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general description the max9752/max9753/max9754 combine a high-effi- ciency, filterless, stereo class d audio power amplifier with a directdrive headphone amplifier in a single device. the class d amplifier operates from a single 4.5v to 5.5v supply and provides 2.2w per channel into a 4 load. the headphone amplifier operates from a single 3v to 5.5v supply, and uses maxim? patented ? directdrive architecture to produce a ground-refer- enced output from a single supply. the max9754 features a class d stereo speaker ampli- fier and headphone driver. the max9752 adds an ana- log volume control and a beep input. the max9753 adds a stereo 2:1 input multiplexer. all devices feature logic-selectable gain, and a headphone sense input that detects the presence of a headphone. the max9752/max9753/max9754 come in 28-pin thin qfn (5mm x 5mm x 0.8mm) packages, and are speci- fied over the extended -40? to +85? temperature range. for a pin-for-pin-compatible class ab version of these devices, refer to the max9750/max9751/ max9755 data sheet. applications notebook pcs flat-panel tvs tablet pcs pc displays portable dvds lcd projectors features ? pc2001 compliant ? 2.2w class d stereo speaker amplifier ? pin-for-pin compatible with class ab max9750/max9751/max9755 ? 85% efficiency (r l = 8 , p out = 1w) ? 62mw directdrive headphone amplifier ? high psrr (70db at 1khz) ? analog volume control (max9752) ? beep input with glitch filter (max9752) ? 2:1 stereo input mux (max9753) ? 8kv esd-protected headphone outputs ? no output dc-blocking capacitors ? industry-leading click-and-pop suppression max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ________________________________________________________________ maxim integrated products 1 ordering information hps class d amp class d amp hps input mux select hps vol beep s s max9752 max9753 max9754 class d amp block diagrams 19-3666; rev 0; 9/05 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 pin-package pkg code m a xim u m g a i n ( d b ) max9752 aeti+ 28 tqfn-ep* t2855-1 13.5 max9752beti+ 28 tqfn-ep* t2855-1 19.5 max9752ceti+ 28 tqfn-ep* t2855-1 10.5 max9753 eti+ 28 tqfn-ep* t2855-1 13.5 max9754 eti+ 28 tqfn-ep* t2855-1 13.5 pin configurations appear at end of data sheet. note: all devices specified for -40c to +85? operation. + denotes lead-free package. * ep = exposed paddle. ? u.s. patent# 7,061,327
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = pv dd = hpv dd = cpv dd = +5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 1, 2) 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. v dd , pv dd , hpv dd , cpv dd to gnd ....................... -0.3v to +6v gnd to pgnd or cpgnd .................................... -0.3v to +0.3v cpv ss or v ss to pgnd ........................................ -6.0v to +0.3v c1n to pgnd .........................................(cpv ss - 0.3v) to +0.3v c1p to pgnd........................................ -0.3v to (cpv dd + 0.3v) hp_ to pgnd......................... (hpv ss - 0.3v) to (hpv dd + 0.3v) hp_ to pgnd.............................................................. -3v to +3v any other pin to pgnd ............................. -0.3v to (v dd + 0.3v) duration of out_ short circuit to pgnd or pv dd ......... continuous duration of out_+ short circuit to out_- .................continuous duration of hp_ short circuit to pgnd ......................continuous continuous current into/out of pv dd , out_, pgnd ...........1.7a continuous current into/out of cpv dd , c1n, cpgnd, c1p, cpv ss , v ss , hpv dd , hp_ ......................................0.85a continuous input current (all other pins) ........................ ?0ma continuous power dissipation (t a = +70?) 28-pin tqfn (derate 21.3mw/? above +70?) .......1702mw operating temperature range ...........................-40? to +85? storage temperature range .............................-65? to +150? junction temperature ......................................................+150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units general supply voltage range, speaker amplifier v dd , pv dd inferred from psrr test 4.5 5.5 v supply voltage range, headphone amplifier hpv dd inferred from psrr test 3.0 5.5 v speaker mode, no load 14 18 quiescent current i dd headphone mode, no load 7.2 9.5 ma shutdown supply current i shdn v shdn = 0v 0.2 8 a gain switching time t swg 3s mux switching time t swm max9753 only 3 ? max9752 10 20 30 input resistance r in max9753/max9754 3.5 6.6 10.0 k turn-on time t on 25 ms class d speaker amplifiers (hps = gnd) t a = +25? ?.6 ?8.8 max9752a, max9752b, max9753, max9754 t a = t min to t max ?5 t a = +25? 7 ?0 output offset voltage out_+ to out_- v os max9752c t a = t min to t max ?0 mv pv dd or v dd = 4.5v to 5.5v, t a = +25? 50 74 f = 1khz, v ripple = 100mv p-p 70 power-supply rejection ratio (note 3) psrr f = 10khz, v ripple = 100mv p-p 60 db
