TDA7295S
80V - 80W DMOS AUDIO AMPLIFIER WITH MUTE/ST-BY
VERY HIGH OPERATING VOLTAGE RANGE
(
38V)
DMOS POWER STAGE
HIGH OUTPUT POWER (80W @ THD = 10%,
MUSIC POWER)
MUTING/STAND-BY FUNCTIONS
NO SWITCH ON/OFF NOISE
VERY LOW DISTORTION
VERY LOW NOISE
SHORT CIRCUIT PROTECTION
THERMAL SHUTDOWN
CLIP DETECTOR
MODULARITY (MORE DEVICES CAN BE
EASILY CONNECTED IN PARALLEL TO
DRIVE VERY LOW IMPEDANCES)
DESCRIPTION
The TDA7295S 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.
The built in muting function with turn on delay
simplifies the 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
optimizing the thermal dissipation of the system.
June 2000
IN-
2
R2
680
C2
22
F
C1 470nF
IN+
R1 22K
3
R3 22K
-
+
MUTE
STBY
4
VMUTE
VSTBY
10
9
SGND
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
D97AU805A
+Vs
C7 100nF
C6 1000
F
BUFFER DRIVER
11
BOOT
LOADER
12
5
VCLIP
CLIP DET
(*)
(*) see Application note
(**) for SLAVE function
(**)
Figure 1: Typical Application and Test Circuit
Multiwatt15
ORDERING NUMBER: TDA7295SV
MULTIPOWER BCD TECHNOLOGY
1/13
ABSOLUTE MAXIMUM RATINGS
Symbol
Parameter
Value
Unit
V
S
Supply Voltage (No Signal)
40
V
V
1
V
STAND-BY
GND Voltage Referred to -V
S
(pin 8)
80
V
V
2
Input Voltage (inverting) Referred to -V
S
80
V
V
2
- V
3
Maximum Differential Inputs
30
V
V
3
Input Voltage (non inverting) Referred to -V
S
80
V
V
4
Signal GND Voltage Referred to -V
S
80
V
V
5
Clip Detector Voltage Referred to -V
S
80
V
V
6
Bootstrap Voltage Referred to -V
S
80
V
V
9
Stand-by Voltage Referred to -V
S
80
V
V
10
Mute Voltage Referred to -V
S
80
V
V
11
Buffer Voltage Referred to -V
S
80
V
V
12
Bootstrap Loader Voltage Referred to -V
S
80
V
I
O
Output Peak Current
10
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
1
2
3
4
5
6
7
9
10
11
8
BUFFER DRIVER
MUTE
STAND-BY
-V
S
(SIGNAL)
+V
S
(SIGNAL)
BOOTSTRAP
CLIP AND SHORT CIRCUIT DETECTOR
SIGNAL GROUND
NON INVERTING INPUT
INVERTING INPUT
STAND-BY GND
TAB CONNECTED TO PIN 8
13
14
15
12
-V
S
(POWER)
OUT
+V
S
(POWER)
BOOTSTRAP LOADER
D97AU806
PIN CONNECTION (Top view)
QUICK REFERENCE DATA
Symbol
Parameter
Test Conditions
Min.
Typ.
Max.
