FEATURES
1.5 W output with THD + N < 1% Differential bridge-tied load 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°
Low distortion: 0.2% THD + N @ 1 W output Excellent power supply rejection
APPLICATIONS
Portable computers
Personal wireless communicators Hands-free telephones Speaker phones Intercoms
Musical toys and talking games
GENERAL DESCRIPTION
The SSM22111 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 a 4 Ω load). The SSM2211 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.
Furthermore, when the ambient temperature is at 25°C, THD + N < 1%, and VS = 5 V on a four-layer PCB, the SSM2211 delivers a 1.5 W output.
1
Protected by U.S. Patent No. 5,519,576.
Rev. E
nformation 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.
Low Distortion, 1.5 W Audio
Power Amplifier
SSM2211
FUNCTIONAL BLOCK DIAGRAM
IN–VIN+OUTAVOUTBBYPASSSHUTDOWNBIASSSM2211100-8V– (GND)5300
Figure 1.
The low differential dc output voltage results in negligible
losses in the speaker winding and makes high value dc blocking capacitors unnecessary. The 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 −40°C to +85°C temperature range. The SSM2211 is available in 8-lead SOIC (narrow body) and LFCSP (lead frame chip scale) surface-mount 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.
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 ©2008 Analog Devices, Inc. All rights reserved.
SSM2211
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 PCB Considerations ...................................................... 20 Outline Dimensions ....................................................................... 21 Ordering Guide .......................................................................... 22
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
REVISION HISTORY
4/08—Rev. D to Rev. E
Changes to Features .......................................................................... 1
Changes to General Description .................................................... 1 Changes to Supply Current in Table 1 and Table 2 ...................... 3 Changes to Supply Current in Table 3 ........................................... 4 Changes to Absolute Maximum Ratings ....................................... 5 Changes to Figure 41 ...................................................................... 14 Changes to Equation 7, Equation 8, and Equation 10 ............... 16 Changes to Figure 47 ...................................................................... 17 Changes to Automatic Shutdown-Sensing Circuit Section ...... 18 Changes to SSM2211Amplifier Design Example Section ......... 19 Changes to Driving Two Speakers Single Endedly Section ...... 20 Changes to Figure 50 ...................................................................... 20 Changes to Evaluation Board Section .......................................... 20 Changes to Figure 51 ...................................................................... 20 Changes to Ordering Guide .......................................................... 22 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. E | Page 2 of 24
SSM2211
ELECTRICAL CHARACTERISTICS
VDD = 5.0 V, TA = 25°C, RL = 8 Ω, CB = 0.1 μF, VCM = VDD/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 Product Phase Margin
AUDIO PERFORMANCE
Total Harmonic Distortion Total Harmonic Distortion Voltage Noise Density
Symbol Conditions VOOS AVD = 2, −40°C ≤ TA ≤ +85°C ZOUT VIH ISY = <100 mA VIL ISY = normal PSRR VS = 4.75 V to 5.25 V ISY VOUTA = VOUTB = 2.5 V, −40°C ≤ TA ≤ +85°C ISD Pin 1 = VDD (see Figure 32), −40°C ≤ TA ≤ +85°C GBP
ΦM
THD + N P = 0.5 W into 8 Ω, f = 1 kHz THD + N P = 1.0 W into 8 Ω, f = 1 kHz en f = 1 kHz
Min Typ Max Unit
4 50 mV 0.1 Ω 3.0 V 1.3 V 66 dB 9.5 20 mA 0.1 1 μA 4 MHz 86 Degrees 0.15 % 0.2 % 85 nV√Hz
VDD = 3.3 V, TA = 25°C, RL = 8 Ω, CB = 0.1 μF, VCM = VDD/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, −40°C ≤ TA ≤ +85°C
ISY = <100 μA ISY = normal
VOUTA = VOUTB = 1.65 V, −40°C ≤ TA ≤ +85°C Pin 1 = VDD (see Figure 32), −40°C ≤ TA ≤ +85°C
P = 0.35 W into 8 Ω, f = 1 kHz
Min 1.7
Typ 5 0.1 5.2 0.1 0.1
Max 50 1 20 1
Unit mV Ω V V mA μA %
Rev. E | Page 3 of 24
SSM2211
VDD = 2.7 V, TA = 25°C, RL = 8 Ω, CB = 0.1 μF, VCM = VDD/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
ISY = <100 mA ISY = normal
VOUTA = VOUTB = 1.35 V, −40°C ≤ TA ≤ +85°C Pin 1 = VDD (see Figure 32), −40°C ≤ TA ≤ +85°C
P = 0.25 W into 8 Ω, f = 1 kHz
Min 1.5
Typ 5 0.1 4.2 0.1 0.1
Max 50 0.8 20 1
Unit mV Ω V V mA μA %
Rev. E | Page 4 of 24
SSM2211
THERMAL RESISTANCE
θJA is specified for the worst-case conditions, that is, a device soldered in a circuit board for surface-mount packages.
