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general description the max9750/max9751/max9755 combine a stereo, 2.6w audio power amplifier and stereo directdrive 110mw headphone amplifier in a single device. the headphone amplifier uses maxim? patented directdrive architecture that produces a ground-referenced output from a single supply, eliminating the need for large dc- blocking capacitors, saving cost, space, and component height. a high 90db psrr and low 0.01% thd+n ensures clean, low-distortion amplification of the audio signal. the max9750 features an analog volume control, and a beep input. the max9751 features a 2:1 input multiplexer, allowing multiple audio sources to be selected. all devices feature a single-supply voltage, a shutdown mode, logic- selectable gain, and a headphone sense input. industry- leading click-and-pop suppression eliminates audible transients during power and shutdown cycles. the max9750/max9751/max9755 are offered in space- saving, thermally efficient 28-pin thin qfn (5mm x 5mm x 0.8mm) and 28-pin tssop packages. both devices have thermal-overload and output short-circuit protec- tion, and are specified over the extended -40? to +85? temperature range. applications notebook pcs flat-panel tvs tablet pcs pc displays portable dvd players lcd projectors features no dc-blocking capacitors required?rovides industry? most compact notebook audio solution pc2001 compliant 5v single-supply operation class ab 2.6w stereo btl speaker amplifiers 110mw directdrive headphone amplifiers high 90db psrr low-power shutdown mode industry-leading click-and-pop suppression low 0.01% thd+n at 1khz short-circuit and thermal protection selectable gain settings analog volume control (max9750) beep input with glitch filter (max9750) 2:1 stereo input mux (max9751) ?kv esd-protected headphone driver outputs available in space-saving, thermally efficient packages 28-pin thin qfn (5mm x 5mm x 0.8mm) 28-pin tssop max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ________________________________________________________________ maxim integrated products 1 ordering information 19-3006; rev 3; 8/04 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. part temp range pin- package m a xim u m g a i n ( d b ) max9750 aeti ? -40 c to +85 c 28 thi n qfn 13.5 max9750aeui* -40 c to +85 c 28 tssop 13.5 max9750beti ? -40 c to +85 c 28 thi n qfn 19.5 max9750beui* -40 c to +85 c 28 tssop 19.5 max9750ceti ? -40 c to +85 c 28 thi n qfn 10.5 max9750ceui* -40 c to +85 c 28 tssop 10.5 max9751 eti ? -40 c to +85 c 28 thi n qfn 10.5 max9751eui* -40 c to +85 c 28 tssop 10.5 max9755 eti ? -40 c to +85 c 28 thi n qfn 10.5 max9755eui* -40 c to +85 c 28 tssop 10.5 * future product?ontact factory for availability. ? lead-free package. vol beep max9750 simplified block diagrams simplified block diagrams continued at end of data sheet.
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. supply voltage (v dd , pv dd , hpv dd , cpv dd to gnd)..........+6v gnd to pgnd.....................................................................0.3v cpv ss , c1n, v ss to gnd .........................-6.0v to (gnd + 0.3v) hpout_ to gnd ....................................................................3v any other pin .............................................-0.3v to (v dd + 0.3v) duration of out_ short circuit to gnd or pv dd ........continuous duration of out_+ short circuit to out_- .................continuous duration of hpout_ short circuit to gnd, v ss or hpv dd .........................................................continuous continuous current (pv dd , out_, pgnd) ...........................1.7a continuous current (cpv dd , c1n, c1p, cpv ss , v ss , hpv dd , hpout_) .......................................................................850ma continuous input current (all other pins) ........................20ma continuous power dissipation (t a = +70 c) 28-pin thin qfn (derate 20.8mw/ c above +70 c) ..1667mw 28-pin tssop (derate 13mw/ c above +70 c) .........1039mw junction temperature ......................................................+150 c operating temperature range ...........................-40 c to +85 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c electrical characteristics (v dd = pv dd = cpv dd = hpv dd = 5v, gnd = pgnd = cpgnd = 0v, shdn = v dd , c bias = 1f, c1 = c2 = 1f, speaker load terminated between out_+ and out_-, headphone load terminated between hpout_ and gnd, gain1 = gain2 = vol = gain = 0v, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units general supply voltage range v dd , pv dd inferred from psrr test 4.5 5.5 v headphone supply voltage cpv dd , hpv dd inferred from psrr test 3 5.5 v hps = gnd, speaker mode, r l = 14 29 quiescent supply current i dd hps = v dd , headphone mode, r l = 713 ma shutdown supply current i shdn shdn = gnd 0.2 5 a bias voltage v bias 1.7 1.8 1.9 v switching time t sw gain or input switching 10 s input resistance r in amplifier inputs (note 2) 10 20 30 k ? turn-on time t son 25 ms speaker amplifier (hps = gnd) max9750a/max9750b/ max9751/max9755 1 15 output offset voltage v os measured between out_+ and out_-, t a = +25 c max9750c 0.4 6 mv pv dd or v dd = 4.5v to 5.5v (t a = +25 c) 75 90 f = 1khz, v ripple = 200mv p-p 80 power-supply rejection ratio (note 3) psrr f = 10khz, v ripple = 200mv p-p 55 db
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dd = pv dd = cpv dd = hpv dd = 5v, gnd = pgnd = cpgnd = 0v, shdn = v dd , c bias = 1f, c1 = c2 = 1f, speaker load terminated between out_+ and out_-, headphone load terminated between hpout_ and gnd, gain1 = gain2 = vol = gain = 0v, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units max9750a/ max9750b/ max9751/ max9755 0.9 1.4 r l = 8 ? max9750c 0.65 0.8 max9750a/ max9750b/ max9751/ max9755 2.3 r l = 4 ? c r l = 3 ? ? , p out = 500mw, f = 1khz 0.01 total harmonic distortion plus noise thd+n r l = 4 ? , p out = 1w, f = 1khz 0.02 % signal-to-noise ratio snr r l = 8 ? , p out = 500mw, bw = 22hz to 22khz 90 db noise v n bw = 22hz to 22khz, a-weighted 80 v rms capacitive-load drive c l no sustained oscillations 200 pf crosstalk l to r, r to l, f = 10khz 75 off-isolation any unselected input to any active input, f = 10khz (max9751), input referred 75 db slew rate sr 1.4 v/s gain1 = 0, gain2 = 0 9 gain1 = 1, gain2 = 0 10.5 gain1 = 0, gain2 = 1 12 max9750a gain1 = 1, gain2 = 1 13.5 gain1 = 0, gain2 = 0 15 gain1 = 1, gain2 = 0 16.5 gain1 = 0, gain2 = 1 18 max9750b gain1 = 1, gain2 = 1 19.5 gain1 = 0, gain2 = 0 6 gain1 = 1, gain2 = 0 7.5 gain1 = 0, gain2 = 1 9 gain (maximum volume setting) a vmax ( spkr ) max9750c gain1 = 1, gain2 = 1 10.5 db gain = 1 9 gain (max9751/max9755) a v gain = 0 10.5 db
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 4 _______________________________________________________________________________________ electrical characteristics (continued) (v dd = pv dd = cpv dd = hpv dd = 5v, gnd = pgnd = cpgnd = 0v, shdn = v dd , c bias = 1f, c1 = c2 = 1f, speaker load terminated between out_+ and out_-, headphone load terminated between hpout_ and gnd, gain1 = gain2 = vol = gain = 0v, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units headphone amplifier (hps = v dd ) output offset voltage v os t a = +25 c 2 7mv hpv dd = 3v to 5.5v, t a = +25 c6075 f = 1khz, v ripple = 200mv p-p 73 power-supply rejection ratio (note 3) psrr f = 10khz, v ripple = 200mv p-p 63 db r l = 32 ? 40 50 output power p out thd+n = 1%, f = 1khz, t a = +25 c r l = 16 ? 110 mw r l = 32 ? , p out = 20mw, f = 1khz 0.007 total harmonic distortion plus noise thd+n r l = 16 ? , p out = 75mw, f = 1khz 0.03 % signal-to-noise ratio snr r l = 32 ? , p out = 50mw, bw = 22hz to 22khz 95 db noise v n bw = 22hz to 22khz 12 v rms capacitive-load drive c l no sustained oscillations 200 pf crosstalk l to r, r to l, f = 10khz 88 off-isolation any unselected input to any active input, f = 10khz (max9751), input referred 74 db slew rate sr 0.4 v/s esd esd iec air discharge 8 kv gain2 = gain = 0, gain1 = x 0 gain a v gain2 = gain = 1, gain1 = x 3 db charge pump charge-pump frequency f osc 500 550 600 khz volume control (max9750_) vol input impedance r vol 100 m ? vol input hysteresis 10 mv full mute input voltage (note 5) 0.858 x hpv dd v channel matching a v = -25db to +13.5db 0.2 db beep input (max9750_) beep signal minimum amplitude v beep r b = 33k ? (note 6) 0.8 v p-p beep signal minimum frequency f beep 400 hz
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers _______________________________________________________________________________________ 5 electrical characteristics (continued) (v dd = pv dd = cpv dd = hpv dd = 5v, gnd = pgnd = cpgnd = 0v, shdn = v dd , c bias = 1f, c1 = c2 = 1f, speaker load terminated between out_+ and out_-, headphone load terminated between hpout_ and gnd, gain1 = gain2 = vol = gain = 0v, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) (note 1) parameter symbol conditions min typ max units logic input ( shdn , gain1, gain2, gain, vol, in1/ 2 ) logic input high voltage v ih 2v logic input low voltage v il 0.8 v logic input current i in 1a logic input headphone (hps) logic input high voltage v ih 2v logic input low voltage v il 0.8 v logic input current i in 10 a note 1: all devices are 100% production tested at room temperature. all temperature limits are guaranteed by design. note 2: guaranteed by design. not production tested. note 3: psrr is specified with the amplifier input connected to gnd through c in . note 4: output power levels are measured with the thin qfn s exposed paddle soldered to the ground plane. note 5: see table 3 for details of the mute levels. note 6: the value of r b dictates the minimum beep signal amplitude (see the beep input section).
