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general description the max9702 combines a highly efficient class d speaker amplifier with a high-linearity class ab head- phone amplifier. this ensures maximum battery life in speaker mode and maximum performance in head- phone mode. the max9702 delivers up to 1.8w per channel into an 8 ? load from a 5v power supply. maxim? 2nd-generation, spread-spectrum modulation scheme renders the traditional class d output filter unnecessary. the max9702 speaker amplifier offers two modulation schemes: a fixed-frequency (ffm) mode and a spread- spectrum (ssm) mode that reduces emi-radiated emis- sions. the max9702 speaker amplifier features a fully differential architecture, full-bridged (btl) output, and comprehensive click-and-pop suppression. the max9702 speaker amplifier features high 75db psrr, low 0.07% thd+n, and snr in excess of 97db. short- circuit and thermal-overload protection prevent the device from being damaged during a fault condition. the headphone amplifier uses maxim? patented directdrive tm architecture that produces a ground-ref- erenced output from a single supply, eliminating the need for large dc-blocking capacitors, saving cost, board space, and component height. a high 80db psrr and low 0.02% thd+n ensures clean, low-distor- tion amplification of the audio signal. an i 2 c interface sets the speaker and headphone gain, mono, stereo, and mute functions. the max9702 is available in 28-pin thin qfn-ep (5mm x 5mm x 0.8mm) and 28-pin tssop packages. the max9702 is specified over the extended -40? to +85? temperature range. applications cellular phones notebook pcs pdas handheld gaming consoles features ? patented spread-spectrum modulation reduces emi emissions ? programmable mono, stereo, mute, and mix functions ? 1.1w stereo output (8 ? , v dd = 5v) ? 48mw headphone output (32 ? , v dd = 3.3v) ? 95% efficiency (r l = 8 ? , p o = 1.1w) ? high 73db psrr (f = 217hz) ? i 2 c programmable gain up to +21db ? integrated click-and-pop suppression ? low-power shutdown mode (0.1a) ? short-circuit and thermal-overload protection ? 8 kv (hbm) esd-protected headphone driver outputs max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ________________________________________________________________ maxim integrated products 1 part pin?ackage i 2 c slave address pkg code MAX9702EUI+ 28 tssop 1001100 u28-1 max9702beui+ 28 tssop 1001110 u28-1 max9702eti+ 28 tqfn-ep* 1001100 t2855-6 max9702beti+ 28 tqfn-ep* 1001110 t2855-6 ordering information 19-3608; rev 0; 6/05 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. note: all devices specified for -40? to +85? operating tem- perature range. * ep = exposed paddle. + denotes lead-free package. pin configurations appear at end of data sheet. * purchase of i 2 c components from maxim integrated products, inc. or one of its sublicensed associated companies, conveys a license under the philips i 2 c patent rights to use these com- ponents in an i 2 c system, provided that the system conforms to the i 2 c standard specification as defined by philips. simplified block diagram max9702 right modulator and h-bridge inr inm inl shdn scl sda i 2 c control input mux gain control sync_out sync oscillator left modulator and h-bridge
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = 3.3v) (v dd = pv dd = cpv dd = shdn = 3.3v, gnd = pgnd = cpgnd = 0v, sync = v dd (ssm), speaker gain = +12db, headphone gain = +1db. speaker load r l connected between out+ and out-, unless otherwise noted, r l = . headphone load r lh connected between hpr/hpl to gnd. c bias = 1? to gnd, 1? capacitor between c1p and c1n, c vss = 1?. t a = t min to t max , unless oth- erwise 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 to gnd ...........................................................................+6v pv dd to pgnd .......................................................................+6v cpv dd to cpgnd..................................................................+6v cpv ss to v ss ......................................................................?.3v cpv ss to cpgnd .....................................................-6v to +0.3v v ss to cpgnd..........................................................-6v to +0.3v c1n .......................................(cpv ss - 0.3v) to (cpgnd + 0.3v) c1p.......................................(cpgnd - 0.3v) to (cpv dd + 0.3v) hp_ to gnd ............................(cpv ss - 0.3v) to (cpv dd + 0.3v) gnd to pgnd and cpgnd................................................?.3v v dd to pv dd and cpv dd ....................................................?.3v sda, scl to gnd.....................................................-0.3v to +6v all other pins to gnd.................................-0.3v to (v dd + 0.3v) continuous current in/out of pv dd , pgnd, cpv dd , cpgnd, out_ ..............................................?00ma continuous current in/out of hp_ ..................................?20ma continuous input current cpv ss ....................................+260ma continuous input current (all other pins) .........................?0ma duration of out_ short circuit to gnd or pv dd ......... continuous duration of short circuit between out__ ..................continuous duration of hp_ short circuit to gnd or pv dd ..................................................................continuous continuous power dissipation (t a = +70?) 28-pin thin qfn (derate 21.3mw/? above +70?)....1702mw 28-pin tssop (derate 12.8mw/? above +70?) .....1026mw junction temperature ......................................................+150? operating temperature range ...........................-40 o c to +85? storage temperature range .............................-65 o c to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units general supply voltage range v dd inferred from psrr test 2.5 5.5 v hps = gnd, speaker mode 10 15 ma quiescent current i dd hps = v dd , headphone mode 7 11 ma hard shutdown, shdn = gnd 0.1 10 shutdown current i shdn soft shutdown (see i 2 c section) 22 30 ? stereo left and right 16.5 24 31.5 input resistance r in mono channel 8.4 12 15.6 k ? debounced delay t debounce delay from hps transition to headphone/speaker turn-on 65 ms hps = gnd (sp mode) 85 turn-on time t on time from shdn transition to full operation hps = v dd (hp mode) 85 ms turn-off time t off 0ms input bias voltage v bias 1.125 1.25 1.375 v speaker amplifiers (hps = gnd) t a = +25? ? ?0 output offset voltage v os t min to t max ?0 mv v dd = 2.5v to 5.5v 54 75 f ripple = 217hz 75 power-supply rejection ratio (note 3) psrr 100mv p-p ripple, v in = 0v, t a = +25? f ripple = 20khz 55 db
