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low distortion, 1.5 w audio power amplifier ssm2211 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 ?2006 analog devices, inc. all rights reserved. features 1.5 w output 1 differential (btl 2 ) 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 applications portable computers personal wireless communicators hands-free telephones speaker phones intercoms musical toys and talking games functional block diagram v out b in? in+ shutdown bypass v out a v? (gnd) bias 00358-001 ssm2211 figure 1. general description the ssm2211 3 is a high performance audio amplifier that delivers 1 w rms of low distortion audio power into a bridge- connected 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 oper- ating 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 C40c to +85c 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. 1 at r l = 4 , t a = 25c, thd + n < 1%, v s = 5 v, 4-layer pcb. 2 bridge-tied load. 3 protected by u.s. patent no. 5,519,576.
ssm2211 rev. d | page 2 of 24 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 performancelfcsp................................................ 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 11/06rev. 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 10/04data sheet changed from rev. b to rev. c updated format..................................................................universal changes to general description .................................................... 1 changes to table 5............................................................................ 4 deleted thermal performancesoic section ........................... 8 changes to figure 31...................................................................... 10 changes to figure 40...................................................................... 12 changes to thermal performancelfcsp section ................. 13 deleted figure 52, renumbered successive figures .................. 14 deleted printed circuit board layoutsoic section ............. 14 changes to output voltage headroom section ......................... 16 changes to start-up popping noise section .............................. 17 changes to ordering guide .......................................................... 20 10/02data sheet changed from rev. a to rev. b deleted 8-lead pdip .........................................................universal updated outline dimensions....................................................... 15 5/02data 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 considerationslfcsp................................................................ 14
ssm2211 rev. d | page 3 of 24 electrical characteristics v s = 5.0 v, t a = 25c, r l = 8 , c b = 0.1 f, v cm = v d /2, unless otherwise noted. table 1. parameter symbol conditions min typ max unit general characteristics differential output offset voltage v oos a vd = 2, C40c t a +85c 4 50 mv output impedance z out 0.1 shutdown control input voltage high v ih i sy = < 100 ma 3.0 v input voltage low v il i sy = normal 1.3 v power supply power supply rejection ratio psrr v s = 4.75 v to 5.25 v 66 db supply current i sy v o1 = v o2 = 2.5 v, C40c t a +85c 9.5 20 ma supply current, shutdown mode i sd pin 1 = v dd (see figure 32 ), C40c < t a < +85c 0.1 1 a dynamic performance gain bandwidth gbp 4 mhz phase margin m 86 degrees audio performance total harmonic distortion thd + n p = 0.5 w into 8 , f = 1 khz 0.15 % total harmonic distortion thd + n p = 1.0 w into 8 , f = 1 khz 0.2 % voltage noise density e n f = 1 khz 85 nv hz v s = 3.3 v, t a = 25c, r l = 8 , c b = 0.1 f, v cm = v d /2, unless otherwise noted. table 2. parameter symbol conditions min typ max unit general characteristics differential output offset voltage v oos a vd = 2, C40c t a +85c 5 50 mv output impedance z out 0.1 shutdown control input voltage high v ih i sy = < 100 a 1.7 v input voltage low v il i sy = normal 1 v power supply supply current i sy v o1 = v o2 = 1.65 v, C40c t a +85c 5.2 20 ma supply current, shutdown mode i sd pin 1 = v dd (see figure 32 ), C40c t a +85c 0.1 1 a audio performance total harmonic distortion thd + n p = 0.35 w into 8 , f = 1 khz 0.1 %