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 6 _______________________________________________________________________________________ typical operating characteristics (measurement bw = 22hz to 22khz, t a = +25 c, unless otherwise noted.) 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (speaker mode) max9750/51 toc01 frequency (hz) thd+n (%) v cc = 5v r l = 3 ? a v = 10.5db output power = 1.5w output power = 500mw 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (speaker mode) max9750/51 toc02 frequency (hz) thd+n (%) v cc = 5v r l = 4 ? a v = 10.5db output power = 1.25w output power = 500mw 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (speaker mode) max9750/51 toc03 frequency (hz) thd+n (%) v cc = 5v r l = 8 ? a v = 10.5db output power = 100mw output power = 600mw 100 0 0.5 1.0 1.5 2.0 2.5 3.0 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (speaker mode) max9750/51 toc04 output power (w) thd+n (%) v cc = 5v r l = 3 ? a v = 10.5db max9750c f in = 10khz f in = 1khz f in = 20hz total harmonic distortion plus noise vs. output power (speaker mode) max9750/51 toc05 output power (w) thd+n (%) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.01 0.1 1 10 100 0.001 0 v dd = 5v a v = 13.5db r l = 3 ? f = 1khz f = 10khz f = 20hz 100 0 0.5 1.0 1.5 2.0 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (speaker mode) max9750/51 toc06 output power (w) thd+n (%) f in = 1khz f in = 20hz v cc = 5v r l = 4 ? a v = 10.5db max9750c f in = 10khz total harmonic distortion plus noise vs. output power (speaker mode) max9750/51 toc07 output power (w) thd+n (%) 2.5 2.0 1.5 1.0 0.5 0.01 0.1 1 10 100 0.001 03.0 v dd = 5v a v = 13.5db r l = 4 ? f = 1khz f = 10khz f = 20hz 100 0 0.2 0.4 0.6 0.8 1.0 1.2 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (speaker mode) max9750/51 toc08 output power (w) thd+n (%) f in = 20hz f in = 1khz f in = 10khz v cc = 5v r l = 8 ? a v = 10.5db max9750c total harmonic distortion plus noise vs. output power (speaker mode) max9750/51 toc09 output power (w) thd+n (%) 1.5 1.0 0.5 0.01 0.1 1 10 100 0.001 0 v dd = 5v a v = 13.5db r l = 8 ? f = 1khz f = 10khz f = 20hz
typical operating characteristics (continued) (measurement bw = 22hz to 22khz, t a = +25 c, unless otherwise noted.) max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers _______________________________________________________________________________________ 7 output power vs. load resistance (speaker mode) max9750/51 toc10 load resistance ( ? ) output power (w) 10 0.5 1.0 1.5 2.0 2.5 3.0 3.5 0 1 100 thd+n = 10% thd+n = 1% output power vs. load resistance (speaker mode) max9750/51 toc11 load resistance ( ? ) output power (w) 3.0 0 0.5 1.0 1.5 2.0 2.5 110100 thd+n = 10% thd+n = 1% v cc = 5v f = 1khz a v = 10.5db max9750c power dissipation vs. output power (speaker mode) max9750/51 toc12 output power (w) power dissipation (w) 3 2 1 1 2 3 4 5 0 04 r l = 4 ? r l = 8 ? v dd = 5v f = 1khz p out = p outl + p outr power dissipation vs. output power (speaker mode) max9750/51 toc13 output power (w) power dissipation (w) 3.5 3.0 2.5 2.0 1.5 1.0 0.5 1 2 3 4 5 0 04.0 r l = 4 ? r l = 8 ? v dd = 5v f = 1khz p out = p outl + p outr max9750c power-supply rejection ratio vs. frequency (speaker mode) max9750/51 toc14 frequency (hz) psrr (db) 10k 1k 100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 10 100k v ripple = 200mv p-p a v = 10.5db output referred 0 -120 10 1k 10k 100 100k crosstalk vs. frequency (speaker mode) max9750/51 toc15 frequency (hz) crosstalk (db) -100 -110 -80 -90 -60 -70 -40 -50 -20 -10 -30 v cc = 5v v ripple = 200mv p-p r l = 4 ? left to right right to left turn-on response (speaker mode) max9750/51 toc16 20ms/div shdn 5v/div 2v/div 100mv/div out_+ and out_- out_+ - out_- r l = 8 ?
