STPA002
4 x 52 W quad bridge power amplifier with low voltage operation
Datasheet - production data
– No external compensation
– No bootstrap capacitors
'!0'03
'!0'03
Flexiwatt25
Protections:
– Output short circuit to GND, to Vs, across
the load
– Very inductive loads
– Overrating chip temperature with soft
thermal limiter
– Output DC offset detection
– Load dump voltage
– Fortuitous open GND
– Reverse battery
– ESD
Flexiwatt27
Features
High output power capability:
– 4 x 52 W/4 Ω max.
– 4 x 30 W/4 Ω @ 14.4 V, 1 kHz, 10 %
– 4 x 85 W/2 Ω max.
– 4 x 55 W/2 Ω @ 14.4V, 1 kHz, 10 %
Description
MOSFET output power stage
Stop-start and hybrid engines compliant
Excellent 2 driving capability
Hi-Fi class distortion
Low output noise
Standby function and mute function
Automute at min. supply voltage detection
Low external component count:
– Internally fixed gain (26 dB)
The STPA002 is a MOSFET class AB audio
power amplifier, designed for high-power car
radio. In addition to the outstanding output current
capability and distortion performance, the
STPA002 is extremely robust against several
kinds of fortuitous misconnections.
It is compliant to the most recent OEM
specifications for low voltage operation in startstop vehicles, and can sustain hybrid vehicles
battery transitions.
It includes a DC offset detector and, in
Flexiwatt27 package, a clipping detector.
Table 1. Device summary
Order code
Package
Packing
STPA002OD-4WX
Flexiwatt25 (with OD)
Tube
STPA002CD-48X
Flexiwatt27 (with CD)
Tube
September 2013
This is information on a product in full production.
DocID024368 Rev 3
1/24
www.st.com
Contents
STPA002
Contents
1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.1
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
1.2
Application circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3
Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.2
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.3
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4
Electrical characteristics typical curves . . . . . . . . . . . . . . . . . . . . . . . . 12
5
General information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2
Battery variations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.3
5.4
5.5
5.2.1
Low voltage operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.2.2
Cranks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
5.2.3
Advanced battery management (hybrid vehicles) . . . . . . . . . . . . . . . . . 17
Protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.3.1
Short circuits and open circuit operation . . . . . . . . . . . . . . . . . . . . . . . . 18
5.3.2
Over-voltage and load dump protection . . . . . . . . . . . . . . . . . . . . . . . . . 18
5.3.3
Thermal protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Warnings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.4.1
DC offset detection (OD pin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
5.4.2
Clipping detection and diagnostics (CD-DIAG pin) . . . . . . . . . . . . . . . . 19
Heat sink definition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2/24
DocID024368 Rev 3
STPA002
List of tables
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Pin functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Document revision history. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
DocID024368 Rev 3
3/24
3
List of figures
STPA002
List of figures
Figure 1.
Figure 2.
Figure 3.
Figure 4.
Figure 5.
Figure 6.
Figure 7.
Figure 8.
Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Figure 14.
Figure 15.
Figure 16.
Figure 17.
Figure 18.
Figure 19.
Figure 20.
Figure 21.
Figure 22.
Figure 23.
Figure 24.
Figure 25.
Figure 26.
Figure 27.
Figure 28.
4/24
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Standard test and application circuit (Flexiwatt25) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Standard test and application circuit (Flexiwatt27) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin connections (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Quiescent current vs. supply voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Output power vs. supply voltage (4 Ω) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Output power vs. supply voltage (2 Ω) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Distortion vs. output power (4 Ω) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Distortion vs. output power (2 Ω) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Distortion vs. frequency (4 Ω) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Distortion vs. frequency (2 Ω) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Distortion vs. output power (4 Ω, Vs = 6 V). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Distortion vs. output power (2 Ω, Vs = 6 V). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Supply voltage rejection vs. frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Crosstalk vs. frequency. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Total power dissipation & efficiency vs. Po (4 Ω, Sine) . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Power dissipation vs. average output power (4 Ω, audio program simulation). . . . . . . . . . 14
Power dissipation vs. average output power (2 Ω, audio program simulation). . . . . . . . . . 14
ITU R-ARM frequency response, weighting filter for transient pop. . . . . . . . . . . . . . . . . . . 14
SVR charge diagram. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Battery cranking curve example 1. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Battery cranking curve example 2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Upwards fast battery transitions diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Load dump protection diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Thermal protection diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Audio section waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Flexiwatt25 (vertical) mechanical data and package dimensions . . . . . . . . . . . . . . . . . . . . 21
Flexiwatt27 (Vertical) mechanical data and package dimensions . . . . . . . . . . . . . . . . . . . 22
DocID024368 Rev 3
STPA002
1
Overview
Overview
The STPA002 is a complementary quad audio power amplifier. It is available in two different
packages, Flexiwatt25 and Flexiwatt27. It embeds four independent amplifiers working in
class AB, a standby, a mute pin and an offset detector output. In the Flexiwatt27 package
also a clipping detection pin with diagnostics information is available. The amplifier is fully
operational down to a battery voltage of 6 V, without producing pop noise and continuing to
play during battery transitions.