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dd = pv dd = hpv dd = cpv dd = +5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units gain1 = 0, gain2 = 0 9.0 gain1 = 0, gain2 = 1 10.5 gain1 = 1, gain2 = 0 12.0 max9752a gain1 = 1, gain2 = 1 13.5 gain1 = 0, gain2 = 0 15.0 gain1 = 0, gain2 = 1 16.5 gain1 = 1, gain2 = 0 18.0 max9752b gain1 = 1, gain2 = 1 19.5 gain1 = 0, gain2 = 0 6.0 gain1 = 0, gain2 = 1 7.5 gain1 = 1, gain2 = 0 9.0 max9752c gain1 = 1, gain2 = 1 10.5 gain = 1 9.0 speaker amplifier gain (note 4) a v_sp max9753/max9754 gain = 0 10.5 db max9752a, max9752b, max9753, max9754 1.3 f = 1khz, thd+n = 1%, t a = +25?, r l = 8 max9752c 0.8 max9752a, max9752b, max9753, max9754 2.2 output power p out_sp f = 1khz, thd+n = 1%, t a = +25?, r l = 4 max9752c 1.7 w r l = 8 = = = = = = = = = r l = 8 , p out = 1w, f = 1khz 85 %
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 4 _______________________________________________________________________________________ electrical characteristics (continued) (v dd = pv dd = hpv dd = cpv dd = +5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units headphone amplifier (hps = v dd ) t a = +25? ?.5 ?.5 output offset voltage v os t a = t min to t max ? mv gain2 = 0 0 max9752, gain1 = don? care gain2 = 1 3 gain = 1 0 maximum headphone amplifier gain (note 6) a v_hp max9753/max9754 gain = 0 3 db hpv dd or v dd = 3v to 5.5v, t a = +25? 66 73 f = 1khz, v ripple = 100mv p-p 80 power-supply rejection ratio (note 3) psrr f = 10khz, v ripple = 100mv p-p 60 db r l = 32 31 output power p out_hp thd+n = 1%, f in = 1khz, t a = +25? r l = 16 62 mw r l = 32 , p out = 31mw 0.005 total harmonic distortion plus noise thd+n f in = 1khz r l = 16 , p out = 62mw 0.005 % unweighted 95 signal-to-noise ratio snr r l = 32 , p out = 31mw, f in = 1khz, bw = 22hz to 22khz a-weighted 101 db into shutdown -33 click-and-pop level (note 7) k cp out of shutdown -37 dbv capacitive-load drive c l_max no sustained oscillations 300 pf crosstalk f = 10khz, p out = 62mw, r l = 16 60 db off-isolation max9753, unselected input to any active input, f = 10khz 60 db slew rate sr 0.8 v/? output impedance hps = gnd (disabled) 1 k charge pump charge-pump frequency f cp 540 600 660 khz volume control (max9752 only) vol input impedance r vol 100 m vol input hysteresis hyst vol v vol falling 50 mv full mute input voltage v vol_mute 0.858 x v dd v full mute attenuation a v_mute f in = 1khz -85 db
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers _______________________________________________________________________________________ 5 electrical characteristics (continued) (v dd = pv dd = hpv dd = cpv dd = +5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units gain 10.5db to 13.5db ?.2 gain 6.0db to 10.0db ?.2 gain -26db to +4.0db ?.3 channel matching gain -62db to +30db ?.0 db beep input (max9752 only) beep signal minimum amplitude (note 8) v beep r beep = 47k logic inputs (gain_, in1 // / / 2 2 2 2 , shdn , hps) input high voltage v ih 2.0 v input low voltage v il 0.8 v gain_, shdn -1 +1 in1/ 2 -2 +2 input leakage current i leak hps -20 +1 ? note 1: all devices are 100% production tested at t a = +25?. all temperature limits are guaranteed by design. note 2: speaker amplifier testing performed with a resistive load in series with an inductor to simulate an actual speaker load. for r l = 4 , l = 33?. for r l = 8 , l = 68?. note 3: measured with the amplifier input connected to gnd through c in . note 4: speaker amplifier gain is defined as a = (v out_+ - v out_- ) / v in_ . note 5: testing performed with 8 resistive load in series with 68? inductive load connected across the btl output. mode transitions are controlled by shdn . peak reading, thd+n = 1%, a-weighted, 32 samples per second. k cp level is calculated as: 20 x log[(peak voltage under normal operation at rated power level) / (peak voltage during mode transition, no input signal)]. note 6: headphone amplifier gain is defined as a = v hp_ / v in_ . note 7: testing performed with 32 resistive load connected from hp_ output to gnd. mode transitions are controlled by shdn . peak reading, thd+n = 1%, a-weighted, 32 samples per second. k cp level is calculated as: 20 x log[(peak voltage under normal operation at rated power level) / (peak voltage during mode transition, no input signal)]. note 8: the value of r beep dictates the minimum beep signal amplitude that is detected (see the beep input (max9752) section).