typical operating characteristics (continued) (measurement bw = 22hz to 22khz, t a = +25 c, unless otherwise noted.) max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 8 _______________________________________________________________________________________ 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (headphone mode) max9750/51 toc19 frequency (hz) thd+n (%) v dd = 5v r l = 32 ? a v = 3db output power = 45mw output power = 10mw 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (headphone mode) max9750/51 toc20 frequency (hz) thd+n (%) v dd = 3.3v r l = 16 ? a v = 3db output power = 30mw output power = 10mw 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (headphone mode) max9750/51 toc21 frequency (hz) thd+n (%) v dd = 3.3v r l = 32 ? a v = 3db output power = 45mw output power = 10mw 1000 100 10 1 0.1 0.01 0.001 075 100 125 50 25 15 total harmonic distortion plus nois vs. output power (headphone mode output power (mw) thd+n (%) v dd = 5v r l = 16 ? a v = 3db f in = 10khz f in = 1khz f in = 20hz 1000 100 10 1 0.1 0.01 0.001 06080 40 20 100 total harmonic distortion plus noise vs. output power (headphone mode) max9750/51 toc23 output power (mw) thd+n (%) v dd = 5v r l = 32 ? a v = 3db f in = 10khz f in = 1khz f in = 20hz 1000 100 10 1 0.1 0.01 0.001 030 40 50 20 10 60 total harmonic distortion plus noise vs. output power (headphone mode) max9750/51 toc24 output power (mw) thd+n (%) v dd = 3.3v r l = 16 ? a v = 3db f in = 10khz f in = 1khz f in = 20hz turn-off response (speaker mode) max9750/51 toc17 20ms/div shdn 5v/div 2v/div 20mv/div out_+ and out_- out_+ - out_- r l = 8 ? 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (headphone mode) max9750/51 toc18 frequency (hz) thd+n (%) v dd = 5v r l = 16 ? a v = 3db output power = 90mw output power = 30mw
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers _______________________________________________________________________________________ 9 output power vs. supply voltage (headphone mode) max9750/51 toc28 supply voltage (v) output power (mw) 5.0 4.5 4.0 3.5 25 50 75 100 125 0 3.0 5.5 r l = 16 ? r l = 32 ? f = 1khz 10 1k 10k 100 100k power-supply rejection ratio vs. frequency (headphone mode) max9750/51 toc29 frequency (hz) psrr (db) v ripple = 200mv p-p a v = 10.5db output referred -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 10 100 1k 10k 100k crosstalk vs. frequency (headphone mode) max9750/51 toc30 frequency (hz) crosstalk (db) v cc = 5v v ripple = 200mv p-p r l = 32 ? left to right right to left -100 -80 -60 -40 -20 0 -120 output power vs. charge-pump capacitance and load resistance max9750/51 toc31 load resistance ( ? ) output power (mw) 40 30 20 20 40 60 80 100 120 140 160 180 200 0 10 50 v dd = 5v f = 1khz thd+n = 1% c1 = c2 = 2.2 f c1 = c2 = 1 f typical operating characteristics (continued) (measurement bw = 22hz to 22khz, t a = +25 c, unless otherwise noted.) output power vs. load resistance (headphone mode) max9750/51 toc26 load resistance ( ? ) output power (mw) 100 20 40 60 80 100 120 140 160 180 0 10 1000 thd+n = 10% thd+n = 1% (headphone mode) max9750/51 toc27 output power (mw) power dissipation (mw) 225 200 150 175 50 75 100 125 25 25 50 75 100 125 150 175 200 225 250 0 0250 v dd = 5v f = 1khz p out = p outl + p outr r l = 16 ? r l = 32 ? 1000 100 10 0.1 1 0.01 0.001 070 80 20 30 40 50 60 10 90 total harmonic distortion plus noise vs. output power (headphone mode) max9750/51 toc25 output power (mw) thd+n (%) v dd = 3.3v r l = 32 ? a v = 3db f in = 10khz f in = 1khz f in = 20hz
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 10 ______________________________________________________________________________________ headphone output spectrum max9750/51 toc32 frequency (hz) magnitude (db) 15 10 5 0 020 -120 -100 -80 -60 -40 -20 -140 v dd = 5v f = 1khz v out = -60db r l = 32 ? turn-on response (headphone mode) max9750/51 toc33 10ms/div shdn 5v/div 20mv/div hpout_ r l = 32 ? turn-off response (headphone mode) max9750/51 toc34 10ms/div shdn 5v/div 20mv/div hpout_ r l = 32 ? supply current vs. supply voltage max9750/51 toc35 supply voltage (v) supply current (ma) 5.25 5.00 4.75 4 2 6 8 12 10 14 16 18 0 4.50 5.50 hps = gnd hps = v dd shutdown supply current vs. supply voltage max9750/51 toc36 supply voltage (v) supply current ( a) 5.25 5.00 4.75 4.50 5.50 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0 typical operating characteristics (continued) (measurement bw = 22hz to 22khz, t a = +25 c, unless otherwise noted.)
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 11 pin description pin max9750 max9751 max9755 thin qfn tssop thin qfn tssop thin qfn tssop name function 15 2 6 inl left-channel audio input 26 beep audible alert beep input 3, 19 7, 23 3, 19 7, 23 3, 19 7, 23 pgnd power ground 484848 outl+ left-channel positive speaker output 595959 outl- left-channel negative speaker output 6, 16 10, 20 6, 16 10, 20 6, 16 10, 20 pv dd speaker amplifier power supply 711711711 cpv dd charge-pump power supply 8 12 8 12 8 12 c1p charge-pump flying-capacitor positive terminal 913913913 cpgnd charge-pump ground 10 14 10 14 10 14 c1n charge-pump flying-capacitor negative terminal 11 15 11 15 11 15 cpv ss charge-pump output. connect to v ss . 12 16 12 16 12 16 v ss headphone amplifier negative power supply 13 17 13 17 13 17 hpoutr right-channel headphone output 14 18 14 18 14 18 hpoutl left-channel headphone output 15 19 15 19 15 19 hpv dd headphone positive power supply 17 21 17 21 17 21 outr- right-channel negative speaker output 18 22 18 22 18 22 outr+ right-channel positive speaker output 20 24 20 24 20 24 hps headphone sense input 21 25 21 25 21 25 bias common-mode bias voltage. bypass with a 1 f capacitor to gnd. 22 26 22 26 22 26 shdn shutdown. drive shdn low to disable the device. connect shdn to v dd for normal operation. 23 27 gain2 gain control input 2 24 28 gain1 gain control input 1 25 1 25 1 25 1 v dd power supply 26 2 26 2 23, 26 2, 27 gnd ground 27 3 28 4 inr right-channel audio input 28 4 vol analog volume control input 15 inl1 left-channel audio input 1 26 inl2 left-channel audio input 2 23 27 in1/ 2 input select 24 28 24 28 gain gain select 27 3 inr1 right-channel audio input 1 28 4 inr2 right-channel audio input 2 1, 27 3, 5 n.c. no connection. not internally connected.
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 12 ______________________________________________________________________________________ detailed description the max9750/max9751/max9755 combine a 2.6w btl speaker amplifier and a 110mw directdrive headphone amplifier with integrated headphone sensing and com- prehensive click-and-pop suppression. the max9750 features an analog volume control, beep input, and four-level gain control. the max9751 features a 2:1 input stereo multiplexer and two-level gain control. all devices feature high 90db psrr, low 0.01% thd+n, industry-leading click-pop performance, and a low- power shutdown mode. each signal path consists of an input amplifier that sets the gain of the signal path and feeds both the speaker and headphone amplifier (figure 1). the speaker amplifier uses a btl architecture, doubling the voltage drive to the speakers and eliminating the need for dc- blocking capacitors. the output consists of two signals, identical in magnitude, but 180 out of phase. the headphone amplifiers use maxim s patented directdrive architecture that eliminates the bulky output dc-blocking capacitors required by traditional head- phone amplifiers. a charge pump inverts the positive supply (cpv dd ), creating a negative supply (cpv ss ). the headphone amplifiers operate from these bipolar supplies with their outputs biased about gnd (figure 2). the amplifiers have almost twice the supply range compared to other single-supply amplifiers, nearly qua- drupling the available output power. the benefit of the gnd bias is that the amplifier outputs no longer have a dc component (typically v dd / 2). this eliminates the large dc-blocking capacitors required with convention- al headphone amplifiers, conserving