December 2011 Doc ID 9814 Rev 4 1/28
1
STA7360
20 W bridge/stereo audio amplifier with clipping detector
Features
Very few external components
No boucherot cells
No bootstrap capacitors
High output power
No switch-on/off noise
Very low standby current
Fixed gain (20 db stereo)
Programmable turn-on delay
Clipping detector
Standby function
Protections
Output AC-DC short-circuit to ground and
to supply voltage
Highly inductive loads
Loudspeaker protection
Overrating chip temperature
ESD protection
Description
The STA7360 is a class-AB audio power amplifier
in the Multiwatt® package.Thanks to the fully
complementary PNP/NPN output configuration,
the high-power performance of the STA7360 is
obtained without bootstrap capacitors.
A delayed turn-on mute circuit eliminates audible
on/off noise, and a short-circuit protection system
prevents spurious intervention with highly
inductive loads.
The device provides a circuit for the detection of
clipping in the output stages. The output, an open
collector, is able to drive systems with automatic
volume control.
Figure 1. Application circuit
Table 1. Device summary
Order code Package Packing
STA7360 Multiwatt11V Tube
MULTIWATT11V
C4
1µF
220µF
C5
100nF
C6
+VS
9
11
7
STAND-BY
SVR
22µF C3
5
IN2(+)
0.22µF C2
1
IN1(+)
0.22µF C1
IN
8
10
OUT2
OUT1
4OUT BRIDGE
63
P-GND
CLIP DET
D00AU1213
RL
20K
2
S-GND
www.st.com
Obsolete Product(s) - Obsolete Product(s)
Contents STA7360
2/28 Doc ID 9814 Rev 4
Contents
1 Device overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1 Block diagrams . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2 Pin connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2 Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1 Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
2.4 Test and application circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
3 Typical operating characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
4 Block description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.1 Polarization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.2 SVR . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.3 Delayed turn-on (muting) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.4 Stereo/bridge switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.5 Standby . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
4.6 Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
4.7 Output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
4.8 Amplifier block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
5 Built-in protection systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.1 Short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.2 Polarity inversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
5.3 DC voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.4 Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
5.5 Loudspeaker protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6 Application hints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.1 Reducing turn-on/off pop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
6.2 Turn-on . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
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STA7360 Contents
Doc ID 9814 Rev 4 3/28
6.3 Turn-off . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
6.4 Balanced input in bridge configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
7 Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
8 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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List of tables STA7360
4/28 Doc ID 9814 Rev 4
List of tables
Table 1. Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Table 2. Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 3. Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Table 4. Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Table 5. Recommended values of the external components (stereo test and application circuit) . . 10
Table 6. Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
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STA7360 List of figures
Doc ID 9814 Rev 4 5/28
List of figures
Figure 1. Application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Figure 2. Block diagram - stereo configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 3. Block diagram - bridge configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Figure 4. Pin connections (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Figure 5. Stereo test and application circuit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Figure 6. Board and layout of the stereo test and application circuit (1:1 scale) . . . . . . . . . . . . . . . . 10
