TDA7370B
QUAD POWER AMPLIFIER FOR CAR RADIO
MINIMUMEXTERNAL COMPONENTCOUNT
HIGHCURRENT CAPABILITY
NO BOOTSTRAPCAPACITORS
NO BOUCHEROTCELLS
CLIP DETECTOR OUTPUT
HIGHOUTPUT POWER
HIGHAPPLICATIONFLEXIBILITY
FIXED GAIN
VERYLOW STAND-BYCURRENT (1µA typ)
NO SWITCH ON/OFF NOISE
PROTECTIONS:
OUTPUT AC/DC SHORT CIRCUIT TO GND
ANDTO V
S
VERYINDUCTIVE LOADS
OVERRATINGCHIP TEMPERATURE
LOADDUMP VOLTAGE
FORTUITOUS OPEN GND
REVERSEBATTERY
ESD
DESCRIPTION
The TDA7370B is a new technology class AB
quad channels Audio Power Amplifier in Multiwatt
packagedesignedfor carradioapplications.
Thanks to the fullycomplementaryPNP/NPNoutput configuration the high powerperformances of
the TDA7370B areobtained withoutbootstrap capacitors.
April 1995
BLOCK DIAGRAM
MULTIWATT15V
ORDERING NUMBER: TDA7370B
1/17
PIN CONNECTION(Top view)
ABSOLUTE MAXIMUM RATINGS
Symbol Parameter Value Unit
V
S
DC Supply Voltage 28 V
V
OP
Operating Supply Voltage 18 V
V
PEAK
Peak SupplyVoltage(t = 50ms) 50 V
I
O
Output Peak Current (not rep. t = 100µs) 4.5 A
I
O
Output Peak Current (rep. f > 10Hz) 3.5 A
P
tot
Power Dissipation(T
case
=85°C) 36 W
T
stg,Tj
Storage and JunctionTemperature -40 to150 °C
THERMAL DATA
Symbol Description Value Unit
R
th j-case
Thermal Resistance Junction-case Max 1.8 °C/W
TDA7370B
2/17
ELECTRICAL CHARACTERISTICS (Refer to thetest circuit; VS=14.4V; RL=4Ω,T
amb
=25°C,
f =1kHz, unless otherwise specified)
Symbol Parameter Test Condition Min. Typ. Max. Unit
V
S
Supply Range 8 18 V
I
d
Total Quiescent Drain Current RL= ∞ 150 mA
P
O
Output Power RL=4Ω; THD = 10%
Single Ended
Bridge
5.5 6.5
20
W
W
d Distortion R
L
=4Ω;
Single Ended, P
O
= 0.1 to 4W
Bridge, P
O
= 0.1to 10W 0.03
0.5 %
%
CT Cross Talk f = 1kHz Bridge
f = 10kHz Bridge
f = 1kHz Single Ended
f = 10kHz Single Ended
65
55
60
50
dB
dB
dB
dB
R
IN
Input Impedance Single Ended
Bridge
20
15
KΩ
KΩ
G
V
Voltage Gain Single Ended
Bridge
20
26
dB
dB
G
V
Voltage Gain Match. 1 dB
E
IN
Input Noise Voltage(*) SINGLE ENDED
Non Inv. Ch., R
g
= 10kΩ
Inv. Ch.,R
g
= 10kΩ
BRIDGE (R
g
= 0 to 10kΩ)
3.0
5
3.5
µV
µV
µV
SVR Supply Voltage Rejection R
g
= 0;f = 100Hz to 10kHz 50 dB
ASB Stand-by Attenuation 60 dB
I
SB
ST-BY Current 1 µA
V
SB ON
ST-BY On ThresholdVoltage 1.5 V
V
SB OFF
ST-BY Off ThresholdVoltage 3.5 V
V
OS
Output Offset Voltage 200 mV
I
CD OFF
ClippingDetector ”OFF”
Output Average Current
THD = 1% (**)
100 µA
I
CD ON
ClippingDetector ”ON”
Output Average Current
THD = 10% (**)
190 µA
(*) Weighted A
(**) Pin 10 Pulled-up to 5V with 10kΩ;
TDA7370B
3/17
APPLICATIONCIRCUIT (QUAD STEREO)
QUAD STEREO P.C. BOARD AND COMPONENT LAYOUT(1:1 SCALE)
B
TDA7370B
4/17
APPLICATIONCIRCUIT (DOUBLE BRIDGE)
DOUBLE BRIDGEP.C. BOARD AND COMPONENTLAYOUT(1:1 SCALE)
B
TDA7370B
5/17
APPLICATIONCIRCUIT (STEREO/BRIDGE)
Figure1: QuiescentDrain Current vs. Supply
Voltage(Bridge/SingleEnded)
Figure2: QuiescentOutputVoltage vs. Supply
Voltage(Bridge/SingleEnded)
TDA7370B
6/17
Figure3: Output Power vs. Supply Voltage
(SingleEnded)
Figure4: OutputPower vs. Supply Voltage
(Bridge)
Figure5: Distortion vs. OutputPower (Single
Ended)
Figure6: Distortionvs. Output Power (Bridge)
Figure7: Output Power vs. Frequency (Single
Ended)
Figure8: OutputPower vs. Frequency (Bridge)
TDA7370B
7/17
Figure9: SupplyVoltage Rejection vs.
