Datasheet TDA7374BV Datasheet (SGS Thomson Microelectronics)

DUAL BRIDGE AUDIO AMPLIFIER FOR CAR RADIO

MINIMUMEXTERNAL COMPONENTCOUNT
NO BOOTSTRAPCAPACITORS
NO BOUCHEROTCELLS
CLIP DETECTOR OUTPUT
HIGHOUTPUT POWER
FIXED GAIN
VERYLOW STAND-BYCURRENT (1µA typ)
NO SWITCH ON/OFF NOISE

PROTECTIONS:

OUTPUT AC/DC SHORT CIRCUIT TO GND
ANDTO V

VERYINDUCTIVE LOADS
OVERRATINGCHIP TEMPERATURE
LOADDUMP VOLTAGE
FORTUITOUS OPEN GND
REVERSEBATTERY
ESD

S

TDA7374B

MULTIWATT15

ORDERING NUMBERS: TDA7374BV

DESCRIPTION

The TDA7374B is a new technology class AB
Audio Dual Bridge Power Amplifier in Multiwatt
packagedesignedfor car radio applications.

Thanks to the fully complementaryPNP/NPN out­put configuration the high power performances of
the TDA7374B are obtained without bootstrap ca­pacitors.

TEST AND APPLICATION CIRCUIT

April 1995

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TDA7374B

PIN CONNECTION (Top view)

ABSOLUTE MAXIMUM RATINGS

Symbol Parameter Value Unit

V

V

V

PEAK

P

T

stg,Tj

OP

I

O

I

O
tot

DC Supply Voltage 28 V

S

Operating Supply Voltage 18 V
Peak Supply Voltage (t = 50ms) 50 V
Output Peak Current (not rep. t = 100µs) 4.5 A
Output Peak Current (rep. f > 10Hz) 3.5 A
Power Dissipation (T

=85°C) 36 W

case

Storage and Junction Temperature -40 to 150 °C

THERMAL DATA

Symbol Description Value Unit

R

th j-case

Thermal Resistance Junction-case Max 1.8 °C/W

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TDA7374B

ELECTRICAL CHARACTERISTICS (Referto the test circuit;VS=14.4V; RL=4Ω,T

amb

=25°C,

f = 1kHz, unlessotherwise specified)

Symbol Parameter Test Condition Min. Typ. Max. Unit

V

S

I

d

P

O

d Distortion R

CT Cross-Talk f = 1kHz

R

IN

G

V

G

V

E

IN

SVR Supply Voltage Rejection R

ASB Stand-by Attenuation 60 dB

I

SB

V

SB ON

V

SB OFF

V

OS

I

CD OFF

I

CD ON

(*) Pin 10 Pulled-up to 5V with 10kΩ;RL=4Ω

Supply Range 8 18 V
Total Quiescent Drain Current RL= ∞ 150 mA
Output Power RL=4Ω; THD = 10% 17 21 W

=4ΩPO= 0.1 to 10W 0.5 %

L

65

f = 10kHz

55
Input Impedance 10 KΩ
Voltage Gain 26 dB
Voltage Gain Match. 1 dB
Input Noise Voltage Rg= 0 to 10kΩ Weight A

22Hz to 22KHz

= 0; f = 100Hz

g

f = 10kHz

48

3.5
10

55

ST-BY Current 1 µA
ST-BY On Threshold Voltage 1.5 V
ST-BY Off Threshold Voltage 3.5 V
Output Offset Voltage 200 mV
ClippingDetector ”OFF”

THD = 1% (*) 100 µA

Output Average Current
ClippingDetector ”ON ”

THD = 10% (*) 190 µA

Output Average Current

dB
dB

µV
µV

dB

3/13

TDA7374B

TEST AND APPLICATION CIRCUIT

P.C. BOARDAND COMPONENTLAYOUT (1:1 scale)

B

4/13

TDA7374B

Figure1: QuiescentDrainCurrent vs. Supply

Voltage

Figure3: Output Power vs.Supply Voltage

Figure2: QuiescentOutputVoltagevs. Supply

Voltage

Figure4: Distortionvs. OutputPower

Figure5: Output Power vs.Frequency

Figure6: SupplyVoltageRejectionvs.

Frequencyfor a Different values of C6
Capacitor

R

g

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TDA7374B

Figure7: Cross-Talkvs. Frequency

R

g

Figure9: Stand-by Attenuationvs. Threshold

Voltage

Figure8: En Input vs. Rg

R

g

Figure10: Stand-byAttenuationvs.Input Voltage

Figure11: Clipping Detector Average Current

(Pin 10) vs. Distortion

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Figure12: TotalPower Dissipationand

Efficiencyvs.Output Power

TDA7374B

OUTPUTSTAGE

The fully complementary output stage was made
possible by the development of a new compo­nent: the ST exclusive power ICV PNP.