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier _______________________________________________________________________________________ 3 electrical characteristics (v dd = 3.3v) (continued) (v dd = pv dd = cpv dd = shdn = 3.3v, gnd = pgnd = cpgnd = 0v, sync = v dd (ssm), speaker gain = +12db, headphone gain = +1db. speaker load r l connected between out+ and out-, unless otherwise noted, r l = . headphone load r lh connected between hpr/hpl to gnd. c bias = 1? to gnd, 1? capacitor between c1p and c1n, c vss = 1?. t a = t min to t max , unless oth- erwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units r l = 8 ? 470 output power p out thd+n = 1%, t a = +25?, f = 1khz, v dd = 3.3v r l = 4 ? 700 mw r l = 8 ? (p out = 400mw), f = 1khz 0.07 total harmonic distortion plus noise thd+n r l = 4 ? (p out = 600mw), f = 1khz 0.13 % ffm 86.5 bw = 22hz to 22khz ssm 87.5 ffm 91.5 signal-to-noise ratio snr v out = 2v rms , r l = 8 ? p out = 2 x 500mw, f in = 1khz, r l = 8 ? , l = 68? 94 % b2 = 0 b1 = 0 b0 = 0 0 b2 = 0 b1 = 0 b0 = 1 +3 b2 = 0 b1 = 1 b0 = 0 +6 b2 = 0 b1 = 1 b0 = 1 +9 b2 = 1 b1 = 0 b0 = 0 +12 b2 = 1 b1 = 0 b0 = 1 +15 b2 = 1 b1 = 1 b0 = 0 +18 gain (see i 2 c section) a v b2 = 1 b1 = 1 b0 = 1 +21 db channel-to-channel gain tracking ?.2 % crosstalk l to r, r to l, f = 10khz, r l = 8 ? , p out = 300mw 65 db
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 4 _______________________________________________________________________________________ electrical characteristics (v dd = 3.3v) (continued) (v dd = pv dd = cpv dd = shdn = 3.3v, gnd = pgnd = cpgnd = 0v, sync = v dd (ssm), speaker gain = +12db, headphone gain = +1db. speaker load r l connected between out+ and out-, unless otherwise noted, r l = . headphone load r lh connected between hpr/hpl to gnd. c bias = 1? to gnd, 1? capacitor between c1p and c1n, c vss = 1?. t a = t min to t max , unless oth- erwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units headphone amplifiers (hps = v dd ) t a = +25? ?.8 ? output offset voltage v os t min to t max ? mv v dd = 2.5v to 5.5v 66 75 f ripple = 217hz 73 power-supply rejection ratio (note 4) psrr 100mv p-p ripple, v in = 0v, t a = +25? f ripple = 20khz 53 db r l = 32 ? 48 output power p out thd+n = 1%, v dd = 3.3v, t a = +25? r l = 16 ? 47 mw r l = 16 ? (p out = 40mw, f = 1khz) 0.03 total harmonic distortion plus noise thd+n r l = 32 ? (p out = 32mw, f = 1khz) 0.015 % bw = 22hz to 22khz 95.5 signal-to-noise ratio snr v out = 1v rms , r l = 32 ? a-weighted 97.9 db charge-pump frequency f cp f osc /2 khz into shutdown 65 click-and-pop level k cp peak voltage, 32 samples/second, a-weighted (note 3) out of shutdown 85 db slew rate sr ?v output step 0.3 v/? b4 = 0 b3 = 0 -2 b4 = 0 b3 = 1 +1 b4 = 1 b3 = 0 +4 gain (see i 2 c section) a v b4 = 1 b3 = 1 +7 db channel-to-channel gain tracking ?.2 % capacitance drive c l no sustained oscillations 300 pf crosstalk l to r, r to l, f = 10khz, r l = 16 ? , p out = 10mw 70 db hp_ resistance to gnd in speaker mode 1 k ? digital inputs ( shdn , sync, sda, scl, hps) input voltage high, shdn , sync, hps v inh 2v input voltage high, scl v inh 0.7 x v dd v input voltage low, shdn , sync, hps v inl 0.8 v
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier _______________________________________________________________________________________ 5 electrical characteristics (v dd = 3.3v) (continued) (v dd = pv dd = cpv dd = shdn = 3.3v, gnd = pgnd = cpgnd = 0v, sync = v dd (ssm), speaker gain = +12db, headphone gain = +1db. speaker load r l connected between out+ and out-, unless otherwise noted, r l = . headphone load r lh connected between hpr/hpl to gnd. c bias = 1? to gnd, 1? capacitor between c1p and c1n, c vss = 1?. t a = t min to t max , unless oth- erwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units input voltage low, sda, scl v inl 0.3 x v dd v input hysteresis, sda, scl v hys 0.05 x v dd v input capacitance sda, scl c in 10 pf input leakage current, shdn , scl i in ? ? input leakage current, hps i in ?0 ? sync input current in play mode 25 ? hps pullup resistance 600 k ? digital outputs (sync_out) output voltage high v oh i oh = 3ma 2.4 v output voltage low v ol i ol = 3ma 0.4 v output fall time, sda t f 300 ns electrical characteristics (v dd = 5v) (v dd = pv dd = cpv dd = shdn = 5v, gnd = pgnd = cpgnd = 0v, sync = v dd (ssm), speaker gain = +12db, headphone gain = +1db. speaker load r l connected between out+ and out-, unless otherwise noted, r l = . headphone load r lh connected between hpr/hpl to gnd. c bias = 1? to gnd, 1? capacitor between c1p and c1n, c vss = 1?. t a = t min to t max , unless oth- erwise noted. typical values are at t a = +25?.) (notes 1, 2) parameter symbol conditions min typ max units general hps = gnd, speaker mode 14 quiescent current i dd hps = v dd , headphone mode 8 ma hard shutdown, shdn = gnd 0.2 shutdown current i shdn soft shutdown (see i 2 c section )25 ? speaker amplifiers (hps = gnd) f ripple = 217hz 73 power-supply rejection ratio (note 3) psrr 100mv p-p ripple, v in = 0v, t a = +25? f ripple = 20khz 50 db r l = 8 ? 1100 output power p out thd+n = 1%, t a = +25?, f = 1khz v dd = 5v r l = 4 ?