ssm2211 rev. d | page 4 of 24 v s = 2.7 v, t a = 25c, r l = 8 , c b = 0.1 f, v cm = v s /2, unless otherwise noted. table 3. parameter symbol conditions min typ max unit general characteristics differential output offset voltage v oos a vd = 2 5 50 mv output impedance z out 0.1 shutdown control input voltage high v ih i sy = < 100 ma 1.5 v input voltage low v il i sy = normal 0.8 v power supply supply current i sy v o1 = v o2 = 1.35 v, C40c t a +85c 4.2 20 ma supply current, shutdown mode i sd pin 1 = v dd (see figure 32 ), C40c t a +85c 0.1 1 a audio performance total harmonic distortion thd + n p = 0.25 w into 8 , f = 1 khz 0.1 %
ssm2211 rev. d | page 5 of 24 absolute maximum ratings absolute maximum ratings apply at 25c, unless otherwise noted. table 4. parameter rating supply voltage 6 v input voltage v dd common-mode input voltage v dd esd susceptibility 2000 v storage temperature range ?65c to +150c operating temperature range ?40c to +85c junction temperature range ?65c to +165c lead temperature range, soldering (60 sec) 300c 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. 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 ja unit 8-lead lfcsp_vd (cp-suffix) 1 50 c/w 8-lead soic_n (s-suffix) 2 121 c/w 1 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. esd caution
ssm2211 rev. d | page 6 of 24 pin configurations a nd function descriptions 00358-002 shutdown 1 bypass 2 in+ 3 in? 4 v out b 8 v? 7 v+ 6 v out a 5 ssm2211 top view (not to scale) 1 shutdown 2 bypass 3 in+ 4 in? 7v? 8v out b 6v+ 5v out a 00358-003 pin 1 indicator top view (not to scale) ssm2211 figure 2. 8-lead soic_n pin configuration (r-8) figu re 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 in+ noninverting input. 4 inC inverting input. 5 v out a output a. 6 v+ positive supply. 7 vC negative supply. 8 v out b output b.
ssm2211 rev. d | page 7 of 24 typical performance characteristics frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 5v a vd = 2 (btl) r l = 8 p l = 500mw 00358-004 figure 4. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 5v a vd = 10 (btl) r l = 8 p l = 500mw 00358-005 figure 5. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0.1 f c b = 1 f t a = 25 c v dd = 5v a vd = 20 (btl) r l = 8 p l = 500mw 00358-006 figure 6. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 5v a vd = 2 (btl) r l = 8 p l = 1w 00358-007 figure 7. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 5v a vd = 10 (btl) r l = 8 p l = 1w 00358-008 figure 8. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0.1 f c b = 1 f t a = 25 c v dd = 5v a vd = 20 (btl) r l = 8 p l = 1w 00358-009 figure 9. thd + n vs. frequency
ssm2211 rev. d | page 8 of 24 p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 5v a vd = 2 (btl) r l = 8 frequency = 20hz c b = 0.1 f 00358-010 figure 10. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 5v a vd = 2 (btl) r l = 8 frequency = 1khz c b = 0.1 f 00358-011 figure 11. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 5v a vd = 2 (btl) r l = 8 frequency = 20khz c b = 0.1 f 00358-012 figure 12. thd + n vs. p output frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 3.3v a vd = 2 (btl) r l = 8 p l = 350mw 00358-013 figure 13. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 3.3v a vd = 10 (btl) r l = 8 p l = 350mw 00358-014 figure 14. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0.1 f c b = 1 f t a = 25 c v dd = 3.3v a vd = 20 (btl) r l = 8 p l = 350mw 00358-015 figure 15. thd + n vs. frequency
