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mono 1.5 w/stereo 250 mw power amplifier ssm2250 rev. a 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 ri ghts 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 ? 2005 analog devices, inc. all rights reserved. features part of soundmax? audio solution for desktop computers mono 1.5 w differential or stereo 250 mw output single-supply operation: 2.7 v to 6 v low shutdown current = 60 a pc99 compliant low distortion: 0.2% thd at 1.5 w wide bandwidth: 4 mhz unity-gain stable applications desktop, portable, and palmtop computers sound cards communication headsets 2-way communications hand-held games general description the ssm2250 is intended for use in desktop computers that have basic audio functions. it is also ideal for any audio system that needs to provide both an internal monaural speaker and a stereo line or headphone output. combined with an ac97 codec, it provides a pc audio system that meets the pc99 requirements. the ssm2250 is compact and requires a mini- mum of external components. the ssm2250 features an audio amplifier capable of delivering 1 .5 w of low distortion power into a mono 4 bridge-tied load (btl) or 2 90 mw into stereo 32 single-ended load (se) headphones. both amplifiers provide rail-to-rail outputs for maximum dynamic range from a single supply. the balanced output provides maximum output from a 5 v supply and eliminates the need for a coupling capacitor. the ssm2250 can automatically switch between an internal m ono speaker and external headphones. the device can run from a single supply, ranging from 2.7 v to 6 v, with an active supply current of 9 ma typical. the ability to shut down the amplifiers (60 a shutdown current) makes the ssm2250 an ideal speaker amplifier for battery-powered applications. the ssm2250 is specified over the industrial (?40c to +85c) t emperature range. it is available in a 14-lead tssop and a 10-lead, surface mount msop package. pin configurations 9 -001 ssm2250 top view (not to scale) left in 1 shutdown 2 se/btl 3 gnd 4 right in 5 left out/btl? v dd btl+ bypass right out 10 9 8 7 6 figure 1. 10-lead ms op pin configuration (rm suffix) 00359-002 nc left in shutdown se/btl +gnd right in nc 11 4 78 ssm2250 nc left out/btl v dd btl+ bypass right out nc nc = no connect figure 2. 14-lead tssop pin configuration (ru suffi x) functional block diagram 00359-003 a1 a2 a3 left se/ mono btl out? v dd v dd mono btl out+ right se out btl/se select shutdown click and pop reduction bias switching circuitry left in bypass cap right in v dd g n d figure 3. obsolete
ssm2250 rev. a | page 2 of 12 table of contents features .............................................................................................. 1 applications ....................................................................................... 1 general description ......................................................................... 1 pin configurations ........................................................................... 1 functional block diagram .............................................................. 1 revision history ............................................................................... 2 specifications ..................................................................................... 3 electrical characteristics, v s = 5.0 v ......................................... 3 electrical characteristics, v s = 2.7 v ..........................................3 absolute maximum ratings ............................................................4 esd caution ...................................................................................4 typical performance characteristics ..............................................5 product overview .............................................................................7 typical application .......................................................................7 outline dimensions ....................................................................... 12 ordering guide .......................................................................... 12 revision history 6/05rev. 0 to rev. a updated format..................................................................universal updated ordering guide............................................................... 12 10/99revision 0: initial version obsolete
