SGS Thomson Microelectronics TDA7294V, TDA7294 Datasheet

TDA7294

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

VERY HIGH OPERATING VOLTAGE RANGE
(±40V)

DMOSPOWERSTAGE
HIGH OUTPUT POWER (UP TO 100W MU-

SIC POWER)
MUTING/STAND-BYFUNCTIONS
NOSWITCH ON/OFF NOISE
NOBOUCHEROTCELLS
VERYLOW DISTORTION
VERYLOW NOISE
SHORTCIRCUIT PROTECTION
THERMALSHUTDOWN

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

Figure1: TypicalApplication and TestCircuit

MULTIPOWERBCD TECHNOLOGY

Multiwatt15

ORDERING NUMBER: TDA7294V

to the high out current capability it is able to sup­ply the highest power into both 4Ω and 8Ω loads
even in presence of poor supply regulation, with
high SupplyVoltage Rejection.

The built in muting function with turn on delay
simplifies the remoteoperation avoiding switching
on-off noises.

+VsC7 100nF C6 1000µF

VM

VSTBY

February 1996

R3 22K

C2

R2

22µF

680Ω

C1 470nF

R1 22K

R5 10K

R4 22K

C3 10µFC410µF

IN- 2

IN+

IN+MUTE

MUTE

STBY

3

4

10
9

TDA7294

MUTE

STBY

1
STBY-GND

+PWVs+Vs

713

-

+

THERMAL

SHUTDOWN

-Vs -PWVs

C9 100nF C8 1000µF

-Vs

S/C

PROTECTION

158

14

6

OUT

C5

22µF

BOOTSTRAP

D93AU011

1/16

TDA7294

PIN CONNECTION (Topview)

TAB connected to -V

BLOCKDIAGRAM

S

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

I

O

P

tot

T

op

T

stg,Tj

2/16

Supply Voltage (No Signal) ±50 V

S

Output Peak Current 10 A
Power Dissipation T

=70°C50W

case

Operating Ambient Temperature Range 0 to 70 °C
Storage and Junction Temperature 150 °C

TDA7294

THERMALDATA

Symbol Description Value Unit

R

th j-case

ELECTRICALCHARACTERISTICS (Refer to the TestCircuit VS= ±35V, RL=8Ω,GV= 30dB;

=50Ω;T

R

g

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

S

I

q

I

b

V

OS

I

OS

P

O

d Total Harmonic Distortion (**) P

SR Slew Rate 7 10 V/µs

G

V

G

V

e

N

f

L,fH

R

i

SVR Supply Voltage Rejection f = 100Hz; V

T

S

STAND-BY FUNCTION (Ref: -V

V

ST on

V

ST off

ATT

st-by

I

q st-by

MUTE FUNCTION (Ref: -V

V

Mon

V

Moff

ATT

mute

Note (*):

MUSIC POWER CONCEPT
MUSIC POWER is the maximal power which the amplifier is capable ofproducingacross the ratedload resistance (regardless of non linearity)
1 sec afterthe application of a sinusoidal input signalof frequency 1KHz.

Note (**): Tested with optimized Application Board (see fig. 2)
Note (***): Limited by themax. allowable current.

Thermal Resistance Junction-case Max 1.5 °C/W

=25°C,f = 1 kHz; unlessotherwisespecified.

amb

Supply Range ±10 ±40 V
Quiescent Current 20 30 60 mA
Input Bias Current 500 nA
Input OffsetVoltage +10 mV
Input OffsetCurrent +100 nA
RMS Continuous OutputPower d = 0.5%:

V

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

= ± 35V, RL=8Ω

S

V

=±31V, RL=6Ω

S

V

=±27V, RL=4Ω

S

d = 10%
R

=8Ω ;VS=±38V

L

R

=6Ω ;VS=±33V

L

R

=4Ω ;VS=±29V (***)

L

= 5W; f = 1kHz

O

P

=0.1to50W;f=20Hzto20kHz

O

= ±27V, RL=4Ω:

V

S

P

= 5W; f = 1kHz

O

P

=0.1to50W;f=20Hzto20kHz

O

60
60
60

70
70
70

100
100
100

0.005

0.01

0.1

0.1

W
W
W

W
W
W

%
%

%
%

Open Loop Voltage Gain 80 dB
Closed Loop Voltage Gain 24 30 40 dB
Total Input Noise A = curve

f = 20Hz to 20kHz

1
25

µV
µV

Frequency Response (-3dB) PO= 1W 20Hz to 20kHz
Input Resistance 100 kΩ

= 0.5Vrms 60 75 dB

ripple

Thermal Shutdown 145 °C

or GND)

S

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

3/16

TDA7294

Figure2: P.C.B.and components layoutof 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 possibleto set both the configuration through the jumper J1.

4/16

TDA7294

APPLICATION SUGGESTIONS(see Test and ApplicationCircuits of the Fig. 1)

The recommendedvalues of the external components are those shown on the applicationcircuit of Fig­ure 1. Differentvaluescan be used;the followingtable can helpthe designer.

COMPONENTS SUGGESTED VALUE PURPOSE

R1 (*) 22k INPUT RESISTANCE INCREASE INPUT

R2 680Ω CLOSED LOOP GAIN

SET TO 30dB (**)

R3 (*) 22k INCREASE OF GAIN DECREASE OFGAIN

R4 22k ST-BY TIME

CONSTANT

R5 10k MUTE TIME

CONSTANT

C1 0.47µF INPUT DC

DECOUPLING

C2 22µF FEEDBACK DC

DECOUPLING

C3 10µF MUTE TIME

CONSTANT

C4 10µF ST-BY TIME

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 GAINHAS TO BE ≥ 24dB

BYPASS

BYPASS

DEGRADATION AT
LOW FREQUENCY

DANGER OF

OSCILLATION

DANGER OF

OSCILLATION

5/16

TDA7294

TYPICALCHARACTERISTICS

(ApplicationCircuit of fig 1 unless otherwisespecified)

Figure3: OutputPower vs. SupplyVoltage.

