SSM2211 [ADI]
Low Distortion 1.5 Watt Audio Power Amplifier; 低失真1.5瓦音频功率放大器
| 型号： | SSM2211 |
| 厂家： | 
ADI |
| 描述： | Low Distortion 1.5 Watt Audio Power Amplifier |
| 文件： | 总16页 (文件大小：215K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Low Distortion 1.5 Watt
Audio Power Amplifier
a
SSM2211*
FUNCTIO NAL BLO CK D IAGRAM
FEATURES
1.5 Watt Output1
Differential (BTL2)Output
V +
Single-Supply Operation: 2.7 V to 5.5 V
Functions Dow n to 1.75 V
Wide Bandw idth: 4 MHz
IN –
IN +
Highly Stable, Phase Margin: > 80 Degrees
Low Distortion: 0.2% THD @ 1 W Output
Excellent Pow er Supply Rejection
V
A
B
OUT
APPLICATIONS
Portable Com puters
Personal Wireless Com m unicators
Hands-Free Telephones
Speakerphones
V
OUT
BYPASS
SHUTDOWN
BIAS
Intercom s
Musical Toys and Speaking Gam es
V – (GND)
GENERAL D ESCRIP TIO N
The low differential dc output voltage results in negligible losses
in the speaker winding, and makes high value dc blocking capaci-
tors unnecessary. Battery life is extended by using the Shutdown
mode, which reduces quiescent current drain to typically 100 nA.
The SSM2211 is a high performance audio amplifier that delivers 1
W RMS of low distortion audio power into a bridge-connected 8 Ω
speaker load, (or 1.5 W RMS into 4 Ω load). It operates over a wide
temperature range and is specified for single-supply voltages between
2.7 V and 5.5 V. When operating from batteries, it will continue to
operate down to 1.75 V. This makes the SSM2211 the best choice
for unregulated applications such as toys and games. Featuring a
4 MHz bandwidth, distortion below 0.2 % THD @ 1 W, and the
patented Thermal Coastlineleadframe, superior performance is de-
livered at higher power or lower speaker load impedance than com-
petitive units. The advanced mechanical packaging of the SSM2211
gives lower chip temperature, which ensures highly reliable operation
and enhanced trouble free life.
The SSM2211 is designed to operate over the –20°C to +85°C
temperature range. See Figure 49 for information on the Thermal
Coastline lead frame. The SSM2211 is available in an SO-8 sur-
face mount package. DIP samples are available; you should request
a special quotation on production quantities. An evaluation board
is available upon request of your local Analog Device sales office.
Applications include personal portable computers, hands-free
telephones and transceivers, talking toys, intercom systems and
other low voltage audio systems requiring 1 W output power.
*P r otected by U.S. P atent No. 5,519,576
11.5 W @ 4 Ω, +25°C am bient, < 1% TH D , 5 V supply, 4 layer P CB.
2
Br idge Tied Load
REV. 0
Inform ation furnished by Analog Devices is believed to be accurate and
reliable. However, no responsibility is assum ed by Analog Devices for its
use, nor for any infringem ents of patents or other rights of third parties
which m ay result from its use. No license is granted by im plication or
otherwise under any patent or patent rights of Analog Devices.
One Technology Way, P.O. Box 9106, Norw ood. MA 02062-9106, U.S.A.
Tel: 781/ 329-4700
Fax: 781/ 326-8703
World Wide Web Site: http:/ / w w w .analog.com
© Analog Devices, Inc., 1997
SSM2211–SPECIFICATIONS
ELECTRICAL CHARACTERISTICS (V = ؉5.0 V, T = ؉25؇C, R = 8 ⍀, C = 0.1 F, V = V /2 unless otherwise noted)
S
A
L
B
CM
D
P aram eter
Sym bol
Conditions
Min
Typ
Max
Units
GENERAL CHARACT ERIST ICS
Differential Output Offset Voltage
Output Impedence
VOOS
ZOUT
AVD = 2
4
0.1
50
mV
Ω
SHUT DOWN CONT ROL
Input Voltage High
Input Voltage Low
VIH
VIL
ISY = < 100 µA
ISY = Normal
3.0
V
V
1.3
POWER SUPPLY
Power Supply Rejection Ratio
Supply Current
Supply Current, Shutdown Mode
PSRR
ISY
ISD
VS = 4.75 V to 5.25 V
VO1 = VO2 = 2.5 V
Pin 1 = VDD, See Figure 29
66
9.5
100
dB
mA
nA
DYNAMIC PERFORMANCE
Gain Bandwidth
Phase Margin
GBP
Ø0
4
86
MHz
degrees
AUDIO PERFORMANCE
T otal Harmonic Distortion
T otal Harmonic Distortion
Voltage Noise Density
T HD + N
T HD + N
en
P = 0.5 W into 8 Ω, f = 1 kHz
P = 1.0 W into 8 Ω, f = 1 kHz
f = 1 kHz
0.15
0.2
85
%
%
nV√Hz
(V = ؉3.3 V, T = ؉25؇C, R = 8 ⍀, C = 0.1F, V = V /2 unless otherwise noted)