ssm2250 rev. a | page 3 of 12 specifications electrical characteristics, v s = 5.0 v v s = 5.0 v, v cm = 2.5 v, t a = 25c, unless otherwise noted. table 1. parameter symbol conditions min typ max unit device characteristics output offset voltage v os btl mode; a v = 2; btl+ to btl? 4 100 mv large signal voltage gain a vo r l = 2 k 2 v/mv output power p out se mode: r l = 32 , thd < 1% 90 mw btl mode: r l = 8 , thd < 1% 1,000 mw output impedance z out 0.1 shutdown input input voltage high v ih i s < 100 a 2.0 v input voltage low v il i s > 1 ma 0.8 v power supply supply current i s btl mode 6.4 ma se mode 6.4 ma supply current/amplifier i s 60 a dynamic performance slew rate sr r l = 100 k, c l = 50 pf 4 v/s gain bandwidth product gbp 4 mhz phase margin o 84 degrees noise performance voltage noise density e n f = 1 khz 45 nv/hz electrical characteristics, v s = 2.7 v v s = 2.7 v, v cm = 1.35 v, t a = 25c, unless otherwise noted. table 2. parameter symbol conditions min typ max unit device characteristics output offset voltage v os btl mode; a v = 2; btl+ to btl? 4 100 mv large signal voltage gain a vo r l = 2 k 2 v/mv output power p out se mode: r l = 32 , thd < 1% 25 mw btl mode: r l = 8 , thd < 1% 300 mw output impedance z out 0.1 shutdown input input voltage high v ih i s < 100 a 2.0 v input voltage low v il i s > 1 ma 0.8 v power supply supply current i s btl mode 6.4 ma se mode 6.4 ma supply current/amplifier i s 32 a dynamic performance slew rate sr r l = 100 k, cl = 50 pf 4 v/s gain bandwidth product gbp 4 mhz phase margin o 84 degrees noise performance voltage noise density e n f = 1 khz 45 nv/hz obsolete
ssm2250 rev. a | page 4 of 12 absolute maximum ratings table 3. parameter rating supply voltage 6 v differential input voltage 1 5 v common-mode input voltage 6 v esd susceptibility 2000 v storage temperature range all packages ?65c to +150c operating temperature range all packages ?40c to +85c junction temperature range all packages ?65c to +165c lead temperature range (soldering, 60 sec) 300c 1 differential input voltage or v s, whichever is lower. stresses above those indicated 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. table 4. package type ja 1 jc unit 10-lead msop (rm) 200 44 c/w 14-lead tssop (ru) 180 35 c/w 1 ja is specified for worst-case conditions; that is, ja is specified for the device soldered in circuit board for surface mount packages. esd caution esd (electrostatic discharge) sensitive device. electros tatic charges as high as 4000 v readily accumulate on the human body and test equipment and can discharge wi thout detection. although this product features proprietary esd protection circuitry, permanent dama ge may occur on devices subjected to high energy electrostatic discharges. therefore, proper esd pr ecautions are recommended to avoid performance degradation or loss of functionality. obsolete
ssm2250 rev. a | page 5 of 12 typical performance characteristics 00359-004 frequency (hz) total harmonic distortion (%) 10 0.1 1 20 20k 100 1k 10k v s = 5v btl mode r l = 8 c b = 1 f p out = 1w a v = 2 figure 4. btl out thd + n vs. frequency 00359-005 frequency (hz) total harmonic distortion (%) 10 0.1 1 20 20k 100 1k 10k v s = 2.7v btl mode r l = 8 c b = 1 f p out = 0.25w a v = 2 figure 5. btl out thd + n vs. frequency 00359-006 total harmonic distortion (%) 10 0.1 1 output power (w) 10m 2 100m 1 2.7v 3.3v v s = varies btl mode r l = 8 c b = 1 f v in = 1khz a v = 2 5.0v figure 6. thd + n vs. output power 00359-007 total harmonic distortion (?%) 1 0.01 0.1 v s = 5v se mode r l = 32 c b = 1 f p out = 60mw a v = 1 frequency (hz) 20 20k 100 1k 10k figure 7. se out thd + n vs. frequency 00359-008 total harmonic distortion (%) 1 0.01 0.1 v s = 2.7v se mode r l = 32 c b = 1 f p out = 15mw a v = 1 frequency (hz) 20 20k 100 1k 10k frequency 20 20k 100 1k 10k figure 8. se out thd + n vs. frequency 00359-009 total harmonic distortion (%) output power (mw) 10 1 0.01 10 200 100 0.1 5v 3.3v 2.7v se mode r l = 32 c b = 1 f v in = 1khz figure 9. btl out thd + n vs. output power obsolete