Frequency(SingleEnded)for different
valuesof pin 6 capacitor.
Figure10: SupplyVoltageRejection vs.
Frequency(Bridge)for different
values of pin 6 capacitor.
Figure11: Cross-Talkvs. Frequency(Bridge) Figure12: Stand-ByAttenuationvs. Threshold
Voltage(SingleEnded/Bridge)
Figure14: En input vs. R
S
(SingleEnded)
Figure13: ClippingDetector AverageCurrent
(pin 10) vs.Distortion(Single Ended)
R
g
R
g
R
g
TDA7370B
8/17
Figure17: TotalPower Dissipation and
Efficiency vs. Ouput Power (Single
Ended)
Figure18: TotalPower Dissipation and
Efficiencyvs.Ouput Power (Bridge)
Figure16: En input vs. R
S
(Bridge)
Figure15: En input vs. R
S
(SingleEnded)
R
g
R
g
TDA7370B
9/17
OUTPUTSTAGE
The fully complementary output stage was made
possible by the development of a new component: the ST exclusive powerICV PNP.
A novel design based upon the connectionshown
in fig. 19 has then allowed the full exploitation of
its possibilities.
The clear advantages this new 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 (R
sat
) each.
Classical solutions adoptingcomposite PNP-NPN
for the upper output stage have higher saturation
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 expensivebootstrapcapacitors.
2 - Absolute Stability Without Any External
Compensation.
Referring to the circuit of Fig. 19 the gain
V
OUT/VIN
is greater than unity, approximately 1 +
R2/R1.The DC output (V
CC
/2) is fixed by an aux-
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 (20 dB).
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 TDA7370B is equipped with an internal circuitable to detectthe output stage saturationproviding a current sinking into a open collector output (pin 10) when a certain distortion level is
reachedat each output.
This particular function allows gain compression
facility whenever the amplifier is overdriven, thus
obtaininghigh quality sound at all listeninglevels.
Figure19: The new Output Stage
Figure20: Clipping DetectionWaveforms
TDA7370B
10/17
OffsetControl
The quiescent output voltage must be as close as
possible to its nominal value, so that less undistortedpower would be available.
For this reason an input bias current compensation is implemented to reduce the voltage drop
across the input resistors, which appears amplified at the outputs.
Gain Internally Fixed to 20dB in Single Ended,
26dB in Bridge
Advantagesof this design choice are 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 device stays in 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.
EasySingle Ended to Bridge Transition.
The change from single ended to bridge configurations is made simply by means of a shortcircuit
across the inputs, that is no need of further external components.
High ApplicationFlexibility
The availability of 4 independentchannels makes
it possible to accomplishseveral kinds of applications ranging from 4 speakers stereo (F/R) to 2
speakersbridgesolutions.
In case of working in single ended conditions the
polarity of the speakers driven by the inverting
amplifier must be reversed respect to those
drivenby non invertingchannels.
This is to avoid phase inconveniences causing
sound alterations especially during the reproduction of low frequencies.
BUILT-INPROTECTIONSYSTEMS
Full Protection of Device and Loudspeakers
Against AC/DC Short Circuits (to Gnd, to Vs,
across the Speakers).
Reliable and safe operation in presence of all
kinds of short circuit involving the outputs is assuredby a built-in protection system 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.The normal working is restoredby a restart circuit going into action as soon as the short
circuitis removed.