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 6 _______________________________________________________________________________________ typical operating characteristics (v dd = pv dd = hpv dd = cpv dd = 5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = +25?, unless otherwise noted.) total harmonic distortion plus noise vs. frequency (speaker mode) max9752/53/54 toc01 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 10 0.001 10 100k r l = 3 p out = 1w p out = 500mw total harmonic distortion plus noise vs. frequency (speaker mode) max9752/53/54 toc02 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 10 0.001 10 100k r l = 4 p out = 1.5w p out = 750mw total harmonic distortion plus noise vs. frequency (speaker mode) max9752/53/54 toc03 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 10 0.001 10 100k r l = 8 p out = 1w p out = 500mw total harmonic distortion plus noise vs. output power max9752 toc04 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 04.0 r l = 3 max9752c f in = 10khz f in = 20hz f in = 1khz total harmonic distortion plus noise vs. output power max9752 toc05 output power (w) thd+n (%) 2.5 1.5 1.0 2.0 0.5 0.01 0.1 1 10 100 0.001 0 3.0 r l = 3 f in = 1khz and 20hz f in = 10khz total harmonic distortion plus noise vs. output power max9752 toc06 output power (w) thd+n (%) 2.5 1.5 1.0 2.0 0.5 0.01 0.1 1 10 100 0.001 03.0 r l = 4 max9752c f in = 1khz f in = 10khz f in = 20hz total harmonic distortion plus noise vs. output power max9752 toc07 output power (w) thd+n (%) 1.5 1.0 2.0 0.5 0.01 0.1 1 10 100 0.001 02.5 r l = 4 f in = 1khz and 20hz f in = 10khz total harmonic distortion plus noise vs. output power max9752 toc08 output power (w) thd+n (%) 0.5 1.0 0.01 0.1 1 10 100 0.001 0 1.5 r l = 8 max9752c f in = 1khz f in = 10khz f in = 20hz total harmonic distortion plus noise vs. output power max9752 toc09 output power (w) thd+n (%) 0.5 1.0 0.01 0.1 1 10 100 0.001 0 1.5 r l = 8 f in = 10khz f in = 1khz and 20hz
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers _______________________________________________________________________________________ 7 output power vs. load resistance (speaker mode) max9752/53/54 toc10 load resistance ( ) output power (w) 10 1 2 3 4 5 0 1 100 thd+n = 10% thd+n = 1% output power vs. load resistance (speaker mode) max9752 toc11 load resistance ( ) output power (w) 10 1 2 3 4 0 1100 thd+n = 10% thd+n = 1% power dissipation vs. output power (speaker mode) max9752 toc12 output power (w) power dissipation (w) 3 2 1 0.5 1.0 1.5 2.0 0 04 r l = 4 r l = 8 turn-on response (speaker mode) max9752/53/54 toc14 4ms/div shdn 5v/div 500mv/div out (1khz, 2v p-p ) out (no audio) 100mv/div turn-off response (speaker mode) max9752/53/54 toc15 2ms/div shdn 5v/div 500mv/div out (1khz, 2v p-p ) out (no audio) 100mv/div typical operating characteristics (continued) (v dd = pv dd = hpv dd = cpv dd = 5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = +25?, unless otherwise noted.) efficiency vs. output power max9752 toc13 output power (w) efficiency (%) 4 2 10 20 30 40 50 60 70 80 90 100 0 06 r l = 8 ||68 h r l = 4 ||33 h
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 8 _______________________________________________________________________________________ typical operating characteristics (continued) (v dd = pv dd = hpv dd = cpv dd = 5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = +25?, 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 (headphone mode) max9752/53/54 toc16 frequency (hz) thd+n (%) v dd = 5v r l = 16 a v = 3db output power = 90mw output power = 30mw 10 1 0.1 0.01 0.001 0.0001 10 1k 10k 100 100k total harmonic distortion plus noise vs. frequency (headphone mode) max9752/53/54 toc17 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) max9752/53/54 toc18 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) max9752/53/54 toc19 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 25 150 total harmonic distortion plus noise vs. output power (headphone mode) max9752/53/54 toc20 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) max9752/53/54 toc21 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) max9752/53/54 toc22 output power (mw) thd+n (%) v dd = 3.3v r l = 16 a v = 3db f in = 10khz f in = 1khz f in = 20hz 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) max9752/53/54 toc23 output power (mw) thd+n (%) v dd = 3.3v r l = 32 a v = 3db f in = 10khz f in = 1khz f in = 20hz output power vs. load resistance (headphone mode) max9752/53/54 toc24 load resistance ( ) output power (mw) 100 20 40 60 80 100 120 140 160 180 0 10 1000 thd+n = 10% thd+n = 1%
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers _______________________________________________________________________________________ 9 power dissipation vs. output power (headphone mode) max9752/53/54 toc25 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 output power vs. supply voltage (headphone mode) max9752/53/54 toc26 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) max9752/53/54 toc27 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) max9752/53/54 toc28 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 max9752/53/54 toc29 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) (v dd = pv dd = hpv dd = cpv dd = 5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = +25?, unless otherwise noted.)
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 10 ______________________________________________________________________________________ headphone output spectrum max9752/53/54 toc30 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) max9752/53/54 toc31 10ms/div shdn 5v/div 20mv/div hpout_ r l = 32 turn-off response (headphone mode) max9752/53/54 toc32 10ms/div shdn 5v/div 20mv/div hpout_ r l = 32 typical operating characteristics (continued) (v dd = pv dd = hpv dd = cpv dd = 5.0v, gnd = pgnd = hpgnd = 0v, v shdn = v dd , cpv ss = v ss , c bias = 1?, c cpvss = 1?, c1 = 1?, speaker impedance = 8 connected between out_+ and out_-, headphone load is terminated to gnd; max9752: gain1 = gain2 = 0, v vol = 0v; max9753: gain = 0, v a /b = 0v; max9754: gain = 0; t a = +25?, unless otherwise noted.)
