SGS Thomson Microelectronics TDA7294S Datasheet



TDA7294S

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

VERY HIGH OPERATING VOLTAGE RANGE
(±45V)

DMOSPOWERSTAGE
HIGH OUTPUT POWER (100W @ THD =

10%, R

L =8Ω,VS=±40V MUSIC POWER)

MUTING/STAND-BY FUNCTIONS
NO SWITCHON/OFFNOISE
VERY LOWDISTORTION
VERY LOWNOISE
SHORTCIRCUITPROTECTION
THERMAL SHUTDOWN
CLIPDETECTOR
MODULARITY (MORE DEVICES CAN BE

EASILY CONNECTED IN PARALLEL TO
DRIVEVERYLOWIMPEDANCES)

DESCRIPTION

The TDA7294S 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-

Figure1: TypicalApplicationandTest Circuit

MULTIPOWER BCD TECHNOLOGY

Multiwatt15

ORDERING NUMBER: TDA7294SV

class TV). Thanks to the wide voltage range and
to the high out current capability it is able to sup­ply the highest power into both4Ω and 8Ω loads.

The built in muting function with turn on delay
simplifiesthe remote operation avoiding switching
on-off noises.
Parallel mode is made possible by connecting
more device through of pin11. High output power
can be delivered to very low impedance loads, so
optimizingthe thermaldissipationof the system.

VMUTE

VSTBY

June 2000

C7 100nF C6 1000µF

R3 22K

C2

R2

22µF

680Ω

C1 470nF

R1 22K

R5 10K

R4 22K

C3 10µFC410µF

IN- 2

IN+

3

4

SGND
(**)

10

MUTE

9

STBY

(*) see Application
(**) for SLAVE function

note

MUTE

STBY

1
STBY-GND

+Vs

BUFFER DRIVER

713

11

-

+

THERMAL

SHUTDOWN

-Vs -PWVs

C9 100nF C8 1000µF

+PWVs+Vs

PROTECTION

158

-Vs

S/C

14

12

6
5

D97AU805A

OUT

BOOT
LOADER

C5

22µF

BOOTSTRAP

CLIP DET

(*)

VCLIP

1/13

TDA7294S

PIN CONNECTION (Top view)

TAB CONNECTED TO PIN 8

15
14
13
12
11
10

9
8
7
6
5
4
3
2
1

D97AU806

-V

(POWER)

S

OUT

(POWER)

+V

S

BOOTSTRAP LOADER
BUFFER DRIVER
MUTE
STAND-BY

-V

(SIGNAL)

S

+VS(SIGNAL)
BOOTSTRAP
CLIP AND SHORT CIRCUIT DETECTOR
SIGNAL GROUND
NON INVERTING INPUT
INVERTING INPUT
STAND-BY GND

QUICK REFERENCE DATA

Symbol Parameter Test Conditions Min. Typ. Max. Unit

V

G

LOOP

P

tot

SVR Supply Voltage Rejection 75 dB

Supply Voltage Operating ±12 ± 45 V

S

Closed Loop Gain 26 40 dB
Output Power VS=±40V; RL=8Ω; THD = 10% 100 W

= ±30V; RL =4Ω; THD = 10% 100 W

V

S

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V
V
V

2 -V3 Maximum DifferentialInputs ±30 V

V

V
V
V
V
V

V

10
11 Buffer Voltage Referred to -VS 100 V

V

12 Bootstrap Loader Voltage Referred to -VS 90 V

V

I

O

P

tot

T

op

T

stg,Tj

Supply Voltage (No Signal) ±50 V

S

VSTAND-BY GND Voltage Referred to -VS (pin 8) 90 V

1

Input Voltage (inverting) Referred to -V

2

3 Input Voltage (non inverting) Referred to -VS 90 V

Signal GND Voltage Referred to -V

4

Clip Detector Voltage Referred to -V

5
6 Bootstrap Voltage Referred to -VS 100 V
9 Stand-by Voltage Referred to -VS 100 V

Mute Voltage Referred to -V

S

S

S

S

90 V

90 V

100 V

100 V

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

THERMALDATA

Symbol Description Typ Max Unit

R

th j-case

Thermal Resistance Junction-case 1 1.5 °C/W

2/13

TDA7294S

ELECTRICAL CHARACTERISTICS (Referto the TestCircuitVS= ±35V, RL=8Ω,GV= 30dB;

R

=50Ω;T

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

I

MAX

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 amplifieris capableof producing acrossthe rated load resistance (regardless ofnon linearity)
1 sec afterthe application of a sinusoidal input signal of frequency 1KHz.