Figure 7. Bridge test and application circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Figure 8. Board and layout of the bridge test and application circuit (1:1 scale) . . . . . . . . . . . . . . . . 11
Figure 9. Output power vs. supply voltage (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 10. Output power vs. supply voltage (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 11. Output power vs. supply voltage (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 12. Output power vs. supply voltage (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Figure 13. Drain current vs. supply voltage (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 14. Distortion vs. output power (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 15. Distortion vs. output power (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 16. Distortion vs. output power (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Figure 17. Distortion vs. output power (bridge) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 18. SVR vs. frequency & C3 (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 19. SVR vs. frequency & C3 (bridge) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 20. Crosstalk vs. frequency (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Figure 21. Power dissipation & efficiency vs. output power (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 22. Power dissipation & efficiency vs. output power (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 23. Power dissipation & efficiency vs. output power (stereo) . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Figure 24. Mute function diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Figure 25. Turn-on delay circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 26. Dual-channel distortion detector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Figure 27. ICV - PNP gain vs. IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 28. ICV - PNP VCE (sat) vs. IC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 29. ICV - PNP cutoff frequency vs. IC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Figure 30. New output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 31. Classical output stage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 32. Amplifier block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Figure 33. Circuitry for short-circuit detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 34. Maximum allowable power dissipation vs. ambient temperature . . . . . . . . . . . . . . . . . . . . 22
Figure 35. Restart circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 36. Turn-on output waveforms compared to the values of Csvr . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Figure 37. Balanced input in bridge configuration, example 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 38. Balanced input in bridge configuration, example 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Figure 39. Multiwatt11V package mechanical data and dimensions. . . . . . . . . . . . . . . . . . . . . . . . . . 26
Obsolete Product(s) - Obsolete Product(s)
Device overview STA7360
6/28 Doc ID 9814 Rev 4
1 Device overview
1.1 Block diagrams
Figure 2. Block diagram - stereo configuration
Figure 3. Block diagram - bridge configuration
INPUT 1
ST-BY
SVR
OUT1
OUT2
OUT BRIDGE
PWGNDGND
D00AU1215
L
R
VCC
INPUT 2
+
-
+
-
CLIPPING
DETECTOR CLIP
DETECT
20K 1µF
D00AU1216
INPUT 1
ST-BY
SVR
OUT1
OUT2
OUT BRIDGE
PWGNDGND
VCC
INPUT 2
+
-
+
-
CLIPPING
DETECTOR CLIP
DETECT
20K 1µF
Obsolete Product(s) - Obsolete Product(s)
STA7360 Device overview
Doc ID 9814 Rev 4 7/28
1.2 Pin connections
Figure 4. Pin connections (top view)
1
2
3
4
5
6
7
9
10
11
8
STAND-BY
OUT1
+VS
OUT2
SVR
P-GND
IN2(+)
OUT BRIDGE
S-GND
CLIP DET
IN1(+)
TAB CONNECTED TO PIN 6
D98AU938A
Obsolete Product(s) - Obsolete Product(s)
Electrical specifications STA7360
8/28 Doc ID 9814 Rev 4
2 Electrical specifications
2.1 Absolute maximum ratings
2.2 Thermal data
Table 2. Absolute maximum ratings
Symbol Parameter Value Unit
VSOperating supply voltage 22 V
IOOutput peak current (non rep. for t = 100 µs) 5 A
IOOutput peak current (rep. freq. > 10 Hz) 4 A
Ptot Power dissipation at Tcase = 85 °C 36 W
Tstg, TJStorage and junction temperature -40 to 150 °C
Table 3. Thermal data
Symbol Parameter Value Unit
Rth j-case Thermal resistance junction-case (max) 1.8 °C/W
Obsolete Product(s) - Obsolete Product(s)
STA7360 Electrical specifications
Doc ID 9814 Rev 4 9/28
2.3 Electrical characteristics
Refer to the test circuits, Tamb = 25 °C, VS = 14.4 V, f = 1 kHz, unless otherwise specified.