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 11 pin descriptions pin max9752 max9753 max9754 name function 1 2 inl left-channel audio input 2 beep audible alert beep input 3, 19 3, 19 3, 19 pgnd power ground 4 4 4 outl+ left-channel positive speaker output 5 5 5 outl- left-channel negative speaker output 6, 16 6, 16 6, 16 pv dd speaker amplifier power supply 7 7 7 cpv dd charge-pump power supply 8 8 8 c1p charge-pump flying-capacitor positive terminal 9 9 9 cpgnd charge-pump ground 10 10 10 c1n charge-pump flying-capacitor negative terminal 11 11 11 cpv ss charge-pump output. connect to v ss . 12 12 12 v ss headphone amplifier negative power supply 13 13 13 hpoutr right-channel headphone output 14 14 14 hpoutl left-channel headphone output 15 15 15 hpv dd headphone positive power supply 17 17 17 outr- right-channel negative speaker output 18 18 18 outr+ right-channel positive speaker output 20 20 20 hps headphone sense input 21 21 21 bias common-mode bias voltage. bypass with a 1? capacitor to gnd. 22 22 22 shdn shutdown. drive shdn low to disable the device. connect shdn to v dd for normal operation. 23 gain2 gain-control input 2 24 gain1 gain-control input 1 25 25 25 v dd power supply 26 26 23, 26 gnd ground 27 28 inr right-channel audio input 28 vol analog volume control input 1 inl1 left-channel audio input 1 2 inl2 left-channel audio input 2 23 in1/ 2 input select 24 24 gain gain select 27 inr1 right-channel audio input 1 28 inr2 right-channel audio input 2 1, 27 n.c. no connection. not internally connected.
max9752/max9753/max9754 detailed description the max9752/max9753/max9754 combine a 2.2w, class d speaker amplifier and a 62mw directdrive headphone amplifier with integrated headphone sens- ing and comprehensive click-and-pop suppression. the speaker amplifiers offer class ab performance with class d efficiency, while occupying minimal board space. a unique filterless modulation scheme and spread-spectrum switching create a compact, flexible, low-noise, efficient audio power amplifier. the max9752 features an analog volume control, beep input, and four-level gain control. the max9753 fea- tures a 2:1 input stereo multiplexer and two-level gain control. the max9754 has only the class d amplifiers and the headphone amplifiers. an input amplifier sets the gain of the signal path, and feeds both the speaker and headphone amplifier (figure 1). the speaker amplifier uses a low-emi, class d architecture to drive the speakers, eliminating the need for an external filter for short speaker cables. the headphone amplifiers use maxim? patented directdrive architecture eliminating the bulky output dc- blocking capacitors required by traditional headphone amplifiers. a charge pump inverts the positive supply (cpv dd ), creating a negative supply (cpv ss ). the head- phone 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 quadrupling the available output power. the benefit of the gnd bias is that the amplifier outputs no longer have a dc compo- nent (typically v dd / 2). this eliminates the large dc- blocking capacitors required with conventional headphone amplifiers, removing the dominant source of click and pop, conserving board space, system cost, and improving frequency response. an undervoltage lockout prevents operation from an insufficient power supply. the amplifiers include ther- mal-overload and short-circuit protection, and can with- stand ?kv esd strikes on the headphone amplifier outputs (iec air-gap discharge). an additional feature of the speaker amplifiers is that there is no phase inver- sion from input to output. class d speaker amplifier the max9752/max9753/max9754 feature a unique, patented spread-spectrum mode that flattens the wide- band spectral components, improving emi emissions that may be radiated by the speaker and cables. the switching frequency varies randomly by ?0khz around the center frequency (1200khz). instead of a large amount of spectral energy present at multiples of the switching frequency, the energy is now spread over a bandwidth that increases with frequency. above a few megahertz, the wideband spectrum looks like white noise for emi purposes (figure 3). 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 12 ______________________________________________________________________________________ out_+ out_ volume control bias in_ vol bias max9752 only bias hpout_ gnd figure 1. max9752/max9753/max9754 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 amplifier output vs. directdrive output
