ST MICROELECTRONICS TDA 7294V Datasheet

®

TDA7294

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

VERY HIG H OPERATI NG VOLTAGE R ANGE
(±40V)

DMOS POWER STAGE
HIGH OUTPUT POWER (UP TO 100W MU-

SIC POWER)
MUTING/STAND- BY FUNC TION S
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

Multiwatt15V Multiwatt15H

ORDERING NUMBERS:

TDA7294V TDA7294HS

to the high out current c apability it is able to sup­ply 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.

+VsC7 100nF C6 1000µF

VM

VSTBY

April 2003

R3 22K

C2

R2

22µF

680Ω

C1 470nF

R1 22K

R5 10K

R4 22K

C3 10µF C4 10µF

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

IN- 2

IN+

IN+MUTE

MUTE

STBY

3

4

10
9

MUTE

STBY

1
STBY-GND

713

-

+

THERMAL

SHUTDOWN

-Vs -PWVs

C9 100nF C8 1000µF

<±25V.

S

+PWVs+Vs

PROTECTION

158

-Vs

S/C

14

OUT

C5

22µF

6

BOOT­STRAP

D93AU011

R6

2.7Ω
C10

100nF

1/17

TDA7294

PIN CONNECTION (Top view)

TAB connected to -V

BLOCK DIAGRAM

S

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

I

O

P

tot

T

op

T

stg

Supply Voltage (No Signal)

S

Output Peak Current 10 A
Power Dissipation T

= 70°C50W

case

Operating Ambient Temperature Range 0 to 70

, TjStorage and Junction Temperature 150

2/17

50 V

±

C

°

C

°

TDA7294

THERMAL DATA

Symbol Description Value Unit

R

th j-case

Thermal Resistance Junction-case Max 1.5

C/W

°

ELECTRICAL CHARACTERISTICS (Refer to the Test Circuit V

= 50 Ω; T

R

g

= 25°C, f = 1 kHz; unless otherwise specified.

amb

= ±35V, RL = 8Ω, GV = 30dB;

S

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

I
I

V

I

OS

P

Supply Range

S

Quiescent Current 20 30 65 mA

q

Input Bias Current 500 nA

b

Input Offset Voltage +10 mV

OS

Input Offset Current +100 nA
RMS Continuous Output Power d = 0.5%:

O

Music Power (RMS)
IEC268.3 RULES - ∆t = 1s (*)

d Total Harmonic Distortion (**) P

V

= ± 35V, RL = 8

S

V

= ± 31V, RL = 6

S

V

= ± 27V, RL = 4

S

Ω
Ω
Ω

d = 10%
R

= 8Ω ; VS = ±38V

L

R

= 6Ω ; VS = ±33V

L

R

= 4Ω ; VS = ±29V (***)

L

= 5W; f = 1kHz

O

P

= 0.1 to 50W; f = 20Hz to 20kHz

O

= ±27V, RL = 4

V

S

P

= 5W; f = 1kHz

O

P

= 0.1 to 50W; f = 20Hz to 20kHz

O

Ω:

10

±

60
60
60

70
70
70

100
100
100

0.005

0.01

40 V

±

0.1

0.1

W
W
W

W
W
W

%
%

%
%

SR Slew Rate 7 10 V/µs

G
G
e

, f

f

L

R

SVR Supply Voltage Rejection f = 100Hz; V

T

STAND-BY FUNCTION (Ref: -V

V

ST on

V

ST off

ATT

I

q st-by

MUTE FUNCTION (Ref: -V

V

Mon

V

Moff

ATT

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 (**):
Note (***):

Open Loop Voltage Gain 80 dB

V

Closed Loop Voltage Gain 24 30 40 dB

V

Total Input Noise A = curve

N

f = 20Hz to 20kHz

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

H

Input Resistance 100 k

i

= 0.5Vrms 60 75 dB

ripple

Thermal Shutdown 145

S

or GND)

S

1
25

Stand-by on Threshold 1.5 V
Stand-by off Threshold 3.5 V
Stand-by Attenuation 70 90 dB

st-by

Quiescent Current @ Stand-by 1 3 mA

or GND)

S

Mute on Threshold 1.5 V
Mute off Threshold 3.5 V
Mute AttenuatIon 60 80 dB

mute

Tested with optimized Application Board (see fig. 2)

Limited by the max. allowable current.

