 TDA7295S

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

VERY HIGH OPERATING VOLTAGE RANGE

(±38V) MULTIPOWER BCD TECHNOLOGY
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 Multiwatt15
SHORT CIRCUIT PROTECTION ORDERING NUMBER: TDA7295SV
THERMAL SHUTDOWN
CLIP DETECTOR
MODULARITY (MORE DEVICES CAN BE class TV). Thanks to the wide voltage range and
EASILY CONNECTED IN PARALLEL TO to the high out current capability it is able to sup-
ply the highest power into both 4Ω and 8Ω loads.
DRIVE VERY LOW IMPEDANCES)
The built in muting function with turn on delay
DESCRIPTION simplifies the remote operation avoiding switching
on-off noises.
The TDA7295S is a monolithic integrated circuit Parallel mode is made possible by connecting
in Multiwatt15 package, intended for use as audio more device through of pin11. High output power
class AB amplifier in Hi-Fi field applications can be delivered to very low impedance loads, so
(Home Stereo, self powered loudspeakers, Top- optimizing the thermal dissipation of the system.

Figure 1: Typical Application and Test Circuit

C7 100nF +Vs C6 1000µF

R3 22K
+Vs BUFFER DRIVER +PWVs
C2
R2 7 11 13
22µF
680Ω IN- 2
-
14 OUT
C1 470nF
IN+ 3
+
BOOT
R1 22K 12 LOADER
SGND 4 C5
22µF (*)
(**)
6
BOOTSTRAP
VMUTE R5 10K MUTE 10 5
MUTE THERMAL S/C VCLIP
CLIP DET
SHUTDOWN PROTECTION
VSTBY STBY 9 STBY
R4 22K
1 8 15
STBY-GND -Vs -PWVs

C3 10µF C4 10µF C9 100nF C8 1000µF

D97AU805A
-Vs
(*) see Application note
(**) for SLAVE function

June 2000 1/13

TDA7295S

PIN CONNECTION (Top view)

15 -VS (POWER)
14 OUT
13 +VS (POWER)
12 BOOTSTRAP LOADER
11 BUFFER DRIVER
10 MUTE
9 STAND-BY
8 -VS (SIGNAL)
7 +VS (SIGNAL)
6 BOOTSTRAP
5 CLIP AND SHORT CIRCUIT DETECTOR
4 SIGNAL GROUND
3 NON INVERTING INPUT
2 INVERTING INPUT
1 STAND-BY GND

TAB CONNECTED TO PIN 8 D97AU806

QUICK REFERENCE DATA

Symbol Parameter Test Conditions Min. Typ. Max. Unit
VS Supply Voltage Operating ±12 ± 38 V
GLOOP Closed Loop Gain 26 40 dB
Output Power VS = ±34V; RL = 8Ω; THD = 10% 80 W
Ptot
VS = ±27V; RL = 4Ω; THD = 10% 80 W
SVR Supply Voltage Rejection 75 dB

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit
VS Supply Voltage (No Signal) ±40 V
V1 VSTAND-BY GND Voltage Referred to -VS (pin 8) 80 V
V2 Input Voltage (inverting) Referred to -VS 80 V
V2 - V3 Maximum Differential Inputs ±30 V
V3 Input Voltage (non inverting) Referred to -VS 80 V
V4 Signal GND Voltage Referred to -VS 80 V
V5 Clip Detector Voltage Referred to -VS 80 V
V6 Bootstrap Voltage Referred to -VS 80 V
V9 Stand-by Voltage Referred to -VS 80 V
V10 Mute Voltage Referred to -VS 80 V
V11 Buffer Voltage Referred to -VS 80 V
V12 Bootstrap Loader Voltage Referred to -VS 80 V
IO Output Peak Current 10 A
Ptot Power Dissipation Tcase = 70°C 50 W
Top Operating Ambient Temperature Range 0 to 70 °C
Tstg, Tj Storage and Junction Temperature 150 °C

