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Low Distortion, 1.5 W Audio Power Amplifier SSM2211
FEATURES
1.5 W output1 Differential (BTL2) output Single-supply operation: 2.7 V to 5.5 V Functions down to 1.75 V Wide bandwidth: 4 MHz Highly stable phase margin: >80 degrees Low distortion: 0.2% THD + N @ 1 W output Excellent power supply rejection
FUNCTIONAL BLOCK DIAGRAM
IN- IN+ VOUTA
VOUTB BYPASS
APPLICATIONS
Portable computers Personal wireless communicators Hands-free telephones Speaker phones Intercoms Musical toys and talking games
SHUTDOWN BIAS
00358-001
SSM2211
V- (GND)
Figure 1.
GENERAL DESCRIPTION
The SSM22113 is a high performance audio amplifier that delivers 1 W rms of low distortion audio power into a bridgeconnected 8 speaker load (or 1.5 W rms into a 4 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 continues 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 and distortion below 0.2% THD + N @ 1 W, superior performance is delivered at higher power or lower speaker load impedance than competitive units. The low differential dc output voltage results in negligible losses in the speaker winding and makes high value dc blocking capacitors unnecessary. Battery life is extended by using shutdown mode, which typically reduces quiescent current drain to 100 nA. The SSM2211 is designed to operate over the -40C to +85C temperature range. The SSM2211 is available in 8-lead SOIC (narrow body) and LFCSP (lead frame chip scale) surfacemount packages. The advanced mechanical packaging of the LFCSP models ensures lower chip temperature and enhanced performance relative to standard packaging options. 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.
1 2 3
At RL = 4 , TA = 25C, THD + N < 1%, VS = 5 V, 4-layer PCB. Bridge-tied load. Protected by U.S. Patent No. 5,519,576.
Rev. D
Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties that may result from its use. Specifications subject to change without notice. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. Trademarks and registered trademarks are the property of their respective owners.
One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781.329.4700 www.analog.com Fax: 781.461.3113 (c)2006 Analog Devices, Inc. All rights reserved.
SSM2211 TABLE OF CONTENTS
Features .............................................................................................. 1 Applications....................................................................................... 1 Functional Block Diagram .............................................................. 1 General Description ......................................................................... 1 Revision History ............................................................................... 2 Electrical Characteristics ................................................................. 3 Absolute Maximum Ratings............................................................ 5 Thermal Resistance ...................................................................... 5 ESD Caution.................................................................................. 5 Pin Configurations and Function Descriptions ........................... 6 Typical Performance Characteristics ............................................. 7 Product Overview........................................................................... 14 Thermal Performance--LFCSP................................................ 14 Typical Applications ....................................................................... 15 Bridged Output vs. Single-Ended Output Configurations ... 15 Speaker Efficiency and Loudness............................................. 15 Power Dissipation....................................................................... 16 Output Voltage Headroom........................................................ 17 Automatic Shutdown-Sensing Circuit..................................... 17 Shutdown-Circuit Design Example ......................................... 18 Start-Up Popping Noise............................................................. 18 SSM2211 Amplifier Design Example .................................. 18 Single-Ended Applications........................................................ 19 Driving Two Speakers Single Endedly..................................... 19 Evaluation Board ........................................................................ 20 LFCSP Printed Circuit Board Layout Considerations .......... 20 Outline Dimensions ....................................................................... 21 Ordering Guide .......................................................................... 21
REVISION HISTORY
11/06--Rev. C to Rev. D Updated Format..................................................................Universal Changes to General Description .................................................... 1 Changes to Electrical Characteristics ............................................ 3 Changes to Absolute Maximum Ratings ....................................... 5 Added Table 6.................................................................................... 6 Changes to Figure 32...................................................................... 11 Changes to the Product Overview Section ................................. 14 Changes to the Output Voltage Headroom Section................... 17 Changes to the Start-Up Popping Noise Section........................ 18 Changes to the Evaluation Board Section ................................... 20 Updated Outline Dimensions ....................................................... 21 Changes to Ordering Guide .......................................................... 21 10/04--Data Sheet Changed from Rev. B to Rev. C Updated Format..................................................................Universal Changes to General Description .................................................... 1 Changes to Table 5............................................................................ 4 Deleted Thermal Performance--SOIC Section ........................... 8 Changes to Figure 31...................................................................... 10 Changes to Figure 40...................................................................... 12 Changes to Thermal Performance--LFCSP Section ................. 13 Deleted Figure 52, Renumbered Successive Figures .................. 14 Deleted Printed Circuit Board Layout--SOIC Section ............. 14 Changes to Output Voltage Headroom Section ......................... 16 Changes to Start-Up Popping Noise Section .............................. 17 Changes to Ordering Guide .......................................................... 20 10/02--Data Sheet Changed from Rev. A to Rev. B Deleted 8-Lead PDIP .........................................................Universal Updated Outline Dimensions....................................................... 15 5/02--Data Sheet Changed from Rev. 0 to Rev. A Edits to General Description ...........................................................1 Edits to Package Type .......................................................................3 Edits to Ordering Guide ...................................................................3 Edits to Product Overview ...............................................................8 Edits to Printed Circuit Board Layout Considerations ............. 13 Added section Printed Circuit Board Layout Considerations--LFCSP................................................................ 14
Rev. D | Page 2 of 24
SSM2211 ELECTRICAL CHARACTERISTICS
VS = 5.0 V, TA = 25C, RL = 8 , CB = 0.1 F, VCM = VD/2, unless otherwise noted. Table 1.