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 6 _______________________________________________________________________________________ electrical characteristics (v dd = 5v) (continued) (v dd = pv dd = cpv dd = shdn = 5v, gnd = pgnd = cpgnd = 0v, sync = v dd (ssm), speaker gain = +12db, headphone gain = +1db. speaker load r l connected between out+ and out-, unless otherwise noted, r l = . headphone load r lh connected between hpr/hpl to gnd. c bias = 1? to gnd, 1? capacitor between c1p and c1n, c vss = 1?. t a = t min to t max , unless oth- erwise noted. typical values are at t a = +25 o c.) (notes 1, 2) parameter symbol conditions min typ max units r l = 8 ? (p out = 900mw), f = 1khz 0.08 total harmonic distortion plus noise thd+n r l = 4 ? (p out = 1500mw), f = 1khz 0.18 % ffm 88 bw = 22hz to 22khz ssm 87 ffm 91 signal-to-noise ratio snr v out = 2v rms , r l = 8 ? ? , l = 68? 95 % channel-to-channel gain tracking ?.2 % crosstalk l to r, r to l, f = 10khz, r l = 8 ? , p out = 300mw 65 db headphone amplifiers (hps = v dd ) f ripple = 217hz 78 power-supply rejection ratio (note 4) psrr 100mv p-p ripple, v in = 0v, t a = +25? f ripple = 20khz 53 db output power p out thd+n = 1%, t a = +25?, r l = 32 ? 45 mw total harmonic distortion plus noise thd+n r l = 32 ? (p out = 32mw, f = 1khz) 0.03 % bw = 22hz to 22khz 94.7 signal-to-noise ratio snr v out = 1v rms , r l = 32 ? a-weighted 97.4 db into shutdown 67 click-and-pop level k cp peak voltage, 32 samples/second, a-weighted (notes 3, 4) out of shutdown 83 db channel-to-channel gain tracking ?.2 % crosstalk l to r, r to l, f = 10khz, r l = 32 ? , p out = 10mw 70 db
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier _______________________________________________________________________________________ 7 i 2 c timing characteristics (v dd = pv dd = cpv dd = shdn = 3.3v, gnd = pgnd = cpgnd = 0v, sync = v dd (ssm), speaker gain = +12db, headphone gain = +1db. speaker load r l connected between out+ and out-, unless otherwise noted. r l = . headphone load r lh connected between hpr/hpl and gnd. c bias = 1? to gnd, 1? capacitor between c1p and c1n, c vss = 1?. t a = t min to t max , unless otherwise noted. typical values are at t a = +25 o c.) (figure 9) parameter symbol conditions min typ max units serial clock f scl 400 khz bus free time between a stop and a start condition t buf 1.3 ? hold time (repeated) start condition t hd , sta 0.6 ? repeated start condition setup time t su , sta 0.6 ? stop condition setup time t su , sto 0.6 ? data hold time t hd , dat 0 0.9 ? data setup time t su , dat 100 ns scl clock low period t low 1.3 ? scl clock high period t high 0.6 ? rise time of sda and scl, receiving t r (note 5) 20 + 0.1cb 300 ns fall time of sda and scl, receiving t f (note 5) 20 + 0.1cb 300 ns fall time of sda, transmitting t f (note 5) 20 + 0.1cb 250 ns pulse width of spike suppressed t sp 050ns capacitive load for each bus line c b 400 pf note 1: all devices are 100% production tested at +25?. all temperature limits are guaranteed by design. note 2: speaker mode testing performed with a resistive load in series with an inductor to simulate an actual speaker load. for r l = 4 ? , l = 34?, r l = 8 ? , l = 68?. note 3: amplifier inputs (stereo/mono) connected to gnd through c in . note 4: speaker mode testing performed with an 8 ? resistive load in series with a 68? inductive load connected across btl out- put. headphone mode testing performed with 32 ? resistive load connected to gnd. mode transitions are controlled by shdn . 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)]. units are expressed in db. note 5: c b = total capacitance of one bus line in pf.
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 8 _______________________________________________________________________________________ t ypical operating characteristics (v dd = pv dd = shdn = 3.3v, gnd = pgnd = 0v, sync = v dd (ssm), speaker gain = 12db.) total harmonic distortion plus noise vs. frequency (speaker mode) max9702 toc01 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k output power = 1.6w v dd = 5v r l = 4 ? output power = 200mw total harmonic distortion plus noise vs. frequency (speaker mode) max9702 toc02 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k output power = 800mw v dd = 5v r l = 8 ? output power = 200mw total harmonic distortion plus noise vs. frequency (speaker mode) max9702 toc03 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k output power = 400mw v cc = 3.3v r l = 4 ? output power = 100mw total harmonic distortion plus noise vs. frequency (speaker mode) max9702 toc04 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k output power = 400mw v cc = 3.3v r l = 8 ? output power = 100mw total harmonic distortion plus noise vs. frequency (speaker mode) max9702 toc05 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k ffm ssm v dd = 5v r l = 8 ? p out = 800mw total harmonic distortion plus noise vs. output power (speaker mode) max9702 toc06 output power (w) thd+n (%) 2.0 1.5 1.0 0.5 0.1 1 10 100 0.01 0 2.5 v dd = 5v r l = 4 ? f in = 20hz f in = 1khz f in = 10khz total harmonic distortion plus noise vs. output power (speaker mode) max9702 toc07 output power (mw) thd+n (%) 1200 900 600 300 0.1 1 10 100 0.01 0150 0 v dd = 5v r l = 8 ? f in = 20hz f in = 1khz f in = 10khz total harmonic distortion plus noise vs. output power (speaker mode) max9702 toc08 output power (mw) thd+n (%) 800 600 400 200 0.1 1 10 100 0.01 0100 0 v dd = 3.3v r l = 4 ? f in = 1khz f in = 20hz f in = 10khz total harmonic distortion plus noise vs. output power (speaker mode) max9702 toc09 output power (mw) thd+n (%) 0.1 1 10 100 0.01 600 500 400 300 200 100 0 700 v dd = 3.3v r l = 8 ? f in = 10khz f in = 20hz f in = 1khz
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier _______________________________________________________________________________________ 9 total harmonic distortion plus noise vs. output power (speaker mode) max9702 toc10 output power (mw) thd+n (%) 1200 900 600 300 0 1500 v dd = 5v r l = 8 ? f in = 1khz ssm 0.01 0.1 1 10 100 0.001 ffm efficiency vs. output power (speaker mode) max9702 toc11 output power (w) efficiency (%) 2.5 2.0 1.5 1.0 0.5 10 20 30 40 50 60 70 80 90 100 0 03.0 v dd = 5v f in = 1khz p out = p outl + p outr r l = 8 ? r l = 4 ? efficiency vs. output power (speaker mode) max9702 toc12 output power (w) efficiency (%) 0.8 0.6 0.4 0.2 10 20 30 40 50 60 70 80 90 100 0 01.0 v dd = 3.3v f in = 1khz p out = p outl + p outr r l = 8 ? r l = 4 ? output power vs. supply voltage max9702 toc13 supply voltage (v) output power (mw) 5.0 4.5 4.0 3.5 3.0 500 1000 1500 2000 2500 3000 0 2.5 5.5 thd+n = 1% r l = 4 ? f in = 1khz thd+n = 10% output power vs. supply voltage max9702 toc14 supply voltage (v) output power (mw) 5.0 4.5 4.0 3.5 3.0 500 1000 1500 2000 0 2.5 5.5 thd+n = 1% r l = 8 ? f in = 1khz thd+n = 10% output power vs. load resistance max9702 toc15 load resistance ( ? ) output power (w) 10 0.5 1.0 1.5 2.0 2.5 0 1 100 thd+n = 10% v dd = 5v f = 1khz thd+n = 1% output power vs. load resistance max9702 toc16 load resistance ( ? ) output power (mw) 10 200 400 600 800 1000 0 1 100 thd+n = 1% thd+n = 10% v dd = 3.3v f = 1khz power-supply rejection ratio vs. frequency (speaker mode) max9702 toc17 frequency (hz) psrr (db) 10k 1k 100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 10 100k v ripple = 100mv p-p r l = 8 ? v dd = 3.3v v dd = 5v crosstalk vs. frequency (speaker mode) max9702 toc18 frequency (hz) crosstalk (db) 10k 1k 100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 10 100k v ripple = 100mv p-p v dd = 3.3v, 5v r l = 8 ? left to right right to left t ypical operating characteristics (continued) (v dd = pv dd = shdn = 3.3v, gnd = pgnd = 0v, sync = v dd (ssm), speaker gain = 12db.)