ELECTRICAL CHARACTERISTICS
S
A
L
B
CM
D
P aram eter
Sym bol
Conditions
Min
Typ
Max
Units
GENERAL CHARACT ERIST ICS
Differential Output Offset Voltage
Output Impedence
VOOS
ZOUT
AVD = 2
5
0.1
50
mV
Ω
SHUT DOWN INPUT
Input Voltage High
Input Voltage Low
VIH
VIL
ISY = < 100 µA
1.7
V
V
1
POWER SUPPLY
Supply Current
Supply Current, Shutdown Mode
ISY
ISD
VO1 = VO2 = 1.65 V
Pin 1 = VDD, See Figure 29
5.2
100
mA
nA
AUDIO PERFORMANCE
T otal Harmonic Distortion
T HD + N
P = 0.35 W into 8 Ω, f = 1 kHz
0.1
%
(V = ؉2.7 V, T = ؉25؇C, R = 8 ⍀, C = 0.1 F, V = V /2 unless otherwise noted)
S
A
L
B
CM
S
ELECTRICAL CHARACTERISTICS
P aram eter
Sym bol
Conditions
Min
Typ
Max
Units
GENERAL CHARACT ERIST ICS
Differential Output Offset Voltage
Output Impedence
VOOS
ZOUT
AVD = 2
5
0.1
50
mV
Ω
SHUT DOWN CONT ROL
Input Voltage High
Input Voltage Low
VIH
VIL
ISY = < 100 µA
ISY = Normal
1.5
V
V
0.8
POWER SUPPLY
Supply Current
Supply Current, Shutdown Mode
ISY
ISD
VO1 = VO2 = 1.35 V
Pin 1 = VDD, See Figure 29
4.2
100
mA
nA
AUDIO PERFORMANCE
T otal Harmonic Distortion
T HD + N
P = 0.25 W into 8 Ω, f = 1 kHz
0.1
%
Specifications subject to change without notic
–2–
REV. 0
SSM2211
ABSO LUTE MAXIMUM RATINGS1,2
O RD ERING GUID E
Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +6 V
Input Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VDD
Common Mode Input Voltage . . . . . . . . . . . . . . . . . . . . . . VDD
ESD Susceptibility. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2000 V
Storage T emperature Range . . . . . . . . . . . . Ϫ65°C to +150°C
Operating T emperature Range . . . . . . . . . . . Ϫ20°C to +85°C
Junction T emperature Range . . . . . . . . . . . . Ϫ65°C to +165°C
Lead T emperature Range (Soldering, 60 sec) . . . . . . . ؉300°C
Tem perature
Range
P ackage
D escription O ptions
P ackage
Model
SSM2211S
SSM2211S-reel
–20°C to +85°C
–20°C to +85°C
SSM2211S-reel7 –20°C to +85°C
8-Lead SOIC SO-8
8-Lead SOIC SO-8
8-Lead SOIC SO-8
8-Lead PDIP N-8*
SSM2211P
–20°C to +85°C
*Special order only.
NOT ES
1Absolute maximum ratings apply at +25°C, unless otherwise noted.
2Stresses above those listed under Absolute Maximum Ratings may cause perma-
nent damage to the device. T his is a stress rating only; the functional operation of
the device at these or any other conditions above those indicated in the operational
sections of this specification is not implied. Exposure to absolute maximum rating
conditions for extended periods may affect device reliability.
P IN CO NFIGURATIO NS
8-Lead SO IC
(SO -8)
SHUTDOWN
BYPASS
+IN
V
B
A
1
2
3
4
8
7
6
5
OUT
1
P ackage Type
Units
JA
JC
–V
+V
V
TOP VIEW
(Not to Scale)
8-Lead SOIC (S)
8-Lead PDIP (P)2
98
43
43
°C/W
°C/W
–IN
OUT
103
NOT ES
1For the SOIC package, θJA is measured with the device soldered to a 4-layer
8-Lead P lastic D IP
(N-8)
printed circuit board.
2Special order only.
SHUTDOWN
BYPASS
+IN
V
B
A
1
2
3
4
8
7
6
5
OUT
–V
+V
V
TOP VIEW
(Not to Scale)
–IN
OUT
CAUTIO N
ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily
accumulate on the human body and test equipment and can discharge without detection. Although
the SSM2211 features proprietary ESD protection circuitry, permanent damage may occur on
devices subjected to high energy electrostatic discharges. T herefore, proper ESD precautions are
recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
10
1
10
1
10
1
T
V
A
R
= ؉25؇C
A
= 5V
DD
C
= 0
B
= 2 (BTL)
VD
C
= 0.1F
B
= 8⍀
= 500mW
L
P
L
C
= 0
C
= 0.1F
B
B
C
= 1F
B
C
= 0.1F
C
= 1F
B
B
C
= 1F
B
0.1
0.1
0.01
0.1
0.01
T
V
A
R
= ؉25؇C
T = ؉25؇C
A
A
= 5V
V
= 5V
DD
DD
= 10 (BTL)
A
= 20 (BTL)
VD
VD
= 8⍀
= 500mW
R = 8⍀
L
L
P
P
= 500mW
100
L
L
0.01
20
1k
FREQUENCY – Hz
10k 20k
20
100
1k
FREQUENCY – Hz
10k 20k
20
100
1k
FREQUENCY – Hz
10k 20k
Figure 3. THD+N vs. Frequency
Figure 2. THD+N vs. Frequency
Figure 1. THD+N vs. Frequency
REV. 0
–3–
SSM2211–Typical Performance Characteristics
10
10
10
1
T
V
A
R
= ؉25؇C
A
C
= 0
B
= 5V
DD
= 2 (BTL)
VD
= 8⍀
L
C
= 0.1F
B
P
= 1W
C
L
C
= 0.1F
1
C
= 0
1
B
B
C
= 1F
= 0.1F
B
B
C
= 1F
B
0.1
0.01
0.1
0.01
0.1