A novel design based upon the connection shown
in fig. 13 has then allowed the full exploitation of
its possibilities.

Figure13: The new OutputStage

The clear advantagesthisnew approachhas over
classicaloutput stages are as follows:

1 - Rail-to-Rail Output Voltage Swing With No
NeedOf BootstrapCapacitors.

The output swing is limited only by the Vcesat of
the output transistors, which are in the range of

0.6 Ohm each.
Classical solutions adoptingcomposite PNP-NPN

for the upper output stage have higher saturation
Figure14: Clipping DetectionWaveforms

loss on the top side of the waveform. This unbal­anced saturation causes a significant power re­duction. The only way to recover power consists
of the addition of expensivebootstrap capacitors.

2 - Absolute Stability Without Any External
Compensation.

Referring to the circuit of Fig. 13 the gain
V

OUT/VIN

R2/R1.The DC Output (V

is greater than unity, approximately 1 +

/2) is fixedby an aux-

CC

iliaryamplifiercommon to all the channels).
By controlling the amount of this local feedback it

is possible to force the loop gain (A * β) to less
than unity at frequency for which the phase shift
is 180 Deg. This means that the output buffer is
intrinsicallystable and not prone to oscillation.

Most remarkably, the above feature has been
achievedin spite of the very low closed loop gain
of the amplifier.

In contrast, with the classical PNP-NPN stage,
the solution adopted for reducing the gain at high
frequencies makes use of external RC networks,
namelythe Boucherot cells.

OTHEROUTSTANDINGCHARACTERISTICS:

Clipping Detector Output

The TDA7374B is equipped with an internal cir­cuitable to detect the outputstage saturationpro­viding a proper current sinking into a open collec­tor output (pin 10) when a certain distortion level
isreached at each output.

This particular function allows gain compression
facility whenever the amplifier is overdriven, thus
obtaininghigh quality sound at all listeninglevels.

7/13

TDA7374B

OffsetControl

The quiescent output voltage must be as close as
possible to its nominal value, so that less undis­tortedpower wouldbe available.

For this reason an input bias current compensa­tion is implemented to riduce the voltage drop
across the input resistors, which appears ampli­fied at the outputs.

Gain Internally Fixed to 26dB

Advantagesof thisdesign choiceare in termsof:

componentsand spacesaving
output noise, supply voltage rejection and dis-

tortionoptimization.

Silent Turn On/Off and Muting/Stand-by Func­tion

The stand-bycan be easily activated by means of
a CMOS level applied to pin 7 througha RC filter.
Under stand-by condition the device is turned off
completely(supply current= 1 µA TYP ; output at­tenuation=90 dB TYP).

Every ON/OFF operation is virtuallypop free.
Furthermore,at turn-on the devicestaysin muting

condition for a time determined by the value as­signed to the SVR capacitor (T= Csvr * 7,000).
While in muting the device outputs becomes in­sensitive to any kinds of signal that may be pre­sent at the input terminals. In other words every
transient coming from previous stages produces
no unpleasantacoustic effect to the speakers.

Anothersituation under which the device is totally
muted is whenever the supply voltage drops
lower than 7V. This is helpful to pop suppression
duringthe turn-off by battery switch.

then an LC filter must be inserted between the
supply and pins 3 and 13, in order to assure that
the pulses at pins 3 and 13 will be held within the
limitsshown.

A suggestedLC network isshown in fig. 15.
With this network, a trainof pulses with amplitude
up to 120V and width of 2ms can be applied at
point A. This type of protection is ON when the
supply voltage (pulse or DC) exceeds 18V. For
this reason the maximum operating supply volt­age is 18V.

Figure15

PolarityInversion
Figure16

BUILT-INPROTECTION SYSTEMS
Full Protection of Device and Loudspeakers

Against AC/DC Short Circuits (to Gnd, to Vs,
acrossthe Speakers).

Reliable and safe operation in presence of all
kinds of short circuit involving the outputs is as­suredby a built-in protectionsystem that operates
in the following way:

In case of overload, a SCR is activated as soon
as the current flowing through the output transis­tors overcomes a preset threshold value depend­ing on the chip temperature. The SCR causes an
interruption of the supply current of the power
transistor.