filterless modulation/common-mode idle the max9752/max9753/max9754 use maxim? unique, patented modulation scheme that eliminates the lc filter required by traditional class d amplifiers, improving effi- ciency, reducing component count, and conserving board space and system cost (figure 4). with no input signal, the outputs are two low-duty-cycle pulses that are in-phase. this lowers the high-frequency energy and spectral content. in comparison, conventional class d amplifiers output a 50% duty cycle when no input signal is present. for most applications with short speaker cables, no filtering is required. efficiency efficiency of a class d amplifier is attributed to the region of operation of the output stage transistors. in a class d amplifier, the output transistors act as switches and consume negligible power. any power loss associ- ated with the class d output stage is mostly due to the i 2 r loss of the mosfet on-resistance, and quiescent current overhead. the theoretical best efficiency of a linear amplifier is 78%, however, that efficiency is only exhibited at peak output powers. under normal operating levels (typical music reproduction levels), efficiency falls below 30%, whereas the max9752/max9753/max9754 still exhibit > 80% efficiencies under the same conditions (figure 5). max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 13 frequency (mhz) amplitude (db v/m) 280 260 240 200 220 80 100 120 140 160 180 60 5 10 15 20 25 30 35 40 45 50 0 30 300 figure 3. max9752/max9753/max9754 radiated emissions with 76mm of speaker cable v in_ = 0v out_- out_+ v out_ + - v out_ - = 0v figure 4. second-generation class d output waveform with no signal 0 30 20 10 50 40 90 80 70 60 100 0 0.5 1.5 1.0 2.0 efficiency vs. output power output power (w) efficiency (%) max9752 max9753 max9754 class ab r l = 8 figure 5. max9752/max9753/max9754 class d efficiency vs. max9750/max9751/max9755 class ab efficiency
max9752/max9753/max9754 headphone amplifier 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 the dc bias from the headphones. maxim? patented directdrive architecture uses a charge pump to create an internal negative supply voltage. this allows the max9752/max9753/max9754 headphone amplifier output to be biased about gnd, almost doubling 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 (220?, typ), the charge pump requires only two small ceramic capacitors (1? typ), conserving board space, reducing cost, and improving the frequency response of the headphone 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 capac- itors 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? 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 line out to other equipment, the bias voltage on the sleeve may conflict 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 and the dc- blocking capacitor form 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 single- 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 atten- uation, but are physically larger, more expensive capacitors. figure 6 shows the relationship between the size of c out and the resulting low-frequency attenuation. note the -3db point for a 16 head- phone with a 100? 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 frequen- cies around the -3db point, the reactance of the capacitor dominates, and the voltage coefficient appears as frequency-dependent distortion. figure 7 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 frequency-dependent distortion compromises audio reproduction. directdrive improves low-frequency reproduction in portable audio equipment that emphasizes low-frequency effects such as multi- media laptops, mp3, cd, and dvd players. f rc db l out ? = 3 1 2 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 14 ______________________________________________________________________________________ 0 -15 10 100 1k 10k 100k low-frequency rolloff (r l = 16 ) -12 -6 -9 -3 frequency (hz) attenuation (db) directdrive 330 f 220 f 100 f 33 f figure 6. low-frequency attenuation of common dc-blocking capacitor values
charge pump the max9752/max9753/max9754 feature a low-noise charge pump. the 600khz 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 parasitic bond wire and trace inductance. although not typically required, additional high-frequency ripple attenuation can be achieved by increasing the size of c2 (see the functional diagrams ). 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 speaker 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 8. 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 the internal 100k pullup resistor. bias the max9752/max9753/max9754 feature an internally generated, power-supply-independent, common-mode bias voltage 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. gain selection max9752 the max9752 features externally controlled gain with four pin-selectable gain ranges. gain1 and gain2 set the maximum gain of the max9752 speaker and head- phone amplifiers (table 1). the voltage at vol varies the gain of the speaker and headphone amplifiers, pro- viding a user-adjusted volume control, see the analog volume control (vol, max9752) section. max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 15 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 7. distortion contributed by dc-blocking capacitors outr outl max9752 max9753 max9754 v dd hps r1 100k figure 8. hps configuration table 1. max9752 gain settings speaker mode gain (db) gain2 gain1 max9752a max9752b max9752c headphone mode gain (db) 0 0 9.0 15.0 6.0 0 0 1 10.5 16.5 7.5 0 1 0 12.0 18.0 9.0 3 1 1 13.5 19.5 10.5 3