0.01
C
= 1F
B
T
V
A
R
P
= ؉25؇C
T
V
A
R
= ؉25؇C
A
A
= 5V
= 5V
DD
DD
= 20 (BTL)
= 10 (BTL)
VD
VD
= 8⍀
= 1W
= 8⍀
= 1W
L
L
P
L
L
20
100
1k
FREQUENCY – Hz
10k 20k
20
100
1k
FREQUENCY – Hz
10k 20k
20
100
1k
10k 20k
FREQUENCY – Hz
Figure 4. THD+N vs. Frequency
Figure 5. THD+N vs. Frequency
Figure 6. THD+N vs. Frequency
10
10
10
T
V
A
= ؉25؇C
T
V
A
= ؉25؇C
A
A
T
= ؉25؇C
A
= 5V
= 5V
DD
DD
V
= 5V
DD
= 2 (BTL)
= 2 (BTL)
VD
VD
A
= 2 (BTL)
= 8⍀
VD
R
= 8⍀
R
= 8⍀
L
L
R
L
FREQUENCY = 20Hz
C = 0.1F
B
FREQUENCY = 1kHz
C = 0.1F
B
FREQUENCY = 20kHz
C = 0.1F
B
1
1
1
0.1
0.1
0.1
0.01
0.01
0.01
20n
0.1
P
1
2
20n
0.1
P
1
2
20n
0.1
P
1
2
– W
– W
OUTPUT
OUTPUT
– W
OUTPUT
Figure 7. THD+N vs. POUTPUT
Figure 8. THD+N vs. POUTPUT
Figure 9. THD+N vs. POUTPUT
10
1
10
1
10
1
T
V
A
R
= ؉25؇C
A
C
= 0
B
= 3.3V
DD
= 2 (BTL)
VD
= 8⍀
= 350mW
L
C
= 0.1F
P
B
L
C
= 0
B
C = 0.1F
B
C
= 1F
B
C
= 0.1F
B
C
= 1F
B
0.1
0.01
T
V
A
R
= ؉25؇C
0.1
0.01
0.1
0.01
A
T = ؉25؇C
A
= 3.3V
DD
C
= 1F
B
V = 3.3V
= 10 (BTL)
DD
VD
A
= 20 (BTL)
VD
= 8⍀
= 350mW
L
R = 8⍀
P
L
L
P
= 350mW
100
L
20
100
1k
FREQUENCY – Hz
10k 20k
20
100
1k
FREQUENCY – Hz
10k 20k
20
1k
FREQUENCY – Hz
10k 20k
Figure 12. THD+N vs. Frequency
Figure 10. THD+N vs. Frequency
Figure 11. THD+N vs. Frequency
–4–
REV. 0
SSM2211
10
1
10
1
10
1
T
V
A
= ؉25؇C
T
V
A
= ؉25؇C
T
V
A
= ؉25؇C
A
A
A
= 3.3V
= 3.3V
= 3.3V
DD
DD
DD
= 2 (BTL)
= 2 (BTL)
= 2 (BTL)
VD
VD
VD
= 8⍀
L
R
= 8⍀
R
= 8⍀
R
L
L
FREQUENCY = 20Hz
= 0.1F
FREQUENCY = 1kHz
= 0.1F
FREQUENCY = 20kHz
C = 0.1F
B
C
C
B
B
0.1
0.01
0.1
0.01
0.1
0.01
20n
0.1
P
1
2
20n
0.1
P
1
2
20n
0.1
P
1
2
– W
– W
– W
OUTPUT
OUTPUT
OUTPUT
Figure 13. THD+N vs. POUTPUT
Figure 14. THD+N vs. POUTPUT
Figure 15. THD+N vs. Frequency
10
10
10
1
T
V
A
R
= ؉25؇C
A
= 2.7V
DD
C
= 0
B
= 2 (BTL)
VD
= 8⍀
= 250mW
L
C = 0.1F
B
P
C
= 0.1F
L
B
C
= 0
B
1
1
C
= 0.1F
B
C
= 1F
B
C
= 1F
B
0.1
0.1
0.1
0.01
T
V
A
R
= ؉25؇C
A
T
V
A
R
= ؉25؇C
A
= 2.7V
DD
= 2.7V
C
= 1F
DD
B
= 20 (BTL)
VD
= 10 (BTL)
VD
= 8⍀
= 250mW
L
= 8⍀
= 250mW
L
P
L
P
L
0.01
0.01
20
100
1k
FREQUENCY – Hz
10k 20k
20
100
1k
10k 20k
20
100
1k
FREQUENCY – Hz
10k 20k
FREQUENCY – Hz
Figure 16. THD+N vs. Frequency
Figure 18. THD+N vs. Frequency
Figure 17. THD+N vs. Frequency
10
10
10
T
V
A
R
= ؉25؇C
A
T
V
A
R
= ؉25؇C
T = ؉25؇C
A
A
= 2.7V
DD
= 2.7V
V
= 2.7V
DD
DD
= 2 (BTL)
VD
= 2 (BTL)
A
= 2 (BTL)
VD
VD
= 8⍀
L
= 8⍀
R = 8⍀
L
L
FREQUENCY = 20Hz
FREQUENCY = 1kHz
FREQUENCY = 20kHz
1
1
1
0.1
0.1
0.1
0.01
0.01
0.01
20n
0.1
P
1
2
20n
0.1
P
1
2
20n
0.1
P
1
2
– W
OUTPUT
– W
– W
OUTPUT
OUTPUT
Figure 19. THD+N vs. POUTPUT
Figure 20. THD+N vs. POUTPUT
Figure 21. THD+N vs. POUTPUT
REV. 0
–5–
SSM2211–Typical Performance Characteristics
10
10
1
10
T
V
A
C
C
= ؉25؇C
T
= ؉25؇C
A
T
V
A
C
C
= ؉25؇C
A
A
= 3.3V
V
A
= 2.7V
= 10 SINGLE ENDED
DD
= 5V
DD
DD
= 10 SINGLE ENDED
VD
= 10 SINGLE ENDED
VD
VD
= 0.1F
= 1000F
C
= 0.1F
B
= 0.1F
= 1000F
B
B
C
= 1000F
C
C
C
1
1
R
= 8⍀
= 85mW
R
= 8⍀
= 65mW
L
R
= 8⍀
= 250mW
L
L
P
P
O
P
O
O
0.1
0.1
0.01
0.1
R
= 32⍀
= 20mW
L
R
= 32⍀
= 60mW
L
R
= 32⍀
L
P
O
P
O
P
= 15mW
O
0.01
0.01
20
100
1k
10k 20k
20
100
1k
10k 20k
20
100
1k
10k 20k
FREQUENCY – Hz
FREQUENCY – Hz
FREQUENCY – Hz
Figure 23. THD+N vs. Frequency
Figure 24. THD+N vs. Frequency
Figure 22. THD+N vs. Frequency
10
10
10
T
A
= ؉25؇C
T
A
= ؉25؇C
T
A
= ؉25؇C
= 2 (BTL)
VD
A
V
= 2.7V
A
A
V
= 2.7V
DD
DD
V
= 3.3V
= 2 (BTL)
DD
= 2 (BTL)
VD
VD
V
= 3.3V
DD
R
= 8⍀
R
= 8⍀
R
= 8⍀
L
L
L
FREQUENCY = 20Hz
= 0.1F
FREQUENCY = 1kHz
= 0.1F
FREQUENCY = 20kHz
C = 0.1F
B
C
C
B
B
1
1
1
V
= 2.7V
DD
V
= 5V
DD
0.1
0.1
0.1
V
= 5V
DD
V
= 3.3V
– W
DD
V
= 5V
DD
0.01
0.01
0.01
20n
0.1
P
1
2
20n
0.1
P
1
2
20n
0.1
1
2
– W
P
– W
OUTPUT
OUTPUT
OUTPUT
Figure 27. THD+N vs. POUTPUT
Figure 25. THD+N vs. POUTPUT
Figure 26. THD+N vs. POUTPUT
10,000
8,000
6,000
4,000
2,000
0
1.5
14
T
= ؉150؇C
J,MAX
V
= +5V
DD
T
R
= ؉25؇C
= OPEN
FREE AIR
NO HEAT SINK
A
12
10
8
L
SOIC = ؉98؇C/W
JA
1
6
0.5
4
2
0
–20
0
0
1
2
3
4
5
0
20
40
60
80
100
0
1
2
3
4
5
6
SHUTDOWN VOLTAGE AT PIN 1 – V
TEMPERATURE – ؇C
SUPPLY VOLTAGE – V
Figure 28. Maxim um Power
Dissipation vs. Am bient Tem perature
Figure 29. Supply Current vs.