Parameter GENERAL CHARACTERISTICS Differential Output Offset Voltage Output Impedance SHUTDOWN CONTROL Input Voltage High Input Voltage Low POWER SUPPLY Power Supply Rejection Ratio Supply Current Supply Current, Shutdown Mode DYNAMIC PERFORMANCE Gain Bandwidth Phase Margin AUDIO PERFORMANCE Total Harmonic Distortion Total Harmonic Distortion Voltage Noise Density Symbol VOOS ZOUT VIH VIL PSRR ISY ISD GBP M THD + N THD + N en P = 0.5 W into 8 , f = 1 kHz P = 1.0 W into 8 , f = 1 kHz f = 1 kHz Conditions AVD = 2, -40C TA +85C Min Typ 4 0.1 3.0 1.3 66 9.5 0.1 4 86 0.15 0.2 85 Max 50 Unit mV V V dB mA A MHz Degrees % % nVHz
ISY = < 100 mA ISY = normal VS = 4.75 V to 5.25 V VO1 = VO2 = 2.5 V, -40C TA +85C Pin 1 = VDD (see Figure 32), -40C < TA < +85C
20 1
VS = 3.3 V, TA = 25C, RL = 8 , CB = 0.1 F, VCM = VD/2, unless otherwise noted. Table 2.
Parameter GENERAL CHARACTERISTICS Differential Output Offset Voltage Output Impedance SHUTDOWN CONTROL Input Voltage High Input Voltage Low POWER SUPPLY Supply Current Supply Current, Shutdown Mode AUDIO PERFORMANCE Total Harmonic Distortion Symbol VOOS ZOUT VIH VIL ISY ISD THD + N Conditions AVD = 2, -40C TA +85C Min Typ 5 0.1 1.7 1 5.2 0.1 0.1 20 1 Max 50 Unit mV V V mA A %
ISY = < 100 A ISY = normal VO1 = VO2 = 1.65 V, -40C TA +85C Pin 1 = VDD (see Figure 32), -40C TA +85C P = 0.35 W into 8 , f = 1 kHz
Rev. D | Page 3 of 24
SSM2211
VS = 2.7 V, TA = 25C, RL = 8 , CB = 0.1 F, VCM = VS/2, unless otherwise noted. Table 3.
Parameter GENERAL CHARACTERISTICS Differential Output Offset Voltage Output Impedance SHUTDOWN CONTROL Input Voltage High Input Voltage Low POWER SUPPLY Supply Current Supply Current, Shutdown Mode AUDIO PERFORMANCE Total Harmonic Distortion Symbol VOOS ZOUT VIH VIL ISY ISD THD + N Conditions AVD = 2 Min Typ 5 0.1 1.5 0.8 4.2 0.1 0.1 20 1 Max 50 Unit mV V V mA A %
ISY = < 100 mA ISY = normal VO1 = VO2 = 1.35 V, -40C TA +85C Pin 1 = VDD (see Figure 32), -40C TA +85C P = 0.25 W into 8 , f = 1 kHz
Rev. D | Page 4 of 24
SSM2211 ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings apply at 25C, unless otherwise noted. Table 4.
Parameter Supply Voltage Input Voltage Common-Mode Input Voltage ESD Susceptibility Storage Temperature Range Operating Temperature Range Junction Temperature Range Lead Temperature Range, Soldering (60 sec) Rating 6V VDD VDD 2000 V -65C to +150C -40C to +85C -65C to +165C 300C
THERMAL RESISTANCE
JA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages. Table 5. Thermal Resistance
Package Type 8-Lead LFCSP_VD (CP-Suffix)1 8-Lead SOIC_N (S-Suffix)2
1
JA 50 121
Unit C/W C/W
For the LFCSP_VD, JA is measured with exposed lead frame soldered to the printed circuit board. 2 For the SOIC_N, JA is measured with the device soldered to a 4-layer printed circuit board.
Stresses above those listed under Absolute Maximum Ratings may cause permanent damage to the device. This is a stress rating only; functional operation of the device at these or any other conditions above those indicated in the operational section of this specification is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ESD CAUTION
Rev. D | Page 5 of 24
SSM2211 PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
SHUTDOWN 1 BYPASS 2 IN+ 3
8
SSM2211
VOUTB V-
00358-002
SHUTDOWN 1 BYPASS 2 IN+ 3 IN- 4
PIN 1 INDICATOR
7
SSM2211
TOP VIEW (Not to Scale)
8 VOUTB 7 V- 6 V+ 5 VOUTA
00358-003
6 V+ TOP VIEW (Not to Scale) IN- 4 5 VOUTA
Figure 2. 8-Lead SOIC_N Pin Configuration (R-8)
Figure 3. 8-Lead LFCSP_VD Pin Configuration (CP-8-2)
Table 6. Pin Function Descriptions
Pin No. 1 2 3 4 5 6 7 8 Mnemonic SHUTDOWN BYPASS IN+ IN- VOUTA V+ V- VOUTB Description Shutdown Enable. Bypass Capacitor. Noninverting Input. Inverting Input. Output A. Positive Supply. Negative Supply. Output B.