ABSOLUTE MAXIMUM RATINGS
Absolute maximum ratings apply at TA = 25°C, unless otherwise noted. Table 4.
Parameter Rating Table 5. Thermal Resistance Supply Voltage 6 V Package Type θJA Unit Input Voltage VDD 8-Lead LFCSP_VD (CP-Suffix)1 50 °C/W Common-Mode Input Voltage VDD 2
8-Lead SOIC_N (S-Suffix) 121 °C/W
ESD Susceptibility 2000 V
1
For the LFCSP_VD, θJA is measured with exposed lead frame soldered to the PCB. Storage Temperature Range −65°C to +150°C 2
For the SOIC_N, θJA is measured with the device soldered to a four-layer PCB.
Operating Temperature Range −40°C to +85°C
Junction Temperature Range −65°C to +165°C
Lead Temperature, Soldering (60 sec) 300°C ESD CAUTION
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.
Rev. E | Page 5 of 24
SSM2211
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
SHUTDOWN1BYPASS2IN+38VOUTBV–00358-002SHUTDOWN1BYPASS2IN+3IN–4PIN 1INDICATORSSM22117SSM2211TOP VIEW(Not to Scale)8VOUTB7V–6V+5VOUTA00358-003
Figure 2. 8-Lead SOIC_N Pin Configuration (R-8)
6V+TOP VIEW(Not to Scale)IN–45VOUTAFigure 3. 8-Lead LFCSP_VD Pin Configuration (CP-8-2)
Table 6. Pin Function Descriptions
Pin No. Mnemonic Description
1 SHUTDOWN Shutdown Enable. 2 BYPASS Bypass Capacitor. 3 N+ Noninverting nput. 4 N− nverting nput. 5 VOUTA Output A. 6 V+ Positive Supply. 7 V− Negative Supply. 8 VOUTB Output B.
II
II
I
Rev. E | Page 6 of 24
SSM2211
TYPICAL PERFORMANCE CHARACTERISTICS
10TA = 25°CVADD = 5VVD = 2 (BTL)RL = 8ΩPL = 500mW1CB = 0)%( N +CB = 0.1μF DHTC0.1B = 1μF0.01201001k10k20kFREQUENCY (Hz)Figure 4. THD + N vs. Frequency
10
CB = 01
CB = 0.1μF)%( N +CB = 1μF DHT0.1
TA = 25°CVADD = 5VVD = 10 (BTL)RL = 8ΩPL = 500mW0.01
201001k
10k20k
FREQUENCY (Hz)
Figure 5. THD + N vs. Frequency
10CB = 0.1μF1)%( CB = 1μFN + DHT0.1TA = 25°CVADD = 5VRVD = 20 (BTL)L = 8ΩPL = 500mW0.01201001k10k20kFREQUENCY (Hz)Figure 6. THD + N vs. Frequency 10TA = 25°CVDD = 5VAVD = 2 (BTL)RL = 8ΩPL = 1W1CB = 0)%( N +CB = 0.1μF DHT0.1CB = 1μF400-853000.01201001k10k20kFREQUENCY (Hz)Figure 7. THD + N vs. Frequency
10CB = 01CB = 0.1μF)%( N + DHCB = 1μFT0.1TA = 25°CVADD = 5VRVD = 10 (BTL)L = 8Ω50P0L = 1W-853000.01201001k10k20kFREQUENCY (Hz)Figure 8. THD + N vs. Frequency
10CB = 0.1μF1)%( N +CB = 1μF DHT0.1TA = 25°CVDD = 5VAVD = 20 (BTL)R60PL = 8Ω0L = 1W-853000.01201001k10k20kFREQUENCY (Hz)Figure 9. THD + N vs. Frequency
Rev. E | Page 7 of 24
700-85300800-85300900-85300SSM2211
10TVA = 25°CDD = 5VARVD = 2 (BTL)L = 8ΩFREQUENCY = 20HzCB = 0.1μF1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 10. THD + N vs. POUTPUT