board space and system cost, and improving frequency response. the max9750 features an analog volume control that varies the gain of the amplifiers based on the dc volt- age applied at vol. both devices feature an undervolt- age lockout that prevents operation from an insufficient power supply and click-and-pop suppression that elim- inates audible transients on startup and shutdown. the amplifiers include thermal-overload and short-circuit protection, and can withstand 8kv esd strikes on the headphone amplifier outputs (iec air discharge). an additional feature of the speaker amplifiers is that there is no phase inversion from input to output. directdrive conventional single-supply headphone amplifiers have their outputs biased about a nominal dc voltage (typi- cally half the supply) for maximum dynamic range. large coupling capacitors are needed to block this dc bias from the headphones. without these capacitors, a out_+ out_ volume control bias in_ vol bias max9750 only bias hpout_ gnd figure 1. max9750/max9751 signal path +v dd -v dd gnd conventional driver-biasing scheme directdrive biasing scheme v dd /2 v dd gnd v out figure 2. traditional headphone amplifier output waveform vs. directdrive headphone amplifier output waveform
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 13 significant amount of dc current flows to the headphone, resulting in unnecessary power dissipation and possible damage to both headphone and headphone amplifier. maxim s patented directdrive architecture uses a charge pump to create an internal negative supply voltage. this allows the max9750/max9751/max9755 headphone amplifier output to be biased about gnd, almost dou- bling the dynamic range while operating from a single supply. with no dc component, there is no need for the large dc-blocking capacitors. instead of two large capacitors (220f typ), the max9750/max9751/ max9755 charge pump requires only two small ceramic capacitors (1f typ), conserving board space, reducing cost, and improving the frequency response of the head- phone amplifier. see the output power vs. charge-pump capacitance and load resistance graph in the typical operating characteristics for details of the possible capacitor values. previous attempts to eliminate the output coupling capacitors involved biasing the headphone return (sleeve) to the dc bias voltage of the headphone amplifiers. this method raised some issues: 1) the sleeve is typically grounded to the chassis. using this biasing approach, the sleeve must be isolated from system ground, complicating product design. 2) during an esd strike, the amplifier s esd structures are the only path to system ground. the amplifier must be able to withstand the full esd strike. 3) when using the headphone jack as a lineout to other equipment, the bias voltage on the sleeve may con- flict with the ground potential from other equipment, resulting in large ground-loop current and possible damage to the amplifiers. low-frequency response in addition to the cost and size disadvantages, the dc- blocking capacitors limit the low-frequency response of the amplifier and distort the audio signal: 1) the impedance of the headphone load to the dc- blocking capacitor forms a highpass filter with the -3db point determined by: where r l is the impedance of the headphone and c out is the value of the dc-blocking capacitor. the highpass filter is required by conventional sin- gle-ended, single-supply headphone amplifiers to block the midrail dc component of the audio signal from the headphones. depending on the -3db point, the filter can attenuate low-frequency signals within the audio band. larger values of c out reduce the attenuation but are physically larger, more expen- sive capacitors. figure 3 shows the relationship between the size of c out and the resulting low-fre- quency attenuation. note that the -3db point for a 16 ? headphone with a 100f blocking capacitor is 100hz, well within the audio band. 2) the voltage coefficient of the capacitor, the change in capacitance due to a change in the voltage across the capacitor, distorts the audio signal. at frequencies around the -3db point, the reactance of the capacitor dominates, and the voltage coefficient appears as frequency-dependent distortion. figure 4 shows the thd+n introduced by two different capacitor dielectrics. note that around the -3db point, thd+n increases dramatically. the combination of low-frequency attenuation and fre- quency-dependent distortion compromises audio reproduction. directdrive improves low-frequency reproduction in portable audio equipment that empha- sizes low-frequency effects such as multimedia lap- tops, and mp3, cd, and dvd players. charge pump the max9750/max9751/max9755 feature a low-noise charge pump. the 550khz switching frequency is well beyond the audio range, and does not interfere with the audio signals. the switch drivers feature a controlled switching speed that minimizes noise generated by turn- on and turn-off transients. limiting the switching speed of the charge pump minimizes the di/dt noise caused by the f rc db l out ? = 3 1 2 0 -30 10 100 1k 10k 100k low-frequency rolloff (r l = 16 ? ) -24 -27 -12 -15 -18 -21 -6 -9 -3 frequency (hz) attenuation (db) directdrive 330 f 220 f 100 f 33 f figure 3. low-frequency attenuation of common dc-blocking capacitor values
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 14 ______________________________________________________________________________________ parasitic bond wire and trace inductance. although not typically required, additional high-frequency ripple atten- uation can be achieved by increasing the size of c2 (see the typical application circuit ). headphone sense input (hps) the headphone sense input (hps) monitors the head- phone jack and automatically configures the device based upon the voltage applied at hps. a voltage of less than 0.8v sets the device to speaker mode. a volt- age of greater than 2v disables the bridge amplifiers and enables the headphone amplifiers. for automatic headphone detection, connect hps to the control pin of a 3-wire headphone jack as shown in figure 5. with no headphone present, the output imped- ance of the headphone amplifier pulls hps low. when a headphone plug is inserted into the jack, the control pin is disconnected from the tip contact and hps is pulled to v dd through a 10a current source. bias the max9750/max9751/max9755 feature an internally generated, power-supply independent, common-mode bias voltage of 1.8v referenced to gnd. bias provides both click-and-pop suppression and sets the dc bias level for the amplifiers. choose the value of the bypass capacitor as described in the bias capacitor section. no external load should be applied to bias. any load lowers the bias voltage, affecting the overall perfor- mance of the device. gain selection max9750 the max9750 features an internally set, selectable gain. the gain1 and gain2 inputs set the maximum gain of the max9750 speaker and headphone amplifiers (table 1). the gain of the device can vary based upon the volt- age at vol (see the analog volume control section). however, the maximum gain cannot be exceeded. max9751/max9755 the gain of the max9751/max9755 is set by the gain input. driving gain high sets the gain of the speaker amplifiers to 9db and the gain of the headphone ampli- fiers to 0db. driving gain low sets the gain of the speaker amplifiers to 10.5db, and the gain of the head- phone amplifiers to 3db (table 2). analog volume control (vol) the max9750 features an analog volume control that varies the gain of the device in 31 discrete steps based upon the dc voltage applied to vol. the input range of v vol is from 0 (full volume) to 0.858 x hpv dd (full mute), with example step sizes shown in table 3. connect the reference of the device driving vol (figure 6) to hpv dd . since the volume control adc is ratiometric to hpv dd , any changes in hpv dd are negated. the gain step sizes are not constant; the step sizes are 0.5db/step at the upper extreme, 2db/step in the midrange, and 4db/step at the lower extreme. figure 7 shows the transfer function of the volume control for a 3.3v supply. additional thd+n due to dc-blocking capacitors frequency (hz) thd+n (%) 10k 1k 100 0.001 0.01 0.1 1 10 0.0001 10 100k tantalum alum/elec figure 4. distortion contributed by dc-blocking capacitors max9750/ max9751/ max9755 10 a 1k ? 1k ? 20 14 13 v dd hps hpoutl hpoutr shutdown control figure 5. hps configuration