max9752/max9753/max9754 table 2 shows the amplifier gain settings needed to attain maximum speaker output power from a given input voltage and load. max9753/max9754 the gain of the max9753/max9754 is set by gain. drive gain high to set the gain of the speaker ampli- fiers to 9db, and the gain of the headphone amplifiers to 0db. drive gain low to set the gain of the speaker amplifiers to 10.5db, and the gain of the headphone amplifiers to 3db (table 3). table 4 shows the amplifier input voltage needed to attain maximum speaker output power from a given gain setting and load. analog volume control (vol, max9752) the max9752 features an analog volume control that varies the speaker and headphone amplifier? gain in 31 discrete steps based upon the dc voltage applied to vol. the input range of vol is from 0 (full volume) to 0.858 x hpv dd (full mute). example step sizes are shown in table 5. control vol with either a dac or potentiome- ter as shown in figure 9. because the vol input is high impedance (typically 100m ), it can also be driven with an rc-filtered pwm signal. connect the reference of the dac or potentiometer to hpv dd . since the volume con- trol is ratiometric to hpv dd , any changes in hpv dd are negated. the gain step sizes are not constant, the step sizes at the upper extreme are 0.5db/step, 2.0db/step in the midrange, and 4.0db/step at the lower extreme. figure 10 shows the transfer function of the volume con- trol for hpv dd = 3.3v. 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 16 ______________________________________________________________________________________ table 2. max9752 speaker amplifier gain settings for maximum output power gain (db) input (v rms ) r l ( ) p out (w) max9752a 9.0 1.004 4 2.0 10.5 0.844 4 2.0 12.0 0.710 4 2.0 13.5 0.598 4 2.0 9.0 1.099 8 1.2 10.5 0.925 8 1.2 12.0 0.778 8 1.2 13.5 0.655 8 1.2 max9752b 15.0 0.503 4 2.0 16.5 0.423 4 2.0 18.0 0.356 4 2.0 19.5 0.300 4 2.0 15.0 0.551 8 1.2 16.5 0.464 8 1.2 18.0 0.390 8 1.2 19.5 0.328 8 1.2 max9752c 6.0 1.418 4 2.0 7.5 1.193 4 2.0 9.0 1.004 4 2.0 10.5 0.844 4 2.0 6.0 1.553 8 1.2 7.5 1.307 8 1.2 9.0 1.099 8 1.2 10.5 0.925 8 1.2 table 3. max9753/max9754 maximum gain settings gain speaker mode gain (db) headphone mode gain (db) 0 10.5 3 1 9.0 0 table 4. max9753/max9754 input voltage and gain settings for maximum output power gain (db) input (v rms ) r l ( ) p out (w) 10.5 0.844 4 2.0 9.0 1.004 4 2.0 10.5 0.925 8 1.2 9.0 1.099 8 1.2
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 17 table 5a. max9752a volume levels v vol (v) speaker mode gain (db) headphone mode gain (db) v min * v max * fraction of 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 0.4900 0.074 9 10.5 12 13.5 0 3 0.4900 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 0.7220 0.207 6 8 10.5 12 -3 1.5 0.7220 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 2.2690 0.675 -34 -30 -24 -18 -43 -33 2.2690 2.3463 0.699 -38 -32 -26 -20 -47 -35 2.3463 2.4237 0.722 -42 -34 -28 -22 -51 -37 2.4237 2.5010 0.746 -46 -38 -30 -24 -55 -39 2.5010 2.5783 0.769 -50 -42 -32 -26 -59 -41 2.5783 2.6557 0.793 -54 -46 -34 -28 -63 -43 2.6557 2.7330 0.816 -58 -50 -38 -30 -67 -47 2.7330 2.8104 0.839 -62 -54 -42 -32 -71 -51 2.8104 3.3000 0.858 mute mute mute mute mute mute * based on hpv dd = 3.3v. x = don? care.
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 18 ______________________________________________________________________________________ table 5b. max9752b volume levels v vol (v) speaker mode gain (db) headphone mode gain (db) v min * v max * fraction of 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 0.4900 0.074 15 16.5 18 19.5 0 3 0.4900 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 0.7220 0.207 12 14 16.5 18 -3 1.5 0.7220 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 2.2690 0.675 -28 -24 -18 -12 -43 -33 2.2690 2.3463 0.699 -32 -26 -20 -14 -47 -35 2.3463 2.4237 0.722 -36 -28 -22 -16 -51 -37 2.4237 2.5010 0.746 -40 -32 -24 -18 -55 -39 2.5010 2.5783 0.769 -44 -36 -26 -20 -59 -41 2.5783 2.6557 0.793 -48 -40 -28 -22 -63 -43 2.6557 2.7330 0.816 -52 -44 -32 -24 -67 -47 2.7330 2.8104 0.839 -56 -48 -36 -26 -71 -51 2.8104 3.3000 0.858 mute mute mute mute mute mute * based on hpv dd = 3.3v. x = don? care.
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 19 table 5c. max9752c volume levels v vol (v) speaker mode gain (db) headphone mode gain (db) v min * v max * fraction of 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 0.4900 0.074 6 7.5 9 10.5 0 3 0.4900 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 0.7220 0.207 3 5 7.5 9 -3 1.5 0.7220 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 2.2690 0.675 -37 -3 -27 -21 -43 -33 2.2690 2.3463 0.699 -41 -35 -29 -23 -47 -35 2.3463 2.4237 0.722 -45 -37 -31 -25 -51 -37 2.4237 2.5010 0.746 -48 -41 -33 -27 -55 -39 2.5010 2.5783 0.769 -53 -45 -35 -29 -59 -41 2.5783 2.6557 0.793 -57 -49 -37 -31 -63 -43 2.6557 2.7330 0.816 -61 -53 -41 -33 -67 -47 2.7330 2.8104 0.839 -65 -57 -45 -35 -71 -51 2.8104 3.3000 0.858 mute mute mute mute mute mute * based on hpv dd = 3.3v. x = don? care.