Shutdown Voltage
Figure 30. Supply Current vs.
Supply Voltage
–6–
REV. 0
SSM2211
80
60
40
20
180
135
90
25
20
15
10
5
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
= 2.7V
DD
SAMPLE SIZE = 300
45
0
–20
–40
0
–45
–90
5V
3.3V
–60
–80
–135
–180
2.7V
0
100
1k
10k
100k
1M
10M 100M
–20 –15 –10 –5
0
5
10 15 20 25
4
8
12 16 20 24 28 32 36 40 44 48
OUTPUT OFFSET VOLTAGE – mV
FREQUENCY – Hz
LOAD RESISTANCE – ⍀
Figure 32. Gain, Phase vs.
Frequency (Single Am plifier)
Figure 33. Output Offset Voltage
Distribution
Figure 31. POUTPUT vs. Load
Resistance
20
600
20
16
12
8
V
= 5.0V
DD
V
= 5.0V
V
= 3.3V
DD
DD
SAMPLE SIZE = 1,700
SAMPLE SIZE = 300
SAMPLE SIZE = 300
500
400
300
200
100
0
16
12
8
4
4
0
–30
0
–30
–20
–10
0
10
20
30
6
7
8
9
10 11 12 13 14 15
–20
–10
0
10
20
30
SUPPLY CURRENT – mA
OUTPUT OFFSET VOLTAGE – mV
OUTPUT OFFSET VOLTAGE – mV
Figure 35. Output Offset Voltage
Distribution
Figure 36. Supply Current
Distribution
Figure 34. Output Offset Voltage
Distribution
–50
T
= ؉25؇C
A
V
= 5V ؎ 100mV
DD
C
= 15 mF
B
A
= 2
VD
–55
–60
–65
–70
20
100
1k
10k
30k
FREQUENCY – Hz
Figure 37. PSRR vs. Frequency
REV. 0
–7–
SSM2211
SSM2211 P RO D UCT O VERVIEW
TYP ICAL AP P LICATIO N
T he SSM2211 is a low distortion speaker amplifier that can run
from a 1.7 V to 5.5 V supply. It consists of a rail-to-rail input
and a differential output that can be driven within 400 mV of
either supply rail while supplying a sustained output current of
350 mA. T he SSM2211 is unity-gain stable, requiring no exter-
nal compensation capacitors, and can be configured for gains of
up to 40 dB. Figure 38 shows the simplified schematic.
R
F
+5V
6
C
S
C
R
C
I
4
3
AUDIO
INPUT
5
8
SPEAKER
8⍀
SSM2211
20k⍀
1
7
V
DD
2
6
C
B
SSM2211
20k⍀
4
3
V
IN
Figure 39. A Typical Configuration
A1
V
V
O1
5
8
Figure 39 shows how the SSM2211 would be connected in a
typical application. T he SSM2211 can be configured for gain
much like a standard op amp. T he gain from the audio input to
the speaker is:
50k⍀
50k⍀
50k⍀
A2
O2
2
RF
A = 2 ×
V
(1)
RI
50k⍀
BIAS
CONTROL
0.1F
T he ϫ 2 factor comes from the fact that Pin 8 is opposite polar-
ity from Pin 5, providing twice the voltage swing to the speaker
from the bridged output configuration.
7
1
SHUTDOWN
Figure 38. Sim plified Schem atic
CS is a supply bypass capacitor to provide power supply filter-
ing. Pin 2 is connected to Pin 3 to provide an offset voltage for
single supply use, with CB providing a low AC impedance to
ground to help power supply rejection. Because Pin 4 is a virtual
AC ground, the input impedance is equal to RI. CC is the input
coupling capacitor which also creates a high-pass filter with a
corner frequency of:
Pin 4 and Pin 3 are the inverting and noninverting terminals to A1.
An offset voltage is provided at Pin 2, which should be connected
to Pin 3 for use in single supply applications. The output of A1
appears at Pin 5. A second op amp, A2, is configured with a fixed
gain of AV = –1 and produces an inverted replica of Pin 5 at Pin 8.
The SSM2211 outputs at Pins 5 and 8 produce a bridged configu-
ration output to which a speaker can be connected. This bridge
configuration offers the advantage of a more efficient power trans-
fer from the input to the speaker. Because both outputs are sym-
metric, the dc bias at Pins 5 and 8 are exactly equal, resulting in
zero dc differential voltage across the outputs. This eliminates the
need for a coupling capacitor at the output.
1
fHP
=
(2)
2 πRI × CC
Because the SSM2211 has an excellent phase margin, a feed-
back capacitor in parallel with RF to band-limit the amplifier is
not required, as it is in some competitor’s products.