ssm2250 rev. a | page 6 of 12 00359-010 total harmonic distortion (%) output power (w) 10 1 0.1 10m 2 100m 1 v s = 5v btl mode r l = 8 c b = 1 f v in = 20hz a v = 2 figure 10. btl out thd + n vs. output power at 20 hz 00359-011 total harmonic distortion (%) output power (mw) 10 1 0.1 10m 2 100m 1 v s = 5v btl mode r l = 8 c b = 1 f v in = 20khz a v = 2 figure 11. btl out thd + n vs. output power at 20 khz 00359-012 total harmonic distortion (%) output power (w) 10 1 0.01 10 200 100 0.1 v s = 5v se mode r l = 32 c b = 1 f v in = 20hz a v = 1 figure 12. se out thd + n vs. output power at 20 hz 00359-013 total harmonic distortion (%) output power (mw) 10 1 0.01 10 200 100 0.1 v s = 5v se mode r l = 8 c b = 1 f v in = 20khz a v = 1 figure 13. se out thd + n vs. output power at 20 khz obsolete
ssm2250 rev. a | page 7 of 12 product overview the ssm2250 is a low distortion power amplifier that can drive a set of stereo headphones or a single 8 loudspeaker. it contains three rail-to-rail output op amps, click-and-pop reduc- tion biasing, and all necessary switching circuitry. in se (single- ended) mode, the device automatically mutes the internal 8 speaker. in btl (bridge-tied load) mode, the internal speaker is activated. the ssm2250 can operate from a 2.7 v to a 5.5 v single supply. the ra il-to-rail outputs can be driven to within 400 mv of either supply rail while supplying a sustained output current of 350 ma into 8 . the device is unity-gain stable and requires no external compensation capacitors. the ssm2250 can be configured for gains of up to 40 db. typical application in se mode, the device operates similarly to a high current output, dual op amp. a1 and a3 are independent amplifiers with a gain of ?r2/r1. the outputs of a1 and a3 are used to drive the external headphones plugged into the headphone jack. amplifier a2 is shut down to a high output impedance state. this prevents current from flowing through the 8 internal speaker, thereby muting it. although the gains of a1 and a3 can be set independently, i t is recommended that the feedback and feedforward resistor around both amplifiers be equal. this prevents one channel from becoming louder than the other. in btl mode, the current into the right in pin is directed to the i nput of a1. this effectively sums the left in and right in audio signals. the a2 amplifier is activated and configured with a fixed gain of a v = ?1. this produces a balanced output con- figuration that drives the internal speaker. because the btl output voltages swing opposite to each other, the gain to the speaker in btl mode is twice the gain of se mode. the voltage across the internal speaker can be written () 1 2 2 r r vv v right left speaker += (1) the bridged output configuration offers the advantage of a m ore efficient power transfer from the input to the speaker. because both outputs are symmetric, the dc voltage bias across the 8 internal speaker is 0. this eliminates the need for a coupling capacitor at the output. in btl mode, the a3 amplifier is shut down to conserve power. in btl mode, the ssm2250 can achieve 1 w continuous output in to 8 at ambient temperatures up to 40c. the power derating curve shown in figure 17 should be observed for p roper operation at higher ambient temperatures. for a standard 14-lead tssop package, typical junction-to-ambient temperature thermal resistance ( ja ) is 180c/w on a 2-layer board and 140c/w on a 4-layer board. internal speaker/external headphones automatic switching pin 4 on the ssm2250 controls the switching between the btl mode and the se mode. logic low to pin 4 activates btl mode, while logic high activates se mode. the