10TA = 25°CVDD = 5VAVD = 2 (BTL)RL = 8ΩFREQUENCY = 1kHzCB = 0.1μF1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 11. THD + N vs. POUTPUT
10TVA = 25°CDD = 5VAVD = 2 (BTL)RL = 8ΩFREQUENCY = 20kHzCB = 0.1μF1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 12. THD + N vs. POUTPUT 10TVA = 25°CADD = 3.3VRVD = 2 (BTL)L = 8ΩPL = 350mW1CB = 0)%( N + DHCB = 0.1μFT0.1CB = 1μF010-853000.01201001k10k20kFREQUENCY (Hz)Figure 13. THD + N vs. Frequency
10CB = 01CB = 0.1μF)%( N + DHT0.1CB = 1μFTA = 25°CVADD = 3.3VRVD = 10 (BTL)L = 8Ω110PL = 350mW-853000.01201001k10k20kFREQUENCY (Hz)Figure 14. THD + N vs. Frequency
10CB = 0.1μF1)%( N +CB = 1μF DHT0.1TA = 25°CVDD = 3.3VAVD = 20 (BTL)R210PL = 8ΩL = 350mW-853000.01201001k10k20k
FREQUENCY (Hz)Figure 15. THD + N vs. Frequency
Rev. E | Page 8 of 24
310-85300410-85300
510-85300
SSM2211
10TA = 25°CVADD = 3.3VVD = 2 (BTL)RFREQUENCY = 20HzL = 8ΩCB = 0.1μF1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 16. THD + N vs. POUTPUT
10TA = 25°CVDD = 3.3VAVD = 2 (BTL)RL = 8ΩFREQUENCY = 1kHzCB = 0.1μF1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 17. THD + N vs. POUTPUT
10TVA = 25°CDD = 3.3VAVD = 2 (BTL)RL = 8ΩFREQUENCY = 20kHzCB = 0.1μF1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 18. THD + N vs. POUTPUT 10TA = 25°CVDD = 2.7VAVD = 2 (BTL)RL = 8ΩPL = 250mW1CB = 0)%( N + CDB = 0.1μFHT0.1CB = 1μF610-853000.01201001k10k20kFREQUENCY (Hz)Figure 19. THD + N vs. Frequency
10CB = 0CB = 0.1μF1)%( N + DHTCB = 1μF0.1TA = 25°CVADD = 2.7VRVD = 10 (BTL)7L = 8Ω10P-L = 250mW853000.01201001k10k20kFREQUENCY (Hz)Figure 20. THD + N vs. Frequency
10CB = 0.1μF1)%( N + DHTCB = 1μF0.1TA = 25°CVDD = 2.7VAVD = 20 (BTL)RL = 8Ω810P-L = 250mW853000.01201001k10k20kFREQUENCY (Hz)Figure 21. THD + N vs. Frequency
Rev. E | Page 9 of 24
910-85300020-85300
120-85300
SSM2211
10TA = 25°CVADD = 2.7VVD = 2 (BTL)RL = 8ΩFREQUENCY = 20Hz1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 22. THD + N vs. POUTPUT
10TA = 25°CVADD = 2.7VVD = 2 (BTL)RL = 8ΩFREQUENCY = 1kHz1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 23. THD + N vs. POUTPUT
10TA = 25°CVADD = 2.7VVD = 2 (BTL)RL = 8ΩFREQUENCY = 20kHz1)%( N + DHT0.10.0120n0.112POUTPUT (W)Figure 24. THD + N vs. POUTPUT 10TVA = 25°CADD = 5VCVD = 10 SINGLE ENDEDB = 0.1μFCC = 1000μF1)%( N + DRL = 8ΩHPTO = 250mW0.1R2PL = 32Ω20O = 60mW-853000.01201001k10k20kFREQUENCY (Hz)Figure 25. THD + N vs. Frequency
10
TA = 25°CVDD = 3.3VAVD = 10 SINGLE ENDEDCB = 0.1μFCC = 1000μF1
)%( N + DRL = 8ΩHPO = 85mWT0.1
R3L = 32Ω20P-O = 20mW853000.01
201001k
10k20k
FREQUENCY (Hz)