The SSM2211 can achieve 1 W continuous output into 8 Ω, even
at ambient temperatures up to +85°C. This is due to a propri-
etary SOIC package from Analog Devices that makes use of an
internal structure called a Thermal Coastline. The Thermal
Coastline provides a more efficient heat dissipation from the die
than in standard SOIC packages. This increase in heat dissipation
allows the device to operate in higher ambient temperatures or at
higher continuous output currents without overheating the die.
Br idged O utput vs. Single Ended O utput Configur ations
T he power delivered to a load with a sinusoidal signal can be ex-
pressed in terms of the signal’s peak voltage and the resistance
of the load:
2
VPK
PL =
(3)
2 RL
For a standard SOIC package, typical junction to ambient tem-
perature thermal resistance (JA) is +158°C/W. In a T hermal
Coastline SOIC package, JA is +98°C/W. Simply put, a die in a
T hermal Coastline package will not get as hot as a die in a stan-
dard SOIC package at the same current output.
By driving a load from a bridged output configuration, the volt-
age swing across the load doubles. An advantage in using a
bridged output configuration becomes apparent from Equation
3 as doubling the peak voltage results in four times the power
delivered to the load. In a typical application operating from a
5 V supply, the maximum power that can be delivered by the
SSM2211 to an 8 Ω speaker in a single ended configuration is
250 mW. By driving this speaker with a bridged output, 1 W of
power can be delivered. T his translates to a 12 dB increase in
sound pressure level from the speaker.
Because of the large amounts of power dissipated in a speaker
amplifier, competitor’s parts operating from a 5 V supply can
only drive 1 W into 8 Ω in ambient temperatures less than
+44°C, or +111°F. With the T hermal Coastline SOIC package,
the SSM2211 can drive an 8 Ω speaker with 1 W from a 5 V
supply with ambient temperatures as high as +85°C (+185°F),
without a heat sink or forced air flow.
–8–
REV. 0
SSM2211
Driving a speaker differentially from a bridged output offers an-
other advantage in that it eliminates the need for an output cou-
pling capacitor to the load. In a single supply application, the
quiescent voltage at the output is 1/2 of the supply voltage. If a
speaker were connected in a single ended configuration, a cou-
pling capacitor would be needed to prevent dc current from
flowing through the speaker. T his capacitor would also need to
be large enough to prevent low frequency roll-off. T he corner
frequency is given by:
T he internal power dissipation of the amplifier is the internal
voltage drop multiplied by the average value of the supply cur-
rent. An easier way to find internal power dissipation is to take
the difference between the power delivered by the supply voltage
source and the power delivered into the load. T he waveform of
the supply current for a bridged output amplifier is shown in
Figure 40.
V
OUT
V
PEAK
1
f−3dB
=
(4)
2 π RLCC
TIME
T
Where RL is the speaker resistance and,
CC is the coupling capacitance
I
SY
For an 8 Ω speaker and a corner frequency of 20 Hz, a 1000 µF
capacitor would be needed, which is quite physically large and
costly. By connecting a speaker in a bridged output configura-
tion, the quiescent differential voltage across the speaker be-
comes nearly zero, eliminating the need for the coupling
capacitor.
I
DD, PEAK
I
DD, AVG
T
TIME
Figure 40. Bridged Am plifier Output Voltage and Supply
Current vs. Tim e
Speaker Efficiency and Loudness
T he effective loudness of 1 W of power delivered into an 8 Ω
speaker is a function of the efficiency of the speaker. T he effi-
ciency of a speaker is typically rated as the sound pressure level
(SPL) at 1 meter in front of the speaker with 1 W of power
applied to the speaker. Most speakers are between 85 dB and
95 dB SPL at 1 meter at 1 W. T able I shows a comparison of
the relative loudness of different sounds.
By integrating the supply current over a period T , then dividing
the result by T , IDD,AVG can be found. Expressed in terms of
peak output voltage and load resistance:
2VPEAK
IDD, AVG
=
(5)
πRL
therefore power delivered by the supply, neglecting the bias cur-
rent for the device is,
Table I. Typical Sound P ressure Levels
Source of Sound
dB SP L
2VDDVPEAK
PSY
=
T hreshold of Pain
120
95
80
65
50
30
0
(6)
πRL
Heavy Street T raffic
Cabin of Jet Aircraft
Average Conversation
Average Home at Night
Quiet Recording Studio
T hreshold of Hearing
Now, the power dissipated by the amplifier internally is simply
the difference between Equation 6 and Equation 3. T he equa-
tion for internal power dissipated, PDISS, expressed in terms of
power delivered to the load and load resistance is:
It can easily be seen that 1 W of power into a speaker can pro-
duce quite a bit of acoustic energy.
2 2 ×VDD
PDISS
=
PL − PL
(7)
π
RL
P ower D issipation
Another important advantage in using a bridged output configu-
ration is the fact that bridged output amplifiers are more effi-
cient than single ended amplifiers in delivering power to a load.
Efficiency is defined as the ratio of power from the power supply
T he graph of this equation is shown in Figure 41.
PL
η =
to the power delivered to the load
. An amplifier
PSY
with a higher efficiency has less internal power dissipation,
which results in a lower die-to-case junction temperature, as
compared to an amplifier that is less efficient. T his is important
when considering the amplifier device’s maximum power dissi-
pation rating versus ambient temperature. An internal power
dissipation versus output power equation can be derived to fully
understand this.