Rev. D | Page 6 of 24
SSM2211 TYPICAL PERFORMANCE CHARACTERISTICS
10 TA = 25C VDD = 5V AVD = 2 (BTL) RL = 8 PL = 500mW CB = 0 CB = 0.1F CB = 1F 10 TA = 25C VDD = 5V AVD = 2 (BTL) RL = 8 PL = 1W CB = 0 CB = 0.1F
1
1
THD + N (%)
0.1
THD + N (%)
0.1
CB = 1F
0.01
00358-004
20
100
1k FREQUENCY (Hz)
10k
20k
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 4. THD + N vs. Frequency
10 CB = 0
10
Figure 7. THD + N vs. Frequency
CB = 0
1
THD + N (%)
CB = 0.1F CB = 1F
THD + N (%)
1
CB = 0.1F
CB = 1F 0.1 TA = 25C VDD = 5V AVD = 10 (BTL) RL = 8 PL = 1W
0.1
00358-005
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 5. THD + N vs. Frequency
10 10
Figure 8. THD + N vs. Frequency
CB = 0.1F 1 1 CB = 1F
CB = 0.1F
THD + N (%)
THD + N (%)
CB = 1F
0.1
00358-006
0.01 20
100
1k FREQUENCY (Hz)
10k
20k
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 6. THD + N vs. Frequency
Figure 9. THD + N vs. Frequency
Rev. D | Page 7 of 24
00358-009
TA = 25C VDD = 5V AVD = 20 (BTL) RL = 8 PL = 500mW
0.1
TA = 25C VDD = 5V AVD = 20 (BTL) RL = 8 PL = 1W
00358-008
TA = 25C VDD = 5V AVD = 10 (BTL) RL = 8 PL = 500mW
00358-007
SSM2211
10 TA = 25C VDD = 5V AVD = 2 (BTL) RL = 8 FREQUENCY = 20Hz CB = 0.1F 10 TA = 25C VDD = 3.3V AVD = 2 (BTL) RL = 8 PL = 350mW CB = 0
1
1
THD + N (%)
THD + N (%)
CB = 0.1F 0.1 CB = 1F
0.1
00358-010
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 10. THD + N vs. POUTPUT
10 TA = 25C VDD = 5V AVD = 2 (BTL) RL = 8 FREQUENCY = 1kHz CB = 0.1F 10
Figure 13. THD + N vs. Frequency
CB = 0
1
1
CB = 0.1F
THD + N (%)
THD + N (%)
0.1
0.1
CB = 1F TA = 25C VDD = 3.3V AVD = 10 (BTL) RL = 8 PL = 350mW
00358-011
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 11. THD + N vs. POUTPUT
10 TA = 25C VDD = 5V AVD = 2 (BTL) RL = 8 FREQUENCY = 20kHz CB = 0.1F
Figure 14. THD + N vs. Frequency
10
CB = 0.1F 1
1
THD + N (%)
THD + N (%)
CB = 1F
0.1
0.1
00358-012
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 12. THD + N vs. POUTPUT
Figure 15. THD + N vs. Frequency
Rev. D | Page 8 of 24
00358-015
TA = 25C VDD = 3.3V AVD = 20 (BTL) RL = 8 PL = 350mW
00358-014
00358-013
SSM2211
10 TA = 25C VDD = 3.3V AVD = 2 (BTL) RL = 8 FREQUENCY = 20Hz CB = 0.1F
10 TA = 25C VDD = 2.7V AVD = 2 (BTL) RL = 8 PL = 250mW CB = 0
1
1
THD + N (%)
THD + N (%)
CB = 0.1F
0.1
0.1 CB = 1F
00358-016 00358-019
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 16. THD + N vs. POUTPUT
10 TA = 25C VDD = 3.3V AVD = 2 (BTL) RL = 8 FREQUENCY = 1kHz CB = 0.1F
10
Figure 19. THD + N vs. Frequency
CB = 0
CB = 0.1F 1
1
THD + N (%)
THD + N (%)
0.1
0.1
CB = 1F TA = 25C VDD = 2.7V AVD = 10 (BTL) RL = 8 PL = 250mW 20 100 1k FREQUENCY (Hz) 10k 20k
00358-017
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
Figure 17. THD + N vs. POUTPUT
10 TA = 25C VDD = 3.3V AVD = 2 (BTL) RL = 8 FREQUENCY = 20kHz CB = 0.1F
Figure 20. THD + N vs. Frequency
10
CB = 0.1F 1
1
THD + N (%)
THD + N (%)
CB = 1F 0.1 TA = 25C VDD = 2.7V AVD = 20 (BTL) RL = 8 PL = 250mW 20 100 1k FREQUENCY (Hz) 10k 20k
0.1
00358-018
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
Figure 18. THD + N vs. POUTPUT
Figure 21. THD + N vs. Frequency
Rev. D | Page 9 of 24
00358-021
00358-020
SSM2211
10 TA = 25C VDD = 2.7V AVD = 2 (BTL) RL = 8 FREQUENCY = 20Hz
10 TA = 25C VDD = 5V AVD = 10 SINGLE ENDED CB = 0.1F CC = 1000F
1
THD + N (%) THD + N (%)
1
RL = 8 PO = 250mW 0.1
0.1
00358-022
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 22. THD + N vs. POUTPUT
10
Figure 25. THD + N vs. Frequency
10
TA = 25C VDD = 2.7V AVD = 2 (BTL) RL = 8 FREQUENCY = 1kHz
TA = 25C VDD = 3.3V AVD = 10 SINGLE ENDED CB = 0.1F CC = 1000F
1
1
THD + N (%)
THD + N (%)
RL = 8 PO = 85mW 0.1
0.1
00358-023
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 23. THD + N vs. POUTPUT
10 TA = 25C VDD = 2.7V AVD = 2 (BTL) RL = 8 FREQUENCY = 20kHz
10