ssm2211 rev. d | page 9 of 24 p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 3.3v a vd = 2 (btl) r l = 8 frequency = 20hz c b = 0.1 f 00358-016 figure 16. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 3.3v a vd = 2 (btl) r l = 8 frequency = 1khz c b = 0.1 f 00358-017 figure 17. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 3.3v a vd = 2 (btl) r l = 8 frequency = 20khz c b = 0.1 f 00358-018 figure 18. thd + n vs. p output frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 2.7v a vd = 2 (btl) r l = 8 p l = 250mw 00358-019 figure 19. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0 c b = 0.1 f c b = 1 f t a = 25 c v dd = 2.7v a vd = 10 (btl) r l = 8 p l = 250mw 00358-020 figure 20. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 c b = 0.1 f c b = 1 f t a = 25 c v dd = 2.7v a vd = 20 (btl) r l = 8 p l = 250mw 00358-021 figure 21. thd + n vs. frequency
ssm2211 rev. d | page 10 of 24 p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 2.7v a vd = 2 (btl) r l = 8 frequency = 20hz 00358-022 figure 22. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 2.7v a vd = 2 (btl) r l = 8 frequency = 1khz 00358-023 figure 23. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c v dd = 2.7v a vd = 2 (btl) r l = 8 frequency = 20khz 00358-024 figure 24. thd + n vs. p output frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 r l = 32 p o = 60mw r l = 8 p o = 250mw t a = 25 c v dd = 5v a vd = 10 single ended c b = 0.1 f c c = 1000 f 00358-025 figure 25. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 r l = 32 p o = 20mw r l = 8 p o = 85mw t a = 25 c v dd = 3.3v a vd = 10 single ended c b = 0.1 f c c = 1000 f 00358-026 figure 26. thd + n vs. frequency frequency (hz) thd + n (%) 10 1 0.01 20 100 20k 1k 10k 0.1 r l = 32 p o = 15mw r l = 8 p o = 65mw t a = 25 c v dd = 2.7v a vd = 10 single ended c b = 0.1 f c c = 1000 f 00358-027 figure 27. thd + n vs. frequency
ssm2211 rev. d | page 11 of 24 p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c a vd = 2 (btl) r l = 8 frequency = 20hz c b = 0.1 f v dd = 2.7v v dd = 5v v dd = 3.3v 00358-028 figure 28. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 t a = 25 c a vd = 2 (btl) r l = 8 frequency = 1khz c b = 0.1 f v dd = 2.7v v dd = 5v v dd = 3.3v 00358-029 figure 29. thd + n vs. p output p output (w) thd + n (%) 10 1 0.01 20n 0.1 2 0.1 1 v dd = 2.7v v dd = 5v v dd = 3.3v t a = 25 c a vd = 2 (btl) r l = 8 frequency = 20khz c b = 0.1 f 00358-030 figure 30. thd + n vs. p output ambient temperature ( c) maximum power dissipation (w) 00358-031 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 ?40 ?30 ?20 ?10 0 10 30 70 20 40 50 60 9080 110100 120 t j,max = 150c free air, no heat sink soic ja = 121 c/w lfcsp ja = 50 c/w 8-lead soic 8-lead lfcsp figure 31. maximum power dissipation vs. ambient temperature shutdown voltage at pin 1 (v) supply current ( a ) 10k 8k 0 05 1234 6k 4k 2k t a = 25c v dd = 5v 00358-032 figure 32. supply current vs. shutdown voltage at pin 1 supply voltage (v) supply current (ma) 14 0 01 6 2345 12 10 8 4 2 6 t a = 25 c r l = open 00358-033 figure 33. supply current vs. supply voltage
ssm2211 rev. d | page 12 of 24 load resistance ( ) output power (w) 1.6 0.6 0 48 48 12 16 20 24 28 32 36 40 44 1.4 0.8 0.4 0.2 1.2 1.0 5v 3.3v 2.7v 00358-034 figure 34. p output vs. load resistance frequency (hz) gain (db) 80 ?60 ?80 ?40 ?20 0 20 40 60 100 1k 100m 10k 100k 1m 10m phase shift (degrees) 180 ?135 ?180 ?90 ?45 0 45 90 135 00358-035 figure 35. gain and phase shift vs. frequency (single amplifier) output offset voltage (mv) frequency 25 20 0 ?20 ?15 25 ?10 ?5 0 10 15 20 5 15 10 5 v dd = 2.7v sample size = 300 00358-036 figure 36. output offset voltage distribution output offset voltage (mv) frequency 20 16 0 ?30 ?20 30 ?10 0 10 20 12 8 4 v dd = 3.3v sample size = 300 00358-037 figure 37. output offset voltage distribution