REV. 0
–9–
SSM2211
1.5
0.35
0.30
0.25
0.20
0.15
0.10
0.05
0
V
= ؉5V
V
= ؉5V
DD
DD
R
= 4⍀
L
R
= 4⍀
L
1.0
0.5
0
R
= 8⍀
L
R
= 8⍀
L
R
= 16⍀
L
R
= 16⍀
L
0
0.1
0.2
0.3
0.4
0
0.5
1.0
1.5
OUTPUT POWER – W
OUTPUT POWER – W
Figure 41. Power Dissipation vs. Output Power
with VDD = 5 V
Figure 42. Power Dissipation vs. Single Ended Output
Power with (VDD = 5 V)
Because the efficiency of a bridged output amplifier (Equation 3
divided by Equation 6) increases with the square root of PL, the
power dissipated internally by the device stays relatively flat, and
will actually decrease with higher output power. T he maximum
power dissipation of the device can be found by differentiating
Equation 7 with respect to load power, and setting the derivative
equal to zero. T his yields:
T he maximum power dissipation for a single ended output is:
2
VDD
2 π2 RL
PDISS,MAX
=
(11)
O utput Voltage H eadr oom
T he outputs of both amplifiers in the SSM2211 can come to
within 400 mV of either supply rail while driving an 8 Ω load.
As compared to other competitors’ equivalent products, the
SSM2211 has a higher output voltage headroom. T his means
that the SSM2211 can deliver an equivalent maximum output
power while running from a lower supply voltage. By running at
a lower supply voltage, the internal power dissipation of the de-
vice is reduced, as can be seen from Equation 9. T his extended
output headroom, along with the T hermal Coastline package,
allows the SSM2211 to operate in higher ambient temperatures
than other competitors’ devices.
−1
∂PDISS
∂PL
2 ×VDD
πRL
2
=
PL
−1 = 0
(8)
And this occurs when:
2
2VDD
PDISS,MAX
=
(9)
π2 RL
Using Equation 9 and the power derating curve in Figure 28,
the maximum ambient temperature can be easily found. T his
insures that the SSM2211 will not exceed its maximum junction
T he SSM2211 is also capable of providing amplification even at
supply voltages as low as 1.7 V. Of course, the maximum power
available at the output is a function of the supply voltage.
T herefore, as the supply voltage decreases, so does the maxi-
mum power output from the device. Figure 43 shows the maxi-
mum output power versus supply voltage at various bridged-tied
load resistances. T he maximum output power is defined as the
point at which the output has 1% T HD.
temperature of 150°C.
T he power dissipation for a single ended output application
where the load is capacitively coupled is given by:
2 2 ×VDD
∂PDISS
=
PL − PL
(10)
π
RL
1.6
1.4
1.2
T he graph of Equation 10 is shown in Figure 42.
R
= 4⍀
L
1.0
R
= 8⍀
L
0.8
0.6
R
= 16⍀
L
0.4
0.2
0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE – V
Figure 43. Maxim um Output Power vs. VSY
–10–
REV. 0
SSM2211
T o find the minimum supply voltage needed to achieve a speci-
fied maximum undistorted output power, simply use Figure 43.
T o find the appropriate component values, first the gain of A2
must be determined by:
For example, an application requires only 500 mW to be output
for an 8 Ω speaker. With the speaker connected in a bridged out-
put configuration, the minimum supply voltage required is 3.3 V.
VSY
A
=
V , MIN
(12)
VTHS
Shutdown Featur e
Where, VSY is the single supply voltage and,
VTHS is the threshold voltage.
The SSM2211 can be put into a low power consumption shut-
down mode by connecting Pin 1 to 5 V. In shutdown mode, the
SSM2211 has an extremely low supply current of less than 10 nA.
This makes the SSM2211 ideal for battery powered applications.
AV should be set to a minimum of 2 for the circuit to work prop-
erly. Next choose R1 and set R2 to:
Pin 1 should be connected to ground for normal operation.
Connecting Pin 1 to VDD will mute the outputs and put the
SSM2211 into shutdown mode. A pull-up or pull-down resistor
is not required. Pin 1 should always be connected to a fixed
potential, either VDD or ground, and never be left floating. Leav-
ing Pin 1 unconnected could produce unpredictable results.
2
R2 = R1 1−
(13)
A
V
Find R3 as:
Autom atic Shutdown Sensing Cir cuit
R1× R2
R3 =
A −1
(14)
(
)
V
Figure 44 shows a circuit that can be used to automatically take
the SSM2211 in and out of shutdown mode. T his circuit can be
set to turn the SSM2211 on when an input signal of a certain
amplitude is detected. T he circuit will also put the SSM2211
into its low-power shutdown mode once an input signal is not
sensed within a certain amount of time. T his can be useful in a
variety of portable radio applications where power conservation
is critical.
R1+ R2
C1 can be arbitrarily set, but should be small enough to not cause
A2 to become capacitively overloaded. R4 and C1 will control the
shutdown rate. To prevent intermittent shutdown with low
frequency input signals, the minimum time constant should be:
10
R4 × C1 ≥
(15)
fLOW
R8
V
DD
Where, fLOW is the lowest input frequency expected.
R7
R5
Shutdown Cir cuit D esign Exam ple
In this example a portable radio application requires the
SSM2211 to be turned on when an input signal greater than
50 mV is detected. T he device should return to shutdown mode
within 500 ms after the input signal is no longer detected. T he
lowest frequency of interest is 200 Hz, and a +5 V supply is
being used.
4
1
C2
DD
5
8
V
SSM2211
A1
V
DD
IN
R6
R4
C1
A2
؊
؉
V
D1
NOTE: ADDITIONAL PINS
OMITTED FOR CLARITY
OP181
R3
T he minimum gain of the shutdown circuit from Equation 12 is
AV = 100. R1 is set to 100 kΩ, and using Equation 13 and
Equation 14, R2 = 98 kΩ and R3 = 4.9 MΩ. C1 is set to
0.01 µF, and based on Equation 15, R4 is set to 10 MΩ. T o
minimize power supply current, R5 and R6 are set to 10 MΩ.
R1
R2
Figure 44. Autom atic Shutdown Circuit
T he input signal to the SSM2211 is also connected to the non-
inverting terminal of A2. R1, R2, and R3 set the threshold volt-
age of when the SSM2211 will be taken out of shutdown mode.
D1 half-wave rectifies the output of A2, discharging C1 to
ground when an input signal greater than the set threshold volt-
age is detected. R4 controls the charge time of C1, which sets
the time until the SSM2211 is put back into shutdown mode af-
ter the input signal is no longer detected.
T he above procedure will provide an adequate starting point for
the shutdown circuit. Some component values may need to be
adjusted empirically to optimize performance.