Figure 26. THD + N vs. Frequency
10TA = 25°CVDD = 2.7VAVD = 10 SINGLE ENDEDCCB = 0.1μFC = 1000μF1)%( N + DRL = 8ΩHPTO = 65mW0.14RΩ20-PL = 328O = 15mW53000.01201001k10k20kFREQUENCY (Hz)Figure 27. THD + N vs. Frequency
Rev. E | Page 10 of 24
520-85300
620-85300720-85300
10TA = 25°CAVDD = 2.7VRVD = 2 (BTL)L = 8ΩFREQUENCY = 20HzCB = 0.1μF1)%( N + DVHDD = 5VTVDD = 3.3V0.10.0120n0.112POUTPUT (W)Figure 28. THD + N vs. POUTPUT
10TA = 25°CAVD = 2 (BTL)VDD = 2.7VRL = 8ΩFREQUENCY = 1kHzCB = 0.1μF1)%( N + DHT0.1VDD = 5VVDD = 3.3V0.0120n0.112POUTPUT (W)Figure 29. THD + N vs. POUTPUT
10TA = 25°CARVD = 2 (BTL)L = 8ΩVDD = 3.3VFREQUENCY = 20kHzCB = 0.1μF1)%( NVDD = 2.7V + DHT0.1VDD = 5V0.0120n0.112POUTPUT (W)Figure 30. THD + N vs. POUTPUT SSM2211
4.0TJ,MAX = 150°C)3.5FREE AIR, NO HEAT SINKWSOICθJA = 121°C/W( NLFCSPθO3.0JA = 50°C/WITAPIS2.58-LEAD LFCSPSID RE2.0WOP1.5 MUMIX1.08-LEAD SOICA82M01-0.58350-380503000–40–30–20–100102030405060708090100110120AMBIENT TEMPERATURE (°C)Figure 31. Maximum Power Dissipation vs. Ambient Temperature
10kTA = 25°CVDD = 5V8k)Aµ( TN6kRERUC YL4kPUPS2k9202-380-5380503000012345SHUTDOWN VOLTAGE AT PIN 1 (V)Figure 32. Supply Current vs. Shutdown Voltage at Pin 1
1412TA = 25°CRL = OPEN)Am10( TNRE8RUC 6LYPUPS40233300--885533000000123456SUPPLY VOLTAGE (V)
Figure 33. Supply Current vs. Supply Voltage
Rev. E | Page 11 of 24
SSM2211
1.625VDD = 2.7V1.4
SAMPLE SIZE = 300201.2S)TIWN( UR1.0 F15WEO OR0.8 PBETUMU10TP0.6NUO0.45V50.23.3V430-02.7V8530004
8
12
16
20
24
28
32
36
40
44
48
–20–15–10–50510152025LOAD RESISTANCE (Ω)
OUTPUT OFFSET VOLTAGE (mV)Figure 34. POUTPUT vs. Load Resistance
Figure 36. Output Offset Voltage Distribution
8018020V = 3.3V60135SAMPLE SIZE = 300DD409016)sSeTIeN2045rgU )BDeF12d(O ( NI00TFRIAHBEGSM –20–45EUN8ASH–40–90P4–60–135530-853–80001001k10k100k1M10M100M–1800–30–20–100102030FREQUENCY (Hz)OUTPUT OFFSET VOLTAGE (mV)Figure 35. Gain and Phase Shift vs. Frequency (Single Amplifier) Figure 37. Output Offset Voltage Distribution
Rev. E | Page 12 of 24
630-85300
730-85300
SSM2211
20VDDDD = 5V = 3.3VSAMPLE SIZE = 300SAMPLE SIZE = 30016STINU F12 ORBEMUN840–30–20–100102030OUTPUT OFFSET VOLTAGE (mV)Figure 38. Output Offset Voltage Distribution
600VSAMPLE SIZE = 1,700DD = 5V500STINU400 F ORBE300MUN20010006789101112131415SUPPLY CURRENT (mA)Figure 39. Supply Current Distribution
–50TA = 25°CVDD = 5V± 100mVCB = 15μFAVD = 2–55)Bd( RR–60SP–65830-85300–70
201001k10k30kFREQUENCY (Hz)Figure 40. PSRR vs. Frequency
930-85300Rev. E | Page 13 of 24
040-85300SSM2211
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.