The STPA002 can drive 2 ohm loads and has a very high immunity to disturbs without need
of external components or compensation. It is protected against any kind of short or open
circuit, over-voltage and over-temperature.
1.1
Block diagram
Figure 1. Block diagram
6CC
6CC
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DocID024368 Rev 3
5/24
23
Overview
1.2
STPA002
Application circuits
Figure 2. Standard test and application circuit (Flexiwatt25)
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Figure 3. Standard test and application circuit (Flexiwatt27)
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6/24
DocID024368 Rev 3
STPA002
2
Pin description
Pin description
Figure 4. Pin connections (top view)
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DocID024368 Rev 3
7/24
23
Pin description
STPA002
Table 2. Pin functions
Pin number Pin number
FW27
FW25
8/24
Pin name
Description
1
1
TAB
Device slug connection
2
25
OD
Offset detector output
3
2
PW-GND2
4
3
OUT2-
Channel 2, negative output
5
4
ST-BY
Stand-by
6
5
OUT2+
Channel 2, positive output
7
6
VCC
8
7
OUT1-
9
8
PW-GND1
10
9
OUT1+
11
10
SVR
Supply voltage rejection pin
12
11
IN1
Channel 1, input
13
12
IN2
Channel 2, input
14
13
S-GND
15
14
IN4
Channel 4, input
16
15
IN3
Channel 3, input
17
16
AC-GND
18
17
OUT3+
19
18
PW-GND3
20
19
OUT3-
21
20
VCC
22
21
OUT4+
Channel 4, positive output
23
22
MUTE
Mute pin
24
23
OUT4-
Channel 4, negative output
25
24
PW-GND4
Channel 4, output power ground
26
n.a
CD-DIAG
Clipping detector and diagnostics output
27
n.a
TAB
Channel 2, output power ground
Supply voltage
Channel 1, negative output
Channel 1, output power ground
Channel 1, positive output
Signal ground
AC ground
Channel 3, positive output
Channel 3, output power ground
Channel 3, negative output
Supply voltage
Device slug connection
DocID024368 Rev 3
STPA002
Electrical specifications
3
Electrical specifications
3.1
Absolute maximum ratings
Table 3. Absolute maximum ratings
Symbol
Parameter
Value
Unit
Operating supply voltage
18
V
VS (DC)
DC supply voltage
28
V
VS (pk)
Peak supply voltage (for t = 50 ms)
50
V
IO
Output peak current
Non repetitive (t = 100 μs)
Repetitive (duty cycle 10 % at f = 10 Hz)
10
9
A
A
Tj
Junction temperature
150
°C
Tstg
Storage temperature
-55 to 150
°C
Ground pin voltage
-0.3 to 0.3
V
-0.3 to 8
V
-0.3 to Vs(pk)
V
-0.3 to 6
V
Value
Unit
1
°C/W
VS
GNDmax
Vin max
Input pin max voltage
VSB max
ST-BY pin max voltage
Vmute max Mute pin max voltage
3.2
Thermal data
Table 4. Thermal data
Symbol
Parameter
Rth j-case
3.3
Thermal resistance junction-to-case
Max.
Electrical characteristics
Refer to the test and application diagram, VS = 14.4 V; RL = 4 Ω; Rg = 600 Ω; f = 1 kHz;
Tamb = 25 °C; unless otherwise specified.
Table 5. Electrical characteristics
Symbol
Parameter
Test condition
Min.
Typ.
Max.
Unit
6
-
18
V
General characteristics
VS
Supply voltage range
-
Iq1
Quiescent current
RL = ∞
100
200
300
mA
Output offset voltage
Mute mode
-75
-
+75
mV
VOS
DocID024368 Rev 3
9/24
23
Electrical specifications
STPA002
Table 5. Electrical characteristics (continued)
Symbol
dVOS
Parameter
During mute ON/OFF output offset
voltage
During standby ON/OFF output
offset voltage
Ri
Input impedance
ISB
Standby current consumption
Test condition
Min.