Figure 26. THD + N vs. Frequency
TA = 25C VDD = 2.7V AVD = 10 SINGLE ENDED CB = 0.1F CC = 1000F
1
1
THD + N (%)
THD + N (%)
RL = 8 PO = 65mW 0.1
0.1
00358-024
0.01 20n
0.1 POUTPUT (W)
1
2
0.01
20
100
1k FREQUENCY (Hz)
10k
20k
Figure 24. THD + N vs. POUTPUT
Figure 27. THD + N vs. Frequency
Rev. D | Page 10 of 24
00358-027
RL = 32 PO = 15mW
00358-026
RL = 32 PO = 20mW
00358-025
RL = 32 PO = 60mW
SSM2211
10 TA = 25C AVD = 2 (BTL) RL = 8 FREQUENCY = 20Hz CB = 0.1F VDD = 2.7V 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 8-LEAD SOIC
00358-031
1
MAXIMUM POWER DISSIPATION (W)
TJ,MAX = 150C FREE AIR, NO HEAT SINK SOIC JA = 121C/W LFCSP JA = 50C/W
THD + N (%)
8-LEAD LFCSP
VDD = 3.3V 0.1
VDD = 5V
0.01 20n
0.1 POUTPUT (W)
1
2
00358-028
-40 -30 -20 -10
0
10
20
30
40
50
60
70
80
90 100 110 120
AMBIENT TEMPERATURE (C)
Figure 28. THD + N vs. POUTPUT
10 TA = 25C AVD = 2 (BTL) RL = 8 FREQUENCY = 1kHz CB = 0.1F
Figure 31. Maximum Power Dissipation vs. Ambient Temperature
10k
VDD = 2.7V
TA = 25C VDD = 5V
8k
1
SUPPLY CURRENT (A)
00358-029
THD + N (%)
6k
0.1 VDD = 3.3V
4k
VDD = 5V
2k
00358-032
0.01 20n
0.1 POUTPUT (W)
1
2
0
0
1
2
3
4
5
SHUTDOWN VOLTAGE AT PIN 1 (V)
Figure 29. THD + N vs. POUTPUT
10 TA = 25C AVD = 2 (BTL) RL = 8 FREQUENCY = 20kHz CB = 0.1F
Figure 32. Supply Current vs. Shutdown Voltage at Pin 1
14
VDD = 3.3V
12
TA = 25C RL = OPEN
SUPPLY CURRENT (mA)
00358-030
1
10 8 6 4 2 0
THD + N (%)
VDD = 2.7V
0.1
VDD = 5V 0.01 20n 0.1 POUTPUT (W) 1 2
0
1
2
3
4
5
6
SUPPLY VOLTAGE (V)
Figure 30. THD + N vs. POUTPUT
Figure 33. Supply Current vs. Supply Voltage
Rev. D | Page 11 of 24
00358-033
SSM2211
1.6 1.4
20 25 VDD = 2.7V SAMPLE SIZE = 300
1.2 OUTPUT POWER (W)
FREQUENCY
1.0 0.8 0.6 0.4 0.2 0 2.7V 4 8 12 16 20 24 28 32 36 40 44 48 LOAD RESISTANCE () 3.3V
15
10
5V
00358-034
5
00358-036
0 -20
-15
-10
-5
0
5
10
15
20
25
OUTPUT OFFSET VOLTAGE (mV)
Figure 34. POUTPUT vs. Load Resistance
80 60 40 20 0 -20 -40 -60 -80 100 180 135 90 45 0 -45 -90
16 20
Figure 36. Output Offset Voltage Distribution
VDD = 3.3V SAMPLE SIZE = 300
PHASE SHIFT (Degrees)
FREQUENCY
GAIN (dB)
12
8
4
00358-035 00358-037
-135 -180 100M
1k
10k
100k
1M
10M
FREQUENCY (Hz)
0 -30
-20
-10
0
10
20
30
OUTPUT OFFSET VOLTAGE (mV)
Figure 35. Gain and Phase Shift vs. Frequency (Single Amplifier)
Figure 37. Output Offset Voltage Distribution
Rev. D | Page 12 of 24
SSM2211
20 VDD = = 3.3V DD 5V SAMPLE SIZE = 300 SAMPLE SIZE = 300 16 -55 -50 TA = 25C VDD = 5V 100mV CB = 15F AVD = 2
FREQUENCY
PSRR (dB)
00358-038
12
-60
8
4
-65
00358-040
0 -30
-20
-10
0
10
20
30
-70
OUTPUT OFFSET VOLTAGE (mV)
20
100
1k FREQUENCY (Hz)
10k
30k
Figure 38. Output Offset Voltage Distribution
600 VDD = 5V SAMPLE SIZE = 1,700 500
Figure 40. PSRR vs. Frequency
400
FREQUENCY
300
200
100
00358-039
0
6
7
8
9
10
11
12
13
14
15
SUPPLY CURRENT (mA)
Figure 39. Supply Current Distribution
Rev. D | Page 13 of 24
SSM2211 PRODUCT OVERVIEW
The SSM2211 is a low distortion speaker amplifier that can run from a 2.7 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. The SSM2211 is unity-gain stable, requiring no external compensation capacitors, and can be configured for gains of up to 40 dB. Figure 41 shows the simplified schematic.
20k VDD 6
VIN
20k
4 3 A1
SSM2211
5 50k 50k 50k VO1
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 operational amplifier, 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 Pin 5 and Pin 8 produce a bridged configuration output to which a speaker can be connected. This bridge configuration offers the advantage of a more efficient power transfer from the input to the speaker. Because both outputs are symmetric, the dc bias at Pin 5 and Pin 8 are exactly equal, resulting in zero dc differential voltage across the outputs. This eliminates the need for a coupling capacitor at the output.