Load Dump Voltage Surge

The TDA 7374 has a circuit which enables it to
withstand a voltage pulse train on pins 3 and 13,
of the type shownin fig. 16.
If the supply voltage peaks to more than 50V,

8/13

High current (up to 10A) can be handled by the
device with no damage for a longer period than
the blow-out time of a quick 2A fuse (normally
connected in series with the supply). This fea­turesis added to avoid destruction,if during fitting
to the car, a mistake on the connection of the
supplyis made.

OpenGround

When the radio is in the ON condition and the
ground is accidentally opened, a standard audio
amplifierwill be damaged. On the TDA7374Bpro­tectiondiodes are includedto avoidany damage.

InductiveLoad

A protection diode is provided to allow use of the
TDA7374Bwithinductiveloads.

TDA7374B

DC Voltage

The maximum operating DC voltage for the
TDA7374Bis 18V.
However the device can withstand a DC voltage
up to 28V with no damage. This could occur dur­ing winter if two batteries are series connectedto
crankthe engine.

ThermalShut-down

The presence of a thermal limiting circuit offers
the following advantages:

1)an overloadon the output (even if it is perma­nent), or an excessive ambient temperature
can be easily withstood.

2)the heatsink can have a smaller factor of
safety compared with that of a conventional
circuit. There is no device damage in case of
excessive junction temperature: all happens
is that P

(and therefore P

o

) and Idare re-

tot

duced.

The maximum allowable power dissipation de­pends upon the size of the external heatsink (i.e.
its thermal resistance); Fig. 17 shows the dissi­pable power as a function of ambienttemperature
for differentthermalresistance.

Figure17: Maximum AllowablePower

Dissipationvs. AmbientTemperature

Loudspeaker Protection

The TDA7374B guarantees safe operations even
for the loudspeaker in case of accidental shortcir­cuit.
Whenevera single OUT to GND, OUT to V

S

short
circuit occurs both the outputs are switched OFF
so limiting dangerous DC current flowing through
the loudspeaker.

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TDA7374B

CLIPPINGDETECTOR

Fig 19 shows an application using the TDA7374B
in combination with the SGS-THOMSON audio­processorTDA7302.

Theoutputclippingis recognizedby the microproc­essor(in this applicationit is simulatedbya PC).

The detailed way to operate of the system is rep­resentedby the flow-chart of fig.18.

The controller detects when the clipping is active
(minimun detection width fixed by a C29 = 12 nF
external capacitor), and reduces the volume (or
bass) bystep of 2 dB (with a programmablewait­ing time), until no more clipping is detected.

Then the controllerwaits for a programmabletime
before increasing the volume again by step of 2
dBuntil clippingis again detected or the panel se­lectedvolume is reached.

Practicaladvantages of this application is a better
sound quality deriving from operation under no
clipping conditions, which also means the avail­ability of higherundistortedpower.

Figure:18: ClippingDetectorControlRoutine

WHAT IS NEEDED FOR A DEMONSTRATION

- a XT or AT IBM compatible PC, supplied with
EGA card

- a SGS-THOMSON audioprocessorapplicationdisk

- a TDA7302 + TDA7374Bboard

- a connector from audioprocessor board to PC
parallelport

GENERALINFORMATION

In the application shown in fig 18 the TDA7302
audioprocessorworks on PC XT or AT IBM com­patible.

Control is accomplished by serial bus ( S-bus or

2

C-bus or SPIbus) sent to the test board through

I
the PC parallel port.

ThePC simulates the behaviour of the microproc­essor in a real application (for example in a car
radio) and the buffer is necessaryonly in this ap­plicationfor protectingthe PC.

10/13

Figure19: Applicationwith TDA7302+ TDA7374B

TDA7374B

TDA7374B

11/13

TDA7374B

MULTIWATT15 (Vertical) PACKAGE MECHANICAL DATA

DIM.

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

MIN. TYP. MAX. MIN. TYP. MAX.

mm inch

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TDA7374B

Information furnished is believed to be accurate and reliable. However, SGS-THOMSON Microelectronics assumes no responsibility for the
consequences of use of such information nor for any infringement ofpatents or otherrights of third parties which may result from itsuse. No
license is granted by implication or otherwise under any patent or patent rights of SGS-THOMSON Microelectronics. Specifications men­tioned in this publication are subject to change without notice. This publication supersedes and replaces all information previously supplied.
SGS-THOMSON Microelectronics products are not authorized for use as critical components in life support devices or systems without ex­press written approval of SGS-THOMSON Microelectronics.

 1995 SGS-THOMSON Microelectronics - All RightsReserved

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