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 15 beep input the max9750 features an audible alert beep input (beep) that accepts a mono system alert signal and mixes it into the stereo audio path. when the amplitude of v beep(out) exceeds 800mv p-p (figure 8) and the frequency of the beep signal is greater than 400hz, the beep signal is mixed into the active audio path (speaker or headphone). if the signal at v beep(out) is either <800mv p-p or <400hz, the beep signal is not mixed into the audio path. the amplitude of the beep signal at the device output is roughly the amplitude of v beep(out) times the gain of the selected signal path. the input resistor (r b ) sets the gain of the beep input amplifier, and thus the amplitude of v beep(out) . choose r b based on: where r int is the value of the beep amplifier feedback resistor (47k ? ) and v in is the beep input amplitude. note that the beep amplifier can be set up as either an attenuator, if the original alert signal amplitude is too large, or set to gain up the alert signal if it is below 800mv p-p . ac couple the alert signal to beep. choose the value of the coupling capacitor as described in the input filtering section. multiple beep inputs can be summed (figure 8). input multiplexer the max9751 features a 2:1 input multiplexer on each amplifier, allowing input selection between two stereo sources. the logic input in1/ 2 controls both multiplex- ers. a logic high selects input in_1 and a logic low selects input in_2. shutdown the max9750/max9751/max9755 features a 0.2a, low-power shutdown mode that reduces quiescent cur- rent consumption and extends battery life. driving shdn low disables the drive amplifiers, bias circuitry, and charge pump, and drives bias and all outputs to gnd. connect shdn to v dd for normal operation. click-and-pop suppression speaker amplifier the max9750/max9751/max9755 speaker amplifiers feature maxim s comprehensive, industry-leading click- and-pop suppression. during startup, the click-pop suppression circuitry eliminates any audible transient sources internal to the device. when entering shut- down, both amplifier outputs ramp to gnd quickly and simultaneously. r vr b in int . 08 max9750 v ref dac hpv dd vol figure 6. volume control circuit gain speaker mode gain (db) headphone mode gain (db) 0 10.5 3 19 0 table 2. max9751 gain settings speaker mode gain (db) gain2 gain1 max9750a max9750b max9750c headphone mode gain (db) 0 09 15 6 0 0 1 10.5 16.5 7.5 0 1 012 18 9 3 1 1 13.5 19.5 10.5 3 table 1. max9750 maximum gain settings
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 16 ______________________________________________________________________________________ v vol (v) speaker mode gain (db) headphone mode gain (db) v min * v max * hpv dd * gain1 = 0, gain2 = 0 gain1 = 1, gain2 = 0 gain1 = 0, gain2 = 1 gain1 = 1 gain2 = 1 gain1 = x, gain2 = 0 gain1 = x, gain2 = 1 0 0.49 0.074 9 10.5 12 13.5 0 3 0.49 0.5673 0.160 8 10 11.5 13 -1 2.5 0.5673 0.6447 0.183 7 9 11 12.5 -2 2 0.6447 0.722 0.207 6 8 10.5 12 -3 1.5 0.722 0.7994 0.230 4 7 10 11.5 -5 1 0.7994 0.8767 0.253 2 6 9 11 -7 0 0.8767 0.9541 0.277 0 4 8 10.5 -9 -1 0.9541 1.0314 0.300 -2 2 7 10 -11 -2 1.0314 1.1088 0.324 -4 0 6 9 -13 -3 1.1088 1.1861 0.347 -6 -2 4 8 -15 -5 1.1861 1.2635 0.371 -8 -4 2 7 -17 -7 1.2635 1.3408 0.394 -10 -6 0 6 -19 -9 1.3408 1.4182 0.418 -12 -8 -2 4 -21 -11 1.4182 1.4955 0.441 -14 -10 -4 2 -23 -13 1.4955 1.5728 0.464 -16 -12 -6 0 -25 -15 1.5728 1.6502 0.488 -18 -14 -8 -2 -27 -17 1.6502 1.7275 0.511 -20 -16 -10 -4 -29 -19 1.7275 1.8049 0.535 -22 -18 -12 -6 -31 -21 1.8094 1.8822 0.558 -24 -20 -14 -8 -33 -23 1.8822 1.9596 0.582 -26 -22 -16 -10 -35 -25 1.9596 2.0369 0.605 -28 -24 -18 -12 -37 -27 2.0369 2.1143 0.628 -30 -26 -20 -14 -39 -29 2.1143 2.1916 0.652 -32 -28 -22 -16 -41 -31 2.1916 2.269 0.675 -34 -30 -24 -18 -43 -33 2.269 2.3463 0.699 -38 -32 -26 -20 -47 -35 2.3463 2.4237 0.722 -42 -34 -28 -22 -51 -37 2.4237 2.501 0.746 -46 -38 -30 -24 -55 -39 2.501 2.5783 0.769 -50 -42 -32 -26 -59 -41 2.5783 2.6557 0.793 -54 -46 -34 -28 -63 -43 2.6557 2.733 0.816 -58 -50 -38 -30 -67 -47 2.733 2.8104 0.839 -62 -54 -42 -32 -71 -51 2.8104 3.3 0.858 mute mute mute mute mute mute table 3a. max9750a volume levels * based on hpv dd = 3.3v x = don? care.
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 17 v vol (v) speaker mode gain (db) headphone mode gain (db) v min * v max * hpv dd * gain1 = 0, gain2 = 0 gain1 = 1, gain2 = 0 gain1 = 0, gain2 = 1 gain1 = 1 gain2 = 1 gain1 = x, gain2 = 0 gain1 = x, gain2 = 1 0 0.49 0.074 15 16.5 18 19.5 0 3 0.49 0.5673 0.160 14 16 17.5 19 -1 2.5 0.5673 0.6447 0.183 13 15 17 18.5 -2 2 0.6447 0.722 0.207 12 14 16.5 18 -3 1.5 0.722 0.7994 0.230 10 13 16 17.5 -5 1 0.7994 0.8767 0.253 8 12 15 17 -7 0 0.8767 0.9541 0.277 6 10 14 16.5 -9 -1 0.9541 1.0314 0.300 4 8 13 16 -11 -2 1.0314 1.1088 0.324 2 6 12 15 -13 -3 1.1088 1.1861 0.347 0 4 10 14 -15 -5 1.1861 1.2635 0.371 -2 2 8 13 -17 -7 1.2635 1.3408 0.394 -4 0 6 12 -19 -9 1.3408 1.4182 0.418 -6 -2 4 10 -21 -11 1.4182 1.4955 0.441 -8 -4 2 8 -23 -13 1.4955 1.5728 0.464 -10 -6 0 6 -25 -15 1.5728 1.6502 0.488 -12 -8 -2 4 -27 -17 1.6502 1.7275 0.511 -14 -10 -4 2 -29 -19 1.7275 1.8049 0.535 -16 -12 -6 0 -31 -21 1.8049 1.8822 0.558 -18 -14 -8 -2 -33 -23 1.8822 1.9596 0.582 -20 -16 -10 -4 -35 -25 1.9596 2.0369 0.605 -22 -18 -12 -6 -37 -27 2.0369 2.1143 0.628 -24 -20 -14 -8 -39 -29 2.1143 2.1916 0.652 -26 -22 -16 -10 -41 -31 2.1916 2.269 0.675 -28 -24 -18 -12 -43 -33 2.269 2.3463 0.699 -32 -26 -20 -14 -47 -35 2.3463 2.4237 0.722 -36 -28 -22 -16 -51 -37 2.4237 2.501 0.746 -40 -32 -24 -18 -55 -39 2.501 2.5783 0.769 -44 -36 -26 -20 -59 -41 2.5783 2.6557 0.793 -48 -40 -28 -22 -63 -43 2.6557 2.733 0.816 -52 -44 -32 -24 -67 -47 2.733 2.8104 0.839 -56 -48 -36 -26 -71 -51 2.8104 3.3 0.858 mute mute mute mute mute mute table 3b. max9750b volume levels * based on hpv dd = 3.3v x = don? care.
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 18 ______________________________________________________________________________________ v vol (v) speaker mode gain (db) headphone mode gain (db) v min * v max *hpv dd * gain1 = 0, gain2 = 0 gain1 = 1, gain2 = 0 gain1 = 0, gain2 = 1 gain1 = 1 gain2 = 1 gain1 = x, gain2 = 0 gain1 = x, gain2 = 1 0 0.49 0.074 6 7.5 9 10.5 0 3 0.49 0.5673 0.160 5 7 8.5 10 -1 2.5 0.5673 0.6447 0.183 4 6 8 9.5 -2 2 0.6447 0.722 0.207 3 5 7.5 9 -3 1.5 0.722 0.7994 0.230 1 4 7 8.5 -5 1 0.7994 0.8767 0.253 -1 3 6 8 -7 0 0.8767 0.9541 0.277 -3 1 5 7.5 -9 -1 0.9541 1.0314 0.300 -5 -1 4 7 -11 -2 1.0314 1.1088 0.324 -7 -3 3 6 -13 -3 1.1088 1.1861 0.347 -9 -5 1 5 -15 -5 1.1861 1.2635 0.371 -11 -7 -1 4 -17 -7 1.2635 1.3408 0.394 -13 -9 -3 3 -19 -9 1.3408 1.4182 0.418 -15 -11 -5 1 -21 -11 1.4182 1.4955 0.441 -17 -13 -7 -1 -23 -13 1.4955 1.5728 0.464 -19 -15 -9 -3 -25 -15 1.5728 1.6502 0.488 -21 -17 -11 -5 -27 -17 1.6502 1.7275 0.511 -23 -19 -13 -7 -29 -19 1.7275 1.8049 0.535 -25 -21 -15 -9 -31 -21 1.8049 1.8822 0.558 -27 -23 -17 -11 -33 -23 1.8822 1.9596 0.582 -29 -25 -9 -13 -35 -25 1.9596 2.0369 0.605 -31 -27 -21 -15 -37 -27 2.0369 2.1143 0.628 -33 -29 -23 -17 -39 -29 2.1143 2.1916 0.652 -35 -31 -2 -19 -41 -31 2.1916 2.269 0.675 -37 -3 -27 -21 -43 -33 2.269 2.3463 0.699 -41 -35 -29 -23 -47 -35 2.3463 2.4237 0.722 -45 -37 -31 -25 -51 -37 2.4237 2.501 0.746 -48 -41 -33 -27 -55 -39 2.501 2.5783 0.769 -53 -45 -35 -29 -59 -41 2.5783 2.6557 0.793 -57 -49 -37 -31 -63 -43 2.6557 2.733 0.816 -61 -53 -41 -33 -67 -47 2.733 2.8104 0.839 -65 -57 -45 -35 -71 -51 2.8104 3.3 0.858 mute mute mute mute mute mute table 3c. max9750c volume levels * based on hpv dd = 3.3v x = don? care.