Table 4. Electrical characteristics
Symbol Parameter Test condition Min. Typ. Max. Unit
VSSupply voltage range 8 18 V
IdTotal quiescent drain current stereo configuration 65 120 mA
ASB Standby attenuation 60 80 dB
ISB Standby current 100 µA
Vst_on Standby on threshold 1 V
Vst_off Standby off threshold 3.5 V
ICO Clip detector prog. current pin 2 pull-up to 5 V d = 1%
with 10 kΩ d = 5 %
70
130
µA
µA
Stereo
PO
Output power (each channel)
THD = 10%
RL = 2 Ω
RL = 3.2 Ω
RL = 4 Ω, 12 V
RL = 4 Ω
7
11
8
4.5
6.5
W
W
W
W
d Distortion PO = 0.1 to 2.5 W; RL = 4 Ω
PO = 0.1 to 4 W; RL = 3.2 Ω
0.05
0.05
0.5
0.5
%
%
SVR Supply voltage rejection Rg = 10 kΩ C3 = 22 µF
f = 100 Hz C3 = 100 µF
45
62
dB
dB
CT Crosstalk f = 1 kHz
f = 10 kHz
45
55
dB
dB
RIInput resistance 50 kΩ
GVVoltage gain 19 20 21 dB
GVVoltage gain match 1 dB
EIN Input noise voltage
22 Hz to 22 kHz Rg = 50 Ω
Rg = 10 kΩ
Rg =
2.5
3
3.5
5
7
µV
µV
µV
Bridge
VOS Output offset voltage 250 mV
POOutput power THD = 10% RL = 4 Ω, 12 V
RL = 4 Ω, 14.4 V 16
15
20
W
W
d Distortion PO = 0.1 to 7 W; RL = 4 Ω0.05 0.5 %
SVR Supply voltage rejection Rg = 10 kΩ C3 = 22 µF
f = 100 Hz C3 = 100 µF
45
62
dB
dB
RIInput resistance 50 kΩ
GVVoltage gain 26 dB
EIN Input noise voltage 22 Hz to 22 kHz Rg = 50 Ω
Rg = 10 kΩ
3.5
4
µV
µV
Obsolete Product(s) - Obsolete Product(s)
Electrical specifications STA7360
10/28 Doc ID 9814 Rev 4
2.4 Test and application circuits
Figure 5. Stereo test and application circuit
Figure 6. Board and layout of the stereo test and application circuit (1:1 scale)
C4
1µF
220µF
C5
100nF
C6
+VS
9
11
7
STAND-BY
SVR
100µF C3
5
IN2(+)
0.22µF C2
1
IN1(+)
0.22µF C1
IN
8
10
OUT2
OUT1
4OUT
BRIDGE
63
P-GNDS-GND
D00AU1214
RL
RL
1000µF C7
1000µF C8
2
CLIP DET
20K
Table 5. Recommended values of the external components (stereo test and application
circuit)
Comp. Recommended
value Purpose Larger than the recommended
value
Smaller than the
recommended value
C1 0.22 µF Input decoupling
(CH1) --
C2 0.22 µF Input decoupling
(CH2) --
C3 100 µF
Supply voltage
rejection filtering
capacitor
Longer turn-on delay
-Worse supply voltage rejection
-Shorter turn-on delay
-Danger of noise (pop)
C4 1 µF Standby ON/OFF
delay
Delayed turn-off with standby
switch Danger of noise (pop)
Obsolete Product(s) - Obsolete Product(s)
STA7360 Electrical specifications
Doc ID 9814 Rev 4 11/28
Figure 7. Bridge test and application circuit
Figure 8. Board and layout of the bridge test and application circuit (1:1 scale)
C5 220 µF (min) Supply bypass Danger of oscillation
C6 100 nF (min) Supply bypass Danger of oscillation
C7 2200 µF Output
decoupling (CH2)
-Decrease of low-frequency cutoff
-Longer turn-on delay
-Increase of low-frequency cutoff
-Shorter turn-on delay
C8 2200 µF Output
decoupling (CH1)
-Decrease of low-frequency cutoff
-Longer turn-on delay
-Increase of low-frequency cutoff
-Shorter turn-on delay
Table 5. Recommended values of the external components (stereo test and application
circuit)
Comp. Recommended
value Purpose Larger than the recommended
value
Smaller than the
recommended value
C4
1µF
220µF
C5
100nF
C6
+VS
9
11
7
STAND-BY
SVR
22µF C3
5
IN2(+)
0.22µF C2
1
IN1(+)
0.22µF C1
IN
8
10
OUT2
OUT1
4OUT BRIDGE
63
P-GND
CLIP DET
D00AU1213
RL
20K
2
S-GND
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Typical operating characteristics STA7360
12/28 Doc ID 9814 Rev 4
3 Typical operating characteristics
Figure 9. Output power vs. supply voltage
(stereo)
Figure 10. Output power vs. supply voltage
(stereo)
Figure 11. Output power vs. supply voltage
(stereo)
Figure 12. Output power vs. supply voltage
(stereo)
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STA7360 Typical operating characteristics
Doc ID 9814 Rev 4 13/28
Figure 13. Drain current vs. supply voltage
(stereo)
Figure 14. Distortion vs. output power
(stereo)
Figure 15. Distortion vs. output power
(stereo)
Figure 16. Distortion vs. output power
(stereo)
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Typical operating characteristics STA7360
14/28 Doc ID 9814 Rev 4
Figure 17. Distortion vs. output power
(bridge)
Figure 18. SVR vs. frequency & C3
(stereo)
Figure 19. SVR vs. frequency & C3
(bridge)
Figure 20. Crosstalk vs. frequency
(stereo)
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STA7360 Typical operating characteristics
Doc ID 9814 Rev 4 15/28
Figure 21. Power dissipation & efficiency vs.
