STA540

STA540
4 x 13 W dual/quad power amplifier
Datasheet − production data
Features
■
High output power capability
– 2x 38 W into 4 Ω at 18 V, 1 kHz, 10% THD
– 2x 34 W into 8 Ω at 22 V, 1 kHz, 10% THD
– 2x 24W into 4Ω at 14.4 V, 1 kHz, 10% THD
– 2x 15 W into 8 Ω at 16 V, 1 kHz, 10% THD
– 4x 13 W into 2 Ω at 15 V, 1 kHz, 10% THD
– 4x 11 W into 4 Ω at 18 V, 1 kHz, 10% THD
– 4x 7 W into 4 Ω at 14.4 V, 1 kHz, 10% THD
■
Minimum external components count:
– no bootstrap capacitors
– no Boucherot cells
– internally fixed gain 20 dB
■
Standby function (CMOS compatible)
■
No audible pop during standby operations
Description
■
Diagnostic facilities:
– clip detector
– output to GND short-circuit detector
– output to VS short-circuit detector
– soft short-circuit check at turn-on
– thermal shutdown warning
The STA540 is a 4-channel, class-AB audio
amplifier designed for high quality sound
applications.
Multiwatt15
The amplifiers have single-ended outputs with
integrated short-circuit protection, thermal
protection and diagnostic functions.
The chip is housed in the 15-pin Multiwatt
ECOPACK® Pb-free package which is RoHS
(2002/95/EC) compliant.
Protection
■
Output AC/DC short circuit
■
Soft short-circuit check at turn-on
■
Thermal cutoff/limiter to prevent chip from
overheating
■
High inductive loads
■
ESD
Table 1.
Device summary
Order code
STA540
Temperature range
-40 to 150° C
April 2012
This is information on a product in full production.
Package
Multiwatt15
Doc ID 13907 Rev 6
Packing
Tube
1/25
www.st.com
1
Contents
STA540
Contents
1
2
Block diagram and pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.1
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
1.2
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Electrical specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.2
Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.3
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3
Standard application circuits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
4
Electrical characteristics curves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5
Thermal information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.1
6
5.1.1
Rth_HS calculation for 4 single-ended channels . . . . . . . . . . . . . . . . . . . 15
5.1.2
Rth_HS calculation for 2 single-ended channels plus 1 BTL channel . . . 15
5.1.3
Calculations using music power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Practical information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.1
Highly flexible amplifier configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.2
Easy single-ended to bridge transition . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.3
Internally fixed gain . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.4
Silent turn on/off and muting/standby function . . . . . . . . . . . . . . . . . . . . . 17
6.5
Driving circuit for standby mode . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.6
Output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
6.7
2/25
Heatsink specification examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.6.1
Rail-to-rail output voltage swing without bootstrap capacitors . . . . . . . . 18
6.6.2
Absolute stability without external compensation . . . . . . . . . . . . . . . . . 18
Built–in protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.7.1
Diagnostic facilities (pin 10) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.7.2
Short-circuit protection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
6.7.3
Clipping detection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
6.7.4
Thermal shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Doc ID 13907 Rev 6
STA540
Contents
6.8
Handling the diagnostic information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
6.9
PCB ground layout . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
6.10
Mute function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
7
Package information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
8
Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Doc ID 13907 Rev 6
3/25
List of tables
STA540
List of tables
Table 1.
Table 2.
Table 3.
Table 4.
Table 5.
Table 6.
4/25
Device summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
Pin description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Absolute maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Thermal data. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Document revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Doc ID 13907 Rev 6
STA540
List of figures
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.
Figure 29.
Figure 30.