Tur n O n P opping Noise
During power-up or release from shutdown mode, the midrail
bypass capacitor, CB, determines the rate at which the
SSM2211 starts up. By adjusting the charging time constant of
CB, the start-up pop noise can be pushed into the sub-audible
range, greatly reducing startup popping noise. On power-up, the
midrail bypass capacitor is charged through an effective resis-
tance of 25 kΩ. T o minimize start-up popping, the charging
time constant for CB should be greater than the charging time
constant for the input coupling capacitor, CC.
R5 and R6 are used to establish a voltage reference point equal
to half of the supply voltage. R7 and R8 set the gain of the
SSM2211. D1 should be a 1N914 or equivalent diode and A2
should be a rail-to-rail output amplifier, such as an OP181 or
equivalent. T his will ensure that C1 will discharge sufficiently to
bring the SSM2211 out of shutdown mode.
(16)
CB × 25 kΩ > CC RI
REV. 0
–11–
SSM2211
For an application where R1 = 10 kΩ and CC = 0.22 µF, the
midrail bypass capacitor, CB, should be at least 0.1 µF to mini-
mize start-up popping noise.
Selecting CB to be 2.2 µF for a practical value of capacitor will
minimize start-up popping noise.
T o summarize the final design:
SSM2211 Am plifier D esign Exam ple
Given:
VDD
R1
RF
CC
CB
5 V
20 kΩ
28 kΩ
2.2 µF
2.2 µF
Maximum Output Power 1 W
Input Impedance
Load Impedance
Input Level
20 kΩ
8 Ω
1 V rms
Max. TA +85°C
Bandwidth
20 Hz – 20 kHz ± 0.25 dB
Single Ended Applications
T he configuration shown in Figure 39 will be used. T he first
thing to determine is the minimum supply rail necessary to ob-
tain the specified maximum output power. From Figure 43, for
1 W of output power into an 8 Ω load, the supply voltage must
be at least 4.6 V. A supply rail of 5 V can be easily obtained
from a voltage reference. T he extra supply voltage will also al-
low the SSM2211 to reproduce peaks in excess of 1 W without
clipping the signal. With VDD = 5 V and RL = 8 Ω, Equation 9
shows that the maximum power dissipation for the SSM2211 is
633 mW. From the power derating curve in Figure 28, the am-
bient temperature must be less than +85°C.
T here are applications where driving a speaker differentially is
not practical. An example would be a pair of stereo speakers
where the minus terminal of both speakers is connected to
ground. Figure 45 shows how this can be accomplished.
10k⍀
+5V
6
10k⍀
4
AUDIO
INPUT
5
0.47F
SSM2211
T he required gain of the amplifier can be determined from
Equation 17:
8
3
1
7
470F
2
250mW
SPEAKER
(8⍀)
PLRL
A =
= 2.8
(17)
V
0.1F
VIN , rms
Figure 45. A Single Ended Output Application
RF
A
V
It is not necessary to connect a dummy load to the unused output
to help stabilize the output. The 470 µF coupling capacitor cre-
ates a high pass frequency cutoff as given in Equation 4 of 42 Hz,
which is acceptable for most computer speaker applications.
=
From Equation 1,
, or
. Since the de-
RF =1.4 × R1
R1
2
sired input impedance is 20 kΩ, R1 = 20 kΩ and R2 = 28 kΩ.
The final design step is to select the input capacitor. Because add-
ing an input capacitor, CC, high pass filter, the corner frequency
needs to be far enough away for the design to meet the bandwidth
criteria. For a 1st order filter to achieve a passband response
within 0.25 dB, the corner frequency should be at least 4.14 times
away from the passband frequency. So, (4.14 ϫ fHP) < 20 Hz.
Using Equation 2, the minimum size of input capacitor can be
found:
T he overall gain for a single ended output configuration is
V = RF/R1, which for this example is equal to 1.
A
D r iving Two Speaker s Single Endedly
It is possible to drive two speakers single endedly with both out-
puts of the SSM2211.
20k⍀
1
CC >
+5V
20 Hz
(18)
2π 20 kΩ
(
)
470F
6
4.14
LEFT
20k⍀
4
3
SPEAKER
(8⍀)
AUDIO
INPUT
5
8
1F
SSM2211
So CC > 1.65 µF. Using a 2.2 µF is a practical choice for CC.
1
7
The gain-bandwidth product for each internal amplifier in the
SSM2211 is 4 MHz. Because 4 MHz is much greater than
4.14
؋
20 kHz, the design will meet the upper frequency band- width criteria. The SSM2211 could also be configured for higher
differential gains without running into bandwidth limitations.
470F
2
RIGHT
SPEAKER
(8⍀)
0.1F
Figure 46. SSM2211 Used as a Dual Speaker Am plifier
Equation 16 shows an appropriate value for CB to reduce start-
up popping noise:
Each speaker is driven by a single ended output. T he trade-off
is that only 250 mW sustained power can be put into each
speaker. Also, a coupling capacitor must be connected in series
with each of the speakers to prevent large DC currents from
flowing through the 8 Ω speakers. T hese coupling capacitors
2.2 µF 20 kΩ
(
)(
)
(19)
CB >
=1.76 µF
25 kΩ
–12–
REV. 0
SSM2211
will produce a high pass filter with a corner frequency given by
Equation 4. For a speaker load of 8 Ω and a coupling capacitor
of 470 µF, this results in a –3 dB frequency of 42 Hz.
must connect the ground lead of the test instrument to either out-
put signal pins, a power line isolation transformer must be used
to isolate the instrument ground from power supply ground.
Because the power of a single ended output is one quarter that of a
bridged output, both speakers together would still be half as loud
(–6 dB SPL) as a single speaker driven with a bridged output.
Recall that
, so for P = 1 W and RL = 8 Ω,
O
V = P × R
V = 2.8 V rms, or 8 V p-p. If the available input signal is 1.4 V
rms or more, use the board as is, with RF = RI = 20 kΩ. If more
gain is needed, increase the value of RF to obtain the desired gain.