Typ.
Max.
Unit
-7.5
-
+7.5
mV
-15
-
+15
mV
45
55
65
kΩ
VSt-by = 1.2 V
-
-
2
μA
VSt-by = 0
-
-
1
μA
VS = 14.4 V; THD = 10 %
VS = 14.4 V; THD = 1 %
27
21
30
24
-
W
W
VS = 14.4 V; THD = 10 %, 2 Ω
VS = 14.4 V; THD = 1 %, 2 Ω
49
39
55
43
-
W
W
ITU R-ARM weighted
-
Audio performances
Po
Output power
Max. output power(1)
VS = 15.2 V; RL = 4 Ω
-
52
-
W
Distortion
Po = 4 W
-
0.01
0.04
%
Gv
Voltage gain
-
25
26
27
dB
dGv
Channel gain unbalance
-
-1
-
+1
dB
eNo
Output Noise
"A" Weighted
Bw = 20 Hz to 20 kHz
-
40
50
70
μV
μV
SVR
Supply voltage rejection
f = 100 Hz; Vr = 1 Vrms
60
70
-
dB
fch
High cut-off frequency
PO = 0.5 W
100
300
-
kHz
CT
Cross talk
f = 1 kHz PO = 4 W
f = 10 kHz PO = 4 W
65
45
75
60
-
dB
dB
AM
Mute attenuation
POref = 4 W
85
95
-
dB
-
-
0.5
μA
Po max.
THD
Control pin characteristics
Ipin5
Standby pin current
VSt-by = 1.2 V to 2.6 V
VSB out
Standby out threshold voltage
(Amp: ON)
2.6
-
-
V
VSB in
Standby in threshold voltage
(Amp: OFF)
-
-
1.2
V
VM out
Mute out threshold voltage
(Amp: Play)
2.6
-
-
V
VM in
Mute in threshold voltage
(Amp: Mute)
-
-
1.2
V
(Amp: Mute)
Att 80 dB; POref = 4 W
4.5
5
5.5
V
(Amp: Play)
Att < 0.1 dB; PO = 0.5 W
-
-
6
V
6
8.5
11
μA
VAM in
Ipin23
10/24
VS automute threshold
Muting pin current
VMUTE = 1.2 V
(Sourced current)
DocID024368 Rev 3
STPA002
Electrical specifications
Table 5. Electrical characteristics (continued)
Symbol
Parameter
Test condition
Min.
Typ.
Max.
Unit
±1
±2
±3
V
Vo > ±3 V, Ioff Det = 1 mA
-
0.2
0.4
V
Vo < ±1 V
-
0
15
μA
Offset detector
VOFF
Detected differential output offset
VOFF_SAT Off detector saturation voltage
VOFF_LK
Off detector leakage current
-
Clipping detector (2)
CDLK
Clip detector high leakage current
Cd off
-
0
1
μA
CDSAT
Clip detector saturation voltage
DC On; ICD = 1 mA
-
0.2
0.4
V
CDTHD
Clip detector THD level
-
-
1
-
%
1. Saturated square wave output
2. Clipping detection is guaranteed till a minimum supply voltage of 7 V.
DocID024368 Rev 3
11/24
23
Electrical characteristics typical curves
4
STPA002
Electrical characteristics typical curves
Figure 5. Quiescent current vs. supply voltage Figure 6. Output power vs. supply voltage (4 Ω)
,T P$
3R :
5/ 7
I N+]
9LQ
5/ 7
3RPD[
7+'
7+'
9V 9
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Figure 7. Output power vs. supply voltage (2 Ω)
'!0'03
9V 9
5/ 7
5/ 7
I N+]
7+'
Figure 8. Distortion vs. output power (4 Ω)
3R :
9V 9
3RPD[
I N +]
7+'
I N+]
7+'
9V 9
Figure 9. Distortion vs. output power (2 Ω)
'!0'03
7+'
'!0'03
7+'
9V 9
5/ 7
9V 9
5/ 7
3R :
I N+]
Figure 10. Distortion vs. frequency (4 Ω)
3R :
I N+]
3R :
'!0'03
12/24
DocID024368 Rev 3
I +]
'!0'03
STPA002
Electrical characteristics typical curves
Figure 11. Distortion vs. frequency (2 Ω)
Figure 12. Distortion vs. output
power (4 Ω, Vs = 6 V)
7+'
7+'
9V 9
5/ 7
3R :
9V 9
5/ 7
I N+]
I +]
I N+]
3R :
'!0'03
'!0'03
Figure 13. Distortion vs. output
power (2 Ω, Vs = 6 V)
Figure 14. Supply voltage rejection vs.