Block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Pin connection (top view) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Quadraphonic . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Alternative single-ended speaker connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Dual bridge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Stereo plus bridge drive . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Quiescent drain current versus supply voltage (single-ended and bridge) . . . . . . . . . . . . . 12
Quiescent output voltage versus supply voltage (single-ended and bridge). . . . . . . . . . . . 12
Output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Distortion versus output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Distortion versus output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Distortion versus output power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Output power versus supply voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Supply voltage rejection versus frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Crosstalk versus frequency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Standby attenuation versus threshold voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Total power dissipation and efficiency versus output power. . . . . . . . . . . . . . . . . . . . . . . . 14
Total power dissipation and efficiency versus output power. . . . . . . . . . . . . . . . . . . . . . . . 14
The new output stage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Shared capacitor in single-ended configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Clipping detection waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Output fault waveforms (see Figure 26) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Fault waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
Waveforms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Interface circuit diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Optional mute function circuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Mechanical data and package dimensions (Multiwatt15) . . . . . . . . . . . . . . . . . . . . . . . . . 23
Doc ID 13907 Rev 6
5/25
Block diagram and pin description
STA540
1
Block diagram and pin description
1.1
Block diagram
Figure 1.
Block diagram
VCC2
VCC2
VCC1
VCC1
13
3
A1
+
1
-
IN1
OUT1
4
A2 INV
+
ST-BY
ST-BY
IN2
7
2
-
OUT2
5
A3
+
15
-
IN3
OUT3
12
A4 INV
+
14
-
IN4
10
11
6
SVR
6/25
8
9
P-GND
S-GND
Doc ID 13907 Rev 6
OUT4
DIAGNOSTIC
DIAGNOSTICD
OUTPUT
D06AU1630
STA540
1.2
Block diagram and pin description
Pin description
Figure 2.
Pin connection (top view)
OUT3
OUT3
OUT4
OUT4
15
14
VCC2
VCC
IN3
IN3
13
12
IN4
IN4
DIAGNOSTICD
DIAGNOSTICD
11
10
9
S-GND
S-GND
8
P-GND
PW-GND
7
ST-BY
STAND-BY
6
SVR
SVR
5
IN2
IN2
4
IN1
IN1
3
VCC1
VCC
2
OUT2
OUT2
1
OUT1
OUT1
D06au1631
Table 2.
Pin description
N°
Name
Type
Function
1
OUT1
OUT
Channel 1 output
2
OUT2
OUT
Channel 2 output
3
VCC1
PWR
Power supply
4
IN1
IN
Channel 1 input
5
IN2
IN
Channel 2 input
6
SVR
IN
Supply voltage rejection
7
ST-BY
IN
Standby control pin
8
P-GND
PWR
Power ground
9
S-GND
PWR
Signal ground
10
DIAGNOSTICD
OUT
Diagnostics output
11
IN4
IN
Channel 4 input
12
IN3
IN
Channel 3 input
13
VCC2
PWR
Power supply
14
OUT4
OUT
Channel 4 output
15
OUT3
OUT
Channel 3 output
Doc ID 13907 Rev 6
7/25
Electrical specifications
STA540
2
Electrical specifications
2.1
Absolute maximum ratings
Table 3.
Absolute maximum ratings
Symbol
Parameter
Value
Unit
Supply voltage idle mode (no signal)
24
V
Supply voltage operating
22
V
Supply voltage AC-DC short safe
20
V
Total power dissipation (Tcase = 85 °C)
36
W
-40 to150
°C
0 to 70
°C
Value
Unit
Rth j-case Thermal resistance junction to case (max)
1.8
°C/W
Rth j-amb Thermal resistance junction to ambient (max)
35
°C/W
Vs
Ptot
Tstg, Tj
Top
2.2
Storage and junction temperature
Operating temperature
Thermal data
Table 4.
Thermal data
Symbol
2.3
Parameter
Electrical characteristics
The test conditions are VS = 14.4 V, RL = 4 Ω, f = 1 kHz, Tamb = 25° C unless otherwise
specified.
Table 5.