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 10 ______________________________________________________________________________________ t ypical operating characteristics (continued) (v dd = pv dd = shdn = 3.3v, gnd = pgnd = 0v, sync = v dd (ssm), speaker gain = 12db.) crosstalk vs. amplitude (speaker mode) max9702 toc19 amplitude (db) crosstalk (db) -10 -20 -30 -40 -50 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 -60 0 right to left r l = 8 ? f = 1khz left to right output frequency spectrum (speaker mode) max9702 toc20 frequency (khz) output magnitude (dbv) 15 10 5 -120 -100 -80 -60 -40 -20 0 -140 020 ffm mode v out = -60dbv f = 1khz r l = 8 ? unweighted output frequency spectrum (speaker mode) max9702 toc21 frequency (khz) output magnitude (dbv) 15 10 5 -120 -100 -80 -60 -40 -20 0 -140 020 ffm mode v out = -60dbv f = 1khz r l = 8 ? a-weighted output frequency spectrum (speaker mode) max9702 toc22 frequency (khz) output magnitude (dbv) 15 10 5 -120 -100 -80 -60 -40 -20 0 -140 020 ssm mode v out = -60dbv f = 1khz r l = 8 ? unweighted output frequency spectrum (speaker mode) max9702 toc23 frequency (khz) output magnitude (dbv) 15 10 5 -120 -100 -80 -60 -40 -20 0 -140 020 ssm mode v out = -60dbv f = 1khz r l = 8 ? a-weighted wideband output spectrum (ffm mode, speaker mode) max9702 toc24 frequency (mhz) output amplitude (dbv) -80 -70 -60 -50 -40 -30 -20 -10 0 10 -90 rbw = 10khz input ac grounded 100 10 11000 wideband output spectrum (ssm mode, speaker mode) max9702 toc25 frequency (mhz) output amplitude (dbv) -80 -70 -60 -50 -40 -30 -20 -10 0 10 -90 rbw = 10khz input ac grounded 100 10 11000 turn-on/turn-off response (speaker mode) max9702 toc26 20ms/div shdn max9702 output f = 1khz r l = 8 ? supply current vs. supply voltage (speaker mode) max9702 toc27 supply voltage (v) supply current (ma) 5.0 4.5 4.0 3.5 3.0 8 11 14 17 20 5 2.5 5.5 ffm ssm
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 11 shutdown current vs. supply voltage (speaker mode) max9702 toc28 supply voltage (v) shutdown current ( a) 5.0 4.5 4.0 3.5 3.0 0.05 0.10 0.15 0.20 0 2.5 5.5 total harmonic distortion plus noise vs. frequency (headphone mode) max9702 toc29 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 10 0.001 10 100k output power = 10mw v dd = 5v r l = 32 ? output power = 30mw total harmonic distortion plus noise vs. frequency (headphone mode) max9702 toc30 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 10 0.001 10 100k output power = 15mw output power = 40mw v dd = 3.3v r l = 16 ? total harmonic distortion plus noise vs. frequency (headphone mode) max9702 toc31 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 10 0.001 10 100k output power = 10mw output power = 30mw v dd = 3.3v r l = 32 ? total harmonic distortion plus noise vs. output power (headphone mode) max9702 toc32 output power (mw) thd+n (%) 50 40 30 20 10 0.01 0.1 1 10 100 0.001 060 v dd = 5v r l = 32 ? f in = 1khz f in = 10khz f in = 20hz total harmonic distortion plus noise vs. output power (headphone mode) max9702 toc33 output power (mw) thd+n (%) 50 40 30 20 10 0.01 0.1 1 10 100 0.001 060 v dd = 3.3v r l = 16 ? f in = 1khz f in = 10khz f in = 20hz t ypical operating characteristics (continued) (v dd = pv dd = shdn = 3.3v, gnd = pgnd = 0v, sync = v dd (ssm), speaker gain = 12db.) total harmonic distortion plus noise vs. output power (headphone mode) max9702 toc34 output power (mw) thd+n (%) 50 40 30 20 10 0.01 0.1 1 10 100 0.001 060 v dd = 3.3v r l = 32 ? f in = 1khz f in = 20hz f in = 10khz power dissipation vs. output power (headphone mode) max9702 toc35 output power (mw) power dissipation (mw) 120 90 60 30 50 100 150 200 250 300 350 0 0 150 v dd = 5v r l = 32 ? p out = p outr + p outl power dissipation vs. output power (headphone mode) max9702 toc36 output power (mw) power dissipation (mw) 120 90 60 30 50 75 100 125 150 175 200 0 0 150 v dd = 3.3v p out = p outr + p outl 25 r l = 16 ? r l = 32 ?
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 12 ______________________________________________________________________________________ output power vs. supply voltage (headphone mode) max9702 toc37 supply voltage (v) output power (mw) 5.0 4.5 3.0 3.5 4.0 10 20 30 40 50 60 70 80 0 2.5 5.5 r l = 32 ? thd+n = 10% thd+n = 1% output power vs. load resistance (headphone mode) max9702 toc38 load resistance ( ? ) output power (mw) 100 10 20 30 40 50 60 70 0 10 1000 thd+n = 10% v dd = 5v f = 1khz thd+n = 1% output power vs. load resistance (headphone mode) max9702 toc39 load resistance ( ? ) output power (mw) 100 10 20 30 40 50 60 70 0 10 1000 thd+n = 10% thd+n = 1% v dd = 3.3v f = 1khz output power vs. charge-pump capacitance (headphone mode) max9702 toc40 load ( ? ) output power (mw) 45 40 20 25 30 35 25 30 35 40 45 50 55 60 20 15 50 f = 1khz thd+n = 1% c1 = c2 = 1 f c1 = c2 = 0.47 f power-supply rejection ratio vs. frequency (headphone mode) max9702 toc41 frequency (hz) psrr (db) 10k 1k 100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 10 100k v ripple = 100mv p-p inputs ac grounded v dd = 3.3v v dd = 5v output frequency spectrum (headphone mode) max9702 toc42 frequency (khz) output magnitude (dbv) 15 10 5 -120 -100 -80 -60 -40 -20 0 -140 020 v out = -60dbv f = 1khz r l = 32 ? crosstalk vs. frequency (headphone mode) max9702 toc43 frequency (hz) crosstalk (db) 10k 1k 100 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -110 10 100k r l = 32 ? f = 1khz v in = 100mv p-p right to left left to right crosstalk vs. amplitude (headphone mode) max9702 toc44 amplitude (dbv) crosstalk (dbv) 0 -10 -30 -20 -40 -50 -100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -110 -60 10 r l = 32 ? f = 1khz left to right right to left turn-on/turn-off response (headphone mode) max9702 toc45 100ms/div shdn max9702 output f = 1khz r l = 32 ? t ypical operating characteristics (continued) (v dd = pv dd = shdn = 3.3v, gnd = pgnd = 0v, sync = v dd (ssm), speaker gain = 12db.)