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.
20kΩV+6IN–20kΩ43A1SSM2211550kΩ50kΩ50kΩVOUTATHERMAL PERFORMANCE—LFCSP
The LFCSP offers the SSM2211 user even greater choices when considering thermal performance criteria. For the 8-lead, 3 mm × 3 mm LFCSP, the θJA is 50°C/W. This is a significant performance improvement over most other packaging options.
2A28VOUTB0.1µF50kΩBIASCONTROL71SHUTDOWN00358-041
Figure 41. Simplified Schematic
Rev. E | Page 14 of 24
SSM2211
RF5VTYPICAL APPLICATIONS
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.
–SPEAKER8V+CS58AUDIOINPUTCCRI64–SSM22113+72CB1
Driving a speaker differentially from a BTL 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
Figure 42. Typical Configuration
00358-042Figure 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
f−3dB=
1
(4)
2πRL×CC
where RL is the speaker resistance and CC is the coupling capacitance.
For an 8 Ω speaker and a corner frequency of 20 Hz, a 1000 μF RF
(1) AV=2×capacitor is needed, which is physically large and costly. By RIThe 2× factor results from Pin 8 having an opposite polarity of Pin 5, providing twice the voltage swing to the speaker from the bridged-output (BTL) configuration.
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 enhance 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
connecting a speaker in a BTL configuration, the quiescent differential voltage across the speaker becomes nearly zero, eliminating the need for the coupling capacitor.
SPEAKER EFFICIENCY AND LOUDNESS
The effective loudness of 1 W of power delivered into an 8 Ω 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.
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
SPL (dB) 120 95 80 65 50 30 0
fHP=
1
(2) Table 7. Typical Sound Pressure Levels
2πRI×CC
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
VPK2
(3) PL=
2×RL
By driving a load from a BTL configuration, the voltage swing across the load doubles. Therefore, an advantage in using a BTL 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
Rev. E | Page 15 of 24
Consequently, Table 7 demonstrates that 1 W of power into a speaker can produce quite a bit of acoustic energy.
SSM2211
The power dissipated internally by the amplifier 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
POWER DISSIPATION
Another important advantage in using a BTL 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 the power from the power supply to the power delivered to the load
PDISS=
22VDDπRL
×PL−PL (7)
η=
PL
PSY
The graph of this equation is shown in Figure 44.
1.5VDD = 5VRL = 4Ω1.0POWER DISSIPATION (W)An amplifier with a higher efficiency has less internal power dissipation, which results in a lower die-to-case junction temperature compared with 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.
VOUTVPEAK0.5RL = 8Ω000.51.01.5OUTPUT POWER (W)00358-044RL = 16Ω
Figure 44. Power Dissipation vs. Output Power with VDD = 5 V
TIMETISYBecause 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, PEAKIDD, AVGT00358-0432VDD∂PDISS1=×−1=0 (8) ∂PLπRLPLand occurs when
Figure 43. Bridged Amplifier Output Voltage and Supply Current vs. Time
TIMEPDISS,MAX=
2VDD2π2RL
(9)
By integrating the supply current over a period, T, and then dividing the result by T, the IDD,AVG can be found. Expressed in terms of peak output voltage and load resistance
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
2VPEAK
junction temperature of 150°C. The power dissipation for a (5) IDD,AVG=
πRLsingle-ended output application where the load is capacitively
coupled is given by Therefore, power delivered by the supply, neglecting the bias current for the device, is
PSY=
2VDD×VPEAK
πRL
PDISS=
22VDD
(6) The graph of Equation 10 is shown in Figure 45.