Symbol
Electrical characteristics
Parameter
VS
Supply voltage range
Id
Total quiescent drain
current
Vos
Output offset voltage
Test condition
ISC
8/25
Typ
8
80
-150
Output power, SE
THD=10%, RL=4 Ω
THD=10%, RL=2 Ω
THD=10%, RL=4 Ω, VS=22 V
Output power, BTL
THD=10%, RL=4 Ω
THD=10%, RL=8 Ω, VS=17 V
THD=10%, RL=8 Ω, VS=22 V
Total harmonic distortion
RL = 4 Ω, Po = 0.1 to 4 W
Po
THD
Min
Short-circuit output current
Doc ID 13907 Rev 6
6.5
21
4.0
Max
Unit
22
V
150
mA
150
mV
7
11.5
16
W
24
20
34
W
0.02
%
A
STA540
Electrical specifications
Table 5.
Symbol
CT
Electrical characteristics (continued)
Parameter
Test condition
f = 1 kHz single-ended
f = 10 kHz single-ended
f = 1 kHz BTL
f = 10 kHz BTL
Crosstalk
Min
Typ
70
60
60
Input impedance
Single-ended BTL
20
10
30
15
Gv
Voltage gain
Single-ended BTL
19
25
20
26
Gv
Voltage gain match
Rgen = 0, "A" weighted, S.E.:
Non-inverting channels
Inverting channels
Input noise voltage
BTL
Rgen = 0, f = 22 Hz to 22 kHz
SVR
Supply voltage rejection
Rgen = 0, f = 300 Hz,
CSVR = 470 μF
50
ASB
Standby attenuation
Po = 1 W
80
ISB
Current consumption in
standby
VST_BY = 0 to 1.5 V
ST-BY OUT threshold
voltage
kΩ
21
27
dB
0.5
dB
2
5
μV
μV
3.5
μV
dB
90
ST-BY IN threshold voltage
VSB
Unit
dB
55
Rin
EN
Max
dB
100
μA
1.5
V
3.5
V
Play mode, VST-BY = 5 V
50
μA
Max driving current under fault
5
mA
IST-BY
Pin ST-BY current
Icd_off
Clipping detector output
average current
d = 1% (*)
90
μA
Icd_on
Clipping detector output
average current
d = 5% (*)
160
μA
VDIAGNO Saturation voltage on pin
DIAGNOSTICD
STICD
IDIAGNOSTICD = 1 mA sinking
0.7
V
TW
Thermal warning
140
°C
TM
Thermal muting
150
°C
TS
Thermal shutdown
160
°C
Doc ID 13907 Rev 6
9/25
Standard application circuits
3
STA540
Standard application circuits
Figure 3.
Quadraphonic
10 kΩ
ST_BY
VS
100 nF
10 µF
IN_1
4 7
13
3
1
220 nF
OUT_1
2200 µF
IN_2
5
STA540
220 nF
IN_3
2
OUT_2
2200 µF
12
15
220 nF
IN_4
11
6 8
OUT_3
2200 µF
220 nF
14
10
9
47 µF
Figure 4.
1000 µF
Suggested applications:
4x 13 W into 2 Ω, at 15 V
4x 11 W into 4 Ω, at 18 V
4x 9 W into 2 Ω, at 12 V
4x 8 W into 4 Ω, at 16 V
4x 5 W into 4 Ω, at 12 V
OUT_4
2200 µF
Alternative single-ended speaker connection
*
1
18
15
2
19
14
470μF
470μF
The best audio performance is obtained with the configuration where each speaker
has its own DC blocking capacitor. However, if the application allows a little
degradation of the spatial image it is possible to connect a couple of speakers with
only one low-value DC blocking capacitor.
Figure 5.
Dual bridge
10 kΩ
ST_BY
VS
100 nF
10 µF
IN_L
4 7
13
3
1
OUT_L
470 nF
5
IN_R
1000 µF
12
2
STA540
15
470 nF
OUT_R
11
6 8
9
14
10
47 µF
10/25
Doc ID 13907 Rev 6
Suggested applications:
2x 38 W into 4 Ω, at 18 V, 1 kHz, 10% THD
2x 34 W into 8 Ω, at 22 V, 1 kHz, 10% THD
2x 24 W into 4 Ω, at 14.4 V, 1 kHz, 10% THD
2x 15 W into 8 Ω, at 16 V, 1 kHz, 10% THD
STA540
Standard application circuits
Figure 6.