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 13 pin description pin tqfn tssop name function 1, 22 4, 25 pv dd h-bridge power supply. connect to v dd and bypass each pv dd with a 0.1? capacitor to pgnd. 25 sync_out clock signal output. float sync_out if not used. 36 scl i 2 c serial clock. connect a pullup resistor to v dd (see i 2 c interface section). 47 sda i 2 c serial data. connect a pullup resistor to v dd (see i 2 c interface section). 58 bias common-mode voltage. bypass to gnd with a 1? capacitor. 69 sync frequency mode select: sync = gnd: fixed-frequency mode with f s = 1100khz. sync = float: fixed-frequency mode with f s = 1340khz. sync = v dd : spread-spectrum mode with f s = 1150khz ?0khz. sync = clocked: fixed-frequency mode with f s = external clock frequency. 710 cpv dd charge-pump power supply. connect to v dd and bypass to cpgnd with a 1? capacitor. 811 c1p charge-pump flying-capacitor positive terminal. connect a 1? capacitor from c1p to c1n. 91 2 cpgnd charge-pump power ground. connect to pgnd. 10 13 c1n charge-pump flying-capacitor negative terminal. connect a 1? capacitor from c1n to c1p. 11 14 cpv ss charge-pump negative output. bypass with a 1? capacitor to cpgnd. 12 15 v ss headphone amplifier negative supply. connect to cpv ss . 13 16 hpl left-channel headphone output 14 17 hpr right-channel headphone output 15 18 v dd analog power supply. bypass with a 1? capacitor to gnd. 16 19 gnd analog ground. connect to pgnd. 17 20 inr right-channel audio input 18 21 inl left-channel audio input 19 22 inm mono audio input 20 23 hps headphone sense: hps = v dd : headphone mode. hps = gnd: speaker mode. 21 24 shdn active-low shutdown. connect to v dd for normal operation. 23 26 outr+ right-channel positive amplifier output 24 27 outr- right-channel negative amplifier output 25, 26 1, 28 pgnd power ground. connect to gnd. 27 2 outl- left-channel negative amplifier output 28 3 outl+ left-channel positive amplifier output ep ep exposed pad. the external pad lowers the package? thermal impedance by providing a direct heat conduction path from the die to the printed circuit board. the exposed pad is internally connected to v ss . connect the exposed thermal pad to an isolated plane if possible or v ss .
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 14 ______________________________________________________________________________________ detailed description the max9702 is a 1.8w, filterless, stereo class d audio power amplifier and directdrive stereo headphone amplifier. the max9702 ssm amplifier features signifi- cant improvements to switch-mode amplifier technolo- gy. the max9702 offers class ab performance with class d efficiency and minimal board space. the device offers mix, mute, mono and stereo input modes, eight selectable gains, and a low-power shutdown mode?ll programmable through an i 2 c interface. the max9702 stereo headphone amplifier features maxim? patented directdrive architecture, which elimi- nates the large output-coupling capacitors required by conventional single-supply headphone amplifiers. a negative supply (v ss ) is created internally by inverting the positive supply (cpv dd ). powering the amplifiers from cpv dd and cpv ss increases the dynamic range of the amplifiers to almost twice that of other single-supply amplifiers, increasing the total available output power. the directdrive outputs of the max9702 are biased at gnd (see figure 7). the benefit of this 0v bias is that the amplifier outputs do not have a dc component, eliminating the need for large dc-blocking capacitors. eliminating the dc-blocking capacitors on the output saves board space, system cost, and improves fre- quency response. the max9702 features extensive click-and-pop sup- pression circuitry on both speaker and headphone amplifiers to eliminate audible clicks-and-pops on start- up and shutdown. the max9702 features an input multiplexer/mixer that allows three different audio sources to be selected or mixed. an i 2 c-compatible interface allows serial com- munication between the max9702 and a microcon- troller. the max9702 is available with two different i 2 c addresses allowing two max9702s to share the same bus (see table 2). the internal command register con- trols the shutdown status of the max9702, sets the maximum gain of the amplifier, and controls the mono/stereo/mixed/mute mux inputs (see table 3). class d speaker amplifier spread-spectrum modulation and synchronizable switching frequency significantly reduce emi emis- sions. comparators monitor the audio inputs and com- pare the complementary input voltages to a sawtooth waveform. the comparators trip when the input magni- tude of the sawtooth exceeds their corresponding input voltage. both comparators reset at a fixed time after the rising edge of the second comparator trip point, gener- ating a minimum-width pulse (t on(min) ,100ns typ) at the output of the second comparator (figure 1). as the input voltage increases or decreases, the duration of the pulse at one output increases while the other output pulse duration remains the same. this causes the net voltage across the speaker (v out+ - v out- ) to change. the minimum-width pulse helps the device to achieve high levels of linearity. operating modes fixed-frequency (ffm) mode the max9702 features two fixed-frequency modes. connect sync to gnd to select a 1.1mhz switching fre- quency. float sync to select a 1.34mhz switching fre- quency. the frequency spectrum of the max9702 consists of the fundamental switching frequency and its associated harmonics (see the wideband fft graph in typical operating characteristics ). program the switch- ing frequency such that the harmonics do not fall within a sensitive frequency band (table 1). audio reproduc- tion is not affected by changing the switching frequency. spread-spectrum (ssm) mode the max9702 features a unique, patented spread- spectrum mode that flattens the wideband spectral components, improving emi emissions that may be radiated by the speaker and cables. this mode is enabled by setting sync = v dd to enable ssm (table 1). in ssm mode, the switching frequency varies ran- domly by ?0khz around the center frequency (1.15mhz). the modulation scheme remains the same, but the period of the sawtooth waveform changes from cycle to cycle (figure 2). 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). a proprietary amplifier topology ensures this does not corrupt the noise floor in the audio bandwidth. table 1. operating modes sync mode gnd ffm with f osc = 1100khz float ffm with f osc = 1340khz v dd ssm with f osc = 1150khz ?0khz clocked ffm with f osc = external clock frequency
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 15 figure 1. max9702 outputs with an input signal applied out+ out- v in- v in+ v out+ - v out- t on(min) t sw
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 16 ______________________________________________________________________________________ figure 2. max9702 output with an input signal applied (ssm mode) v out_+ - v out_- t sw t sw t sw t sw v in_- v in_+ out_+ out_- t on(min)
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 17 external clock mode the sync input allows the max9702 to be synchro- nized to an external clock, or another maxim class d amplifier, creating a fully synchronous system, minimiz- ing clock intermodulation, and allocating spectral com- ponents of the switching harmonics to insensitive frequency bands. applying a ttl clock signal between 1mhz and 2mhz to sync synchronizes the max9702. the period of the sync clock can be randomized, allowing the max9702 to be synchronized to another maxim class d amplifier operating in ssm mode. sync_out allows several maxim class d amplifiers to be cascaded. the synchronized output minimizes inter- ference due to clock intermodulation caused by the switching spread between single devices using sync_out. the modulation scheme remains the same when using sync_out, and audio reproduction is not affected (see figure 4). figure 3. max9702 emi with 76mm of speaker cable max9702 fig03 frequency (mhz) amplitude (db v/m) 160 180 200 220 240 260 280 300 140 120 100 80 60 20 25 30 35 40 45 50 15 30 max9702 fcc emi limit figure 4. cascading two amplifiers max9702 outl+ outl- max9700 out+ out- outr+ outr- sync sync_out sync sync input
