DMOSPOWER STAGE
HIGH OUTPUT POWER (THD = 10%, UP TO
60W)
MUTING/STAND-BY FUNCTIONS
NO SWITCHON/OFFNOISE
VERY LOW DISTORTION
VERY LOW NOISE
SHORTCIRCUIT PROTECTION
THERMAL SHUTDOWN
CLIPDETECTOR
MODULARITY (MORE DEVICES CAN BE
EASILY CONNECTED IN PARALLEL TO
DRIVEVERY LOW IMPEDANCES)
DESCRIPTION
The TDA7296S 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: Typical Application andTest Circuit
MULTIPOWERBCD TECHNOLOGY
Multiwatt15
ORDERING NUMBER: TDA7296SV
class TV). Thanks to the wide voltage range and
to the high out current capability it is able to supply the highest powerinto both4Ω and8Ω 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 thermal dissipationof the system.
VMUTE
VSTBY
June 2000
C7 100nFC6 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 100nFC8 1000µF
+PWVs+Vs
PROTECTION
158
-Vs
S/C
14
12
6
5
D97AU805A
OUT
BOOT
LOADER
C5
22µF
BOOTSTRAP
CLIP DET
(*)
VCLIP
1/11
TDA7296S
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
5
6Bootstrap Voltage Referred to -VS60V
9Stand-by Voltage Referredto -VS60V
Mute Voltage Referred to -V
S
S
S
S
60V
60V
60V
60V
Output Peak Current10A
Power Dissipation T
=70°C50W
case
Operating Ambient Temperature Range0to 70°C
Storage and JunctionTemperature150°C
THERMALDATA
SymbolDescriptionTypMaxUnit
R
th j-case
Thermal Resistance Junction-case11.5°C/W
2/11
TDA7296S
ELECTRICAL CHARACTERISTICS (Referto the Test Circuit VS= ±24V,RL=8Ω,GV= 30dB;
R
=50Ω;T
g
SymbolParameterTest ConditionMin.Typ.Max.Unit
V
S
I
q
I
b
V
OS
I
OS
P
O
dTotal Harmonic Distortion (**)P
SRSlew Rate710V/µs
G
V
G
V
e
N
f
L,fH
R
i
SVRSupply Voltage Rejectionf = 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 is themaximal power which the amplifieris capable of producing across the rated load resistance (regardless of non linearity)
1 sec after the applicationof a sinusoidal input signal of frequency 1KHz.
Note (**): Tested withoptimized Application Board (see fig. 2)
Open Loop Voltage Gain80dB
Closed Loop Voltage Gain243040dB
Total Input NoiseA = curve
f = 20Hz to 20kHz
1
25
µV
µV
Frequency Response (-3dB)PO= 1W20Hz to 20kHz
Input Resistance100kΩ
= 0.5Vrms6075dB
ripple
Thermal Shutdown150
or GND)
S
°
Stand-by on Threshold1.5V
Stand-by off Threshold3.5V
Stand-by Attenuation7090dB
Quiescent Current @ Stand-by13mA
or GND)
S
Mute on Threshold1.5V
Mute off Threshold3.5V
Mute Attenuation6080dB
C
3/11
TDA7296S
Figure2: Typical ApplicationP.C. Board and ComponentLayout (scale1:1)
4/11
TDA7296S
APPLICATION SUGGESTIONS(seeTest and Application Circuits 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 helpthe designer.
COMPONENTSSUGGESTED VALUEPURPOSE
LARGER THAN
SUGGESTED
R1 (*)22kINPUT RESISTANCEINCREASE INPUT
IMPEDANCE
R2680
Ω
CLOSED LOOP GAIN
DECREASE OF GAIN INCREASE OF GAIN
SMALLER THAN
SUGGESTED
DECREASE INPUT
IMPEDANCE
SET TO 30dB (**)
R3 (*)22kINCREASE OF GAIN DECREASE OF GAIN
R422kST-BY TIME
CONSTANT
LARGER ST-BY
ON/OFF TIME
SMALLER ST-BY
ON/OFF TIME;
POP NOISE
R510kMUTE TIME
CONSTANT
C10.47µFINPUT DC
DECOUPLING
LARGER MUTE
ON/OFF TIME
SMALLER MUTE
ON/OFF TIME
HIGHER LOW
FREQUENCY
CUTOFF
C222µFFEEDBACK DC
DECOUPLING
HIGHER LOW
FREQUENCY
CUTOFF
C310µFMUTE TIME
CONSTANT
C410µFST-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
C522µFXN (***)BOOTSTRAPPINGSIGNAL
C6, C81000µFSUPPLY VOLTAGE
C7, C90.1µFSUPPLY VOLTAGE
(*) R1 = R3 for pop optimization
(**) Closed Loop Gain has to be ≥ 26dB
(***) Multiply this value for the number ofmodular 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 output and GND, a BoucherotCell, in order to
avoid dangerous spurious oscillations when the
speakersterminalare shorted.