Stereo plus bridge drive
10 kΩ
ST_BY
VS
100 nF
10 µF
IN_L
4 7
13
3
1
220 nF
IN_R
2200 µF
5
STA540
220 nF
IN_Bridge
1000 µF
2
2200 µF
12
OUT_L
OUT_R
15
470 nF
OUT_Bridge
11
6 8
9
14
10
47 µF
Suggested applications:
2x 9 W into 2 Ω, +1x 18 W into 4 Ω, at 12 V
2x 12 W into 2 Ω, +1x 26 W into 4 Ω, at 14.4 V
2x 8 W into 4 Ω, +1x 16 W into 8 Ω, at 16 V
Doc ID 13907 Rev 6
11/25
Electrical characteristics curves
STA540
4
Electrical characteristics curves
Figure 7.
Quiescent drain current versus
supply voltage (single-ended and
bridge)
Figure 9.
Output power versus supply voltage Figure 10. Output power versus supply voltage
20
18
16
14
12
10
8
6
4
2
0
Po (W)
THD= 10 %
SINGLE ENDED
RL= 2 Ω
f= 1 KHz
THD= 1 %
8
9
10
11
12
13 14
Vs (V)
15
16
17
18
Figure 8.
12
11
10
9
8
7
6
5
4
3
2
1
0
Quiescent output voltage versus
supply voltage (single-ended and
bridge)
Po (W)
SINGLE ENDED
THD= 10 %
RL= 4Ω
f= 1 KHz
THD= 1 %
8
9
10
11
12
13 14
Vs (V)
15
16
17
18
Figure 11. Output power versus supply voltage Figure 12. Distortion versus output power
12/25
Doc ID 13907 Rev 6
STA540
Electrical characteristics curves
Figure 13. Distortion versus output power
Figure 14. Distortion versus output power
Figure 15. Output power versus supply voltage Figure 16. Output power versus supply voltage
Po(W) 35
12
Po(W)
32.5
11
30
S.E.
10
9
Rl=8ohm
25
f=1KHz
8
22.5
7
20
T.H.D=10%
6
f=1KHz
T.H.D=10%
17.5
15
5
12.5
4
T.H.D=1%
T.H.D=1%
10
3
7.5
2
5
1
2.5
0
BTL
27.5
Rl=8ohm
0
+8
+10
+12
+14
+16
Vs(V)
+18
+20
+22
+24
+8
+10
+12
+14
+16
+18
+20
+22
Vs(V)
Figure 17. Supply voltage rejection versus
frequency
Figure 18. Crosstalk versus frequency
Doc ID 13907 Rev 6
13/25
Electrical characteristics curves
STA540
Figure 19. Standby attenuation versus
threshold voltage
Figure 20. Total power dissipation and
efficiency versus output power
Figure 21. Total power dissipation and
efficiency versus output power
14/25
Doc ID 13907 Rev 6
STA540
5
Thermal information
Thermal information
In order to avoid the intervention of the thermal protection, placed at Tj =150° C for thermal
muting and Tj=160° C for thermal shutdown, it is important to calculate the heatsink thermal
resistance, Rth_HS, correctly.
The parameters that influence the calculation are:
●
maximum dissipated power for the device (Pdmax)
●
maximum thermal resistance junction to case (Rth_j-case)
●
maximum ambient temperature Tamb_max
There is also an additional term that depends on the Iq (quiescent current).