THERMAL PERFORMANCE--LFCSP
The addition of the LFCSP to the Analog Devices, Inc., package portfolio offers the SSM2211 user even greater choice when considering thermal performance criteria. For the 8-lead, 3 mm x 3 mm LFCSP, the JA is 50C/W. This is a significant performance improvement over most other packaging options.
2
A2
8
VO2
0.1F
50k
BIAS CONTROL 7 1 SHUTDOWN
Figure 41. Simplified Schematic
Rev. D | Page 14 of 24
00358-041
SSM2211 TYPICAL APPLICATIONS
RF 5V CS 5 1 7 2 CB
00358-042
AUDIO INPUT
CC
RI
6 4 -
-
SSM2211
3 +
SPEAKER 8V
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 speaker in a single-ended configuration is 250 mW. By driving this speaker with a bridged output, 1 W of power can be delivered. This translates to a 12 dB increase in sound pressure level from the speaker. Driving a speaker differentially from a bridged output offers another advantage in that it eliminates the need for an output coupling capacitor to the load. In a single-supply application, the quiescent voltage at the output is half of the supply voltage. If a speaker is connected in a single-ended configuration, a coupling capacitor is needed to prevent dc current from flowing through the speaker. This capacitor also needs to be large enough to prevent low frequency roll-off. The corner frequency is given by f -3dB = 1 2R L x C C (4)
8
+
Figure 42. Typical Configuration
Figure 42 shows how the SSM2211 is connected in a typical application. The SSM2211 can be configured for gain much like a standard operational amplifier. The gain from the audio input to the speaker is
R AV = 2 x F RI
The 2x factor comes from the fact that Pin 8 has the opposite polarity of Pin 5, providing twice the voltage swing to the speaker from the bridged-output configuration.
(1)
where RL is the speaker resistance and CC is the coupling capacitance. For an 8 speaker and a corner frequency of 20 Hz, a 1000 F capacitor would be needed, which is physically large and costly. By connecting a speaker in a bridged-output configuration, the quiescent differential voltage across the speaker becomes nearly zero, eliminating the need for the coupling capacitor.
CS is a supply bypass capacitor used to provide power supply filtering. 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
SPEAKER EFFICIENCY AND LOUDNESS
The effective loudness of 1 W of power delivered into an 8 speaker is a function of speaker efficiency. The efficiency 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. Table 7 shows a comparison of the relative loudness of different sounds.
Table 7. Typical Sound Pressure Levels
Source of Sound Threshold of Pain Heavy Street Traffic Cabin of Jet Aircraft Average Conversation Average Home at Night Quiet Recording Studio Threshold of Hearing dB SPL 120 95 80 65 50 30 0
f HP =
1 2R I x C C
(2)
Because the SSM2211 has an excellent phase margin, a feedback capacitor in parallel with RF to band limit the amplifier is not required, as it is in some competitor products.
BRIDGED OUTPUT VS. SINGLE-ENDED OUTPUT CONFIGURATIONS
The power delivered to a load with a sinusoidal signal can be expressed in terms of the peak voltage of the signal and the resistance of the load as
PL = V PK 2 2 x RL (3)
By driving a load from a bridged-output configuration, the voltage swing across the load doubles. Therefore, an advantage in using a bridged-output configuration becomes apparent from Equation 3, as doubling the peak voltage results in four times
It can easily be seen that 1 W of power into a speaker can produce quite a bit of acoustic energy.
Rev. D | Page 15 of 24
SSM2211
POWER DISSIPATION
Another important advantage in using a bridged-output configuration is the fact that bridged-output amplifiers are more efficient than single-ended amplifiers in delivering power to a load. Efficiency is defined as the ratio of power from the power supply to power delivered to the load
The power dissipated by the amplifier internally is simply the difference between Equation 6 and Equation 3. The equation for internal power dissipated, PDISS, expressed in terms of power delivered to the load and load resistance, is
PDISS =
2 2VDD x VPEAK
RL
(7)
=
PL PSY
The graph of this equation is shown in Figure 44.
1.5 VDD = 5V
POWER DISSIPATION (W)
An amplifier 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. This is important when considering the amplifier maximum power dissipation rating vs. ambient temperature. An internal power dissipation vs. output power equation can be derived to fully understand this. The internal power dissipation of the amplifier is the internal voltage drop multiplied by the average value of the supply current. An easier way to find internal power dissipation is to measure the difference between the power delivered by the supply voltage source and the power delivered into the load. The waveform of the supply current for a bridged-output amplifier is shown in Figure 43.
VOUT VPEAK
RL = 4 1.0
0.5
RL = 8
0
0
0.5
1.0
1.5
OUTPUT POWER (W)
Figure 44. Power Dissipation vs. Output Power with VDD = 5 V
TIME T ISY
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 actually decreases with higher output power. The 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. This yields
IDD, PEAK IDD, AVG T
00358-043
PDISS PL
=
2 x V DD
R L
2 V DD 2 2 RL
x PL
-1
2
-1 = 0
00358-044
RL = 16
(8)
and occurs when PDISS, MAX = (9)
TIME
Figure 43. Bridged Amplifier Output Voltage and Supply Current vs. Time
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
I DD , AVG =
2VPEAK R L
(5)
Therefore, power delivered by the supply, neglecting the bias current for the device, is
PSY = 2 VDD x VPEAK RL (6)
Using Equation 9 and the power derating curve in Figure 31, the maximum ambient temperature can be found easily. This ensures that the SSM2211 does not exceed its maximum junction temperature of 150C. The power dissipation for a single-ended output application where the load is capacitively coupled is given by
PDISS =
2 2 x V DD RL
x P L - PL
(10)
The graph of Equation 10 is shown in Figure 45.
