TDA7295
80V - 80W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY
VERY HIGH OPERATING VOLTAGE RANGE
(
40V)
DMOS POWER STAGE
HIGH OUTPUT POWER (UP TO 80W MUSIC
POWER)
MUTING/STAND-BY FUNCTIONS
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, Top-
class TV). Thanks to the wide voltage range and
to the high out current capability it is able to sup-
ply the highest power into both 4
and 8
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.
July 1999
IN-
2
R2
680
C2
22
F
C1 470nF
IN+
R1 22K
3
R3 22K
-
+
MUTE
STBY
4
VM
VSTBY
10
9
IN+MUTE
MUTE
STBY
R4 22K
THERMAL
SHUTDOWN
S/C
PROTECTION
R5 10K
C3 10
F
C4 10
F
1
STBY-GND
C5
22
F
7
13
14
6
15
8
-Vs
-PWVs
BOOTSTRAP
OUT
+PWVs
+Vs
C9 100nF
C8 1000
F
-Vs
D93AU011
+Vs
C7 100nF
C6 1000
F
Figure 1: Typical Application and Test Circuit
Multiwatt 15
ORDERING NUMBER: TDA7295V
MULTIPOWER BCD TECHNOLOGY
1/13
BLOCK DIAGRAM
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V
S
Supply Voltage
40
V
I
O
Output Peak Current
6
A
P
tot
Power Dissipation T
case
= 70
C
50
W
T
op
Operating Ambient Temperature Range
0 to 70
C
T
stg
, T
j
Storage and Junction Temperature
150
C
PIN CONNECTION (Top view)
TDA7295
2/13
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
S
=
30V, R
L
= 8
, G
V
= 30dB;
R
g
= 50
; T
amb
= 25
C, f = 1 kHz; unless otherwise specified.
Symbol
Parameter
Test Condition
Min.
Typ.
Max.
Unit
V
S
Operating Supply Range
10
40
V
I
q
Quiescent Current
20
30
60
mA
I
b
Input Bias Current
500
nA
V
OS
Input Offset Voltage
+10
mV
I
OS
Input Offset Current
+100
nA
P
O
RMS Continuous Output Power
d = 0.5%:
V
S
=
30V, R
L
= 8
V
S
=
26V, R
L
= 6
S
=
22V, R
L
= 4
45
45
45
50
50
50
W
W
W
Music Power (RMS) (*)
t = 1s
d = 10%;
R
L
= 8
; V
S
=
34V
(***) R
L
= 4
; V
S
=
26V
80
80
W
W
d
Total Harmonic Distortion (**)
P
O
= 5W; f = 1kHz
P
O
= 0.1 to 30W; f = 20Hz to 20kHz
0.005
0.1
%
%
V
S
=
22V, R
L
= 4
:
P
O
= 5W; f = 1kHz
P
O
= 0.1 to 30W; f = 20Hz to 20kHz
0.01
0.1
%
%
SR
Slew Rate
7
10
V/
s
G
V
Open Loop Voltage Gain
80
dB
G
V
Closed Loop Voltage Gain
24
30
40
dB
e
N
Total Input Noise
A = curve
f = 20Hz to 20kHz
1
2
5
V
V
f
L
, f
H
Frequency Response (-3dB)
P
O
= 1W
20Hz to 20kHz
R
i
Input Resistance
100
k
SVR
Supply Voltage Rejection
f = 100Hz; V
ripple
= 0.5Vrms
60
75
dB
T
S
Thermal Shutdown
145
C
STAND-BY FUNCTION (Ref: -V
S
or GND)
V
ST on
Stand-by on Threshold
1.5
V
V
ST of f
Stand-by off Threshold
3.5
V
ATT
st-by
Stand-by Attenuation
70
90
dB
I
q st-by
Quiescent Current @ Stand-by
1
3
mA
MUTE FUNCTION (Ref: -V
S
or GND)
V
Mon
Mute on Threshold
1.5
V
V
Moff
Mute off Threshold
3.5
V
ATT
mute
Mute AttenuatIon
60
80
dB
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 (**): Tested with optimized Application Board (see fig. 2)
Note (***): Limited by the max. allowable out current
TDA7295
3/13
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.
TDA7295
4/13
APPLICATION SUGGESTIONS (see Test and Application Circuits of the Fig. 1)
The recommended values of the external components are those shown on the 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
680
CLOSED 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
0.47
F
INPUT DC
DECOUPLING
HIGHER LOW
FREQUENCY
CUTOFF
C2
22
F
FEEDBACK DC
DECOUPLING
HIGHER LOW
FREQUENCY
CUTOFF
C3
10
F
MUTE TIME
CONSTANT
LARGER MUTE
ON/OFF TIME
SMALLER MUTE
ON/OFF TIME
C4
10
F
ST-BY TIME
CONSTANT
LARGER ST-BY
ON/OFF TIME
SMALLER ST-BY
ON/OFF TIME;
POP NOISE
C5
22
F
BOOTSTRAPPING
SIGNAL
DEGRADATION AT
LOW FREQUENCY
C6, C8
1000
F
SUPPLY VOLTAGE
BYPASS
DANGER OF
OSCILLATION
C7, C9
0.1
F
SUPPLY VOLTAGE
BYPASS
DANGER OF
OSCILLATION
(*) R1 = R3 FOR POP OPTIMIZATION
(**) CLOSED LOOP GAIN HAS TO BE
24dB
TDA7295
5/13
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 CHARACTERISTICS
(Application Circuit of fig 1 unless otherwise specified)
Figure 6: Distortion vs. Output Power
Figure 7: Distortion vs. Frequency
TDA7295
6/13
Figure 14: Power Dissipation vs. Output Power
Figure 13: Power Dissipation vs. Output Power
Figure 11: Mute Attenuation vs. V
pin10
Figure 12: St-by Attenuation vs. V
pin9
Figure10: SupplyVoltage Rejection vs. Frequency
TYPICAL CHARACTERISTICS (continued)
Figure 9: Quiescent Current vs. Supply Voltage
TDA7295
7/13
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 design 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 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 ca-
pable of handling extremely 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 fullfil the above require-
ments, allowing a simple and effective quiescent
current setting.
Proper biasing of the power output transistors
alone is however not enough 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.
TDA7295
8/13
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 (@
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.
1N4148
10K
30K
20K
10
F
10
F
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
5V
5V
+Vs
(V)
+35
-35
VMUTE
PIN #10
(V)
VST-BY
PIN #9
(V)
-Vs
VIN
(mV)
IP
(mA)
VOUT
(V)
Figure 16: Turn ON/OFF Suggested Sequence
TDA7295
9/13
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:
- 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.
22K
0.56
F
2200
F
0.22
F
+
-
22
F
22K
680
22K
3
1
4
13
7
+Vs
Vi
8
15
2
14
6
10
9
+
-
3
0.56
F
22K
1
4
2
14
6
22
F
22K
680
10
9
22
F
15
8
-Vs
2200
F
0.22
F
22
F
20K
10K
30K
1N4148
ST-BY/MUTE
13
7
D93AU015A
Figure 18: Bridge Application Circuit
TDA7295
10/13
Figure 20: Distortion vs. Output Power
Figure 19: Frequency Response of the Bridge
Application
Figure 21: Distortion vs. Output Power
TDA7295
11/13
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
TDA7295
12/13
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of use of such informationnor for any infringementof patentsor otherrights of third parties which may result from its use. No license is
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TDA7295
13/13
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