5.1
Heatsink specification examples
5.1.1
Rth_HS calculation for 4 single-ended channels
Given VS = 14.4 V, RL = 4 Ω x 4 channels, Rth_j-case = 1.8° C/W, Tamb_max = 50° C and
Pout = 4 x 7 W then
the maximum power dissipated in the device is:
P
2
V
CC - = 4 ⋅ 2.62 = 10.5W
= NChannel ⋅ ------------------dmax
2
2Π R
L
and the required thermal resistance of the heatsink is:
150 – T amb_max
– 50- – 1.8 = 7.7°C/W
R th_HS = --------------------------------------------- – R th_j-case = 150
--------------------P dmax
10.5
5.1.2
Rth_HS calculation for 2 single-ended channels plus 1 BTL channel
Given VS = 14.4 V, RL = 2x 2 Ω (SE) + 1x 4 Ω (BTL), Pout = 2 x 12 W + 1 x 26 W then
the maximum power dissipated in the device is:
2
2
V
2V
CC
CC
P
= 2 ⋅ -------------------- + -------------------- = 2 ⋅ 5.25 + 10.5 = 21W
dmax
2
2
2Π R
Π R
L
L
and the required thermal resistance of the heatsink is:
R
150 – T
amb_max- – R
– 50- – 1.8 = 3°C/W
= --------------------------------------------= 150
--------------------th_HS
th_j-case
P
21
dmax
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Thermal information
5.1.3
STA540
Calculations using music power
The thermal resistance value calculated in each of the two above examples specifies a
heatsink capable of sustaining the maximum dissipated power. Realistically, however, and
as explained in the Application Note (AN1965), the heatsink can be smaller when the
application is musical content.
When music power is considered the resulting dissipation is about 40% less than the
calculated maximum. Thus, smaller or cheaper heatsinks can be employed. The heatsink
thermal resistance values are modified as follows:
for example 5.1.1: 10.5 W - 40% = 6.3 W, thus giving Rth_c-amb = 14° C/W,
for example 5.1.2: 21 W - 40% = 12.6 W, thus giving Rth_c-amb = 6° C/W.
16/25
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STA540
Practical information
6
Practical information
6.1
Highly flexible amplifier configuration
The availability of four independent channels makes it possible to accomplish several kinds
of applications ranging from four speakers stereo (F/R) to two-speaker bridge solutions.
When working with single-ended configurations, the polarity of the speakers driven by the
inverting amplifier must be reversed with respect to those driven by non-inverting channels.
This is to avoid phase irregularities causing sound alterations especially during the
reproduction of low frequencies.
6.2
Easy single-ended to bridge transition
The change from single-ended to bridge configuration is made simple by connecting the two
inputs together and also the speaker directly between the two outputs (no need for
additional external components, in fact the output DC blocking capacitors are eliminated).
However, take care to use an inverting/non-inverting amplifier pair.
6.3
Internally fixed gain
The advantages in internally fixing the gain (to 20 dB in single-ended configuration and to
26 dB in bridge configuration) are:
6.4
●
components and space saving,
●
output noise, supply voltage rejection and distortion optimization.
Silent turn on/off and muting/standby function
The standby mode can be easily activated by means of a CMOS logic level applied to
pin ST-BY through a RC filter.
Under standby conditions, the device is turned off completely (supply current = 1 mA typical,
output attenuation = 80 dB minimum).
All on/off operations are virtually pop-free. Furthermore, at turn-on the device stays in mute
condition for a time determined by the value of the SVR capacitor. This prevents transients,
coming from previous stages, from producing unpleasant acoustic effects at the speakers.
6.5
Driving circuit for standby mode
Some precautions need to be taken when designing the driving circuit for pin 7, ST-BY. For
instance, the pin cannot be directly driven by a voltage source having a current capability
higher than 5 mA. In practical cases a series resistance must be inserted, giving it the
double purpose of limiting the current at pin 7 and to smooth down the standby on/off
transitions. And, when done in combination with a capacitor, prevents output pop.
A capacitor of at least 100 nF from pin 7 to S-GND, with no resistance in between, is
necessary to ensure correct turn-on.
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Practical information
6.6
STA540
Output stage
The fully complementary output stage is possible with the power ICV PNP component.
This novel design is based on the connection shown in Figure 22 and allows the full
exploitation of its capabilities. The clear advantages this new approach has over classical
output stages are described in the following sections.