ssm2211 rev. d | page 13 of 24 output offset voltage (mv) 20 16 0 ?30 ?20 30 ?10 0 10 20 12 8 4 v dd = 3.3v sample size = 300 frequency v dd = 5v sample size = 300 00358-038 figure 38. output offset voltage distribution supply current (ma) frequency 600 300 0 6 7 8 9 10 11 12 13 14 15 500 400 200 100 v dd = 5v sample size = 1,700 00358-039 figure 39. supply current distribution frequency (hz) psrr (db) ?70 20 100 30k 1k 10k t a = 25 c v dd = 5v 100mv c b = 15 f a vd = 2 ?65 ?60 ?55 ?50 00358-040 figure 40. psrr vs. frequency
ssm2211 rev. d | page 14 of 24 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. 4 3 shutdown v o1 v dd a2 a1 2 v in 20k 20k 50k 0.1 f 7 8 5 6 ssm2211 50k 50k 50k v o2 bias control 00358-041 1 figure 41. simpli fied schematic 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 a v = ?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 differ- ential voltage across the outputs. this eliminates the need for a coupling capacitor at the output. thermal performancelfcsp 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 3 mm lfcsp, the ja is 50c/w. this is a significant performance improvement over most other packaging options.
ssm2211 rev. d | page 15 of 24 typical applications ssm2211 a udio input speaker 8v r f c s 5v 2 7 1 8 5 6 4 3 ? + c c r i c b ? + 00358-042 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 i f v r r a = (1) the 2 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. c s 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 c b 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 r i . c c is the input coupling capacitor, which also creates a high-pass filter with a corner frequency of c i hp cr f = 2 1 (2) because the ssm2211 has an excellent phase margin, a feedback capacitor in parallel with r f 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 l pk l r v p = 2 2 (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 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 c l cr f = ? 2 1 db3 (4) where r l is the speaker resistance and c c 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. 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 db spl threshold of pain 120 heavy street traffic 95 cabin of jet aircraft 80 average conversation 65 average home at night 50 quiet recording studio 30 threshold of hearing 0 it can easily be seen that 1 w of power into a speaker can produce quite a bit of acoustic energy.
ssm2211 rev. d | page 16 of 24 power dissipation another important advantage in using a bridged-output config- uration 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 sy l p p = an amplifier with a higher efficiency has less internal power dissipation, which results in a lower die-to-case junction tem- perature 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. t t 00358-043 v out v peak i sy i dd, peak time i dd, avg 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, i dd,avg can be found. expressed in terms of peak output voltage and load resistance l peak avg dd r v i 2 , = (5) therefore, power delivered by the supply, neglecting the bias current for the device, is l peak dd sy r v v p = 2 (6) the power dissipated by the amplifier internally is simply the difference between equation 6 and equation 3. the equation for internal power dissipated, p diss , expressed in terms of power delivered to the load and load resistance, is l peak dd diss r v v p = 2 2 (7) the graph of this equation is shown in figure 44. output power (w) 1.5 0 0 1.5 power dissipation (w) 0.5 1.0 1.0 0.5 v dd = 5v r l = 4 r l = 8 r l = 16 00358-044 figure 44. power dissipation vs. output power with v dd = 5 v because the efficiency of a bridged-output amplifier (equation 3 divided by equation 6) increases with the square root of p l , 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 0 1 2 2 1 = ? = ? ? ? l l dd l diss p r v p p (8) and occurs when l dd max diss r v p 2 2 , 2 = (9) 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 l l l dd diss p p r v p ? = ? 2 2 (10) the graph of equation 10 is shown in figure 45.