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

Tested withoptimized Application Board(see fig. 2)

Limitedby the max. allowablecurrent.

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

amb

Operating Supply Range ±12 ±45 V
Quiescent Current 20 30 60 mA
Input Bias Current 500 nA
Input Offset Voltage ±10 mV
Input Offset Current ±100 nA
RMS Continuous OutputPower d = 0.5%:

W
W
W

W
W
W

%
%

%
%

Music Power (RMS) (*)

∆t=1s

V

= ± 35V, RL=8Ω

S

V

=±32V, RL=6Ω

S

V

=±28V, RL=4

S

Ω

d = 10%;
R

=8Ω ;VS=±40V

L

R

=6Ω ;VS=±35V

L

R

=4Ω;VS=±30V (***)

L

= 5W; f = 1kHz

O

P

=0.1to 20W;f = 20Hzto 20kHz

O

= ±28V, RL=4Ω:

V

S

P

= 5W; f = 1kHz

O

P

=0.1to 20W;f = 20Hzto 20kHz

O

60
60
60

70
70
70

100
100
100

0.005

0.1

0.01

0.1

Overcurrent Protection Threshold 6.5 A

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
µ

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

= 0.5Vrms 60 75 dB

ripple

Thermal Shutdown 150 °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

V

3/13

TDA7294S

Figure2: Typical ApplicationP.C. Boardand ComponentLayout (scale1:1)

4/13

TDA7294S

APPLICATION SUGGESTIONS (seeTestand ApplicationCircuits 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 followingtable can help the designer.

COMPONENTS SUGGESTED VALUE PURPOSE

LARGER THAN

SUGGESTED

R1 (*) 22k INPUT RESISTANCE INCREASE INPUT

IMPEDANCE

R2 680

Ω

CLOSED LOOP GAIN

DECREASE OF GAIN INCREASE OF GAIN

SMALLER THAN

SUGGESTED

DECREASE INPUT

IMPEDANCE

SET TO 30dB (**)

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

C1 0.47µF INPUT DC

DECOUPLING

LARGER MUTE

ON/OFF TIME

SMALLER MUTE

ON/OFF TIME
HIGHER LOW

FREQUENCY

CUTOFF

C2 22µF FEEDBACK DC

DECOUPLING

HIGHER LOW

FREQUENCY

CUTOFF

C3 10µF MUTE TIME

CONSTANT

C4 10µF ST-BY TIME

CONSTANT

LARGER MUTE

ON/OFF TIME

LARGER ST-BY

ON/OFF TIME

SMALLER MUTE

ON/OFF TIME

SMALLER ST-BY

ON/OFF TIME;

POP NOISE

C5 22µFXN (***) BOOTSTRAPPING SIGNAL

C6, C8 1000µF SUPPLY VOLTAGE

C7, C9 0.1µF SUPPLY VOLTAGE

(*) R1 = R3 for pop optimization
(**) Closed LoopGain has tobe ≥ 26dB
(***) Multiplythis value for thenumber of modular part connected

Slave function: pin 4 (Ref to pin 8 -VS)

-V

+3V

S

-V

+1V

S

-V

S

MASTER

UNDEFINED

SLAVE

D98AU821

DEGRADATION AT
LOW FREQUENCY

BYPASS

DANGER OF

BYPASS

OSCILLATION

Note:

If in the application, the speakers are connected
via long wires, it is a good rule to add between
the outputand GND, a BoucherotCell, in order to
avoid dangerous spurious oscillations when the
speakersterminal are shorted.

The suggested Boucherot Resistor is 3.9Ω/2W
and the capacitoris 1µF.

5/13

TDA7294S

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 phoenomenon. It limits the safe operating
area (SOA) of the power devices, and, as a con­sequence, the maximum attainable output power,
especiallyin presence of highlyreactiveloads.

Moreover, full exploitation of the SOA translates
into a substantial increase in circuit and layout
complexity due to the need of sophisticated pro­tectioncircuits.

To overcome these substantial drawbacks, the
use of power MOS devices, which are immune
fromsecondarybreakdownis highlydesirable.