Rev. D | Page 16 of 24
SSM2211
0.35 VDD = 5V 0.30
POWER DISSIPATION (W)
1.6 RL = 4 1.4
0.25 0.20 0.15 0.10 0.05 0 RL = 16
00358-045
MAX POUT @ 1% THD (W)
1.2 RL = 4 1.0 0.8 0.6 RL = 16 0.4
00358-046
RL = 8
RL = 8
0.2 0
0
0.1
0.2 OUTPUT POWER (W)
0.3
0.4
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
SUPPLY VOLTAGE (V)
Figure 45. Power Dissipation vs. Single-Ended Output Power with VDD = 5 V
Figure 46. Maximum Output Power vs. VSY Shutdown Feature
The maximum power dissipation for a single-ended output is
PDISS , MAX = VDD 2 2 RL
2
(11)
OUTPUT VOLTAGE HEADROOM
The outputs of both amplifiers in the SSM2211 can come to within 400 mV of either supply rail while driving an 8 load. As compared to equivalent competitor products, the SSM2211 has a higher output voltage headroom. This 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 device is reduced, as can be seen in Equation 9. This extended output headroom, along with the LFCSP package, allows the SSM2211 to operate in higher ambient temperatures than competitor devices. The SSM2211 is also capable of providing amplification even at supply voltages as low as 2.7 V. The maximum power available at the output is a function of the supply voltage. Therefore, as the supply voltage decreases, so does the maximum power output from the device. The maximum output power vs. supply voltage at various bridge-tied load resistances is shown in Figure 46. The maximum output power is defined as the point at which the output has 1% total harmonic distortion (THD + N). To find the minimum supply voltage needed to achieve a specified maximum undistorted output power use Figure 46. For example, an application requires only 500 mW to be output for an 8 speaker. With the speaker connected in a bridged-output configuration, the minimum supply voltage required is 3.3 V.
The SSM2211 can be put into a low power consumption shutdown 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. Connect Pin 1 to ground for normal operation. Connecting Pin 1 to VDD mutes the outputs and puts the device 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. Leaving Pin 1 unconnected can produce unpredictable results.
AUTOMATIC SHUTDOWN-SENSING CIRCUIT
Figure 47 shows a circuit that can be used to take the SSM2211 in and out of shutdown mode automatically. This circuit can be set to turn the SSM2211 on when an input signal of a certain amplitude is detected. The circuit also puts the device into low power shutdown mode if an input signal is not sensed within a certain amount of time. This can be useful in a variety of portable radio applications, where power conservation is critical.
R8 VDD R7 VDD R6 VDD - 4 5
C2 VIN
R5
SSM2211
1 A1 8
R4
OP181
+ A2 D1 C1 R3 R2
00358-047
R1
NOTE ADDITIONAL PINS OMITTED FOR CLARITY
Figure 47. Automatic Shutdown Circuit
Rev. D | Page 17 of 24
SSM2211
The input signal to the SSM2211 is also connected to the noninverting terminal of A2. R1, R2, and R3 set the threshold voltage at which the SSM2211 is to 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 voltage is detected. R4 controls the charge time of C1, which sets the time until the SSM2211 is put back into shutdown mode after the input signal is no longer detected. 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. A 1N914 or equivalent diode is required for D1, and A2 must be a rail-to-rail output amplifier, such as OP181 or equivalent. This ensures that C1 discharges sufficiently to bring the SSM2211 out of shutdown mode. To find the appropriate component values, first, the gain of A2 must be determined by AV,MIN = VSY VTHS (12)
SHUTDOWN-CIRCUIT DESIGN EXAMPLE
In this example, a portable radio application requires the SSM2211 to be turned on when an input signal greater than 50 mV is detected. The device needs to return to shutdown mode within 500 ms after the input signal is no longer detected. The lowest frequency of interest is 200 Hz, and a 5 V supply is used. The minimum gain of the shutdown circuit, from Equation 12, is AV = 100. R1 is set to 100 k. Using Equation 13 and Equation 14, R2 = 98 k and R3 = 4.9 M. C1 is set to 0.01 F, and based on Equation 15, R4 is set to 10 M . To minimize power supply current, R5 and R6 are set to 10 M. The previous procedure provides an adequate starting point for the shutdown circuit. Some component values may need to be adjusted empirically to optimize performance.
START-UP POPPING 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 subaudible range, greatly reducing start-up popping noise. On power-up, the midrail bypass capacitor is charged through an effective resistance of 25 k. To minimize start-up popping, the charging time constant for CB needs to be greater than the charging time constant for the input coupling capacitor, CC. CB x 25 k > CC x R1 (16) For an application where R1 = 10 k and CC = 0.22 F, CB must be at least 0.1 F to minimize start-up popping noise.
where: VSY is the single supply voltage. VTHS is the threshold voltage. AV must be set to a minimum of 2 for the circuit to work properly. Next, choose R1 and set R2 to
2 R2 = R1 1 - A V
(13)
Find R3 as R3 = R1x R2 R2 + R2
SSM2211 Amplifier Design Example
(A
V
- 1)
(14)
C1 can be arbitrarily set but should be small enough to prevent A2 from becoming capacitively overloaded. R4 and C1 control the shutdown rate. To prevent intermittent shutdown with low frequency input signals, the minimum time constant must be R4 x C1 10 f LOW (15)
Maximum Output Power Input Impedance Load Impedance Input Level Bandwidth
1W 20 k 8 1 V rms 20 Hz - 20 kHz 0.25 dB
where fLOW is the lowest input frequency expected.