The suggested Boucherot Resistor is 3.9Ω/2W
and the capacitor is 1µF.
5/11
TDA7296S
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 presenceof highlyreactive loads.
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
fromsecondary breakdown is highlydesirable.
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 DMOSunity - gain output
bufferof the TDA7296S.
This large-signal, high-power buffer must be capable of handling extremely high current and voltage levels while maintaining acceptably low harmonic distortion andgoodbehaviour over
frequency response; moreover, an accurate control of quiescentcurrent 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 enoughto 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 connection of the Miller capacitor
at the amplifier’s output to introduce a local AC
feedbackpath enclosing the outputstage itself.
2) Protections
In designing a power IC, particularattention must
be reserved to the circuits devoted to protection
of the device from short circuit or overload conditions.
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 maximum dissipation.
In addition to the overload protection described
Figure3: PrincipleSchematicof a DMOSunity-gain buffer.
6/11
Figure4: Turn ON/OFFSuggested Sequence
+Vs
(V)
+40
-40
-Vs
V
IN
(mV)
V
ST-BY
PIN
(V)
5V
#9
TDA7296S
#10
5V
OFF
ST-BY
PLAY
MUTEMUTE
V
MUTE
PIN
(mA)
V
(V)
IQ
OUT
(V)
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 electrostaticdischarges on
everypin is included.
Figure5: SingleSignalST-BY/MUTEControl
Circuit
MUTESTBY
MUTE/
ST-BY
20K
10K30K
1N4148
10µF10µF
D93AU014
3) Other Features
The device is provided with both stand-by and
mute functions, independently driven by two
CMOSlogic compatibleinput pins.
The circuits dedicated to the switchingon and off
of the amplifier have been carefully optimized to
ST-BYOFF
D98AU817
avoid any kind of uncontrolledaudibletransient at
the output.
The sequence that we recommend during the
ON/OFFtransientsis shown by Figure4.
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
BRIDGEAPPLICATION
Another application suggestion is the BRIDGE
configuration,where two TDA7296S are used.
In this application, the value of the load must not
be lower than 8 Ohm for dissipation and current
capabilityreasons.
A suitable field of application includes HI-FI/TV
subwoofersrealizations.
Themain advantagesoffered by this solution are:
- High power performanceswith limited supply
voltagelevel.
- Considerablyhigh output powereven with high
load values (i.e. 16 Ohm).
With Rl= 8 Ohm, Vs = ±23V the maximum output
powerobtainable is 120W (Music Power)
7/11
TDA7296S
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 masterand 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 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 ballast resistance.
Figure6: ModularApplication Circuit
C7 100nFC6 1000µF
IN+
SGND
MUTE
STBY
IN-2
C4 10µF
R3 22K
3
4
10
9
-
+
MUTE
STBY
1
STBY-GND
C7 100nFC6 1000µF
MASTER
VMUTE
VSTBY
C2
22µF
R1 22K
R5 10K
R4 22K
R2
680Ω
C1 470nF
C3 10µF
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 bootstrap capacitor 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 boostrapcapacitor can be
connectedboth betweenthe bootstrap pin (6) and
the output pin (14) or between the boostrap pin
(6) and the bootstraploader pin (12).
+Vs
BUFFER
DRIVER
11
713
THERMAL
SHUTDOWN
-Vs-PWVs
C9 100nFC8 1000µF
PROTECTION
158
-Vs
+Vs
+PWVs+Vs
OUT
14
C10
C5
47µF
100nF
R7
2Ω
S/C
12
6
5
BOOT
LOADER
BOOTSTRAP
CLIP DET
8/11
SLAVE
IN+3
SGND
MUTE
STBY
IN-2
BUFFER
DRIVER
11
713
-
+
4
10
MUTE
9
STBY
1
STBY-GND
THERMAL
SHUTDOWN
-Vs-PWVs
C9 100nFC8 1000µF
PROTECTION
158
-Vs
+PWVs+Vs
OUT
14
BOOT
12
LOADER
6
BOOTSTRAP
S/C
5
D97AU808C
TDA7296S
Figure7a: Modular Application P.C.Board and ComponentLayout (scale 1:1) (Component SIDE)
Figure7b: ModularApplication P.C. Board and ComponentLayout (scale1:1) (SolderSIDE)
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