max9752/max9753/max9754 beep input (max9752) the max9752 features an audible alert beep input (beep). beep serves as the alert signal detector and the alert input to the amplifiers. ac-couple the alert output of a ? to beep. the max9752 monitors the signal at beep. when a signal exceeding 400mv p-p with a fre- quency greater than 300hz is detected at beep, the max9752 connects the signal to the amplifiers after eight periods of the input signal. in speaker mode, the alert signal appears at both speaker outputs, mixed with any audio that may be present. in headphone mode, the alert signal appears at the headphone outputs, mixed with any audio that may be present. a signal with less than eight input periods is ignored. multiple beep signals can be summed as shown in figure 11. adding external resistors in series with beep increase the minimum volt- age amplitude sensitivity. input mux (max9753) the max9753 features a 2:1 input multiplexer on each amplifier, allowing input selection between two stereo sources. the logic input in1/ 2 controls both multiplexers. a logic-high selects input in_1 and a logic-low selects input in_2. the unselected inputs are high impedance. shutdown the max9752/max9753/max9754 feature an 8a, low- power shutdown mode reducing quiescent current con- sumption and extending battery life. driving shdn low disables the drive amplifiers, bias circuitry, charge pump, and sets the headphone amplifier output imped- ance to 1k , and drives bias to gnd. connect shdn to v dd for normal operation. 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 20 ______________________________________________________________________________________ max9752 v ref dac hpv dd vol figure 9. max9752 volume-control circuit -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 max9752b volume-control transfer function v vol (v) gain (db) audio taper pot gain1 = gain2 = 0 speaker mode headphone mode figure 10b. max9752b volume-control transfer functions -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 max9752a volume-control transfer function v vol (v) gain (db) audio taper pot gain1 = gain2 = 0 speaker mode headphone mode figure 10a. max9752a volume-control transfer functions -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 max9752c volume-control transfer function v vol (v) gain (db) audio taper pot gain1 = gain2 = 0 speaker mode headphone mode figure 10c. max9752c volume-control transfer functions
click-and-pop suppression the max9752/max9753/max9754 feature maxim? comprehensive, industry-leading click-and-pop sup- pression eliminating audible transients at startup. the turn-on and turn-off response waveforms in the typical operating characteristics show that there are minimal spectral components in the audible range at the output upon startup and shutdown. applications information compatibility with max9750/max9751/max9755 the max9752/max9753/max9754 provide a high-effi- ciency, class d speaker driver with very low emi (see the typical operating characteristics ). if a class ab output is desired, the max9750/max9751/max9755 can be substituted. the max9750, max9751, and max9755 are pin-for-pin compatible with the max9752, max9753, and max9754, respectively. filterless operation the max9752/max9753/max9754 do not require an output filter in most applications. the devices rely on the inherent inductance of the speaker coil and the nat- ural filtering of both the speaker and the human ear to recover the audio component of the square-wave out- put. eliminating the output filter results in a smaller, less costly, more efficient solution. voice coil movement due to the square-wave frequency is very small because the switching frequency is well beyond the bandwidth of speakers. although this move- ment is small, a speaker not designed to handle the additional power can be damaged. use a speaker with a series inductance > 30? for optimum results. typical 8 speakers exhibit series inductances in the 30? to 100? range. highest efficiency is achieved with speak- er inductances > 60?. power dissipation and heat sinking because the max9752/max9753/max9754 have high- efficiency, class d speaker drivers, the intrinsic pack- age power dissipation capabilities are sufficient for cooling. no special heatsinking is needed in normal operating conditions. headphone amplifier output power the headphone amplifiers have been specified for the worst-case scenario?hen both inputs are in-phase. under this condition, the drivers simultaneously draw cur- rent 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 magnitude and phase, subsequently leading to an increase in the maximum attainable output power. figure 12 shows the two cases for in- and out-of-phase. in reality, the available power lies between these extremes. max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 21 max9752 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 (0.4v p-p threshold) frequency detector (300hz threshold) speaker/headphone amplifier inputs v out(beep) figure 11. max9752 beep summing circuit output power (mw) thd+n (%) 125 100 75 50 25 0.01 0.1 1 10 100 1000 0.001 0150 v dd = 5v r l = 16 a v = 3db outputs in-phase outputs 180 out-of-phase figure 12. thd+n vs. p out with headphone output signals in- and out-of-phase
max9752/max9753/max9754 power supplies the max9752/max9753/max9754 have different sup- plies for each portion of the device allowing for the opti- mum combination of headroom, power dissipation, and noise immunity. the speaker amplifiers are powered 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 negative supply input for the headphone amplifiers. connect v ss to cpv ss . the charge pump is powered by cpv dd , which ranges from 3v to 5.5v. cpv dd should be the same potential as hpv dd . the charge pump inverts the voltage at cpv dd , and the resulting voltage appears at cpv ss . the remain- der 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 functional diagrams ). 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? internal input resistance value given in the electrical characteristics table. choose c in so f -3db is well below the lowest frequency of interest. setting f -3db too high affects the amplifier? low-frequency response. use capacitors with low-voltage coefficient dielectrics, such as tantalum or aluminum electrolytic. capacitors with high-voltage coefficients, such as ceram- ics, may result in increased distortion at low frequencies. optional output filtering in most applications, the low-emi, class d outputs do not require output filters. the device passes fcc emissions standards with 76mm of unshielded speaker cables. output filtering can be used if lower emi is desired. use a ferrite bead filter when radiated frequencies above 10mhz are of concern. use an lc filter when radiated fre- quencies below 10mhz are of concern, or when long leads (> 76mm) connect the amplifier to the speaker. 