6.6.1
Rail-to-rail output voltage swing without bootstrap capacitors
The output swing is limited only by the VCEsat of the output transistors, which are in the
range of 0.3 Ω (Rsat) each.
Classical solutions adopting composite 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 includes of the addition of expensive bootstrap capacitors.
6.6.2
Absolute stability without external compensation
With reference to the circuit shown in Figure 22, the low frequency gain Vout/Vin is greater
than unity, that is, approximately 1 + R2/R1. The DC output level (VCC / 2) is fixed by an
auxiliary amplifier common 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 where the phase shift is 180°. This means that the output buffer
is intrinsically stable and not prone to oscillation.
The above feature has been achieved even though there is very low closed-loop gain of the
amplifier.
This contrasts with the classical PNP-NPN stage which makes use of external RC networks,
namely the Boucherot cells, for reducing the gain at high frequencies.
Figure 22. The new output stage
18/25
Doc ID 13907 Rev 6
STA540
Practical information
6.7
Built–in protection
6.7.1
Diagnostic facilities (pin 10)
The STA540 is equipped with diagnostic circuitry that is able to detect the following events:
●
clipping of the output signal,
●
thermal shutdown,
●
output fault:
–
short circuit to GND,
–
short circuit to VS,
–
soft short circuit at turn-on.
The event is signalled when the open collector output of pin 10 begins to sink current.
6.7.2
Short-circuit protection
Reliable and safe operation in the presence of all kinds of output short circuit is assured by
the built-in protection. As well as the AC/DC short circuit to GND and to VS, and across the
speaker, there is a soft short-circuit condition, which is signalled on pin 10 (DIAGNOSTICD)
during the turn-on phase, to verify output circuit integrity in order to ensure correct amplifier
operation.
This particular kind of protection acts in such a way as to prevent the device being turned on
(via pin ST-BY) when a resistive path (that is a DC path) less than 16 Ω exists between the
output and GND. This would avoid loud speaker damage should, for example, the output
coupling capacitor develop an internal short circuit.
As mentioned previously, it is important to limit the external current driving pin ST-BY
to 5 mA. The reason is that the associated circuitry is normally disabled with currents
greater than 5 mA.
The soft short-circuit protection is particularly attractive when, in the single-ended
configuration, one capacitor is shared between two outputs (see Figure 23).
Figure 23. Shared capacitor in single-ended configuration
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Practical information
6.7.3
STA540
Clipping detection
Figure 24. Clipping detection waveforms
Current sinking at pin 10 occurs when a certain distortion level is reached at each output.
This function initiates a gain-compression facility whenever the amplifier is overdriven.
6.7.4
Thermal shutdown
With the thermal shutdown feature, the diagnostics output (pin 10) signals the closeness of
the junction temperature to the shutdown threshold. Typically, current sinking at pin 10 starts
approximately 10° C before the shutdown temperature is reached.
Figure 25. Output fault waveforms (see Figure 26)
Figure 26. Fault waveforms
ST-BY PIN
VOLTAGE
2V
t
OUT TO Vs SHORT
OUTPUT
WAVEFORM
SOFT SHORT
t
OUT TO GND SHORT
Vpin 10
CORRECT TURN-ON
FAULT DETECTION
t
CHECK AT TURN-ON
(TEST PHASE)
20/25
D05AU1603mod
Doc ID 13907 Rev 6
SHORT TO GND
OR TO Vs
STA540
6.8
Practical information
Handling the diagnostic information
As different diagnostic information (clipping detection, output fault, approaching thermal
shutdown) becomes available at pin 10 so the behavior of the signal at this pin changes.
In order to discriminate the event, signal DIAGNOSTICD, pin 10, must be interpreted
correctly. Figure 27 shows a combination of events on the output waveform and the
corresponding output on pin 10.
This events could be diagnosed based on the timing of the output signal on pin 10. For
example, the clip-detector signalling under fault conditions could produce a low level for a
short time. On the other hand, an output short circuit would probably produce a low level for
a much longer time. With these assumptions, an interface circuit based on the one shown in
Figure 28 could differentiate the information and flag the appropriate circuits.