ssm2211 rev. d | page 17 of 24 output power (w) 0.35 0.30 0 0 0.4 0.1 power dissipation (w) 0.2 0.3 0.20 0.15 0.10 0.05 0.25 v dd = 5v r l = 4 r l = 8 r l = 16 00358-045 figure 45. power dissipation vs . single-ended output power with v dd = 5 v the maximum power dissipation for a single-ended output is l dd maxdiss r v p 2 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. supply voltage (v) 0 1.5 5.0 2.0 max p out @ 1% thd (w) 2.5 3.0 3.5 4.0 4.5 1.6 1.0 0.8 0.4 0.2 1.4 1.2 0.6 rl = 4 rl = 8 rl = 16 00358-046 figure 46. maximum output power vs. v sy shutdown feature 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. connect pin 1 to ground for normal operation. connecting pin 1 to v dd 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 v dd 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. ssm2211 v in v dd c2 r5 r6 r1 r3 r2 d1 c1 r4 r7 4 v dd op181 a2 1 5 r8 a1 ? + v dd 8 note additional pins omitted for clarity 00358-047 figure 47. automatic shutdown circuit
ssm2211 rev. d | page 18 of 24 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. 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 ths sy minv, v v a = (12) where: v sy is the single supply voltage. v ths is the threshold voltage. a v must be set to a minimum of 2 for the circuit to work properly. next, choose r1 and set r2 to ? ? ? ? ? ? ? ? ?= v a r1r2 2 1 (13) find r3 as ( 1 ? + = v a r2r2 r2r1 r3 ) (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 low f c1r4 10 ? (15) where f low is the lowest input frequency expected. 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 a v = 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, c b , determines the rate at which the ssm2211 starts up. by adjusting the charging time constant of c b , 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 c b needs to be greater than the charging time constant for the input coupling capacitor, c c . c b 25 k > c c r 1 (16) for an application where r1 = 10 k and c c = 0.22 f, c b must be at least 0.1 f to minimize start-up popping noise. ssm2211 amplifier design example maximum output power 1 w input impedance 20 k load impedance 8 input level 1 v rms bandwidth 20 hz ? 20 khz 0.25 db 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
ssm2211 rev. d | page 19 of 24 voltage reference. the extra supply voltage also allows the ssm2211 to reproduce peaks in excess of 1 w without clipping the signal. with v dd = 5 v and r l = 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 8.2 = = rmsin, ll v v rp a (17) from equation 1 2 v i f a r r = or r f = 1.4 r i . because the desired input impedance is 20 k, r i = 20 k and r2 = 28 k. the final design step is to select the input capacitor. when adding an input capacitor, c c , 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. so, (4.14 f hp ) < 20 hz. using equation 2, the minimum size of input capacitor can be found. ? ? ? ? ? ? ? ? > 144 hz20 k 202 1 . c c (18) therefore, c c > 1.65 f. using a 2.2 f is a practical choice for c c . 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 c b to reduce start- up popping noise. ( ) ( ) f761 k 25 k 20f22 . . c b = > (19) selecting c b to be 2.2 f for a practical value of capacitor minimizes start-up popping noise. to summarize the final design: v dd 5 v r1 20 k r f 28 k c 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. ssm2211 5v 2 7 1 8 5 6 4 3 0.47 f 470 f + ? + ? 10k 10k 250mw speaker (8 ) audio input 0.1 f 00358-048 ssm2211 5v 2 7 1 8 5 6 4 3 0.47 f 470 f + ? + ? 10k 10k 250mw speaker (8 ) audio input 0.1 f 00358-048 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 a v = r f /r 1 , 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. ssm2211 5v 2 7 1 8 5 6 4 3 1 f 470 f + ? + ? 20k 20k right speaker (8 ) a udio input 0.1 f 00358-049 470 f + ? left speaker (8 ) figure 49. ssm2211 used as a dual-speaker amplifier 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. c 2.2 f c b 2.2 f t a, max 85c