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 19 headphone amplifier in conventional single-supply headphone amplifiers, the output-coupling capacitor is a major contributor of audible clicks and pops. upon startup, the amplifier charges the coupling capacitor to its bias voltage, typi- cally half the supply. likewise, during shutdown, the capacitor is discharged to gnd. a dc shift across the capacitor results, which in turn appears as an audible transient at the speaker. since the max9750/max9751/ max9755 do not require output-coupling capacitors, no audible transient occurs. additionally, the max9750/max9751/max9755 features extensive click-and-pop suppression that eliminates any audible transient sources internal to the device. the power-up/down waveform in the typical operating characteristics shows that there are minimal spectral components in the audible range at the output upon startup and shutdown. figure 7a. volume control transfer function -80 -60 -70 -40 -50 -20 -30 -10 10 0 20 0 1.0 1.5 0.5 2.0 2.5 3.0 3.5 4.0 max9750a volume control transfer function v vol (v) gain (db) audio taper pot gain1 = gain2 = 0 speaker mode headphone mode figure 7b. volume control transfer function -80 -60 -70 -40 -50 -20 -30 -10 10 0 20 0 1.0 1.5 0.5 2.0 2.5 3.0 3.5 4.0 max9750b volume control transfer function v vol (v) gain (db) audio taper pot gain1 = gain2 = 0 speaker mode headphone mode figure 7c. volume control transfer function -80 -60 -70 -40 -50 -20 -30 -10 10 0 20 0 1.0 1.5 0.5 2.0 2.5 3.0 3.5 4.0 max9750c volume control transfer function v vol (v) gain (db) audio taper pot gain1 = gain2 = 0 speaker mode headphone mode max9750 r s3 47k ? beep 0.47 f source 3 r s2 47k ? 0.47 f source 2 r s1 47k ? 0.47 f source 1 r int 47k ? bias window detector (0.3v p-p threshold) frequency detector (300hz threshold) speaker/headphone amplifer inputs v out(beep) figure 8. beep input
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 20 ______________________________________________________________________________________ applications information btl speaker amplifiers the max9750/max9751/max9755 feature speaker amplifiers designed to drive a load differentially, a con- figuration referred to as bridge-tied load (btl). the btl configuration (figure 9) offers advantages over the sin- gle-ended configuration, where one side of the load is connected to ground. driving the load differentially doubles the output voltage compared to a single- ended amplifier under similar conditions. thus, the device s differential gain is twice the closed-loop gain of the input amplifier. the effective gain is given by: substituting 2 x v out(p-p) into the following equation yields four times the output power due to double the output voltage: since the differential outputs are biased at midsupply, there is no net dc voltage across the load. this elimi- nates the need for dc-blocking capacitors required for single-ended amplifiers. these capacitors can be large and expensive, can consume board space, and can degrade low-frequency performance. power dissipation and heat sinking under normal operating conditions, the max9750/ max9751/max9755 can dissipate a significant amount of power. the maximum power dissipation for each package is given in the absolute maximum ratings under continuous power dissipation, or can be calcu- lated by the following equation: where t j(max) is +150 c, t a is the ambient tempera- ture, and ja is the reciprocal of the derating factor in c/w as specified in the absolute maximum ratings section. for example, ja of the thin qfn package is +42 c/w. for optimum power dissipation, the exposed paddle of the package should be connected to the ground plane (see the layout and grounding section). for 8 ? applications, the worst-case power dissipation occurs when the output power is 1.1w/channel, resulting in a power dissipation of about 1w. in this case, both the tssop and tqfn packages can be used without violat- ing the maximum power dissipation or exceeding the thermal protection threshold. for 4 ? applications, the tssop package may require heat-sinking or forced air cooling to prevent the device from reaching its thermal limit. the more thermally efficient tqfn package is sug- gested for speaker loads less than 8 ? . output power (speaker amplifier) the increase in power delivered by the btl configura- tion directly results in an increase in internal power dis- sipation over the single-ended configuration. the p tt disspkg max j max a ja () () = ? v v p v r rms out p p out rms l = = ? () 22 2 a r r vd f in = 2 +1 v out(p-p) 2 x v out(p-p) v out(p-p) -1 figure 9. bridge-tied load configuration output power (mw) thd+n (%) 125 100 75 50 25 0.01 0.1 1 10 100 1000 0.001 0 150 v dd = 5v r l = 16 ? a v = 3db outputs in phase outputs 180 out of phase figure 10. total harmonic distortion plus noise vs. output power with inputs in/out of phase (headphone mode)
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 21 maximum power dissipation for a given v dd and load is given by the following equation: if the power dissipation for a given application exceeds the maximum allowed for a given package, either reduce v dd , increase load impedance, decrease the ambient temperature, or add heatsinking to the device. large output, supply, and ground pc board traces improve the maximum power dissipation in the package. thermal-overload protection limits total power dissipa- tion in these devices. when the junction temperature exceeds +160 c, the thermal-protection circuitry dis- ables the amplifier output stage. the amplifiers are enabled once the junction temperature cools by 15 c. this results in a pulsing output under continuous ther- mal-overload conditions as the device heats and cools. output power (headphone amplifier) the headphone amplifiers have been specified for the worst-case scenario when both inputs are in phase. under this condition, the drivers simultaneously draw current from the charge pump, leading to a slight loss in headroom of v ss . in typical stereo audio applications, the left and right signals have differences in both magni- tude and phase, subsequently leading to an increase in the maximum attainable output power. figure 10 shows the two extreme cases for in and out of phase. in reality, the available power lies between these extremes. power supplies the max9750/max9751/max9755 have different sup- plies for each portion of the device, allowing for the opti- mum combination of headroom and power dissipation and noise immunity. the speaker amplifiers are pow- ered from pv dd . pv dd ranges from 4.5v to 5.5v. the headphone amplifiers are powered from hpv dd and v ss . hpv dd is the positive supply of the headphone amplifiers and ranges from 3v to 5.5v. v ss is the nega- tive supply of the headphone amplifiers. connect v ss to cpv ss . the charge pump is powered by cpv dd . cpv dd ranges from 3v to 5.5v and should be the same potential as hpv dd . the charge pump inverts the volt- age at cpv dd , and the resulting voltage appears at cpv ss . the remainder of the device is powered by v dd . component selection input filtering the input capacitor (c in ), in conjunction with the ampli- fier input resistance (r in ), forms a highpass filter that removes the dc bias from an incoming signal (see the typical application circuit ). the ac-coupling capacitor allows the amplifier to bias the signal to an optimum dc level. assuming zero source impedance, the -3db point of the highpass filter is given by: r in is the amplifier s internal input resistance value given in the electrical characteristics . choose c in such that f -3db is well below the lowest frequency of interest. setting f -3db too high affects the amplifier s low-fre- quency response. use capacitors with low-voltage coefficient dielectrics, such as tantalum or aluminum electrolytic. capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies. bias capacitor bias is the output of the internally generated dc bias voltage. the bias bypass capacitor, c bias , improves psrr and thd+n by reducing power supply and other noise sources at the common-mode bias node, and also generates the clickless/popless, startup/shutdown dc bias waveforms for the speaker amplifiers. bypass bias with a 1f capacitor to gnd. charge-pump capacitor selection use capacitors with an esr less than 100m ? for opti- mum performance. low-esr ceramic capacitors mini- mize the output resistance of the charge pump. for best performance over the extended temperature range, select capacitors with an x7r dielectric. table 4 lists suggested manufacturers. flying capacitor (c1) the value of the flying capacitor (c1) affects the load regulation and output resistance of the charge pump. a c1 value that is too small degrades the device s ability to provide sufficient current drive, which leads to a loss of output voltage. increasing the value of c1 improves load regulation and reduces the charge-pump output f rc db in in ? = 3 1 2 p v r diss max dd l () = 2 2 2 supplier phone fax website taiyo yuden 800-348-2496 847-925-0899 www.t-yuden.com tdk 807-803-6100 847-390-4405 www.component.tdk.com table 4. suggested capacitor manufacturers
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 22 ______________________________________________________________________________________ resistance to an extent. see the output power vs. charge-pump capacitance and load resistance graph in the typical operating characteristics . above 2.2f, the on-resistance of the switches and the esr of c1 and c2 dominate. output capacitor (c2) the output capacitor value and esr directly affect the ripple at cpv ss . increasing the value of c2 reduces output ripple. likewise, decreasing the esr of c2 reduces both ripple and output resistance. lower capacitance values can be used in systems with low maximum output power levels. see the output power vs. charge-pump capacitance and load resistance graph in the typical operating characteristics . cpv dd bypass capacitor the cpv dd bypass capacitor (c3) lowers the output impedance of the power supply and reduces the impact of the max9750/max9751/max9755 s charge- pump switching transients. bypass cpv dd with c3, the same value as c1, and place it physically close to cpv dd and pgnd (refer to the max9750 evaluation kit for a suggested layout). powering other circuits from a negative supply an additional benefit of the max9750/max9751/ max9755 is the internally generated negative supply volt- age (cpv ss ). cpv ss is used by the max9750/ max9751/max9755 to provide the negative supply for the headphone amplifiers. it can also be used to power other devices within a design. current draw from cpv ss should be limited to 5ma, exceeding this affects the oper- ation of the headphone amplifier. a typical application is a negative supply to adjust the contrast of lcd modules. when considering the use of cpv ss in this manner, note that the charge-pump voltage of cpv ss is roughly proportional to cpv dd and is not a regulated voltage. the charge-pump output impedance plot appears in the typical operating characteristics . layout and grounding proper layout and grounding are essential for optimum performance. use large traces for the power-supply inputs and amplifier outputs to minimize losses due to parasitic trace resistance, as well as route head away from the device. good grounding improves audio per- formance, minimizes crosstalk between channels, and prevents any switching noise from coupling into the audio signal. connect cpgnd, pgnd and gnd together at a single point on the pc board. route cpgnd and all traces that carry switching transients away from gnd, pgnd, and the traces and compo- nents in the audio signal path. connect all components associated with the charge pump (c2 and c3) to the cpgnd plane. connect v ss and cpv ss together at the device. place the charge- pump capacitors (c1, c2, and c3) as close to the device as possible. bypass hpv dd and pv dd with a 0.1f capacitor to gnd. place the bypass capacitors as close to the device as possible. use large, low-resistance output traces. as load imped- ance decreases, the current drawn from the device out- puts increase. at higher current, the resistance of the output traces decrease the power delivered to the load. for example, when compared to a 0 ? trace, a 100m ? trace reduces the power delivered to a 4 ? load from 2.1w to 2w. large output, supply, and gnd traces also improve the power dissipation of the device. the max9750/max9751/max9755 thin qfn package features an exposed thermal pad on its underside. this pad lowers the package s thermal resistance by provid- ing a direct heat conduction path from the die to the printed circuit board. connect the exposed thermal pad to gnd by using a large pad and multiple vias to the gnd plane. max9750 inr inl 1 f 1 f 22nf outl+ outl- outr+ outr- out- out+ 22 f 22 f 10nf 20k ? 20k ? in 10k ? 10k ? max9711 figure 11. stereo plus subwoofer application circuit
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 23 simplified block diagrams (continued) max9751 max9755 mux
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 24 ______________________________________________________________________________________ hpv dd hps inr bias vol gain1 gain2 beep 3v to 5.5v cpv dd c1p c1n cpv ss v ss gnd pgnd c1 1 f c bias 1 f c in 1 f c in 1 f c2 1 f 1 f 1 f cpgnd inl 27 (3) 21 (25) 28 (4) 24 (28) 23 (27) 2 (6) 22 (26) 7 (11) 8 (12) 10 (14) 9 (13) 11 (15) 12 (16) 26 (2) 3, 19 (7, 23) 1 (5) 10 f 3v to 5.5v 6, 16 (10, 20) 4 (8) 25 (1) 5 (9) 18 (22) 17 (21) 15 (19) 20 (24) 14 (18) 13 (17) hpoutl hpoutr max9750 0.1 f 0.1 f 4.5v to 5.5v gain/ volume control btl amplifier right-channel audio input outr+ outr- charge pump gain/ volume control headphone detection beep detection shutdown control gain/ volume control btl amplifier left-channel audio input outl+ pv dd 4.5v to 5.5v v dd outl- v dd v dd v dd shdn 47k ? ( ) tssop pin. block diagrams
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 25 hpv dd hps inr1 bias gain in1/2 shdn 3v to 5.5v cpv dd v dd v dd v dd c1p c1n cv ss v ss gnd pgnd c1 1 f c bias 1 f c in 1 f c in 1 f c2 1 f 1 f cpgnd inl1 27 (3) 21 (25) 28 (4) 24 (28) 23 (27) 2 (6) 22 (26) 7 (11) 8 (12) 10 (14) 9 (13) 11 (15) 12 (16) 26 (2) 3, 19 (7, 23) 1 (5) 10 f 3v to 5.5v 6, 16 (10, 20) 4 (8) 25 (1) 5 (9) 18 (22) 17 (21) 15 (19) 20 (24) 14 (18) 13 (17) hpoutl hpoutr max9751 0.1 f 0.1 f 4.5v to 5.5v btl amplifier right channel audio input inr2 c in 1 f right channel audio input outr+ outr- charge pump mux and gain control headphone detection shutdown control input mux input mux btl amplifier left channel audio input c in 1 f inl2 left channel audio input outl+ pv dd 4.5v to 5.5v v dd outl- ( ) tssop pin. logic pins configured for: gain = 1, 9db speaker gain/0db headphone gain. in1/2 = 1, selected input line 1. shdn = 1, part active. block diagrams (continued)
