal for a high efficiency amplifier which can be

adopted for both HI-FI and CAR-RADIO applica-

tions.

The TDA7294 is a monolithic MOS power ampli-

fier whic h can be operated at 80V supply voltage

(100V with no signal applied) while delivering out-

put 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 f or a class AB amplifier, c om-

pared 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 %.

From fig. 20, where the maximum power is

around 200 W, we get an aver age of 20 W, in t his

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 tem-

perature exceedes 150 oC, the thermal resistance

of the heatsink must be 0.038 oC/W (@ max am-

bient 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 op-

erate when the output power reaches a certain

threshold (e.g. 20 W). If the output power in-

creases, these t ransistors are switched on during

the portion of the signal where more output volt-

age swing is needed, thus "bootstrapping" the

power supply pins (#13 and #15).

The current generators formed by T4, T7, zener

TDA7294

10/17

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 mini-

mum drop across the power MOS transistors of

the TDA7294. L1, L2, L3 and the snubbers C9,

R1 and C10, R2 stabilize the loops form ed by the

"bootstrap" circuits and the output stage of the

TDA7294.

In figures 21,22 the performances of the system

in term s of distortion and output power at various

frequencies (measured on PCB shown in fig. 19)

are displayed.

The output power that the TDA7294 in high-

efficiency 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 dissipa-

tion, 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 sav-

ings can be obtained while optimizing the power

supply, even with a high headroom.

TDA7294

11/17

Figure 21: Distortion vs. Output Power

Figure 20: Power Dissipation vs. Output Power

Figure 23: Power Dissipation vs. Output Power

Figure 22: Distortion vs. Output Power

Figure 24: Power Dissipation vs. Output Power

HIGH-EFFICIENCY

TDA7294

12/17

BRIDGE APPLICA TION

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.

22K0.56µF

2200µF0.22µF

TDA7294

22µF

22K

680

22K

137

+Vs

815

10 9

0.56µF 22K

622µF

22K

680

10 9

22µF

15 8

-Vs

2200µF0.22µF

22µF

20K

10K 30K

1N4148

ST-BY/MUTE

TDA7294

137

D93AU015A

Figure 25: Bridge Application Circuit

TDA7294

13/17

Figure 27: Distortion vs. Output Power

Figure 26: Frequency Response of the Bridge

Application

Figure 28: Distortion vs. Output Power

TDA7294

14/17

Multiwatt15 V

DIM. mm inch

MIN. TYP. MAX. MIN. TYP. MAX.

A 5 0.197

B 2.65 0.104

C 1.6 0.063

D 1 0.039

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

Dia1 3.65 3.85 0.144 0.152

OUTLINE AND

MECHANICAL DATA

TDA7294

15/17

DIM. mm inch

MIN. TYP. MAX. MIN. TYP. MAX.

A 5 0.197

B 2.65 0.104

C 1.6 0.063

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 20.57 0.810

L1 18.03 0.710

L2 2.54 0.100

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

L5 5.28 0.208

L6 2.38 0.094

L7 2.65 2.9 0.104 0.114

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

Multiwatt15 H

OUTLINE AND

MECHANICAL DATA

TDA7294

16/17

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grante d by implication or otherwis e under any patent or patent righ ts of STMi croel ectronic s. Speci fication mentioned in this publication are

subj ect to change without notic e. This public ation supers edes and rep laces all informat ion p reviousl y supplied. STMi croelec tron ics product s

are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

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TDA7294

17/17