max9702 filterless modulation/common-mode idle the max9702 uses maxim? unique, patented modula- tion scheme that eliminates the lc filter required by tradi- tional class d amplifiers, improving efficiency, reducing component count, conserving board space and system cost. conventional class d amplifiers output a 50% duty- cycle square wave when no signal is present. with no fil- ter, the square wave appears across the load as a dc voltage, resulting in finite load current, increasing power consumption, especially when idling. when no signal is present at the input of the max9702, the outputs switch as shown in figure 5. because the max9702 drives the speaker differentially, the two outputs cancel each other, resulting in no net idle mode voltage across the speaker, minimizing power consumption. efficiency efficiency of a class d amplifier is due to the switching operation of the output stage transistors. in a class d amplifier, the output transistors act as current-steering switches and consume negligible additional power. any power loss associated 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 max9702 still exhibits >80% efficiencies under the same conditions (figure 6). 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 18 ______________________________________________________________________________________ figure 5. max9702 outputs with no input signal v in_ = 0v out_- out_+ v out_+ - v out_- = 0v 0.4 0.3 0.2 0.1 0 0.5 efficiency vs. output power output power (w) efficiency (%) 10 20 30 40 50 60 70 80 90 100 0 v dd = 5v f in = 1khz r l = 8 ? max9702 class ab figure 6. max9702 efficiency vs. class ab efficiency
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. this results in dc shift across the capacitor, which in turn, appears as an audible transient at the speaker. since the max9702 headphone amplifier does not require output-coupling capacitors, this does not arise. the max9702 offers four headphone amplifier gain set- tings controlled through the i 2 c interface. headphone amplifier gains of -2db, +1db, +4db, and +7db are set by command register bits 3 and 4 (table 5). additionally, the max9702 features extensive click-and- pop suppression that eliminates any audible transient sources internal to the device. in most applications, the output of the preamplifier dri- ving the max9702 has a dc bias of typically half the supply. during startup, the input-coupling capacitor is charged to the preamplifier? dc bias voltage through the rf of the max9702, resulting in a dc shift across the capacitor and an audible click-and-pop. an internal delay of 40ms eliminates the clicks-and-pops caused by the input filter. directdrive traditional single-supply headphone amplifiers have outputs biased at a nominal dc voltage (typically half the supply) for maximum dynamic range. large-cou- pling capacitors are needed to block this dc bias from the headphone. without these capacitors, a significant amount of dc current flows to the headphone, resulting in unnecessary power dissipation and possible dam- age to both headphone and headphone amplifier. maxim? patented directdrive architecture uses a charge pump to create an internal negative supply volt- age. this allows the headphone outputs of the max9702 to be biased at gnd, almost doubling 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 (220?, typ) tantalum capacitors, the max9702 charge pump requires two small ceramic capacitors, conserving board space, reducing cost, and improving the fre- quency 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 sizes. there is a low dc voltage on the driver outputs due to amplifier offset. however, the offset of the max9702 is typically 1.1mv, which, when combined with a 32 ? load, results in less than 56? of dc current flow to the headphones. in addition to the cost and size disadvantages of the dc-blocking capacitors required by conventional head- phone amplifiers, these capacitors limit the amplifier? low-frequency response and can distort the audio sig- nal. previous attempts at eliminating the output-cou- pling capacitors involved biasing the headphone return (sleeve) to the dc bias voltage of the headphone amplifiers. this method raises some issues: 1) the sleeve is typically grounded to the chassis. using the midrail biasing approach, the sleeve must be isolated from system ground, complicating prod- uct design. 2) during an esd strike, the driver? esd structures are the only path to system ground. thus, the driver 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 equip- ment, resulting in possible damage to the drivers. max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 19 v dd +v dd -v dd v dd /2 gnd gnd conventional amplifier biasing scheme directdrive biasing scheme figure 7. traditional amplifier output vs. max9702 directdrive output
max9702 charge pump the max9702 features a low-noise charge pump. the switching frequency of the charge pump is 1/2 the switching frequency of the class d amplifier. when sync is driven externally, the charge pump switches at 1/2 f sync . when sync = v dd , the charge pump switch- es with a spread-spectrum pattern. the nominal switch- ing frequency is well beyond the audio range, and thus does not interfere with the audio signals, resulting in an snr of 97db. the switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. by limiting the switching speed of the charge pump, the di/dt noise caused by the parasitic bond wire and trace inductance is mini- mized. although not typically required, additional high- frequency noise attenuation can be achieved by increasing the size of c2 (see typical application circuit ). the charge pump is active in both speaker and headphone modes. input multiplexer/mixer the max9702 features an input multiplexer/mixer that allows three different audio sources to be selected and mixed. command register bits 5 and 6 select the input channel (see table 6), and the audio signal is output to the active amplifier. when the mono path is selected (bit 6 = 0, bit 5 = 1), the mono input is present on both the outputs (with a gain according to tables 4 and 5). when the stereo path is selected, the left and right inputs are present on the outputs (with a gain accord- ing to tables 4 and 5). when in mixer mode, the mono input is added to each of the stereo inputs and present at the output (with a gain according to tables 4 and 5). the mono and stereo signals are attenuated by 6db prior to mixing to maintain dynamic range. in mute, none of input signals is present at output. headphone sense input (hps) the headphone sense input (hps) monitors the head- phone jack, and automatically configures the max9702 based on the voltage applied at hps. a voltage of less than 0.8v sets the max9702 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 8. with no headphone present, the output impedance of the headphone amplifier pulls hps to less than 0.8v. 