πRL
×PL−PL (10)
Rev. E | Page 16 of 24
0.35VDD = 5V0.30RL = 4Ω1.61.4SSM2211
POWER DISSIPATION (W)0.250.200.150.100.050RL = 16Ω00358-045MAX POUT @ 1% THD (W)1.2RL = 4Ω1.0RL = 8Ω0.80.6RL = 16Ω0.400358-046RL = 8Ω0.2000.10.2OUTPUT POWER (W)0.30.41.52.02.53.03.54.04.55.0
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
The SSM2211 can be put into a low power consumption shut-down mode by connecting Pin 1 to 5 V. In shutdown mode,
VDD2
the SSM2211 has an extremely low supply current of less than PDISS,MAX= (11)
2π2RL10 nA. This makes the SSM2211 ideal for battery-powered
applications. OUTPUT VOLTAGE HEADROOM
The outputs of both amplifiers in the SSM2211 can come within
400 mV of either supply rail while driving an 8 Ω load. As compared with 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 shown in Equation 9. This extended output headroom, along with the LFCSP, 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 BTL 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 Ω speaker. With the speaker connected in a bridged-output configuration, the minimum supply voltage required is 3.3 V.
VDDConnect 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.
R8VDDR7VDDR6–45R5C2IN–VOUTASSM22111A18VOUTBR4AD8500+D1C1R3R200358-047R1NOTES1. ADDITIONAL PINS OMITTED FOR CLARITY.
Figure 47. Automatic Shutdown Circuit
Rev. E | Page 17 of 24
SSM2211
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 kΩ. 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. To minimize power supply current, R5 and R6 are set to 10 MΩ. The previous procedure provides an adequate starting point for the shutdown circuit. Some component values may need to be adjusted empirically to optimize performance.
The input signal to the SSM2211 is also connected to the non-inverting terminal of A2. R1, R2, and R3 set the threshold voltage at which the SSM2211 is to be taken out of shutdown mode. The diode, 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 AD8500 or equivalent. This ensures that C1 discharges sufficiently to bring the SSM2211 out of shutdown mode.
To find the appropriate component values, the gain of A2 must be determined by
START-UP POPPING NOISE
During power-up or release from shutdown mode, the midrail bypass capacitor, CB, determines the rate at which the SSM2211 (12) AV,MIN=
VTHSstarts up. By adjusting the charging time constant of CB, the start-up pop noise can be pushed into the subaudible range, greatly where:
reducing start-up popping noise. On power-up, the midrail VSY is the single supply voltage.
bypass capacitor is charged through an effective resistance of VTHS is the threshold voltage.
25 kΩ. To minimize start-up popping, the charging time constant AV must be set to a minimum of 2 for the circuit to work
for CB needs to be greater than the charging time constant for properly.
the input coupling capacitor, CC.
Next, choose R1 and set R2 to
CB × 25 kΩ > CC × R1 (16)
VSY
⎛2⎞For an application where R1 = 10 kΩ and CC = 0.22 μF, CB must ⎟ (13) R2=R1⎜1−⎟⎜AV⎠be at least 0.1 μF to minimize start-up popping noise. ⎝
Find R3 as SSM2211 Amplifier Design Example
R3=
R1×R2R2+R2
(AV−1) (14) Input impedance: 20 kΩ
Maximum output power: 1 W Load impedance: 8 Ω
Input level: 1 V rms
Bandwidth: 20 Hz − 20 kHz ± 0.25 dB
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
The configuration shown in Figure 42 is used. The first thing to determine is the minimum supply rail necessary to obtain the
10specified maximum output power. From Figure 46, for 1 W of
R4×C1≥ (15)
output power into an 8 Ω load, the supply voltage must be at fLOW
least 4.6 V. A supply rail of 5 V can be easily obtained from a
where fLOW is the lowest input frequency expected.
Rev. E | Page 18 of 24
SSM2211
SINGLE-ENDED APPLICATIONS
There are applications in which driving a speaker differentially is not practical, for example, a pair of stereo speakers where the negative terminal of both speakers is connected to ground. Figure 48 shows how this can be accomplished.
10kΩ5Vvoltage 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 Ω, 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 50°C for the SOIC and 121°C for the LFCSP.
The required gain of the amplifier can be determined from Equation 17 as
6AUDIOINPUT10kΩ4–51720.1μF8470μF+AV=
PL×RLVIN,rms
=2.80.47μF (17) 3SSM2211+From Equation 1
–00358-04800358-049RFAV
= RI2
or RF = 1.4 × RI. Because the desired input impedance is 20 kΩ, RI = 20 kΩ and R2 = 28 kΩ.