The device described has therefore been devel­oped in a mixed bipolar-MOS high voltage tech­nologycalledBCDII100.

1) Output Stage

The main design task in developping a power op­erational amplifier, independently of the technol­ogyused, is that of realizationof theoutput stage.

The solution shown as a principle shematic by
Fig3 represents the DMOS unity - gain output
bufferof the TDA7294S.

This large-signal, high-power buffer must be ca­pable of handlingextremely 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
currentsetting.

Proper biasing of the power output transistors
alone is however not enough to guaranteethe ab­sence of crossoverdistortion.

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 connectionof the Miller capacitor
at the amplifier’s output to introduce a local AC
feedbackpathenclosingthe 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 overloadcondi­tions.

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 maximumdissipation.

Figure3: PrincipleSchematicof a DMOS unity-gain buffer.

6/13

Figure4: Turn ON/OFFSuggestedSequence

+Vs

(V)

+40

-40

-Vs

VIN

(mV)

V

ST-BY

PIN #9

(V)

5V

TDA7294S

V

MUTE

PIN #10

(V)

IQ

(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 = 150
Tj = 160

o

C).

o

C) and then into stand-by (@

Full protection against electrostatic discharges on
everypin is included.

Figure5: Single Signal ST-BY/MUTE Control

Circuit

MUTE STBY

MUTE/

ST-BY

20K

10K 30K

1N4148

10µF10µF

D93AU014

3) Other Features

The device is provided with both stand-by and

ST-BY OFF

D98AU817

mute functions, independently driven by two
CMOSlogiccompatible 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/OFFtransientsis shown by Figure 4.

The application of figure 5 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.

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 6) is described a circuit pro­posal for a high efficiency amplifier which can be
adopted for both HI-FI and CAR-RADIO applica­tions.

7/13

TDA7294S

The TDA7294Sis a monolithicMOS power ampli­fier which can be operated at 90V supply voltage
(100V with no signal applied)while delivering out­put currentsup to ±6.5 A.
This allows the use of this device as a very high
power amplifier (up to 100W 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.
The typical junction-to-case thermal resistance of
the TDA7294Sis 1
To avoid that, in worst case conditions, the chip
temperature exceedes 150
tance of the heatsink must be 0.038
max ambienttemperatureof50

o

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

o

C, the thermal resis-

o

C).

o

C/W (@

As the above value is pratically unreachable; a
high efficiency system is needed in those cases
where the continuous RMSoutput power is higher
than 50-60W.
The TDA7294S was designed to work also in
higherefficiencyway.
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
diodes Z1, Z2 and resistors R7,R8 define the
minimum drop across the power MOS transistors
of the TDA7294S. L1, L2, L3 and the snubbers
C9, R1 and C10, R2 stabilize the loops formed by
the ”bootstrap” circuitsandthe output stage of the
TDA7294S.

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 =±45V and Rl= 8Ohm).

2.2
All components (TDA7294S and power tran­sistors T1 and T2) can be placed on a

o

C/W heatsink, with the power darlingtons

1.5
electricallyinsulated from theheatsink.
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 witha highheatsink.

BRIDGEAPPLICATION

Another application suggestion is the BRIDGE
configuration,where two TDA7294S are used.
In this application, the value of the load must not
be lower than 8Ohm for dissipation and current
capabilityreasons.
A suitable field of application includes HI-FI/TV
subwoofersrealizations.

Themain advantagesofferedby this solution are:

- High power performanceswithlimited supply
voltagelevel.

- Considerablyhigh output power even with high
load values (i.e. 16 Ohm).

With Rl= 8 Ohm, Vs = ±25V the maximum output
power obtainable is 150 W, while with Rl=16
Ohm, Vs = ±40V the maximum Pout is 200W
(MusicPower).

APPLICATION NOTE:(ref.fig.7)
ModularApplication (more Devices in Parallel)

The use of the modular application lets very high
power be delivered to very low impedance loads.
The modular application implies one device to act
as a masterandthe othersas slaves.
The slave power stages are driven by the master
device and work in parallel all together,while the
input and the gain stages of the slave device are
disabled, the figure below shows the connections
required to configure two devices to work to­gether.

The master chip connections are the same as
the normal single ones.

The outputs can be connected together with-

out the need of any ballastresistance.

The slave SGND pin must be tied to the nega­tivesupply.

The slave ST-BY pin must be connected to
ST-BYpin.