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 600k ? pullup resistor. when driving hps from an exter- nal logic source, drive hps low when the max9702 is shut down. place a 10k ? resistor in series with hps and the headphone jack to ensure ?kv esd protection. click-and-pop suppression the max9702 features comprehensive click-and-pop suppression that eliminates audible transients on start- up and shutdown. while in shutdown, the h-bridge is in a high-impedance state. during startup or power-up, the input amplifiers are muted and an internal loop sets the modulator bias voltages to the correct levels, pre- venting clicks and pops when the h-bridge is subse- quently enabled. current-limit and thermal protection the max9702 features current limiting and thermal pro- tection to protect the device from short circuits and overcurrent conditions. the headphone amplifier puls- es in the event of an overcurrent condition. the speaker amplifiers?current-limiting protection clamps the output current without shutting down the outputs. this can result in a distorted output. the max9702 has thermal protection that disables the device into shutdown at +120? until the temperature decreases to +110?. 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 20 ______________________________________________________________________________________ max9702 100k ? 10k ? 10k ? v dd hps sda shdn scl hpl i 2 c control hpr shutdown control figure 8. hps configuration
i 2 c interface the max9702 features an i 2 c 2-wire serial interface consisting of a serial data line (sda) and a serial clock line (scl). sda and scl facilitate communication between the max9702 and the master at clock rates up to 400khz. figure 9 shows the 2-wire interface timing diagram. the max9702 is a receive-only slave device relying on the master to generate the scl signal. the max9702 cannot write to the sda bus except to acknowledge the receipt of data from the master. the max9702 does not acknowledge a read command from the master. the master, typically a microcontroller, generates scl and initiates data transfer on the bus. a master device communicates to the max9702 by transmitting the proper address followed by the data word. each transmit sequence is framed by a start (s) or repeated start (s r ) condition and a stop (p) con- dition. each word transmitted over the bus is 8 bits long and is always followed by an acknowledge clock pulse. the max9702 sda line operates as both an input and an open-drain output. a pullup resistor, greater than 500 ? , is required on the sda bus. the max9702 scl line operates as an input only. a pullup resistor, greater than 500 ? , is required on scl if there are multiple mas- ters on the bus, or if the master in a single-master sys- tem has an open-drain scl output. series resistors in line with sda and scl are optional. series resistors protect the digital inputs of the max9702 from high- voltage spikes on the bus lines, and minimize crosstalk and undershoot of the bus signals. bit transfer one data bit is transferred during each scl cycle. the data on sda must remain stable during the high period of the scl pulse. changes in sda while scl is high are control signals (see the start and stop conditions section). sda and scl idle high when the i 2 c bus is not busy. start and stop conditions a master device initiates communication by issuing a start condition. a start condition is a high-to-low transition on sda with scl high. a stop condition is a low-to-high transition on sda while scl is high (figure 10). a start (s) condition from the master signals the beginning of a transmission to the max9702. the mas- ter terminates transmission and frees the bus by issu- ing a stop (p) condition. the bus remains active if a repeated start (sr) condition is generated instead of a stop condition. max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 21 scl sda start condition stop condition repeated start condition start condition t hd, sta t su, sta t hd, sta t sp t buf t su, sto t low t su, dat t hd, dat t high t r t f figure 9. 2-wire serial-interface timing diagram scl sda ssrp figure 10. start, stop, and repeated start conditions
max9702 early stop conditions the max9702 recognizes a stop condition at any point during data transmission except if the stop condition occurs in the same high pulse as a start condition. slave address the max9702 is available with one of two preset slave addresses (see table 2). the address is defined as the 7 most significant bits (msbs) followed by the read/ write bit. the address is the first byte of informa- tion sent to the max9702 after the start condition. the max9702 is a slave device only capable of being written to. the read/ write bit must always be a zero when configuring the max9702. the max9702 does not acknowledge the receipt of its address even if r/ w is set to 1. acknowledge the acknowledge bit (ack) is a clocked 9th bit that the max9702 uses to handshake receipt each byte of data (see figure 11). the max9702 pulls down sda during the master-generated 9th clock pulse. the sda line must remain stable and low during the high period of the acknowledge clock pulse. monitoring ack allows for detection of unsuccessful data transfers. an unsuc- cessful data transfer occurs if a receiving device is busy or if a system fault has occurred. in the event of an unsuccessful data transfer, the bus master may reattempt communication. write data format a write to the max9702 includes transmission of a start condition, the slave address with the r/ w bit set to zero (see table 2), 1 byte of data to configure the command register, and a stop condition. figure 12 illustrates the proper format for one frame. the max9702 only accepts write data, but it acknowl- edges the receipt of its address byte with the r/ w bit set high. the max9702 does not write to the sda bus in the event that the r/ w bit is set high. subsequently, the master reads all 1s from the max9702. always set the r/ w bit to zero to avoid this situation. 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 22 ______________________________________________________________________________________ table 2. max9702 address map max9702 slave address part a6 a5 a4 a3 a2 a1 a0 r/ w max9702 1 0 0 1 1 0 0 0 max9702b 1 0 0 1 1 1 0 0 1 scl start condition sda 289 clock pulse for acknowledgment acknowledge not acknowledge sa 0 acknowledge from max9702 r/w acknowledge from max9702 b7 b6 b5 b4 b3 b2 command byte is stored on receipt of stop condition ap b1 b0 slave address command byte figure 11. acknowledge figure 12. write data format example
command register the max9702 has one command register that is used to set speaker and headphone gain, select an input mode, and enable/disable shutdown. table 3 describes the function of the bits contained in the command register. programmable speaker gain the max9702 has eight internally set speaker gains selected by b0?2 (see table 4). programmable headphone gain the max9702 has four headphone gain settings select- ed by b3 and b4 (see table 5). programmable input modes the max9702 features a multiplexer that selects between the stereo and mono inputs. the mux also acts as a mixer when the mono and stereo inputs are enabled at the same time. the mute function disables the input signal to the output. all modes are selected through b5 and b6 (see table 6). the mix function attenuates and mixes the mono and stereo signals. each input signal is attenuated by 6db prior to being mixed. this attenuation preserves headroom at the output. the output signal is represent- ed by the following equation when in mix mode: where a v is the amplifier gain. out out or hp in inm a v _() __ _ _ + () = + ? ? ? ? ? ? ? 2 max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 23 bit function default b0 speaker gain-setting bit 0 b1 speaker gain-setting bit 0 b2 speaker gain-setting bit 1 b3 headphone gain-setting bit 1 b4 headphone gain-setting bit 0 b5 mono enable bit (0 = mute) 0 b6 stereo enable bit (0 = mute) 1 b7 shutdown bit (1 = normal, 0 = shutdown) 1 table 3. command bits and description b4 b3 function gain (db) 00 headphone gain -2 01 headphone gain (default) +1 10 headphone gain +4 11 headphone gain +7 table 5. programmable headphone gain b6 b5 function 00 mute (no input on the output) 01 mono (mono input sent to the output) 10 stereo (left and right inputs sent to the outputs) (default) 11 mix (mono and stereo inputs are mixed and output) table 6. programmable input modes b2 b1 b0 function gain (db) 00 0 speaker gain +0 00 1 speaker gain +3 01 0 speaker gain +6 01 1 speaker gain +9 100 speaker gain +12 10 1 speaker gain +15 11 0 speaker gain +18 11 1 speaker gain +21 table 4. programmable speaker gain