configuration shown in figure 14 provides the appropriate logic voltages to pin 4, m uting the internal speaker when headphones are plugged into the jack. a stereo headphone jack with a normalizing pin is required for t he application. with no plug inserted, a mechanical spring connects the normalizing pin to the output pin in the jack. once a plug is inserted, this connection is broken. in figure 14 , pin 4 of the ssm2250 is connected to the nor- ma lizing pin for the right channel output. this pin, located in the headphone jack, hits the ring on the headphone plug. a 100 k pull-up resistor to 5 v is also connected at this point. with a headphone plug inserted, the normalizing pin discon- n ects from the output pin, and pin 4 is pulled up to 5 v, activating se mode on the ssm2250. this mutes the internal speaker while driving the stereo headphones. once the headphone plug is removed, the normalizing pin co nnects to the output pin. this drives the voltage at pin 4 to 50 mv, as this point is pulled low by the 1 k resistor now connected to the node. the ssm2250 goes into btl mode, deactivating the right se amplifier to prevent the occurrence of any false mode switching. it is important to connect pin 4 and the 100 k pull-up resistor t o the normalizing pin for the right output in the headphone jack. connecting them to the left output normalizing pin results in improper operation from the device. the normalizing pin to the left output in the headphone jack should be left open. coupling capacitors output coupling capacitors are not required to drive the internal speaker from the btl outputs. however, coupling capacitors are required between the amplifiers se outputs and the headphone jack to drive external headphones. this prevents dc current from flowing through the headphone speakers, whose resistances are typically about 80 . obsolete
ssm2250 rev. a | page 8 of 12 00359-014 nc nc nc left in right in s hutdown 5v btl out 5v 100k + ? + 220 f + 220 f 1k 1k 1 f 1 f r1 20k 10 f r2 20k r2 20k r1 20k ssm2250 5 14 1 2 3 4 13 12 11 10 6 7 9 8 nc nc = no connect nc figure 14. typical application the output coupling capacitor creates a high-pass filter with a c utoff frequency of c l db cr f = ? 2 1 3 (2) where: r l is the resistance of the headphone. c c is the output coupling capacitor. although a majority of headphones have approximately 80 of r esistance, the resistance can vary between models and manu- facturers. headphone resistances are commonly between 32 to 600 . using a 220 f capacitor, as shown in figure 14 , the w orst-case ?3 db corner frequency would be 22 hz, with a 32 headphone load. smaller output capacitors could be used at the expense of low frequency response to the headphones. an input coupling capacitor should be used to remove dc bias f rom the inputs to the ssm2250. again, the input coupling capacitor in combination with the input resistor creates a high- pass filter with a corner frequency of 112 1 3 cr f db = ? (3) using the values shown in figure 14 , where r1 = 20 k and c1 = 1 f , creates a corner frequency of 8 hz. this is acceptable, as the pc99 audio requirement specifies the computer audio system bandwidth to be 20 hz to 20 khz. pin 10 on the ssm2250 provides the proper bias voltage for th e amplifiers. a 0.1 f capacitor should be connected here to reduce sensitivity to noise on the power supply. a larger capaci- tor can be used if more rejection from power supply noise is required. the ssm2250 has excellent phase margin and is stable even un der heavy loading. therefore, a feedback capacitor in parallel with r2 is not required, as it is in some competitors products. power dissipation an important advantage in using a bridged output configura- tion is that bridged output amplifiers are more efficient than single-ended amplifiers in delivering power to a load. output power (w) power dissipation (w) 1.50 1.25 1.00 0.75 0.50 0.25 0 0 0.75 0.50 0.25 1.00 1.25 1.50 00359-015 v dd = 5v r l = 4 r l = 16 r l = 8 figure 15. power dissipation vs. output power in btl mode l dd max,diss r v p 2 2 2 = (4) using equation 4 and the power derating curve in figure 17 , t he maximum ambient temperature can be easily found. this ensures that the ssm2250 does not exceed its maximum junction temperature of 150c. the power dissipation for a single-ended output application wher e an output coupling capacitor is used is shown in figure 16 . obsolete