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 4.14× away from the pass-band frequency. Therefore, (4.14 × fHP) < 20 Hz. Using Equation 2, the minimum size of an input capacitor can be found.
250mWSPEAKER(8Ω)
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 μF coupling capa-citor 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 config-uration is AV = RF/R1, which for this example is equal to 1.
DRIVING TWO SPEAKERS SINGLE ENDEDLY
CC>
1
⎛20Hz⎞
2π×20kΩ⎜⎟⎜4.14⎟
⎠⎝
It is possible to drive two speakers single endedly with both
outputs of the SSM2211.
(18) 20kΩ5V470μF6AUDIOINPUT20kΩ1μF34–51720.1μF8470μF+–LEFTSPEAKER(8Ω)Therefore, CC > 1.65 μF. Using a 2.2 μF 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 × 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 start-up popping noise.
+SSM2211+RIGHTSPEAKER(8Ω)–
CB>
(2.2μF)(20kΩ)25kΩ
Figure 49. SSM2211 Used as a Dual-Speaker Amplifier
Each speaker is driven by a single-ended output. The trade-off =1.76μF (19)
is that only 250 mW of sustained power can be put into each speaker. In addition, 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. These coupling
capacitors 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. Because the power of a single-ended output is one-quarter that of a BTL, both speakers together are still half as loud (−6 dB SPL) as a single speaker driven with a BTL.
Selecting CB to be 2.2 μF for a practical value of capacitor minimizes start-up popping noise. To summarize the final design VDD = 5 V R1 = 20 kΩ RF = 28 kΩ CC = 2.2 μF CB = 2.2 μF TA, MAX = 85°C
Rev. E | Page 19 of 24
SSM2211
Recall that
The polarity of the speakers is important because each output is 180° out of phase with the other. By connecting the negative terminal of Speaker 1 to Pin 5 and the positive 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 dissipa-tion caused by each load, and then take the sum to find the total power dissipated by the SSM2211.
V=P×R
Therefore, for POUT = 1 W and RL = 8 Ω, V = 2.8 V rms or 8 V pp. If the available input signal is 1.4 V rms or more, use the PCB as is, with RF = RI = 20 kΩ. If more gain is needed, increase the value of RF.
When the closed-loop gain required by your source level is
determined, it can develop 1 W across the 8 Ω load resistor with the normal input signal level, replace the resistor with a speaker. The speaker can be connected across the VOUTA and VOUTB posts for bridged-mode operation only after the 8 Ω load resistor is removed. For no phase inversion, VOUTB must be connected to the positive (+) terminal of the speaker.
VOUTB5CH AEVALUATION BOARD
An evaluation board for the SSM2211 is available. For more information, call 1-800-ANALOGD.
R151kΩV++SHUTDOWNON1AUDIOINPUT+VOLUME20kΩ POT.CWCIN1µFRI20kΩ2347RF20kΩ5J268J1VOUTBC210µFC10.1µFSSM22112.5VCOMMONMODE88Ω1WGNDPROBESSSM2211RL1W 8ΩCH BVOUTAVOUTAOSCILLOSCOPE00358-051CH BDISPLAYINV. ONA+B
Figure 51. Using an Oscilloscope to Display the Bridged-Output Voltage
To use the SSM2211 in a single-ended-output configuration, replace J1 and J2 jumpers with electrolytic capacitors of a suitable
C1value, with the negative terminals to the output Terminal VOUTA 0.1µF
and Terminal VOUTB. The single-ended loads can then be returned
Figure 50. Evaluation Board Schematic
to ground. Note that the maximum output power is reduced to
The voltage gain of the SSM2211 is given by Equation 20. 250 mW (one-quarter of the rated maximum), due to the maxi-mum swing in the nonbridged mode being one-half and power RF
(20) AV=2×being proportional to the square of the voltage. For frequency RI
response down to 3 dB at 100 Hz, a 200 μF capacitor is required
If desired, the input signal can be attenuated by turning the with 8 Ω speakers. 10 kΩ potentiometer in the CW (clockwise) direction. CIN
The SSM2211 evaluation board also comes with a shutdown
isolates the input common-mode voltage (VDD/2) present at
switch, which allows the user to switch between on (normal
Pin 2 and Pin 3. With V+ = 5 V, there is a 2.5 V common-mode
operation) and the power-conserving shutdown mode.
voltage present at both output terminals, VOUTA and VOUTB, as well.