frequency
7+'
695 G%
9V 9
5/ 7
5J 7
9ULSSOH 9UPV
I N+]
I N+]
3R :
I +]
'!0'03
Figure 15. Crosstalk vs. frequency
'!0'03
Figure 16. Total power dissipation & efficiency
vs. Po (4 Ω, Sine)
&52667$/. G%
H
3GLVV :
H
9V 9
5/ [7
[
I N+]
5/ 7
3R :
5J 7
3GLVV
I +]
'!0'03
DocID024368 Rev 3
3R :
'!0'03
13/24
23
Electrical characteristics typical curves
STPA002
Figure 17. Power dissipation vs. average output Figure 18. Power dissipation vs. average output
power (4 Ω, audio program simulation)
power (2 Ω, audio program simulation)
3GLVV :
9V 9
5/ [
3,1.12,6(
3GLVV :
9V 9
5/ [
3,1.12,6(
&/,367$57
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3RDYJ :
'!0'03
Figure 19. ITU R-ARM frequency response,
weighting filter for transient pop
/UTPUTATTENUATIOND"
14/24
(Z
'!0'03
DocID024368 Rev 3
3RDYJ :
'!0'03
STPA002
General information
5
General information
5.1
Operation
The STPA002's inputs are ground-compatible. If the standard value for the input capacitors
(0.22 μF) is adopted, the low frequency cut-off will amount to 16 Hz. The input capacitors
should have the same value of the capacitor connected to AC-GND pin for optimum pop
performances (see Figure 2: Standard test and application circuit (Flexiwatt25)).
Standby and mute pins are 3.3 V and 5 V compatible.
RC cells at both mute and stand-by pins have always to be used in order to smooth the
transitions for preventing any audible transient noise. A time constant slower than 2.5 V/ms
is suggested for the stand-by pin and 0.5 V/ms for the mute pin.
In case the standby function is not used, it could steadily be connected to Vs through a
470 kΩ resistor.
The capacitance on SVR sets the start-up and shut-down times and helps to have pop-noise
free transitions. Its minimum recommended value is 10 μF. However, to have a fast start-up
time, the internal resistor on SVR pin, used to set the time constant, is reduced from 100 kΩ
to 3 kΩ till voltage on SVR reaches VCC/4 -2VBE and then released. In this way the
capacitor on SVR is charged very quickly to VCC/4, as shown in the following figure.
Figure 20. SVR charge diagram
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SVR pin accomplishes multiple functions:
it is used as a reference voltage for input pins (VCC/4)
the capacitor connected to SVR helps the supply voltage ripple rejection
it is used as a reference to generate the half supply voltage for the output
When the amplifier goes in stand-by mode or goes out from this condition, it is suggested to
put the amplifier in mute to ensure the absence of audible noise. Then the standby pin can
be set to the appropriate value (ground or > 2.6 V) and the capacitance on SVR pin is
discharged or charged consequently.
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General information
STPA002
5.2
Battery variations
5.2.1
Low voltage operation
The most recent OEM specifications require automatic stop of car engine at traffic lights, in
order to reduce emissions of polluting substances. The STPA002, thanks to its innovating
design, allows a continuous operation when battery falls down. At 6 V it is still fully
operational, only the maximum output power is reduced accordingly to the available voltage
supply.
If the battery voltage drops below the minimum operating voltage of 6 V the amplifier is fast
muted, the capacitor on SVR is discharged and the amplifier restarts when the battery
voltage returns to the correct voltage.
5.2.2
Cranks
STPA002 can sustain worst case cranks from 16 V to 6 V, continuing to play and without
producing any pop noise.
Examples of battery cranking curves are shown below, indicating the shape and duration of
allowed battery transitions.