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 26 ______________________________________________________________________________________ hpv dd hps bias gain shdn 3v to 5.5v cpv dd v dd v dd c1p c1n cpv ss v ss gnd pgnd c1 1 f c bias 1 f c2 1 f 1 f cpgnd 21 (25) 28 (4) 24 (28) 2 (6) 22 (26) 7 (11) 8 (12) 10 (14) 9 (13) 11 (15) 12 (16) 23, 26 (2, 27) 3, 19 (7, 23) 10 f 3v to 5.5v 6, 16 (10, 20) 4 (8) 25 (1) 5 (9) 18 (22) 17 (21) 15 (19) 20 (24) 14 (18) 13 (17) hpoutl hpoutr max9755 0.1 f 0.1 f 4.5v to 5.5v btl amplifier inr c in 1 f right channel audio input outr+ outr- charge pump gain control headphone detection shutdown control btl amplifier c in 1 f inl left channel audio input outl+ pv dd 4.5v to 5.5v v dd outl- ( ) tssop pin. logic pins configured for: gain = 1, 9db speaker gain/0db headphone gain. shdn = 1, part active. block diagrams (continued)
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 27 codec max4060 aux_in bias in+ in- out 3v to 5.5v max9750 inr 4.5v to 5.5v 3v to 5.5v inl cpv dd bias beep 1 f 0.1 f 1 f 1 f 1 f 1 f 1 f 1 f 1 f 1 f 1 f c 2k ? 2k ? c1p c1n gnd pgnd shdn outl+ outl- vol cpv ss v ss cpgnd outr+ gain1 gain2 outr- hps hpoutl hpoutr v dd hpv dd pv dd 10 f hpv dd 33k ? system diagrams
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 28 ______________________________________________________________________________________ codec max4060 aux_in bias in+ in- out 3v to 5.5v max9751 inl2 4.5v to 5.5v 3v to 5.5v inl1 cpv dd 0.1 f 1 f 1 f 1 f 1 f 1 f 1 f 1 f c 2k ? 2k ? c1p c1n gnd pgnd shdn outl+ outl- outr+ in1/2 gain outr- hps hpoutl hpoutr v dd hpv dd pv dd inr1 inr2 1 f 10 f 1 f bias cpv ss v ss cpgnd system diagrams (continued) chip information max9750 transistor count: 9591 max9751 transistor count: 8632 max9755 transistor count: 7834 process: bicmos
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers ______________________________________________________________________________________ 29 28 27 26 25 24 23 22 vol inr gnd v dd gain1 gain2 shdn 8 9 10 11 12 13 14 c1p cpgnd c1n cpv ss v ss hpoutr hpoutl 15 16 17 18 19 20 21 hpv dd pv dd outr- outr+ pgnd hps bias 7 6 5 4 3 2 1 cpv dd pv dd outl- outl+ pgnd beep inl max9750 thin qfn top view 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 gain1 gain2 shdn bias hps pgnd cpv ss outr+ outr- pv dd hpv dd hpoutl hpoutr v ss c1n cpgnd c1p cpv dd pv dd outl- outl+ pgnd beep inl vol inr gnd v dd tssop top view max9750 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 gain1 in1/2 shdn bias hps pgnd cpv ss outr+ outr- pv dd hpv dd hpoutl hpoutr v ss c1n cpgnd c1p cpv dd pv dd outl- outl+ pgnd inl2 inl1 inr2 inr1 gnd v dd tssop max9751 28 27 26 25 24 23 22 inr n.c. gnd v dd gain gnd shdn 8 9 10 11 12 13 14 c1p cpgnd c1n cpv ss v ss hpoutr hpoutl 15 16 17 18 19 20 21 hpv dd pv dd outr- outr+ pgnd hps bias 7 6 5 4 3 2 1 cpv dd pv dd outl- outl+ pgnd inl n.c. max9755 thin qfn 28 27 26 25 24 23 22 inr2 inr1 gnd v dd gain in1/2 shdn 8 9 10 11 12 13 14 c1p cpgnd c1n cpv ss v ss hpoutr hpoutl 15 16 17 18 19 20 21 hpv dd pv dd outr- outr+ pgnd hps bias 7 6 5 4 3 2 1 cpv dd pv dd outl- outl+ pgnd inl2 inl1 max9751 thin qfn 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 gain1 gnd shdn bias hps pgnd cpv ss outr+ outr- pv dd hpv dd hpoutl hpoutr v ss c1n cpgnd c1p cpv dd pv dd outl- outl+ pgnd inl n.c. inr n.c. gnd v dd tssop max9755 pin configurations
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers 30 ______________________________________________________________________________________ package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) qfn thin.eps d2 (nd-1) x e e d c pin # 1 i.d. (ne-1) x e e/2 e 0.08 c 0.10 c a a1 a3 detail a 0.15 c b 0.15 c a e2/2 e2 0.10 m c a b pin # 1 i.d. b 0.35x45 l d/2 d2/2 l c l c e e l c c l k k l l detail b l l1 e xxxxx marking f 1 2 21-0140 package outline, 16, 20, 28, 32l thin qfn, 5x5x0.8mm -drawing not to scale- common dimensions 3.35 3.15 t2855-1 3.25 3.35 3.15 3.25 max. 3.20 exposed pad variations 3.00 t2055-2 3.10 d2 nom. min. 3.20 3.00 3.10 min. e2 nom. max. ne nd pkg. codes 1. dimensioning & tolerancing conform to asme y14.5m-1994. 2. all dimensions are in millimeters. angles are in degrees. 3. n is the total number of terminals. 4. the terminal #1 identifier and terminal numbering convention shall conform to jesd 95-1 spp-012. details of terminal #1 identifier are optional, but must be located within the zone indicated. the terminal #1 identifier may be either a mold or marked feature. 5. dimension b applies to metallized terminal and is measured between 0.25 mm and 0.30 mm from terminal tip. 6. nd and ne refer to the number of terminals on each d and e side respectively. 7. depopulation is possible in a symmetrical fashion. 8. coplanarity applies to the exposed heat sink slug as well as the terminals. 9. drawing conforms to jedec mo220, except exposed pad dimension for t2855-1, t2855-3 and t2855-6. notes: symbol pkg. n l1 e e d b a3 a a1 k 10. warpage shall not exceed 0.10 mm. jedec t1655-1 3.20 3.00 3.10 3.00 3.10 3.20 0.70 0.80 0.75 4.90 4.90 0.25 0.25 0 -- 4 whhb 4 16 0.35 0.30 5.10 5.10 5.00 0.80 bsc. 5.00 0.05 0.20 ref. 0.02 min. max. nom. 16l 5x5 3.10 t3255-2 3.00 3.20 3.00 3.10 3.20 2.70 t2855-2 2.60 2.60 2.80 2.70 2.80 l 0.30 0.50 0.40 -- - -- - whhc 20 5 5 5.00 5.00 0.30 0.55 0.65 bsc. 0.45 0.25 4.90 4.90 0.25 0.65 - - 5.10 5.10 0.35 20l 5x5 0.20 ref. 0.75 0.02 nom. 0 0.70 min. 0.05 0.80 max. -- - whhd-1 28 7 7 5.00 5.00 0.25 0.55 0.50 bsc. 0.45 0.25 4.90 4.90 0.20 0.65 - - 5.10 5.10 0.30 28l 5x5 0.20 ref. 0.75 0.02 nom. 0 0.70 min. 0.05 0.80 max. -- - whhd-2 32 8 8 5.00 5.00 0.40 0.50 bsc. 0.30 0.25 4.90 4.90 0.50 - - 5.10 5.10 32l 5x5 0.20 ref. 0.75 0.02 nom. 0 0.70 min. 0.05 0.80 max. 0.20 0.25 0.30 down bonds allowed no yes 3.10 3.00 3.20 3.10 3.00 3.20 t2055-3 3.10 3.00 3.20 3.10 3.00 3.20 t2055-4 t2855-3 3.15 3.25 3.35 3.15 3.25 3.35 t2855-6 3.15 3.25 3.35 3.15 3.25 3.35 t2855-4 2.60 2.70 2.80 2.60 2.70 2.80 t2855-5 2.60 2.70 2.80 2.60 2.70 2.80 t2855-7 2.60 2.70 2.80 2.60 2.70 2.80 3.20 3.00 3.10 t3255-3 3.20 3.00 3.10 3.20 3.00 3.10 t3255-4 3.20 3.00 3.10 no no no no no no no no yes yes yes yes 3.20 3.00 t1655-2 3.10 3.00 3.10 3.20 yes no 3.20 3.10 3.00 3.10 t1655n-1 3.00 3.20 3.35 3.15 t2055-5 3.25 3.15 3.25 3.35 y 3.35 3.15 t2855n-1 3.25 3.15 3.25 3.35 n 3.35 3.15 t2855-8 3.25 3.15 3.25 3.35 y 3.20 3.10 t3255n-1 3.00 no 3.20 3.10 3.00 l 0.40 0.40 ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** ** see common dimensions table ?0.15 11. marking is for package orientation reference only. f 2 2 21-0140 package outline, 16, 20, 28, 32l thin qfn, 5x5x0.8mm -drawing not to scale- 12. number of leads shown are for reference only.
max9750/max9751/max9755 2.6w stereo audio power amplifiers and directdrive headphone amplifiers maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 31 ? 2004 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) tssop4.40mm.eps

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