ssm2250 rev. a | page 9 of 12 output power (w) power dissipation (w) 0.35 0.3 0.25 0.2 0.15 0.1 0.05 0 0 0.3 0.2 0.1 0.4 00359-016 v dd = 5v r l = 16 r l = 8 r l = 4 figure 16. power dissipation vs . single -ended output power (v dd = 5 v) the maximum power dissipation for a single-ended output is l dd maxdiss r v p 2 2 , 2 = (5) because the ssm2250 is designed to drive two single-ended lo ads simultaneously, the worst-case maximum power dissipation in se mode is twice the value of equation 5. a thorough mathematical explanation behind equation 4 and e quation 5 is provided in the ssm2211 data sheet. example given worst-case stereo headphone loads of 32 , the maxi- mum power dissipation of the ssm2250 in se mode with a 5 v supply is () mw v p maxdiss 79 322 5 2 2 , = ? = (6) with an 8 internal speaker attached, the maximum power dissi pation in btl mode is (from equation 4) () mw v p maxdiss 633 8 52 2 2 , = ? = (7) it can easily be seen that power dissipation from btl mode o peration is of greater concern than se mode. solving for maximum ambient temperature to protect the ssm2250 against thermal damage, the junction temperature of the die should not exceed 150c. the maximum allowable ambient temperature of the application can be easily found by solving for the expected maximum power dissipation in equation 4 and equation 5, and using equation 8. continuing from the previous example, the ja of the ssm2250 14-lead tssop package on a 4-layer board is 140c/w. to ensure that the ssm2250 die junction temperature stays below 150c, the maximum ambient temperature can be solved using equation 8. ( c w wcc pc t maxdiss ja maxamb o o o o 61 633.0/140 150 150 , , += ?+= ?+= ) (8) the maximum ambient temperature must remain below 61c t o protect the device against thermal damage. another method for finding the maximum allowable ambient t emperature is to use the power derating curve in figure 17 . the y-axis co rresponds to the expected maximum power dissipation, and the x-axis is the corresponding maximum ambient temperature. either method returns the same answer. ambient temperature (c) power dissipation (w) 1.0 0.8 0.6 0.4 0.2 0 07 50 25 100 00359-017 5 14-lead tssop ja = 140c/w 10-lead msop ja = 180c/w t jmax = 150c/w free air no heat sink figure 17. maximum power dissipation vs. ambient temperature maximum output power the maximum amount of power that can be delivered to a speaker is a function of the supply voltage and the resistance of the speaker. figure 17 shows the maximum btl output power p ossible from the ssm2250. maximum output power is defined as the point at which the output has greater than 1% distortion. obsolete
ssm2250 rev. a | page 10 of 12 supply voltage (v) maximum output @ thd 1% (w) 1.6 0.8 1.0 1.2 1.4 0.6 0.4 0.2 0 1.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 00359-018 r l = 4 r l =8 r l = 16 figure 18. maximum btl output power vs. v s use figure 18 to find the minimum supply voltage needed to achie ve a specified maximum undistorted output power. the output power in se mode is exactly one-fourth the e quivalent output power in btl mode. this is because twice the voltage swing across the two btl outputs results in 4 the power delivered to the load. figure 19 shows the maximum o utput power in se mode vs. supply voltage for various headphone loads. supply voltage (v) maximum output @ thd 1% (mw) 100 25 50 75 0 1.5 5.0 4.5 4.0 3.5 3.0 2.5 2.0 00359-019 r l = 32 r l = 128 r l = 64 figure 19. maximum se output power vs. v s example an application requires only 500 mw to be output in btl mode into an 8 speaker. by inspection, the minimum supply voltage required is 3.3 v. speaker efficiency and loudness