ssm2211 rev. d | page 20 of 24 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. therefore, for p o = 1 w and r l = 8 , 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 r f = r i = 20 k. if more gain is needed, increase the value of r f . 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 v o1 and v o2 posts for bridged-mode operation only after the 8 load resistor is removed. for no phase inversion, v o2 must be connected to the (+) terminal of the speaker. 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, then take the sum to find the total power dissipated by the ssm2211. evaluation board an evaluation board for the ssm2211 is available. for more information, call 1-800-analogd. 8 ssm2211 5 v o2 gnd ch a ch b probes ch b inv. on display a+b oscilloscope 2.5v common mode v o1 8 1w 00358-051 v + 8 4 ssm2211 5 3 2 1 v o2 6 j1 j2 c1 0.1f 7 c in 1f cw on shutdown r1 51k ? + + r i 20k ? r f 20k ? v o1 r l 1w 8 ? volume 20k ? pot. a udio input c1 0.1f c2 10f 00358-050 figure 51. using an oscilloscope to display the bridged-output voltage figure 50. evaluation board schematic the voltage gain of the ssm2211 is given by equation 20. i f v r r a = 2 (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 v o1 and v o2 . 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. c in isolates the input common-mode voltage (v d /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, v o1 and v o2 , as well. 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 amkors microlead frame (mlf) packages. this can be downloaded from the amkor technology website, www.amkor.com, as a product application note. 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 v o2 terminal post. connect channel b probe to the v o1 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 rpv =
ssm2211 rev. d | page 21 of 24 outline dimensions 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. compliant to jedec standards ms-012-a a 060506-a 0.25 (0.0098) 0.17 (0.0067) 1.27 (0.0500) 0.40 (0.0157) 0.50 (0.0196) 0.25 (0.0099) 45 8 0 1.75 (0.0688) 1.35 (0.0532) seating plane 0.25 (0.0098) 0.10 (0.0040) 4 1 85 5.00 (0.1968) 4.80 (0.1890) 4.00 (0.1574) 3.80 (0.1497) 1.27 (0.0500) bsc 6.20 (0.2440) 5.80 (0.2284) 0.51 (0.0201) 0.31 (0.0122) coplanarity 0.10 figure 52. 8-lead standard small outline package [soic_n] narrow body, s-suffix (r-8) dimensions shown in millimeters and (inches) 1 0.50 bsc 0.60 max pin 1 indicato r 1.50 ref 0.50 0.40 0.30 2.75 bsc sq top view 12 max 0.70 max 0.65 typ seating plane pin 1 indicator 0.90 max 0.85 nom 0.30 0.23 0.18 0.05 max 0.01 nom 0.20 ref 1.89 1.74 1.59 4 1.60 1.45 1.30 3.00 bsc sq 5 8 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 ordering guide model temperature range package description package option branding SSM2211CP-R2 C40c to +85c 8-lead lfcsp_vd cp-8-2 b5a ssm2211cp-reel C40c to +85c 8-lead lfcsp_vd cp-8-2 b5a ssm2211cp-reel7 C40c to +85c 8-lead lfcsp_vd cp-8-2 b5a ssm2211cpz-r2 1 C40c to +85c 8-lead lfcsp_vd cp-8-2 b5a# ssm2211cpz-reel 1 C40c to +85c 8-lead lfcsp_vd cp-8-2 b5a# ssm2211cpz-reel7 1 C40c to +85c 8-lead lfcsp_vd cp-8-2 b5a# ssm2211s C40c to +85c 8-lead soic_n r-8 (s-suffix) ssm2211s-reel C40c to +85c 8-lead soic_n r-8 (s-suffix) ssm2211s-reel7 C40c to +85c 8-lead soic_n r-8 (s-suffix) ssm2211sz 1 C40c to +85c 8-lead soic_n r-8 (s-suffix) ssm2211sz-reel 1 C40c to +85c 8-lead soic_n r-8 (s-suffix) ssm2211sz-reel7 1 C40c to +85c 8-lead soic_n r-8 (s-suffix) ssm2211-eval evaluation board 1 z = pb-free part; # denotes lead-free product may be top or bottom marked.
ssm2211 rev. d | page 22 of 24 notes
ssm2211 rev. d | page 23 of 24 notes
ssm2211 rev. d | page 24 of 24 notes ?2006 analog devices, inc. all rights reserved. trademarks and registered trademarks are the property of their respective owners. c00358-0-11/06(d)

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