Figure 27. Waveforms
ST-BY PIN
VOLTAGE
t
Vs
OUTPUT
WAVEFORM
t
Vpin 10
WAVEFORM
t
CLIPPING
D05AU1604mod
SHORT TO GND
OR TO Vs
THERMAL
PROXIMITY
Figure 28. Interface circuit diagram
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Practical information
6.9
STA540
PCB ground layout
The device has two distinct ground pins, P-GND (power ground) and S-GND (signal ground)
which are disconnected from each other at chip level. For superior performance the pins
P-GND and S-GND must be connected together on the PCB by low-resistance tracks.
For the PCB-ground configuration, a star-like arrangement, where the center is represented
by the supply-filtering electrolytic capacitor ground, is recommended. In an arrangement
such as this, at least two separate paths must be provided, one for P-GND and one for
S-GND.
The correct ground assignments are as follows:
●
●
on S-GND:
–
standby capacitor (pin 7, or any other standby driving networks),
–
SVR capacitor (pin 6), to be placed as close as possible to the device,
–
input signal ground (from active/passive signal processor stages)
on P-GND:
–
6.10
power supply filtering capacitors for pins 3 and 13. The negative terminal of the
electrolytic capacitor(s) must be directly tied to the battery negative line and this
should represent the starting point for all the ground paths.
Mute function
If the mute function is desired, it can be implemented on pin 6, SVR, as shown in Figure 29.
Figure 29. Optional mute function circuit
10K
VS
ST-BY
10μF
IN L
IN R
IN BRIDGE
0.22μF
0.47μF
470μF
R2 10K
13
7
4
3
1000μF
1
OUT L
2200μF
5
2
2200μF
12
6
8
OUT R
15
OUT
BRIDGE
11
R1 3.3K
MUTE
5V
0
PLAY
0.22μF
100nF
9
10
14
DIAGNOSTICS
D06AU1632
VS = 10 to 16 V,
mute off: VSVR ≥ 0.6 to 0.8 V,
mute on: VSVR ≥ 0.2 V
Using a different value for R1 than the suggested 3.3 kΩ, results in two different situations:
●
●
22/25
R1 > 3.3 kΩ:
–
pop noise improvement,
–
lower mute attenuation;
R1 < 3.3 kΩ:
–
pop noise degradation,
–
higher mute attenuation.
Doc ID 13907 Rev 6
STA540
7
Package information
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 30. Mechanical data and package dimensions (Multiwatt15)
DIM.
mm
MIN.
TYP.
inch
MAX.
MIN.
TYP.
MAX.
A
5
0.197
B
2.65
0.104
C
1.6
D
OUTLINE AND
MECHANICAL DATA
0.063
1
0.039
E
0.49
0.55
0.019
F
0.66
0.75
0.026
0.022
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
0.030
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
0.87
0.886
L2
17.65
18.1
0.695
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
0.713
L7
2.65
2.9
0.104
M
4.25
4.55
4.85
0.167
0.179
0.191
0.114
M1
4.73
5.08
5.43
0.186
0.200
0.214
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
Multiwatt15 (Vertical)
0016036 J
Doc ID 13907 Rev 6
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Revision history
8
STA540
Revision history
Table 6.
24/25
Document revision history
Date
Revision
Changes
May-2006
1
Initial release
Sep-2006
2
Minor non-technical edits
Oct-2007
3
Updated description on page 1
Updated pin naming, numbering in all relevant figures
Minor non-technical edits
21-Jan-2008
4
Updated power specifications on pages 1, 6 and 8
Updated short-circuit output current in Table 5
02-Apr-2012
5
Modified VST-BY to VSB and updated parameters in Table 5: Electrical
characteristics
Updated ECOPACK® text in Section 7: Package information
24-Apr-2012
6
Updated dimension A in Figure 30: Mechanical data and package
dimensions (Multiwatt15)
Doc ID 13907 Rev 6
STA540
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