output power (stereo)
Figure 22. Power dissipation & efficiency vs.
output power (stereo)
Figure 23. Power dissipation & efficiency vs.
output power (stereo)
Obsolete Product(s) - Obsolete Product(s)
Block description STA7360
16/28 Doc ID 9814 Rev 4
4 Block description
4.1 Polarization
The device is organized with the gain resistors directly connected to the signal ground pin
i.e. without gain capacitors (Figure 2).
The non-inverting inputs of the amplifiers are connected to the SVR pin by means of resistor
dividers, equal to the feedback networks. This allows the outputs to track the SVR pin which
is sufficiently slow to avoid audible turn-on and turn-off transients.
4.2 SVR
The voltage ripple on the outputs is equal to the one on the SVR pin: with appropriate
selection of CSVR, more than 60 dB of ripple rejection can be obtained.
4.3 Delayed turn-on (muting)
The CSVR sets a signal turn-on delay too. A circuit is included which mutes the device until
the voltage on the SVR pin reaches ~2.5 V typ. (Figure 25). The mute function is obtained
by duplicating the input differential pair (Figure 24); it can be switched to the signal source or
to an internal mute input. This feature is necessary to prevent transients at the inputs
reaching the loudspeaker(s) immediately after power-on).
Figure 25 represents the detailed turn-on transient with reference to the stereo
configuration. At power-on the output decoupling capacitors are charged through an internal
path but the device itself remains switched off (phase 1 of the represented diagram).
When the outputs reach the voltage level of about 1 V (this means that there are no short-
circuits) the device switches on, the SVR capacitor starts charging itself and the output
tracks exactly the SVR pin. During this phase the device is muted until the SVR reaches the
"Play" threshold (~2.5 V typ.), after which the music signal starts being played.
4.4 Stereo/bridge switching
There is also no need for external components for changing from stereo to bridge
configuration (Figure 2, 3). A simple short-circuit between two pins allows phase reversal at
one output, yet maintaining the quiescent output voltage.
4.5 Standby
The device is also equipped with a standby function, so that a low current, and hence a low
cost switch, can be used for turn-on/off.
Obsolete Product(s) - Obsolete Product(s)
STA7360 Block description
Doc ID 9814 Rev 4 17/28
4.6 Stability
The device is provided with an internal compensation which allows reaching low values of
closed loop gain. In this way better performances of the S/N ratio and SVR can be obtained.