THERMAL DATA
Symbol Description Typ Max Unit
Rth j-case Thermal Resistance Junction-case 1 1.5 °C/W

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 TDA7295S

ELECTRICAL CHARACTERISTICS (Refer to the Test Circuit VS = ±30V, RL = 8Ω, GV = 30dB;

Rg = 50 Ω; Tamb = 25°C, f = 1 kHz; unless otherwise specified).
Symbol Parameter Test Condition Min. Typ. Max. Unit
VS Operating Supply Range ±10 ±38 V
Iq Quiescent Current 20 30 60 mA
Ib Input Bias Current 500 nA
VOS Input Offset Voltage ±10 mV
IOS Input Offset Current ±100 nA
PO RMS Continuous Output Power d = 0.5%:
VS = ± 30V, R L = 8Ω 45 50 W
VS = ± 26V, R L = 6Ω 45 50 W
VS = ± 22V, R L = 4Ω 45 50 W
Music Power (RMS) (*) d = 10%;
∆t = 1s RL = 8Ω ; VS = ±34V 80 W
(***)RL = 4Ω; VS = ±27V 80 W
d Total Harmonic Distortion (**) PO = 5W; f = 1kHz 0.005 %
PO = 0.1 to 30W; f = 20Hz to 20kHz 0.1 %
VS = ±22V, R L = 4Ω:
PO = 5W; f = 1kHz 0.01 %
PO = 0.1 to 30W; f = 20Hz to 20kHz 0.1 %
IMAX Overcurrent Protection Threshold 6 A
SR Slew Rate 7 10 V/µs
GV Open Loop Voltage Gain 80 dB
GV Closed Loop Voltage Gain 24 30 40 dB
eN Total Input Noise A = curve 1 µV
f = 20Hz to 20kHz 2 5 µV
fL, fH Frequency Response (-3dB) PO = 1W 20Hz to 20kHz
Ri Input Resistance 100 kΩ
SVR Supply Voltage Rejection f = 100Hz; Vripple = 0.5Vrms 60 75 dB
TS Thermal Shutdown 150 °C
STAND-BY FUNCTION (Ref: -VS or GND)
VST on Stand-by on Threshold 1.5 V
VST off Stand-by off Threshold 3.5 V
ATTst-by Stand-by Attenuation 70 90 dB
Iq st-by Quiescent Current @ Stand-by 1 3 mA
MUTE FUNCTION (Ref: -VS or GND)
VMon Mute on Threshold 1.5 V
VMoff Mute off Threshold 3.5 V
ATTmute 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

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TDA7295S

Figure 2: Typical Application P.C. Board and Component Layout (scale 1:1)

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 TDA7295S

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.