Figure 21. Battery cranking curve example 1
6BATT6
6
6
6
6
T
T
T
T T
T
T
TS
V1 = 16 V; V2 = 6 V; V3 = 7 V; V4 = 8 V
t1 = 2 ms; t2 = 50 ms; t3 = 5 ms; t4 = 300 ms; t5 =10 ms; t6 = 1 s; t7 = 2 ms
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STPA002
General information
Figure 22. Battery cranking curve example 2
6BATT6
6
6
6
T
T T
T
T
TS
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V1 = 16 V; V2 = 6 V; V3 = 7 V
t1 = 2 ms; t2 = 5 ms; t3 = 15 ms; t5 = 1 s; t6 = 50 ms
5.2.3
Advanced battery management (hybrid vehicles)
In addition to compatibility with low Vbatt, the STPA002 is able to sustain upwards fast
battery transitions without causing unwanted audible effects, like pop noise, and without any
sound interruption thanks to the innovative circuit topology. In fact, in hybrid vehicles, the
engine ignition causes a fast increase of battery voltage which can reach 16 V in less than
10 ms.
Figure 23. Upwards fast battery transitions diagram
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General information
STPA002
5.3
Protections
5.3.1
Short circuits and open circuit operation
When the IC detects a short circuit to ground, to Vsupply or across the load, the output of the
amplifier is put in three-state (high impedance condition). The power stage remains in this
condition until the short is removed.
In case of short circuit to ground or Vcc, the amplifier exits from the three-state condition
only when the output returns inside the limits imposed by an internal voltage comparator.
When a short across the load is present, the power stage sees an over-current and is
brought in protection mode for 150 μs. After this time, if the short circuit condition is
removed the amplifier returns to play, otherwise the high impedance state is maintained and
the check is repeated every 150 μs.
Disconnection of load (open load condition) doesn't damage the amplifier, which continues
to play.
5.3.2
Over-voltage and load dump protection
When the battery voltage is higher than 19 V, the amplifier is switched to a high impedance
state. It stops playing till the supply voltage returns in the permitted range.
The amplifier is protected against load dump surges having amplitude as high as 50 V and a
rising time lower than 5 ms (see Figure 24).
Figure 24. Load dump protection diagram
66DUMP
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5.3.3
Thermal protection
If the junction temperature of the IC reaches Tj = 150 °C, a smooth mute is applied to reduce
output power and limit power dissipation. If this is not enough and the junction temperature
continues to increase, the amplifier is switched off when it reaches the maximum
temperature of 170 °C.
/UTPUTPOWER
Figure 25. Thermal protection diagram
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STPA002
General information
5.4
Warnings
5.4.1
DC offset detection (OD pin)
The STPA002 integrates a DC offset detector to avoid that an anomalous input DC offset is
multiplied by the amplifier gain producing a dangerous large offset at the output. In fact an
output offset may lead to speakers damage for overheating. To correctly detect a DC offset,
the power amplifier has to be un-muted with no input signal.
When the differential output voltage is out of a window comparator with thresholds ± 2 V
(typ), the OD pin is pulled down.
5.4.2
Clipping detection and diagnostics (CD-DIAG pin)
When clipping occurs, the output signal is distorted. If the signal distortion on one of the
output channels exceeds 1 %, the CD-DIAG pin is pulled down. This information can be
sent to an audio processor in order to reduce the input signal of the amplifier and reduce the
clipping. Thanks to a particular internal circuitry, the clip detector is always functional till 7 V.
A short to ground and short to Vcc is signaled by CD-DIAG. This pin is pulled down to
ground till these shorts are present to inform the user a protection occurred.
CD-DIAG acts also as thermal warning. In fact every time Tj exceeds 140 °C, it is pulled
down to notify this occurrence.
Figure 26. Audio section waveforms
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General information
5.5
STPA002
Heat sink definition
Assuming we have a dissipated power of 26 W (e.g. in the worst case situation of frequent
clipping occurrence, with music signal), considering Tj max is 150 °C and assuming ambient
temperature is 70 °C, the available temperature gap for a correct dissipation is 80 °C.
This means the thermal resistance of the system Rth has to be 80 °C/26 W = 3 °C/W.
The junction to case thermal resistance is 1 °C/W. So the heat sink thermal resistance
should be approximately 2 °C/W. This would avoid any thermal shutdown occurrence even
after long-term and full-volume operation.
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STPA002
Package information
In order to meet environmental requirements, ST offers these devices in different grades of
ECOPACK® packages, depending on their level of environmental compliance. ECOPACK®
specifications, grade definitions and product status are available at: www.st.com.
ECOPACK® is an ST trademark.
Figure 27. Flexiwatt25 (vertical) mechanical data and package dimensions
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Package information
STPA002
Figure 28. Flexiwatt27 (Vertical) mechanical data and package dimensions
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