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 1? capacitor to gnd. charge-pump capacitor selection use capacitors with less than 100m of equivalent series resistance (esr). low-esr ceramic capacitors minimize the output impedance of the charge pump. capacitors with an x7r dielectric provide the best per- formance over the extended temperature range. flying capacitor (c1) the value of the flying capacitor (c1) affects the load regulation and output resistance of the charge pump. choosing c1 too small degrades the ability to provide sufficient current drive, which leads to a loss of output voltage. increasing the value of c1 improves load regu- lation and reduces the charge-pump output resistance. see the output power vs. charge-pump capacitance and load resistance graph in the typical operating characteristics . above 2.2?, the on-resistance of the switches and the esr of c1 and c2 dominate. the rec- ommended range of capacitors is from 0.33? to 3.3?. output capacitor (c2) the output capacitor value and esr directly affect the ripple at cpv ss . increasing the value of c2 reduces output ripple. 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 . c2 must be greater than or equal to c1. the recommended range of capacitors is from 0.33? to 3.3?. cpv dd bypass capacitor the cpv dd bypass capacitor (c3) lowers the output impedance of the power supply and reduces the impact of the charge-pump switching transients on the headphone driver outputs. bypass cpv dd with c3, the same value as c1, and place it physically close to cpv dd and pgnd. 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. large traces also aid in mov- ing heat away from the package. proper grounding improves audio performance, 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, pgnd, and all traces that carry switching transients away from gnd and the traces and components in the audio signal path. f rc db in in ? = 3 1 2 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 22 ______________________________________________________________________________________
connect all components associated with the charge pump (c2 and c3) to cpgnd. connect v ss and cpv ss together at c2. place the charge-pump capacitors (c1, c2, and c3) as close to the device as possible. bypass hpv dd with 1? to gnd. bypass pv dd with a 0.1? capacitor and a 100? capacitor to pgnd. place the bypass capacitors as close to the device as possible. use large, low-resistance output traces. current drawn from the outputs increases as load impedance decreases. high-output-trace resistance decreases the power delivered to the load. for example, when com- pared to a 0 trace, a 100m trace reduces the power delivered to a 4 load from 2.1w to 2.0w. large out- put, supply, and gnd traces allow more heat to move from the max9752/max9753/max9754 to the air, reducing the thermal impedance of the system. the max9752/max9753/max9754 thin qfn packages feature exposed pads on their undersides. connect the exposed pad to gnd with a large copper pad and mul- tiple vias to the ground plane. measuring class d outputs with an analog analyzer filterless class d amplifiers use the loudspeaker? coil inductance to filter out switching energy. additionally, the loudspeaker does not respond to the switching frequen- cy of class d amplifiers, nor could human ears hear these frequencies. however, audio analyzers and oscil- loscopes can detect these signals. on an oscilloscope, the switching components obscure the audio signal. on an audio analyzer they overload the input signal, degrad- ing the measurement from the true audio performance of the amplifier. a simple rc filter can be used (figure 13) to aid in evaluation of class d amplifiers in the lab. this circuit provides a single-pole response at 34khz, with a minimal insertion loss. more complex designs such as l- c filters can provide more performance, but must be veri- fied to ensure they do not add their own distortion signature to the amplifier? output. max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 23 47nf 47nf r l 100 100 class d modulator and h-bridge audio analyzer out_+ out_- in+ in- figure 13. connecting a class d output to an analog analyzer
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 24 ______________________________________________________________________________________ max9752 functional diagram 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 21 28 24 23 2 22 7 8 10 9 11 12 26 3, 19 1 1 f 3v to 5.5v 6, 16 4 25 5 18 17 15 20 14 13 hpoutl hpoutr max9752 0.1 f 1 f 4.5v to 5.5v gain/ volume control class d amplifier right-channel audio input outr+ outr- charge pump gain/ volume control headphone detection beep detection shutdown control gain/ volume control class d amplifier left-channel audio input outl+ pv dd 4.5v to 5.5v v dd outl- v dd v dd v dd shdn 47k
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 25 max9753 functional diagram 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 21 28 24 23 2 22 7 8 10 9 11 12 26 3, 19 1 1 f 3v to 5.5v 6, 16 4 25 5 18 17 15 20 14 13 hpoutl hpoutr max9753 0.1 f 1 f 4.5v to 5.5v class d 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 class d 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- logic pins configured for: gain = 1, 9db speaker gain/0db headphone gain. in1/2 = 1, selected input line 1. shdn = 1, part active.
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 26 ______________________________________________________________________________________ max9754 functional diagram 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 28 24 2 22 7 8 10 9 11 12 23, 26 3, 19 1 f 3v to 5.5v 6, 16 4 25 5 18 17 15 20 14 13 hpoutl hpoutr max9754 0.1 f 1 f 4.5v to 5.5v class d amplifier inr c in 1 f right-channel audio input outr+ outr- charge pump gain control headphone detection shutdown control class d amplifier c in 1 f inl left-channel audio input outl+ pv dd 4.5v to 5.5v v dd outl- logic pins configured for: gain = 1, 9db speaker gain/0db headphone gain. shdn = 1, part active.
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers ______________________________________________________________________________________ 27 pin configurations 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 max9752 thin qfn top view 28 27 26 25 24 23 22 inr n.c. gnd v dd gain gnd 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. max9754 thin qfn shdn 28 27 26 25 24 23 22 inr2 inr1 gnd v dd gain 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 max9753 thin qfn shdn in1/2 chip information max9752 transistor count: 12,263 max9753/max9754 transistor count: 12,137 process: bicmos
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with directdrive headphone amplifiers 28 ______________________________________________________________________________________ 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
max9752/max9753/max9754 2.2w, low-emi, stereo, class d power amplifiers with 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 ____________________ 29 2005 maxim integrated products is a registered trademark of maxim integrated products, inc. 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 .)

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