the effective loudness of 1 w of power delivered into an 8 speaker is a function of the efficiency of the speaker. the efficiency of a speaker is typically rated at 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 one meter at 1 w of power. table 5 shows a com- p arison of the relative loudness of different sounds. table 5. typical sound pressure levels source of sound d 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. shutdown feature the ssm2250 can be put into a low power consumption shutdown mode by connecting pin 3 to v dd . in shutdown mode, the ssm2250 has low supply current of 60 a. pin 3 should be connected to ground for normal operation. c onnecting pin 3 to v dd shuts down all amplifiers and puts all outputs into a high impedance state, effectively muting the ssm2250. a pull-up or pull-down resistor is not required. pin 3 should never be left floating, as this could produce unpre- dictable results. pc99-compliant computer audio reference design the schematic shown in figure 20 is a reference design for a co mplete audio system in a computer. the design is compliant with the pc99 standard for computer audio. the ad1881a is an ac97, version 2.1, audio codec, available f rom analog devices. the stereo output from the ad1881a is coupled into the ssm2250, which is used to drive a mono internal speaker and stereo headphones. the internal speaker switching is controlled by the ssm2250 through the normaliz- ing pin on the headphone jack. the ad1881a controls the shutdown pin on the ssm2250, and is activated through the power management software drivers installed on the computer. for more information, refer to the ad1881a data sheet. obsolete
ssm2250 rev. a | page 11 of 12 36 35 34 33 32 31 30 29 28 27 26 25 1 2 3 4 5 6 7 8 9 10 11 12 1 2 3 4 5 6 7 48 47 46 45 44 43 42 41 40 39 38 37 13 14 15 16 17 18 19 20 21 22 23 24 14 13 12 11 10 9 8 nc c9 c10 c13 c15 c16 c17 c12 c14 line out right line out left nc mono out ad1881a nc = no connect nc nc nc nc nc nc nc nc nc r1 20k r5 20k r2 100 r3 1k r4 1k to speaker? to speaker+ av dd = 5v av dd = 5v av dd = 5v av dd = 5v ssm2250 nc nc nc nc nc c1 10 f c4 10 f c3 0.1 f c2 10 f c7 0.1 f c6 10 f c5 100 f + + + ac clk c8 22pf c23 0.1 f c11 22pf c20 27pf c22 1 f c26 1 f c29 1 f c31 1 f c27 1 f c25 1 f c24 1 f c21 0.1 f c16 10 f c19 0.1 f 270pf 270pf 1 f 1 f 0.1 f 1 f 1 f 0.047 f c28 0.001 f c30 1 f c32 1 f c33 1 f y1 24.576mhz smt sdata out bitclk sync sdata in 0 rst# pcbeep mono phone aux left aux in r8 47 r10 10k r11 1k r12 4.7k r14 4.7k r17 4.7k r19 4.7k r18 4.7k r15 4.7k r13 4.7k r9 2k r7 20k r6 20k r16 4.7k line in right line in left mic in cd right cd gnd cd left 00359-020 figure 20. pc99 compliant audio system reference design obsolete
ssm2250 rev. a | page 12 of 12 outline dimensions 0.23 0.08 0.80 0.60 0.40 8 0 0.15 0.00 0.27 0.17 0.95 0.85 0.75 seating plane 1.10 max 10 6 5 1 0.50 bsc 3.00 bsc 3.00 bsc 4.90 bsc pin 1 coplanarity 0.10 compliant to jedec standards mo-187-ba figure 21. 10-lead mini small outline package [msop] (r m-10) dimensions shown in millimeters 4.50 4.40 4.30 14 8 7 1 6.40 bsc pin 1 5.10 5.00 4.90 0.65 bsc seating plane 0.15 0.05 0.30 0.19 1.20 max 1.05 1.00 0.80 0.20 0.09 8 0 0.75 0.60 0.45 coplanarity 0.10 compliant to jedec standards mo-153-ab-1 figure 22. 14-lead thin shrink s mall outline package [tssop] (ru-14) dimensions shown in millimeters ordering guide model temperature range package description package option branding ssm2250rm-r2 ?40c to +85c 10-lead msop rm-10 ak ssm2250rm-reel ?40c to +85c 10-lead msop rm-10 ak ssm2250rmz-r2 1 ?40c to +85c 10-lead msop rm-10 ak# ssm2250rmz-reel 1 ?40c to +85c 10-lead msop rm-10 ak# ssm2250ru-reel ?40c to +85c 14-lead tssop ru-14 ssm2250ruz-reel 1 ?40c to +85c 14-lead tssop ru-14 1 z = pb-free part, # denotes pb-fre e part; may be top or bottom marked. ? 2005 analog devices, inc. all rights reserved. trademarks and registered trademarks are the prop erty of their respective owners. c00359C0C6/05(a) obsolete

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