LARGER THAN SMALLER THAN

COMPONENTS SUGGESTED VALUE PURPOSE
SUGGESTED SUGGESTED

R1 (*) 22k INPUT RESISTANCE INCREASE INPUT DECREASE INPUT

IMPEDANCE IMPEDANCE

R2 680Ω CLOSED LOOP GAIN DECREASE OF GAIN INCREASE OF GAIN

SET TO 30dB (**)
R3 (*) 22k INCREASE OF GAIN DECREASE OF GAIN

R4 22k ST-BY TIME LARGER ST-BY SMALLER ST-BY

CONSTANT ON/OFF TIME ON/OFF TIME;
POP NOISE

R5 10k MUTE TIME LARGER MUTE SMALLER MUTE

CONSTANT ON/OFF TIME ON/OFF TIME

C1 0.47µF INPUT DC HIGHER LOW

DECOUPLING FREQUENCY
CUTOFF

C2 22µF FEEDBACK DC HIGHER LOW

DECOUPLING FREQUENCY
CUTOFF

C3 10µF MUTE TIME LARGER MUTE SMALLER MUTE

CONSTANT ON/OFF TIME ON/OFF TIME

C4 10µF ST-BY TIME LARGER ST-BY SMALLER ST-BY

CONSTANT ON/OFF TIME ON/OFF TIME;
POP NOISE

C5 22µFXN (***) BOOTSTR APPING SIGNAL

DEGRADATION AT
LOW FREQUENCY

C6, C8 1000µF SUPPLY VOLTAGE

BYPASS

C7, C9 0.1µF SUPPLY VOLTAGE DANGER OF

BYPASS OSCILLATION

(*) R1 = R3 for pop optimization

(**) Closed Loop Gain has to be ≥ 26dB

(***) Multiply this value for the number of modular part connected

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

If in the application, the speakers are connected
via long wires, it is a good rule to add between
MASTER the output and GND, a Boucherot Cell, in order to
-VS +3V avoid dangerous spurious oscillations when the
speakers terminal are shorted.
UNDEFINED The suggested Boucherot Resistor is 3.9Ω/2W
-VS +1V
and the capacitor is 1µF.

SLAVE
-VS
D98AU821

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TDA7295S

INTRODUCTION frequency response; moreover, an accurate con-

trol of quiescent current is required.
In consumer electronics, an increasing demand
has arisen for very high power monolithic audio A local linearizing feedback, provided by differen-
amplifiers able to match, with a low cost, the per- tial amplifier A, is used to fullfil the above require-
formance obtained from the best discrete de- ments, allowing a simple and effective quiescent
signs. current setting.
The task of realizing this linear integrated circuit Proper biasing of the power output transistors
in conventional bipolar technology is made ex- alone is however not enough to guarantee the ab-
tremely difficult by the occurence of 2nd break- sence of crossover distortion.
down phoenomenon. It limits the safe operating While a linearization of the DC transfer charac-
area (SOA) of the power devices, and, as a con- teristic of the stage is obtained, the dynamic be-
sequence, the maximum attainable output power, haviour of the system must be taken into account.
especially in presence of highly reactive loads. A significant aid in keeping the distortion contrib-
Moreover, full exploitation of the SOA translates uted by the final stage as low as possible is pro-
into a substantial increase in circuit and layout vided by the compensation scheme, which ex-
complexity due to the need of sophisticated pro- ploits the direct connection of the Miller capacitor
tection circuits. at the amplifier’s output to introduce a local AC
To overcome these substantial drawbacks, the feedback path enclosing the output stage itself.
use of power MOS devices, which are immune
from secondary breakdown is highly desirable. 2) Protections
The device described has therefore been devel- In designing a power IC, particular attention must
oped in a mixed bipolar-MOS high voltage tech- be reserved to the circuits devoted to protection
nology called BCDII 100. of the device from short circuit or overload condi-
tions.
1) Output Stage Due to the absence of the 2nd breakdown phe-
The main design task in developping a power op- nomenon, the SOA of the power DMOS transis-
erational amplifier, independently of the technol- tors is delimited only by a maximum dissipation
ogy used, is that of realization of the output stage. curve dependent on the duration of the applied
stimulus.
The solution shown as a principle shematic by
Fig3 represents the DMOS unity - gain output In order to fully exploit the capabilities of the
buffer of the TDA7295S. power transistors, the protection scheme imple-
mented in this device combines a conventional
This large-signal, high-power buffer must be ca- SOA protection circuit with a novel local tempera-
pable of handling extremely high current and volt- ture sensing technique which ” dynamically” con-
age levels while maintaining acceptably low har- trols the maximum dissipation.
monic distortion and good behaviour over
Figure 3: Principle Schematic of a DMOS unity-gain buffer.