Figure5: OutputPower vs. SupplyVoltage

Figure 4: Distortion vs. Output Power

Figure 6: Distortion vs. Output Power

Figure7: Distortionvs. Frequency

6/16

Figure 8: Distortion vs. Frequency

TYPICALCHARACTERISTICS (continued)

TDA7294

Figure9: QuiescentCurrentvs. Supply Voltage

Figure11: Mute Attenuationvs. V

pin10

Figure10:SupplyVoltage Rejectionvs.Frequency

Figure 12: St-byAttenuationvs. V

pin9

Figure13: PowerDissipationvs. OutputPower

Figure 14: PowerDissipation vs. OutputPower

7/16

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 attainableoutput power,
especiallyin presence of highlyreactive 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 quiescentcurrent 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 crossoverdistortion.

While a linearization of the DC transfer charac­teristic of the stage is obtained, the dynamic be­haviour of thesystemmust 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

feedbackpath 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 tech­nologycalled BCD100.

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

Themain design taskone is confrontedwith while
developing an integrated circuit as a power op­erational amplifier, independently of the technol­ogyused, is that of realizing theoutput stage.

Thesolution shown as a principleshematicby 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 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.
Figure15: PrincipleSchematicof a DMOSunity-gain buffer.

8/16

Figure16: Turn ON/OFF SuggestedSequence

+Vs

(V)

+35

-35

-Vs

VIN

(mV)

V

ST-BY

PIN #9

(V)

5V

TDA7294

V

MUTE

PIN #10

(V)

IP

(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
circuitwhich initially puts the device into a muting
state (@ Tj = 145

o

C) and then into stand-by (@

Figure17: SingleSignal ST-BY/MUTEControl

Circuit

MUTE STBY

MUTE/

ST-BY

20K

10K 30K

1N4148

10µF10µF

D93AU014

ST-BY OFF

D93AU013

o

Tj =150

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

CMOSlogic compatibleinput pins.

The circuits dedicated to the switchingon 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.

9/16

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, com­paredwith a high efficiencyone.

In orderto 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 equalto 65 W.

The typical junction-to-case thermal resistance of

the TDA7294 is 1

avoid that, in worst caseconditions, the chip tem-

perature exceedes 150

of the heatsink must be 0.038

bient temperatureof 50

o

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

o

C, the thermal resistance

o

o

C).

C/W (@ max am-

As the above value is pratically unreachable; a

high efficiency system is needed in those cases

where the continuousRMS output poweris 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 supplypins (#13 and #15).

The current generators formed by T4, T7, zener

Figure18: High Efficiency ApplicationCircuit

+40V

+20V

C9

C7

100nF

C8

100nF

330nF

C10

330nF

R1

R2

2

PLAY

ST-BY

2

1N4148

GND

-20V

-40V

C1

1000µF

C2

1000µF

C3

100nF

C4

100nF

C5

1000µF

C6

1000µF

IN

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

2

6

1

270

T2

BDX54A

D3 1N4148

R3 680

R16
13K

C15

22µF

D4 1N4148

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

D93AU016

R5

270

R6

20K

R10

270

T5

BC393

C16

1.8nF

OUT

C17

1.8nF

T8

BC394

R11
29K

10/16

Figure19: P.C.B.and ComponentsLayout of the Circuit of figure 18 (1:1 scale)

TDA7294

diodesZ1,Z2 and resistorsR7,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 outputpower that the TDA7294 in high­efficiency 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

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.

11/16

TDA7294

Figure20: PowerDissipationvs. OutputPower

HIGH-EFFICIENCY

Figure22: Distortionvs. Output Power

Figure 21: Distortionvs. Output Power

Figure 23: PowerDissipation vs. OutputPower

Figure24: PowerDissipationvs. OutputPower

12/16

TDA7294

BRIDGEAPPLICATION

Another application suggestion is the BRIDGE
configuration, where two TDA7294 are used, as
shownby the schematicdiagram 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
subwoofersrealizations.

Themain advantagesoffered by this solutionare:

Figure25: BridgeApplicationCircuit

+Vs

2200µF0.22µF

Vi

22K0.56µF

ST-BY/MUTE

20K

3

1
4

10

- High powerperformanceswith limited supply

voltagelevel.

- Considerablyhigh 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 maximumoutput
power obtainable is 150 W, while with Rl=16
Ohm, Vs = ±35V the maximum Pout is 170 W.

137

6

22µF

+

-

TDA7294

9

14

2

815

22K

680

22µF

1N4148

10K 30K

0.56µF 22K

22µF

9

10

TDA7294

3

1
4

15 8

+

-

137

2200µF 0.22µF

6

22µF

14

2

22K

680

22K

-Vs

D93AU015A

13/16

TDA7294

Figure26: FrequencyResponse of the Bridge

Application

Figure28: Distortionvs. Output Power

Figure 27: Distortionvs. Output Power

14/16

MULTIWATT15 PACKAGE MECHANICAL DATA (Vertical)

TDA7294

DIM.

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 1.14 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

mm inch

15/16

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 fromits 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 lifesupport devices or systems without ex­press written approval of SGS-THOMSON Microelectronics.

 1996 SGS-THOMSON Microelectronics AllRights Reserved

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16/16