The configuration shown in Figure 42 is used. The first thing to determine is the minimum supply rail necessary to obtain the specified maximum output power. From Figure 46, for 1 W of output power into an 8 load, the supply voltage must be at least 4.6 V. A supply rail of 5 V can be easily obtained from a
Rev. D | Page 18 of 24
SSM2211
voltage reference. The extra supply voltage also allows the SSM2211 to reproduce peaks in excess of 1 W without clipping the signal. With VDD = 5 V and RL = 8 , Equation 9 shows that the maximum power dissipation for the SSM2211 is 633 mW. From the power derating curve in Figure 31, the ambient temperature must be less than 73C for the SOIC and 118C for the LFCSP. The required gain of the amplifier can be determined from Equation 17 as
AV = PL x RL VIN,rms
SINGLE-ENDED APPLICATIONS
There are applications in which driving a speaker differentially is not practical, for example, a pair of stereo speakers where the minus terminal of both speakers is connected to ground. Figure 48 shows how this can be accomplished.
10k 5V
= 2 .8
(17)
AUDIO INPUT
10k 0.47F
6 4 - 5 1 7 2 8 470F +
SSM2211
3 +
From Equation 1
0.1F
-
or RF = 1.4 x RI. Because the desired input impedance is 20 k, RI = 20 k and R2 = 28 k. The final design step is to select the input capacitor. When adding an input capacitor, CC, to create a high-pass filter, the corner frequency needs to be far enough away for the design to meet the bandwidth criteria. For a first-order filter to achieve a pass-band response within 0.25 dB, the corner frequency must be at least 4.14x away from the pass-band frequency. So, (4.14 x fHP) < 20 Hz. Using Equation 2, the minimum size of input capacitor can be found.
Figure 48. Single-Ended Output Application
It is not necessary to connect a dummy load to the unused output to help stabilize the output. The 470 F coupling capacitor creates a high-pass frequency cutoff of 42 Hz, as given in Equation 4, which is acceptable for most computer speaker applications. The overall gain for a single-ended output configuration is AV = RF/R1, which for this example is equal to 1.
DRIVING TWO SPEAKERS SINGLE ENDEDLY
It is possible to drive two speakers single endedly with both outputs of the SSM2211.
20k 5V - 470F 6 - 5 1 7 2 0.1F 8 470F + + 4 LEFT SPEAKER (8)
CC >
1 20 Hz 2 x 20 k 4.14
(18)
Therefore, CC > 1.65 F. Using a 2.2 F is a practical choice for CC. The gain bandwidth product for each internal amplifier in the SSM2211 is 4 MHz. Because 4 MHz is much greater than 4.14 x 20 kHz, the design meets the upper frequency bandwidth criteria. The SSM2211 can also be configured for higher differential gains without running into bandwidth limitations. Equation 16 shows an appropriate value for CB to reduce startup popping noise. CB >
AUDIO INPUT 20k 1F 3
SSM2211
+
-
(2.2 F)(20 k)
25 k
Figure 49. SSM2211 Used as a Dual-Speaker Amplifier
= 1.76 F
(19)
Selecting CB to be 2.2 F for a practical value of capacitor minimizes start-up popping noise. To summarize the final design: VDD R1 RF CC CB TA, MAX 5V 20 k 28 k 2.2 F 2.2 F 85C
Each speaker is driven by a single-ended output. The trade-off is that only 250 mW of 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 speakers. These coupling capacitors produce a high-pass filter with a corner frequency given by Equation 4. For a speaker load of 8 and a coupling capacitor of 470 F, this results in a -3 dB frequency of 42 Hz. Because the power of a single-ended output is one-quarter that of a bridged output, both speakers together are still half as loud (-6 dB SPL) as a single speaker driven with a bridged output.
Rev. D | Page 19 of 24
00358-049
RIGHT SPEAKER (8)
00358-048
RF AV = RI 2
250mW SPEAKER (8)
SSM2211
The polarity of the speakers is important, as each output is 180 degrees 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. The maximum power dissipation of the device, assuming both loads are equal, can be found by doubling Equation 11. If the loads are different, use Equation 11 to find the power dissipation caused by each load, then take the sum to find the total power dissipated by the SSM2211. Therefore, for PO = 1 W and RL = 8 , V = 2.8 V rms, or 8 V pp. If the available input signal is 1.4 V rms or more, use the board as is, with RF = RI = 20 k. If more gain is needed, increase the value of RF. When you have determined the closed-loop gain required by your source level, and can develop 1 W across the 8 load resistor with the normal input signal level, replace the resistor with your speaker. Your speaker can be connected across the VO1 and VO2 posts for bridged-mode operation only after the 8 load resistor is removed. For no phase inversion, VO2 must be connected to the (+) terminal of the speaker.
VO2 5
+ SHUTDOWN ON 1 AUDIO INPUT + VOLUME 20k POT. CW CIN 1F RI 20k 2 3 4 7 RF 20k
00358-050
EVALUATION BOARD
An evaluation board for the SSM2211 is available. For more information, call 1-800-ANALOGD.