LoadDump Voltage Surge
The TDA7370B has a circuit which enables it to
withstand a voltage pulse train on pins 3 and 13,
of the type shown in fig. 22.
If the supply voltage peaks to more than 50V,
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 networkis shown in fig. 21.
With this network, a train of 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.
Figure21
Figure22
TDA7370B
11/17
PolarityInversion
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 features is added to avoid destruction,if during fitting
to the car, a mistake on the connection of the
supplyis made.
Open Ground
When the radio is in the ON condition and the
ground is accidentally opened, a standard audio
amplifierwill be damaged. On the TDA7370Bprotectiondiodes are includedto avoid any damage.
InductiveLoad
A protection diode is provided to allow use of the
TDA7370Bwith inductiveloads.
DC Voltage
The maximum operating DC voltage for the
TDA7370Bis 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 connected to
crankthe engine.
ThermalShut-down
The presence of a thermal limiting circuit offers
the following advantages:
1)an overload on 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
o
(and therefore P
tot
) and Idare re-
duced.
The maximum allowable power dissipation depends upon the size of the external heatsink (i.e.
its thermal resistance); Fig. 23 shows the dissipablepower as a function of ambienttemperature
for different thermal resistance.
Loudspeaker Protection
TheTDA7370Bguaranteessafe operat ion sevenfor
thelouds peakerin caseofacci dent alshortc i rcuit.
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.
Figure23: MaximumAllowablePower
Dissipationvs. Ambient Temperature
TDA7370B
12/17
CLIPPINGDETECTOR
Figures 25 and 26 show an application using the
TDA7370B in combination with the SGS-THOMSONaudioprocessorTDA7302.
Theoutputclippingis recognizedby the microprocessor(in this applicationit is simulatedby a PC).
The detailed way to operate of the system is representedby the flow-chartof fig.24
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 ) by steps of 2 dB (with a programmable
waiting time), until no more clippingis detected.
Then the controller waits for a programmabletime
before increasing the volume again by step of 2
dBuntil clippingis again detected or the panelselectedvolume is reached.
Practicaladvantages of this application is a better
sound quality deriving from operation under no
clipping conditions, which also means the availability of higherundistorted power.
WHAT IS NEEDED FOR A DEMONSTRATION
- a XT or AT IBM compatible PC, supplied with
EGA card
- a SGS-THOMSONaudioprocessor application disk
- a TDA 7302 + TDA7370Bboard
- a connector from audioprocessorboard to PC
parallelport
GENERALINFORMATION
In the application shown in figures 25 and 26 the
TDA7302 audioprocessorworks on PC XT or AT
IBM compatible.
Control is accomplished by serial bus ( S-bus or
I
2
C-bus or SPI bus) sent to the test board through
the PC parallel port.
ThePC simulatesthe behaviourof the microproc-
essor in a real application (for example in a car
radio) and the buffer is necessary only in this applicationfor protectingthe PC.
Figure24: Clipping DetectorControl Routine
TDA7370B
13/17
Figure25: Applicationwith TDA7302 + TDA7370B (QUAD STEREO)
TDA7370B
TDA7370B
14/17
Figure26: Applicationwiyh TDA7302 + TDA7370B(DOUBLEBRIDGE)
TDA7370B
TDA7370B
15/17
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 1.14 1.27 1.4 0.045 0.050 0.055
G1 17.57 17.78 17.91 0.692 0.700 0.705
H1 19.6 0.772
H2 20.2 0.795
L 22.1 22.6 0.870 0.890
L1 22 22.5 0.866 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 4.2 4.3 4.6 0.165 0.169 0.181
M1 4.5 5.08 5.3 0.177 0.200 0.209
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
MECHANICAL DATA AND DIMENSIONS OF THE MULTIWATT15(Vertical)
TDA7370B
16/17
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 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 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
MULTIWATT is a Registered Trademark of the SGS-THOMSON Microelectronics
SGS-THOMSON Microelectronics GROUPOF COMPANIES
Australia - Brazil - France - Germany - Hong Kong - Italy - Japan - Korea - Malaysia - Malta - Morocco - The Netherlands - Singapore -
Spain - Sweden - Switzerland - Taiwan - Thaliand - United Kingdom - U.S.A.
TDA7370B
17/17
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