T he polarity of the speakers is important, as each output is 180°
out of phase with the other. By connecting the minus terminal
of Speaker 1 to Pin 5, and the plus terminal of Speaker 2 to
Pin 8, proper speaker phase can be established.
When you have determined the closed-loop gain required by
your source level, and can develop 1 W across the 8 Ω load re-
sistor with the normal input signal level, replace the resistor
with your speaker. Your speaker may be connected across the
VO1 and VO2 posts for bridged mode operation only after the
8 Ω load resistor is removed. For no phase inversion, VO2
should be connected to the (+) terminal of the speaker.
T he maximum power dissipation of the device can be found by
doubling Equation 11, assuming both loads are equal. If the
loads are different, use Equation 11 to find the power dissipa-
tion caused by each load, then take the sum to find the total
power dissipated by the SSM2211.
Evaluation Boar d
V
O2
CH A
An evaluation board for the SSM2211 is available. Contact
your local sales representative or call 1-800-ANALOGD for
more information.
5
GND
2.5V
COMMON
MODE
8⍀
1W
PROBES
SSM2211
V+
R1
51k⍀
8
+
CH B CH B DISPLAY
INV. ON A+B
C
C
1
0.1F
2
V
O1
10F
SHUTDOWN
OSCILLOSCOPE
V
6
02
Figure 48. Using an Oscilloscope to Display the Bridged
Output Voltage
J1
8
AUDIO
INPUT
ON
1
2
T o use the SSM2211 in a single ended output configuration,
replace J1 and J2 jumpers with electrolytic capacitors of a suit-
able value, with the NEGAT IVE terminals to the output termi-
nals VO1 and VO2. T he single ended loads may then be returned
to ground. Note that the maximum output power is reduced to
250 mW, one quarter of the rated maximum, due to the maxi-
mum swing in the non-bridged mode being one-half, and power
being proportional to the square of the voltage. For frequency
response down 3 dB at 100 Hz, a 200 µF capacitor is required
with 8 Ω speakers.
R
L
SSM2211
7
1W 8⍀
3
4
+
5
J2
C
R
IN
IN
V
01
VOLUME
20k⍀ POT.
CW
1f 20k⍀
R
F
20k⍀
C
1
0.1F
Figure 47. Evaluation Board Schem atic
T he SSM2211 evaluation board also comes with a SHUT -
DOWN switch which allows the user to switch between ON
(normal operation) and the power conserving shutdown mode.
The voltage gain of the SSM2211 is given by Equation 20 below:
RF
P r inted Cir cuit Boar d Layout Consider ation
All surface mount packages rely on the traces of the PC board
to conduct heat away from the package.
A = 2 ×
V
(20)
RIN
If desired, the input signal may be attenuated by turning the
In standard packages, the dominant component of the heat re-
sistance path is the plastic between the die attach pad and the
individual leads. In typical thermally enhanced packages, one or
more of the leads are fused to the die attach pad, significantly
decreasing this component. T o make the improvement mean-
ingful, however, a significant copper area on the PCB must be
attached to these fused pins.
10 kΩ potentiometer in the CW direction. CIN isolates the input
common mode voltage (V+/2) present at Pin 2 and 3. With
V+ = 5 V, there is +2.5 V common-mode voltage present at
both output terminals VO1 and VO2 as well.
CAUTIO N: T he ground lead of the oscilloscope probe, or any
other instrument used to measure the output signal, must not be
connected to either output, as this would short out one of the
amplifier’s outputs and possibly damage the device.
T he patented T hermal Coastline lead frame design used in the
SSM2211 (Figure 49) uniformly minimizes the value of the
dominant portion of the thermal resistance. It ensures that heat
is conducted away by all pins of the package. T his yields a very
low, 98°C/W, thermal resistance for an SO-8 package, without
any special board layer requirements, relying on the normal
traces connected to the leads. T he thermal resistance can be de-
creased by approximately an additional 10% by attaching a few
A safe method of displaying the differential output signal using a
grounded scope is shown in Figure 48. Simply connect the Chan-
nel A probe to VO2 terminal post, connect the Channel B probe to
VO1 post, invert Channel B and add the two channels together.
Most multichannel oscilloscopes have this feature built in. If you
REV. 0
–13–
SSM2211
square cm of copper area to the ground pins. It is recommended
that the solder mask and/or silk screen on the PCB traces adja-
cent to the SSM2211 pins be deleted, thus reducing further the
junction to ambient thermal resistance of the package.
COPPER
LEAD-FRAME
1
8
2
3
7
6
COPPER PADDLE
4
5
Figure 49. Therm al Coastline
–14–
REV. 0
SSM2211
O UTLINE D IMENSIO NS
D imensions shown in inches and (mm).
8-Lead SO IC
(S0-8)
0.1968 (5.00)
0.1890 (4.80)
8
1
5
4
0.1574 (4.00)
0.1497 (3.80)
0.2440 (6.20)
0.2284 (5.80)
PIN 1
0.0688 (1.75)
0.0532 (1.35)
0.0196 (0.50)
0.0099 (0.25)
x 45°
0.0098 (0.25)
0.0040 (0.10)
8°
0°
0.0500
(1.27)
BSC
0.0192 (0.49)
0.0138 (0.35)
SEATING
PLANE
0.0098 (0.25)
0.0075 (0.19)
0.0500 (1.27)
0.0160 (0.41)
8-Lead P lastic D IP
(N-8)*
0.430 (10.92)
0.348 (8.84)
8
5
0.280 (7.11)
0.240 (6.10)
1
4
0.325 (8.25)
0.300 (7.62)
0.060 (1.52)
0.015 (0.38)
PIN 1
0.195 (4.95)
0.115 (2.93)
0.210 (5.33)
MAX
0.130
(3.30)
MIN
0.160 (4.06)
0.115 (2.93)
0.015 (0.381)
0.008 (0.204)
SEATING
PLANE
0.100
(2.54)
BSC
0.022 (0.558)
0.014 (0.356)
0.070 (1.77)
0.045 (1.15)
*Special or der only.
REV. 0
–15–
–16–
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