Unit
V
S
Supply Voltage Operating
12
38
V
G
LOOP
Closed Loop Gain
26
40
dB
P
tot
Output Power
V
S
=
34V; R
L
= 8
; THD = 10%
80
W
V
S
=
27V; R
L
= 4
; THD = 10%
80
W
SVR
Supply Voltage Rejection
75
dB
THERMAL DATA
Symbol
Description
Typ
Max
Unit
R
th j-case
Thermal Resistance Junction-case
1
1.5
C/W
TDA7295S
2/13
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
38
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
V
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
=
27V
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
%
%
I
MAX
Overcurrent Protection Threshold
6
A
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
150
C
STAND-BY FUNCTION (Ref: -V
S
or GND)
V
ST on
Stand-by on Threshold
1.5
V
V
ST off
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
TDA7295S
3/13
Figure 2: Typical Application P.C. Board and Component Layout (scale 1:1)
TDA7295S
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
IMPEDANCE
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
FXN (***)
BOOTSTR APPING
SIGNAL
DEGRADATION AT
LOW FREQUENCY
C6, C8
1000
F
SUPPLY VOLTAGE
BYPASS
C7, C9
0.1
F
SUPPLY VOLTAGE
BYPASS
DANGER OF
OSCILLATION
(*) R1 = R3 for pop optimization
(**) Closed Loop Gain has to be
26dB
(***) Multiply this value for the number of modular part connected
MASTER
UNDEFINED
SLAVE
-V
S
+3V
-V
S
+1V
-V
S
D98AU821
Slave function: pin 4 (Ref to pin 8 -V
S
)
Note:
If in the application, the speakers are connected
via long wires, it is a good rule to add between
the output and GND, a Boucherot Cell, in order to
avoid dangerous spurious oscillations when the
speakers terminal are shorted.
The suggested Boucherot Resistor is 3.9
/2W
and the capacitor is 1
F.
TDA7295S
5/13
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 phoenomenon. 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 of 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 BCDII 100.
1) Output Stage
The main design task in developping a power op-
erational amplifier, independently of the technol-
ogy used, is that of realization of the output stage.
The solution shown as a principle shematic by
Fig3 represents the DMOS
unity - gain output
buffer of the TDA7295S.
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
frequency response; moreover, an accurate con-
trol 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 3: Principle Schematic of a DMOS unity-gain buffer.
TDA7295S
6/13
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 = 150
o
C) and then into stand-by (@
Tj = 160
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 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 appli-
cable 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 effi-
ciency of conventional AB class amplifier ap-
proaches.
Here below (figure 6) is described a circuit pro-
posal for a high efficiency amplifier which can be
adopted for both HI-FI and CAR-RADIO applica-
tions.
1N4148
10K
30K
20K
10
F
10
F
MUTE
STBY
D93AU014
MUTE/
ST-BY
Figure 5: Single Signal ST-BY/MUTE Control
Circuit
PLAY
OFF
ST-BY
MUTE
MUTE
ST-BY
OFF
D98AU817
5V
5V
+Vs
(V)
+40
-40
VMUTE
PIN #10
(V)
VST-BY
PIN #9
(V)
-Vs
VIN
(mV)
IQ
(mA)
VOUT
(V)
Figure 4: Turn ON/OFF Suggested Sequence
TDA7295S
7/13
The TDA7295S is a monolithic MOS power ampli-
fier which can be operated at 76V supply voltage
(80V with no signal applied) while delivering out-
put currents up to
6A.
This allows the use of this device as a very high
power amplifier (up to 80W 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 TDA7295S is 1
o
C/W (max= 1.5
o
C/W). To
avoid that, in worst case conditions, the chip tem-
perature exceedes 150
o
C, the thermal resistance
of the heatsink must be 0.038
o
C/W (@ max am-
bient temperature of 50
o
C).
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 TDA7295S 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
operate 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
diodes Z1, Z2 and resistors R7,R8 define the
minimum drop across the power MOS transistors
of the TDA7295S. 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
TDA7295S.
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
2.2
o
C/W (Vs =
38V and Rl= 8 Ohm).
All components (TDA7295S and po wer tran-
sistors 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 sav-
ings can be obtained while optimizing the power
supply, even with a high heatsink .
BRIDGE APPLICATION
Another application suggestion is the BRIDGE
configuration, where two TDA7295S are used.
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:
- High power performances with limited supply
voltage level.
- Considerably high output power even with high
load values (i.e. 16 Ohm).
With Rl = 8 Ohm, V
S
=
25V the maximum output
power obtainable is 150W (Music Power)
APPLICATION NOTE: (ref. fig. 7)
Modular Application (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 master and the others as 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 to-
gether.
The master chip connections are the same as
the normal single ones.