Figure 24. Mute function diagram
Obsolete Product(s) - Obsolete Product(s)
Block description STA7360
18/28 Doc ID 9814 Rev 4
Figure 25. Turn-on delay circuit
Figure 26. Dual-channel distortion detector
DISTORTION
DETECTOR
IN1
CLIP DET
IN2
OUT1
OUT2
D98AU959
Obsolete Product(s) - Obsolete Product(s)
STA7360 Block description
Doc ID 9814 Rev 4 19/28
4.7 Output stage
Poor current capability and low cutoff frequency are well-known limits of the standard lateral
PNP. Composite PNP-NPN power output stages have been widely used, regardless of their
high saturation drop. This drop can be overcome only at the expense of external
components, namely, the bootstrap capacitors. The availability of 4 A isolated collector PNP
(ICV PNP) adds versatility to the design. The performance of this component, in terms of
gain, VCEsat and cutoff frequency, is shown in Figure 27, 28, and 29 respectively. It is
realized in a new bipolar technology, characterized by top-bottom isolation techniques,
allowing the implementation of low leakage diodes, too. It guarantees BVCEO > 20 V and
BVCBO > 50 V both for NPN and PNP transistors. Basically, the connection shown in
Figure 30 has been chosen. First of all because its voltage swing is rail-to-rail, limited only
by the VCEsat of the output transistors, which are in the range of 0.3 W each. Then, the gain
VOUT/VIN is greater than unity, approximately 1+R2/R1. (VCC/2 is fixed by an auxiliary
amplifier common to both channel). It is possible, controlling the amount of this local
feedback, to force the loop gain (A * b) to less than unity at frequencies for which the phase
shift is 180°. This means that the output buffer is intrinsically stable and not prone to
oscillation.
Figure 27. ICV - PNP gain vs. ICFigure 28. ICV - PNP VCE (sat) vs. IC
Figure 29. ICV - PNP cutoff frequency vs. IC
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Block description STA7360
20/28 Doc ID 9814 Rev 4
Figure 30. New output stage
In contrast, with the circuit of Figure 31, the solution adopted to reduce the gain at high
frequencies is the use of an external RC network.
4.8 Amplifier block diagram
The block diagram of each voltage amplifier is shown in Figure 32. Regardless of production
spread, the current in each final stage is kept low, with enough margin on the minimum,
below which crossover distortion would appear.
Figure 31. Classical output stage
Figure 32. Amplifier block diagram
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STA7360 Built-in protection systems
Doc ID 9814 Rev 4 21/28
5 Built-in protection systems
5.1 Short-circuit protection
The maximum current the device can deliver can be calculated by considering the voltage
that may be present at the terminals of a car radio amplifier and the minimum load
impedance.
Apart from consideration concerning the area of the power transistors, it is not difficult to
achieve peak currents of this magnitude (5 A peak).However, it becomes more complicated
if AC and DC short-circuit protection is also required. In particular, with a protection circuit
which limits the output current following the SOA curve of the output transistors, it is possible
that in some conditions (highly reactive loads, for example) the protection circuit may
intervene during normal operation. For this reason each amplifier has been equipped with a
protection circuit that intervenes when the output current exceeds 4 A.
Figure 33 shows the protection circuit for an NPN power transistor (a symmetrical circuit
applies to PNP). The VBE of the power is monitored and gives out a signal, available
through a cascode.
This cascode is used to avoid the intervention of the short-circuit protection when the
saturation is below a given limit.
The signal sets a flip-flop which forces the amplifier outputs into a high impedance state.
In case of DC short-circuit when the short-circuit is removed, the flip-flop is reset and
restarts the circuit (Figure 35). In case of AC short-circuit or load shorted in bridge
configuration, the device is continuously switched in ON/OFF conditions and the current is
limited.
Figure 33. Circuitry for short-circuit detection
5.2 Polarity inversion
High current (up to 10 A) can be handled by the device with no damage for a longer period
than the blow-out time of a quick 2 A 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 supply is made.
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Built-in protection systems STA7360
22/28 Doc ID 9814 Rev 4
5.3 DC voltage
The maximum operating DC voltage for the STA7360 is 18 V.
5.4 Thermal shutdown
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 the case of excessive junction temperature: all
that happens is that Po (and therefore Ptot) and Id are reduced.
The maximum allowable power dissipation depends upon the size of the external heatsink
(i.e. its thermal resistance). Figure 34 shows the dissipable power as a function of ambient
temperature for different thermal resistance.
Figure 34. Maximum allowable power dissipation vs. ambient temperature
5.5 Loudspeaker protection
The STA7360 guarantees safe operations even for the loudspeaker in case of accidental
short-circuit. Whenever a single OUT to GND, OUT to VS short-circuit occurs, both the
outputs are switched OFF, thus limiting dangerous DC current flowing through the
loudspeaker.
Figure 35. Restart circuit
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