V

µ

V

µ

Ω

C

°

3/17

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.

4/17

TDA7294

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

The recommended values of t he external components are t hose shown on t he application circuit o f Fig­ure 1. Different values can be used; the following table can help the designer.

COMPONENTS SUGGESTED VALUE PURPOSE

R1 (*) 22k INPUT RESISTANCE INCREASE INPUT

R2 680

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

R4 22k ST-BY TIME

R5 10k MUTE TIME

C1 0.47µF INPUT DC

C2 22µF FEEDBACK DC

C3 10µF MUTE TIME

C4 10µF ST-BY TIME

Ω

CLOSED LOOP GAIN

SET TO 30dB (**)

CONSTANT

CONSTANT

DECOUPLING

DECOUPLING

CONSTANT

CONSTANT

LARGER THAN

SUGGESTED

IMPRDANCE

DECREASE OF GAIN INCREASE OF GAIN

LARGER ST-BY

ON/OFF TIME

LARGER MUTE

ON/OFF TIME

LARGER MUTE

ON/OFF TIME

LARGER ST-BY

ON/OFF TIME

SMALLER THAN

SUGGESTED

DECREASE INPUT

IMPEDANCE

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

C5 22µF BOOTSTRAPPING SIGNAL

C6, C8 1000µF SUPPLY VOLTAGE

C7, C9 0.1µF SUPPLY VOLTAGE

(*) R1 = R3 FOR POP OPTIMIZATION
(**) CLOSED LOOP GAIN HAS TO BE ≥ 24dB

BYPASS

BYPASS

DEGRADATION AT
LOW FREQUENCY

DANGER OF

OSCILLATION

DANGER OF

OSCILLATION

5/17

TDA7294

TYPICAL CHARACTERISTICS

(Application Circuit of fig 1 unless otherwise specified)

Figure 3: Output Power vs. Supply Voltage.

Figure 5: Output Power vs. Supply Voltage

Figure 4: Distortion vs. Output Power

Figure 6: Distortion vs. Output Power

Figure 7: Distortion vs. Frequency

6/17

Figure 8: Distortion vs. Frequency

TYPICAL CHARACTERISTICS (continued)

TDA7294

Figure 9: Quiescent Current vs. Supply Voltage

Figure 11: Mute Attenuation vs. V

pin10

Figure 10: Supply Voltage Rejection vs. Frequency

Figure 12: St-by Attenuation vs. V

pin9

Figure 13: Power Dissipation vs. Output Power

Figure 14: Power Dissipation vs. Output Power

7/17

TDA7294

INTRODUCTION

In consumer electronics, an increasing demand
has arisen for very high power monolithic audio
amplifiers able to match, with a low cost th e 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

monic 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.
from secondary breakdown is highly desirable.
The device described has therefore been devel-

oped in a mixed bipolar-MOS high voltage tech­nology called BCD 100.

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-

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 har-

tions.

Due to the absence of the 2nd breakdown phe-

nomenon, the SOA of the power DMOS tr ansis-

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.

8/17

Figure 16: Turn ON/OFF Suggested Sequence

+Vs

(V)

+35

-35

-Vs

V

IN

(mV)

V

ST-BY

PIN #9

(V)

5V

TDA7294

V

MUTE

PIN #10

(V)

I

P

(mA)

V

OUT
(V)

5V

OFF

ST-BY

PLAY

MUTE MUTE

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

o

C) and then into stand-by (@

Figure 17: Single Signal ST-BY/MUTE Control

Circuit

MUTE STBY

MUTE/

ST-BY

20K

10K 30K

1N4148

10µF10µF

D93AU014

ST-BY OFF

D93AU013

Tj = 150

o

C).