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 TDA7295S

Figure 4: Turn ON/OFF Suggested Sequence

+Vs
(V)
+40

-40

-Vs
VIN
(mV)

V ST-BY
PIN #9 5V
(V)

VMUTE 5V
PIN #10
(V)

IQ
(mA)

V OUT
(V)
OFF

ST-BY
PLAY ST-BY OFF

MUTE MUTE
D98AU817

In addition to the overload protection described mute functions, independently driven by two
above, the device features a thermal shutdown CMOS logic compatible input pins.
circuit which initially puts the device into a muting The circuits dedicated to the switching on and off
state (@ Tj = 150 oC) and then into stand-by (@ of the amplifier have been carefully optimized to
Tj = 160 oC). avoid any kind of uncontrolled audible transient at
Full protection against electrostatic discharges on the output.
every pin is included. The sequence that we recommend during the
ON/OFF transients is shown by Figure 4.
Figure 5: Single Signal ST-BY/MUTE Control The application of figure 5 shows the possibility of
Circuit 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.
MUTE STBY
MUTE/ 20K
ST-BY
APPLICATION INFORMATION
10K 30K HIGH-EFFICIENCY
10µF 10µF Constraints of implementing high power solutions
1N4148 are the power dissipation and the size of the
D93AU014 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
3) Other Features adopted for both HI-FI and CAR-RADIO applica-
The device is provided with both stand-by and tions.

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TDA7295S

The TDA7295S is a monolithic MOS power ampli- In this application, the value of the load must not
fier which can be operated at 76V supply voltage be lower than 8 Ohm for dissipation and current
(80V with no signal applied) while delivering out- capability reasons.
put currents up to ±6A.
This allows the use of this device as a very high A suitable field of application includes HI-FI/TV
power amplifier (up to 80W as peak power with subwoofers realizations.
T.H.D.=10 % and Rl = 4 Ohm); the only drawback The main advantages offered by this solution are:
is the power dissipation, hardly manageable in - High power performances with limited supply
the above power range. voltage level.
The typical junction-to-case thermal resistance of
the TDA7295S is 1 oC/W (max= 1.5 oC/W). To - Considerably high output power even with high
avoid that, in worst case conditions, the chip tem- load values (i.e. 16 Ohm).
perature exceedes 150 oC, the thermal resistance With Rl = 8 Ohm, VS = ±25V the maximum output
of the heatsink must be 0.038 oC/W (@ max am- power obtainable is 150W (Music Power)
bient temperature of 50 oC).
As the above value is pratically unreachable; a
high efficiency system is needed in those cases APPLICATION NOTE: (ref. fig. 7)
where the continuous RMS output power is higher
than 50-60 W. Modular Application (more Devices in Parallel)
The TDA7295S was designed to work also in The use of the modular application lets very high
higher efficiency way. power be delivered to very low impedance loads.
For this reason there are four power supply pins: The modular application implies one device to act
two intended for the signal part and two for the as a master and the others as slaves.
power part.
T1 and T2 are two power transistors that only The slave power stages are driven by the master
operate when the output power reaches a certain device and work in parallel all together, while the
threshold (e.g. 20 W). If the output power in- input and the gain stages of the slave device are
creases, these transistors are switched on during disabled, the figure below shows the connections
the portion of the signal where more output volt- required to configure two devices to work to-
age swing is needed, thus ”bootstrapping” the gether.
power supply pins (#13 and #15).
The current generators formed by T4, T7, zener The master chip connections are the same as
diodes Z1, Z2 and resistors R7,R8 define the the normal single ones.
minimum drop across the power MOS transistors The outputs can be connected together with-
of the TDA7295S. L1, L2, L3 and the snubbers out the need of any ballast resistance.
C9, R1 and C10, R2 stabilize the loops formed by The slave SGND pin must be tied to the nega-
the ”bootstrap” circuits and the output stage of the tive supply.
TDA7295S.
The slave ST-BY pin must be connected to
By considering again a maximum average ST-BY pin.
output power (music signal) of 20W, in case
The bootstrap lines must be connected to-
of the high efficiency application, the thermal
resistance value needed from the heatsink is gether and the bootstrap capacitor must be in-
o
2.2 C/W (Vs =±38V and Rl= 8 Ohm). creased: for N devices the boostrap capacitor
All components (TDA7295S and power tran- must be 22µF times N.
sistors T1 and T2) can be placed on a The slave Mute and IN-pins must be grounded.
1.5oC/W heatsink, with the power darlingtons
electrically insulated from the heatsink. THE BOOTSTRAP CAPACITOR
Since the total power dissipation is less than that
of a usual class AB amplifier, additional cost sav- For compatibility purpose with the previous de-
ings can be obtained while optimizing the power vices of the family, the boostrap capacitor can be
supply, even with a high heatsink . connected both between the bootstrap pin (6) and
the output pin (14) or between the boostrap pin
(6) and the bootstrap loader pin (12).
BRIDGE APPLICATION
Another application suggestion is the BRIDGE
configuration, where two TDA7295S are used.

