ST TDA7295 User Manual

®

TDA7295

80V - 80W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY

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

DMOS POWER STAGE
HIGH OUTPUT POWER (UP TO 80W MUSIC

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 TDA7295 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

Multiwatt 15

ORDERING NUMBER:

TDA7295

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

1/13

TDA7295

PIN CONNECTION (Top view)

BLOCK DIAGRAM

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

I

O

P

tot

T

op

T

stg

Supply Voltage

S

Output Peak Current 6 A
Power Dissipation T

= 70°C50W

case

Operating Ambient Temperature Range 0 to 70

, TjStorage and Junction Temperature 150

2/13

40 V

±

C

°

C

°

TDA7295

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

= ±30V, RL = 8Ω, GV = 30dB;

S

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

I
I

V

I

OS

P

Operating 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) (*)
∆t = 1s

d Total Harmonic Distortion (**) P

V

= ± 30V, RL = 8

S

V

= ± 26V, RL = 6

S

= ± 22V, RL = 4

ς

S

Ω
Ω

Ω

d = 10%;
R

= 8Ω ; VS = ±34V

L

(***) R

= 4Ω; VS = ±26V

L

= 5W; f = 1kHz

O

P

= 0.1 to 30W; f = 20Hz to 20kHz

O

= ±22V, RL = 4

V

S

P

= 5W; f = 1kHz

O

P

= 0.1 to 30W; f = 20Hz to 20kHz

O

Ω:

10

±

45
45
45

50
50
50

80
80

0.005

0.01

40 V

±

0.1

0.1

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 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 out current

V

µ

V

µ

Ω

C

°

3/13

TDA7295

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.

4/13

TDA7295

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

5/13

TDA7295

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

6/13

Figure 8: Distortion vs. Frequency

TYPICAL CHARACTERISTICS (continued)

TDA7295

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

7/13

TDA7295

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 realising the output stage.

The solution shown as a principle schematic by
Fig 15 represents the DMOS unity-gain output
buffer of the TDA7295.

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.

8/13

Figure 16: Turn ON/OFF Suggested Sequence

+Vs

(V)

+35

-35

-Vs

V

IN

(mV)

V

ST-BY

PIN #9

(V)

5V

TDA7295

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.

9/13

TDA7295

BRIDGE APPLICATION

Another application suggestion is the BRIDGE
configuration, where two TDA7295 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 realisations.

The main advantages offered by this solution are:

Figure 18: Bridge Application Circuit

+Vs

2200µF0.22µF

Vi

22K0.56µF

ST-BY/MUTE

20K

- 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 20 and 21,

measured with loads respectively 8 Ohm and 16

Ohm.

With Rl= 8 Ohm, Vs = ±22V the maximum output

power obtainable is 100W, while with Rl=16 Ohm,

Vs = ±30V the maximum Pout is 100W.

137

3

1
4

10

+

-

9

6

22µF

14

2

815

22K

680

22µF

1N4148

10K 30K

0.56µF 22K

22µF

10

3

1
4

9

15 8

+

-

137

2200µF

6

14

2

22K

-Vs

0.22µF

22µF

22K

680

D93AU015A

10/13

TDA7295

Figure 19: Frequency Response of the Bridge

Application

Figure 21: Distortion vs. Output Power

Figure 20: Distortion vs. Output Power

11/13

TDA7295

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 1.02 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

mm inch

OUTLINE AND

MECHANICAL DATA

Multiwatt15 V

12/13

TDA7295

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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
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13/13