The outputs can be connected together with-
out the need of any ballast resistance.
The slave SGND pin must be tied to the nega-
tive supply.
The slave ST-BY pin must be connected to
ST-BY pin.
The bootstrap lines must be connected to-
gether and the bootstrap capacitor must be in-
creased: for N devices the boostrap capacitor
must be 22
F times N.
The slave Mute and IN-pins must be grounded.
THE BOOTSTRAP CAPACITOR
For compatibility purpose with the previous de-
vices of the family, the boostrap capacitor can be
connected both between the bootstrap pin (6) and
the output pin (14) or between the boostrap pin
(6) and the bootstrap loader pin (12).
TDA7295S
8/13
3
1
4
13
7
8
15
2
14
6
10
R3 680
C11 22
F
L3 5
H
R18 270
R16
13K
C15
22
F
9
R12
13K
C13 10
F
R13 20K
C12 330nF
R15 10K
C14
10
F
R14 30K
D5
1N4148
PLAY
ST-BY
R17 270
L1 1
H
T1
BDX53A
T3
BC394
D3 1N4148
R4
270
R5
270
T4
BC393
T5
BC393
R6
20K
R7
3.3K
C16
1.8nF
R8
3.3K
C17
1.8nF
Z2 3.9V
Z1 3.9V
L2 1
H
R19 270
D4 1N4148
D2 BYW98100
R1
2
R2
2
C9
330nF
C10
330nF
T2
BDX54A
T6
BC393
T7
BC394
T8
BC394
R9
270
R10
270
R11
20K
OUT
IN
C7
100nF
C5
1000
F
35V
C8
100nF
C6
1000
F
35V
C1
1000
F
63V
C2
1000
F
63V
C3
100nF
C4
100nF
+50V
+25V
D1 BYW98100
GND
-25V
-50V
D97AU807C
12
D6
1N4001
R20
20K
R21
20K
D7
1N4001
R22
10K
R23
10K
P
ot
Figure 6: High Efficiency Application Circuit
Figure 6a: PCB and Component Layout of the fig. 6
TDA7295S
9/13
IN-
2
R2
680
C2
22
F
C1 470nF
IN+
R1 22K
3
R3 22K
-
+
MUTE
STBY
4
10
9
SGND
MUTE
STBY
R4 22K
THERMAL
SHUTDOWN
S/C
PROTECTION
R5 10K
C3 10
F
C4 10
F
1
STBY-GND
C5
47
F
7
13
14
6
15
8
-Vs
-PWVs
BOOTSTRAP
OUT
+PWVs
+Vs
C9 100nF
C8 1000
F
-Vs
D97AU808C
+Vs
C7 100nF
C6 1000
F
BUFFER
DRIVER
11
BOOT
LOADER
12
IN-
2
IN+
3
-
+
MUTE
STBY
4
10
9
SGND
MUTE
THERMAL
SHUTDOWN
S/C
PROTECTION
1
STBY-GND
7
13
14
6
15
8
-Vs
-PWVs
BOOTSTRAP
OUT
+PWVs
+Vs
C9 100nF
C8 1000
F
-Vs
+Vs
C7 100nF
C6 1000
F
BUFFER
DRIVER
11
BOOT
LOADER
12
5
CLIP DET
5
MASTER
SLAVE
C10
100nF
R7
2
VMUTE
VSTBY
STBY
Figure 7: Modular Application Circuit
Figure 6b: PCB - Solder Side of the fig. 6.
TDA7295S
10/13
Figure 8b: Modular Application P.C. Board and Component Layout (scale 1:1) (Solder SIDE)
Figure 8a: Modular Application P.C. Board and Component Layout (scale 1:1) (Component SIDE)
TDA7295S
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
TDA7295S
12/13
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of use of such information nor for any infringement of patents or other rights of third parties which may result from its use. No license is
granted by implication or otherwise under any patent or patent rights of STMicroelectronics. Specification mentioned in this publication are
subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics 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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TDA7295S
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