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.

9/17

TDA7294

APPLICATION IN FOR MATION

HIGH-EFFI CI ENC Y
Constraints of implementing high power s olutions

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 oper ated 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 c lass 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 %.

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

avoid that, in worst case conditions, the chip tem-

perature exceedes 150

of the heatsink must be 0.038

o

C/W (max= 1.5 oC/W). To

o

C, the thermal resistance

o

C/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 transistors 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

Figure 18: High Efficiency Application Circuit

+40V

+20V

C9

330nF

R1

2

PLAY

ST-BY

R2

2

C10

C8

330nF

1N4148

GND

-20V

-40V

C1

1000µF

C2

1000µF

C3

100nF

C4

100nF

C5

1000µF

C6

1000µF

100nF

100nF

INC7

D5

D1 BYW98100

C11 330nF

R16
13K

C13 10µF

R13 20K

R14 30K

R15 10K

C14

10µF

D2 BYW98100

3

4

TDA7294

9

815

10

T3

BC394

T1

BDX53A

270

L1 1µH

137

14

L2 1µH

270

BDX54A

2

6

1

D3 1N4148

R3 680

R16

13K

C15

22µF

D4 1N4148

T2

T6

BC393

C11 22µF

L3 5µH

270

R4

270

T4

BC393

Z1 3.9V

Z2 3.9V

T7

BC394

R9

270

R7

3.3K

R8

3.3K

R5

270

R6

20K

R10
270

D93AU016

T5

BC393

C16

1.8nF

OUT

C17

1.8nF

T8

BC394

R11

29K

10/17

Figure 19: P.C.B. and Components Layout of the Circuit of figure 18 (1:1 scale)

TDA7294

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 out put powe r that the TDA729 4 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 th e high eff iciency a pplication , the the rmal

resistance value needed from the heatsink is

o

C/W (Vs =±40 V and Rl= 4 Ohm).

2.2

All components (TDA7294 and power transistors

T1 and T2) can be placed on a 1.5

o

C/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.

11/17

TDA7294

Figure 20: Power Dissipation vs. Output Power

HIGH-EFFICI ENCY

Figure 22: Distortion vs. Output Power

Figure 21: Distortion vs. Output Power

Figure 23: Power Dissipation vs. Output Power

Figure 24: Power Dissipation vs. Output Power

12/17

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:

Figure 25: Bridge Application Circuit

+Vs

2200µF0.22µF

Vi

22K0.56µF

ST-BY/MUTE

20K

3

1
4

10

- 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.

137

6

+

-

TDA7294

9

815

14

22µF

2

22K

680

22µF

1N4148

10K 30K

0.56µF 22K

22µF

9

10

TDA7294

3

1
4

15 8

+

-

137

2200µF

6

14

2

22K

-Vs

0.22µF

22µF

22K

680

D93AU015A

13/17

TDA7294

Figure 26: Frequency Response of the Bridge

Application

Figure 28: Distortion vs. Output Power

Figure 27: Distortion vs. Output Power

14/17

TDA7294

DIM.

Dia1 3.65 3.85 0.144 0.152

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

mm inch

OUTLINE AND

MECHANICAL DATA

Multiwatt15 V

15/17

TDA7294

DIM.

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

mm inch

OUTLINE AND

MECHANICAL DATA

Multiwatt15 H

16/17

TDA7294

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granted by impli cation or otherwis e under any patent or patent righ ts of STMicroelect ronics. Specifica tion mentioned in this publication are
subject to change without notic e. This public ation supers edes and replaces all information prev iously supplied. STMic roelec tronic s products
are not authorized for use as critical components in life support devices or systems without express written approval of STMicroelectronics.

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17/17