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 TDA7295S

Figure 6: High Efficiency Application Circuit

+50V
T3
D6 BC394 R4 R5
T1
1N4001 BDX53A 270 270
D1 BYW98100 T4 T5
+25V BC393 BC393
R17 270

L1 1µH D3 1N4148 R6
20K
C12 330nF Z1 3.9V
7 13
R20 C1 C3 C5 C7 C9 IN 3 C11 22µF
20K 1000µF 100nF 1000µF 100nF 330nF R3 680
R12 2 R7 C16
63V 35V
R22 R1 13K 3.3K 1.8nF
R16 L3 5µH
10K 2 4 13K
OUT
PLAY C13 10µF 14
GND R18 270
9 6
ST-BY R13 20K C15 P ot
22µF R8 C17
R23 R2 R14 30K 1 3.3K 1.8nF
10K 2 D5 12
1N4148 R15 10K
R21 C2 C4 C6 C8 C10 10 8 15
20K 1000µF 100nF 1000µF 100nF 330nF Z2 3.9V
C14
63V 35V
10µF L2 1µH D4 1N4148
T7 T8
D2 BYW98100 BC394 BC394
R19 270
-25V
T2 R9 R10 R11
D7 BDX54A
1N4001 T6 270 270 20K
BC393
-50V
D97AU807C

Figure 6a: PCB and Component Layout of the fig. 6

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TDA7295S

Figure 6b: PCB - Solder Side of the fig. 6.

Figure 7: Modular Application Circuit

C7 100nF +Vs C6 1000µF

R3 22K
MASTER
BUFFER
+Vs DRIVER +PWVs
C2
R2 7 11 13
22µF
680Ω IN- 2
-
14 OUT
C1 470nF
IN+ 3 C10
+ 100nF
BOOT
R1 22K 12 LOADER R7
2Ω
SGND 4
C5
47µF
VMUTE R5 10K MUTE 10 6
MUTE BOOTSTRAP
THERMAL S/C 5
VSTBY STBY 9 CLIP DET
STBY SHUTDOWN PROTECTION
R4 22K
1 8 15
STBY-GND -Vs -PWVs
C4 10µF
C9 100nF C8 1000µF
C3 10µF
-Vs
+Vs
C7 100nF C6 1000µF

BUFFER
+Vs DRIVER +PWVs
7 11 13
IN- 2
-
14 OUT
IN+ 3
+
BOOT
SLAVE 12 LOADER
SGND 4

MUTE 10 6
MUTE BOOTSTRAP
9 THERMAL S/C 5
STBY
STBY SHUTDOWN PROTECTION

1 8 15
STBY-GND -Vs -PWVs

C9 100nF C8 1000µF
D97AU808C
-Vs

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 TDA7295S

Figure 8a: Modular Application P.C. Board and Component Layout (scale 1:1) (Component SIDE)

Figure 8b: Modular Application P.C. Board and Component Layout (scale 1:1) (Solder SIDE)

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TDA7295S

mm inch
DIM.
MIN. TYP. MAX. MIN. TYP. MAX. OUTLINE AND
A 5 0.197 MECHANICAL DATA
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 Multiwatt15 V
Dia1 3.65 3.85 0.144 0.152

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 TDA7295S

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subject to change without notice. This publication supersedes and replaces all information previously supplied. STMicroelectronics products
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