The bootstrap lines must be connected to­gether and the bootstrapcapacitor must be in­creased: for N devices the boostrap capacitor
mustbe 22µF times N.

The slave Mute and IN-pins must be grounded.

THE BOOTSTRAP CAPACITOR

For compatibility purpose with the previous de­vices of the family, the boostrap capacitor can be
connectedboth between the bootstrappin (6) and
the output pin (14) or between the boostrap pin
(6) and the bootstraploader pin (12).
When the bootcap is connected between pin 6
and 14, the maximum supply voltage in presence
of output signal is limited to 80V, due the boot­strapcapacitorovervoltage.
When the bootcap is connected between pins 6
and 12 themaximum supply voltageextendto the
full voltage that the technologycan stand: 100V.

This is accomplished by the clamp introduced at
the bootstrap loader pin (12): this pin follows the
output voltage up to 100V and remains clamped
at 100V. This feature lets the output voltage
swing up to a gate-source voltage from the posi­tivesupply(V

S -3to 6V)

8/13

Figure6: High EfficiencyApplicationCircuit

TDA7294S

+50V

D6

1N4001

PLAY

ST-BY

D5

1N4148

IN

D1 BYW98100

C12 330nF

C13 10µF

R13 20K

R14 30K

R15 10K

10µF

D2 BYW98100

R20
20K

R21
20K

+25V

GND

-25V

-50V

C1

1000µF

63V

C2

1000µF

63V

C3

100nF

C4

100nF

C5

1000µF

35V

C6

1000µF

35V

C7

100nF

R22

10K

R23

10K

C8

100nF

C9

330nF

C10

330nF

D7

1N4001

R1

2

R2

2

Figure6a: PCB and ComponentLayout of the fig. 6

C14

R12
13K

3

4

9

1

10

137

815

BDX53A

R17 270

L1 1µH

2

14

6

12

L2 1µH

R19 270

BDX54A

T3

BC394

T1

D3 1N4148

R3 680

R16
13K

C15

22µF

D4 1N4148

T2

T6

BC393

C11 22µF

L3 5µH

R18 270

270

BC393

Z1 3.9V

Z2 3.9V

BC394

270

R4

R5

270

T4

T7

R9

20K

R7

3.3K

R8

3.3K

R10
270

D97AU807C

T5

BC393

R6

C16

1.8nF
OUT

P

C17

1.8nF

T8

BC394

R11
20K

ot

9/13

TDA7294S

Figure6b: PCB- Solder Side of the fig. 6.

Figure7: ModularApplicationCircuit

MASTER

VMUTE

VSTBY

SLAVE

C2

22µF

R1 22K

R5 10K

R4 22K

R2

680Ω

C1 470nF

R3 22K

IN- 2

IN+

SGND

MUTE

STBY

C4 10µF

C3 10µF

IN- 2

IN+ 3

SGND

MUTE

STBY

C7 100nF C6 1000µF

BUFFER

DRIVER

713

-

3

4

10

9

4

10
9

+

MUTE
STBY

1
STBY-GND

C7 100nF C6 1000µF

+

MUTE
STBY

1
STBY-GND

THERMAL

SHUTDOWN

-Vs -PWVs

C9 100nF C8 1000µF

BUFFER

DRIVER

713

-

THERMAL

SHUTDOWN

-Vs -PWVs

C9 100nF C8 1000µF

+Vs

PROTECTION

158

-Vs
+Vs

PROTECTION

158

-Vs

+PWVs+Vs

14

OUT

BOOT

12

LOADER

6

BOOTSTRAP

S/C

+PWVs+Vs

S/C

5

14

12

6
5

CLIP DET

OUT

BOOT
LOADER

BOOTSTRAP

C5

47µF

D97AU808C

C10

100nF

R7
2Ω

11

11

10/13

TDA7294S

Figure8a: ModularApplicationP.C.Board and ComponentLayout (scale 1:1) (ComponentSIDE)

Figure8b: ModularApplicationP.C. Board and ComponentLayout(scale1:1) (SolderSIDE)

11/13

TDA7294S

DIM.

Dia1 3.65 3.85 0.144 0.152

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

A5
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
L2 17.65 18.1 0.695
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

0.197

0.886

0.713

OUTLINE AND

MECHANICAL DATA

Multiwatt15 V

12/13

TDA7294S

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13/13