00358-050Caution: The ground lead of the oscilloscope probe, or any other instrument used to measure the output signal, must not be connected to either output because this shorts out one of the amplifier outputs and may 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 VOUTB terminal post. Connect Channel B probe to the VOUTA 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 of the output signal pins, a power-line isolation transformer must be used to isolate the instrument ground from the power supply ground.
LFCSP PCB 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 θJA 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. 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.
Rev. E | Page 20 of 24
SSM2211
5.00(0.1968)4.80(0.1890)OUTLINE DIMENSIONS
4.00 (0.1574)3.80 (0.1497)81546.20 (0.2440)5.80 (0.2284)1.27 (0.0500)BSC0.25 (0.0098)0.10 (0.0040)COPLANARITY0.10SEATINGPLANE1.75 (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)COMPLIANTTO JEDEC STANDARDS MS-012-AACONTROLLING DIMENSIONSARE IN MILLIMETERS; INCH DIMENSIONS(INPARENTHESES)ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FORREFERENCE ONLYANDARE NOTAPPROPRIATE FOR USE IN DESIGN.060506-A
Figure 52. 8-Lead Standard Small Outline Package [SOIC_N]
Narrow Body, S-Suffix
(R-8)
Dimensions shown in millimeters and (inches)
0.500.400.303.00BSC SQ0.60 MAXPIN 1INDICATOR81PIN 1INDICATORTOPVIEW2.75BSC SQ0.50BSC1.50REF541.891.741.590.90 MAX0.85 NOM12° MAX0.70 MAX0.65 TYP0.05 MAX0.01 NOM1.601.451.30SEATINGPLANE0.300.230.180.20 REF
Figure 53. 8-Lead Lead Frame Chip Scale Package [LFCSP_VD]
3 mm × 3 mm Body, Very Thin, Dual Lead
(CP-8-2)
Dimensions shown in millimeters
Rev. E | Page 21 of 24
SSM2211
ORDERING GUIDE
Model Temperature Range Package Description Package Option Branding SSM2211CP-R2 –40°C to +85°C 8-Lead LFCSP_VD CP-8-2 B5A SSM2211CP-REEL –40°C to +85°C 8-Lead LFCSP_VD CP-8-2 B5A SSM2211CP-REEL7 –40°C to +85°C 8-Lead LFCSP_VD CP-8-2 B5A SSM2211CPZ-R21–40°C to +85°C 8-Lead LFCSP_VD CP-8-2 B5A#
1
SSM2211CPZ-REEL–40°C to +85°C 8-Lead LFCSP_VD CP-8-2 B5A# SSM2211CPZ-REEL7 –40°C to +85°C 8-Lead LFCSP_VD CP-8-2 B5A# SSM2211S –40°C to +85°C 8-Lead SOIC_N R-8 (S-Suffix) SSM2211S-REEL –40°C to +85°C 8-Lead SOIC_N R-8 (S-Suffix) SSM2211S-REEL7 –40°C to +85°C 8-Lead SOIC_N R-8 (S-Suffix)
1
SSM2211SZ–40°C to +85°C 8-Lead SOIC_N R-8 (S-Suffix) SSM2211SZ-REEL1–40°C to +85°C 8-Lead SOIC_N R-8 (S-Suffix)
1
SSM2211SZ-REEL7–40°C to +85°C 8-Lead SOIC_N R-8 (S-Suffix) SSM2211-EVAL Evaluation Board
1
SSM2211-EVALZ Evaluation Board
1
Z = RoHS Compliant Part; # denotes RoHS compliant product may be top or bottom marked.
Rev. E | Page 22 of 24
SSM2211
NOTES
Rev. E | Page 23 of 24
SSM2211
NOTES
©2008 Analog Devices, nc. All rights reserved. Trademarks and registered trademarks are the property of their respective owners. D00358-0-4/08(E)
Rev. E | Page 24 of 24
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