R1 51k V+
CH A GND PROBES
C2 10F
C1 0.1F VO2
SSM2211
2.5V COMMON MODE 8
8 1W
8
VO1
OSCILLOSCOPE
RL 1W 8
SSM2211
5 J2
Figure 51. Using an Oscilloscope to Display the Bridged-Output Voltage
VO1
C1 0.1F
Figure 50. Evaluation Board Schematic
The voltage gain of the SSM2211 is given by Equation 20.
AV = 2 x
RF RI
(20)
To use the SSM2211 in a single-ended-output configuration, replace J1 and J2 jumpers with electrolytic capacitors of a suitable value, with the negative terminals to the output terminals VO1 and VO2. The single-ended loads can 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 maximum swing in the nonbridged 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 F capacitor is required with 8 speakers. The SSM2211 evaluation board also comes with a shutdown switch, which allows the user to switch between on (normal operation) and the power-conserving shutdown mode.
If desired, the input signal may be attenuated by turning the 10 k potentiometer in the CW (clockwise) direction. CIN isolates the input common-mode voltage (VD/2) present at Pin 2 and Pin 3. With V+ = 5 V, there is 2.5 V common-mode voltage present at both output terminals, VO1 and VO2, as well. CAUTION: The 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 shorts out one of the amplifier outputs and can possibly damage the device. A safe method of displaying the differential output signal using a grounded scope is shown in Figure 51. Connect Channel A probe to the VO2 terminal post. Connect Channel B probe to the VO1 post. Invert Channel B, and add the two channels together. Most multichannel oscilloscopes have this feature built in. If you must connect the ground lead of the test instrument to either output signal pins, a power-line isolation transformer must be used to isolate the instrument ground from the power supply ground. Recall that
V= PxR
LFCSP PRINTED CIRCUIT BOARD LAYOUT CONSIDERATIONS
The LFCSP is a plastic encapsulated package with a copper lead frame substrate. This is a leadless package with solder lands on the bottom surface of the package, instead of conventional formed perimeter leads. A key feature that allows the user to reach the quoted JA performance is the exposed die attach paddle (DAP) on the bottom surface of the package. When soldered to the PCB, the DAP can provide efficient conduction of heat from the die to the PCB. In order to achieve optimum package performance, consideration should be given to the PCB pad design for both the solder lands and the DAP. For further information the user is directed to the Amkor Technology document, "Application Notes for Surface Mount Assembly of Amkor's MicroLead Frame (MLF) Packages." This can be downloaded from the Amkor Technology website, www.amkor.com, as a product application note.
Rev. D | Page 20 of 24
00358-051
6
CH B
J1
CH B DISPLAY INV. ON A+B
SSM2211 OUTLINE DIMENSIONS
5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497)
8 1 5 4
6.20 (0.2440) 5.80 (0.2284)
1.27 (0.0500) BSC 0.25 (0.0098) 0.10 (0.0040) COPLANARITY 0.10 SEATING PLANE
1.75 (0.0688) 1.35 (0.0532)
0.50 (0.0196) 0.25 (0.0099) 8 0 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157)
45
0.51 (0.0201) 0.31 (0.0122)
COMPLIANT TO JEDEC STANDARDS MS-012-A A CONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS (IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FOR REFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.
Figure 52. 8-Lead Standard Small Outline Package [SOIC_N] Narrow Body, S-Suffix (R-8) Dimensions shown in millimeters and (inches)
0.50 0.40 0.30
3.00 BSC SQ
0.60 MAX
PIN 1 INDICATOR
8
1
PIN 1 INDICATOR
TOP VIEW
2.75 BSC SQ
0.50 BSC
1.50 REF
5 4
1.89 1.74 1.59
0.90 MAX 0.85 NOM
12 MAX
0.70 MAX 0.65 TYP 0.05 MAX 0.01 NOM 0.30 0.23 0.18 0.20 REF
1.60 1.45 1.30
SEATING PLANE
Figure 53. 8-Lead Lead Frame Chip Scale Package [LFCSP_VD] 3 mm x 3 mm Body, Very Thin, Dual Lead (CP-8-2) Dimensions shown in millimeters
ORDERING GUIDE
Model SSM2211CP-R2 SSM2211CP-REEL SSM2211CP-REEL7 SSM2211CPZ-R21 SSM2211CPZ-REEL 1 SSM2211CPZ-REEL71 SSM2211S SSM2211S-REEL SSM2211S-REEL7 SSM2211SZ1 SSM2211SZ-REEL1 SSM2211SZ-REEL71 SSM2211-EVAL
1
Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C -40C to +85C
Package Description 8-Lead LFCSP_VD 8-Lead LFCSP_VD 8-Lead LFCSP_VD 8-Lead LFCSP_VD 8-Lead LFCSP_VD 8-Lead LFCSP_VD 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N 8-Lead SOIC_N Evaluation Board
Package Option CP-8-2 CP-8-2 CP-8-2 CP-8-2 CP-8-2 CP-8-2 R-8 (S-Suffix) R-8 (S-Suffix) R-8 (S-Suffix) R-8 (S-Suffix) R-8 (S-Suffix) R-8 (S-Suffix)
060506-A
Branding B5A B5A B5A B5A# B5A# B5A#
Z = Pb-free part; # denotes lead-free product may be top or bottom marked.
Rev. D | Page 21 of 24
SSM2211 NOTES
Rev. D | Page 22 of 24
SSM2211 NOTES
Rev. D | Page 23 of 24
SSM2211 NOTES
(c)2006 Analog Devices, Inc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. C00358-0-11/06(D)
Rev. D | Page 24 of 24

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