max9702 shutdown the max9702 features a 0.1? shutdown mode that reduces power consumption to extend battery life. shutdown is controlled by the hardware or software interface. drive shdn low to disable the drive ampli- fiers, bias circuitry, charge pump, and set the head- phone amplifier output impedance to 1k ? . similarly, the max9702 enters shutdown when bit 7 (b7) in the con- trol register is set to zero. connect shdn to v dd and set bit 7 = 1 for normal operation (see table 7). the i 2 c interface is active and the contents of the command register are not affected when in shutdown. this allows the master to write to the max9702 while in shutdown. applications information filterless class d operation traditional class d amplifiers require an output filter to recover the audio signal from the amplifier? pwm out- put. the filters add cost, increase the solution size of the amplifier, and can decrease efficiency. the tradi- tional pwm scheme uses large differential output swings 2 x v dd(p-p) and causes large ripple currents. any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. the max9702 does not require an output filter. the device relies on the inherent inductance of the speaker coil and the natural filtering of both the speaker and the human ear to recover the audio component of the square wave output. by eliminating the output filter, this results in a smaller, less costly, more efficient solution. because the frequency of the max9702 output is well beyond the bandwidth of most speakers, voice coil movement due to the square wave frequency is very small. although this movement is small, a speaker not designed to handle the additional power may be dam- aged. for optimum results, use a speaker with a series inductance >10?. typical 8 ? speakers, for portable audio applications, exhibit series inductances in the range of 20? to 100?. class d output offset unlike a class ab amplifier, the output offset voltage of class d amplifiers does not noticeably increase quies- cent current draw when a load is applied. this is due to the power conversion of the class d amplifier. for example, an 8mv dc offset across an 8 ? load results in 1ma extra current consumption in a class ab device. in the class d case, an 8mv offset into 8 ? equates to an additional power drain of 8?. due to the high efficiency of the class d amplifier, this repre- sents an additional quiescent current draw of 8?/(v dd /100 x ), which is on the order of a few microamps. dc-coupled input the input amplifier can accept dc-coupled inputs that are biased to the amplifier? bias voltage. dc-coupling eliminates the input-coupling capacitors, reducing component count to potentially one external component (see the system diagram ). however, the highpass fil- tering effect of the capacitors is lost, allowing low-fre- quency signals to feed through to the load. power supplies the max9702 has different supplies for each portion of the device, allowing for the optimum combination of headroom power dissipation and noise immunity. the speaker amplifiers are powered from pv dd . pv dd can range from 2.5v to 5.5v and must be connected to the same potential as v dd . the headphone amplifiers are powered from v dd and v ss . v dd is the positive supply of the headphone amplifiers and can range from 2.5v to 5.5v. v ss is the negative supply of the headphone amplifiers. connect v ss to cpv ss . the charge pump is powered by cpv dd . connect cpv dd to v dd for normal operation. the charge pump inverts the voltage at cpv dd , and the resulting voltage appears at cpv ss . the remainder of the device is powered by v dd . component selection input filter an input capacitor, c in , in conjunction with the input impedance of the max9702 forms a highpass filter that removes the dc bias from an incoming signal. the ac- coupling capacitor allows the amplifier to automatically bias the signal to an optimum dc level. assuming zero- source impedance, the -3db point of the highpass filter is given by: choose c in such that f -3db is well below the lowest fre- quency of interest. use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or alu- minum electrolytic. capacitors with high-voltage coeffi- cients, such as ceramics, may result in increased distortion at low frequencies. f rc db in in ? = 3 1 2 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 24 ______________________________________________________________________________________ b7 function 0 soft shutdown 1 normal operation table 7. shutdown control (shdn )
other considerations when designing the input filter include the constraints of the overall system and the actual frequency band of interest. although high-fidelity audio calls for a flat-gain response between 20hz and 20khz, portable voice-reproduction devices such as cellular phones and two-way radios need only concen- trate on the frequency range of the spoken human voice (typically 300hz to 3.5khz). in addition, speakers used in portable devices typically have a poor response below 300hz. taking these two factors into considera- tion, the input filter may not need to be designed for a 20hz to 20khz response, saving both board space and cost due to the use of smaller capacitors. output filter the max9702 does not require an output filter. the device passes fcc emissions standards with 75mm of unshielded speaker cables. however, output filtering can be used if a design is failing radiated emissions due to board layout or cable length, or the circuit is near emi-sensitive devices. use a ferrite bead filter when radiated frequencies above 10mhz are of con- cern. use an lc filter when radiated frequencies below 10mhz are of concern, or when long leads (>200mm) connect the amplifier to the speaker. figure 13 shows optional speaker amplifier output filters. max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 25 max9702 outl+ outl- outr+ outr- max9702 outl+ outl- outr+ outr- max9702 outl+ outl- outr+ outr- (a) typical application <75mm of speaker cable. (b) common-mode choke for applications using cable lengths greater than 75mm. (c) lc filter when using cable lengths longer than 200mm in applications that are sensitive to emi below 10mhz. 100pf 800 ? at 100mhz 800 ? at 100mhz 100pf 100pf 100pf 22 ? 0.068 f 0.068 f 0.033 f 0.033 f 0.033 f 0.068 f 15 h 15 h 15 h 15 h 22 ? 22 ? 22 ? 0.15 f 0.068 f 0.033 f 0.15 f figure 13. optional speaker amplifier output filter
max9702 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 an esr less than 100m ? for opti- mum performance. low-esr ceramic capacitors mini- mize the output resistance of the charge pump. most surface-mount ceramic capacitors satisfy the esr requirement. for best performance over the extended temperature range, select capacitors with an x7r dielectric. table 8 lists suggested manufacturers. flying capacitor (c1) the value of the flying capacitor (c1) affects the output resistance of the charge pump. a c1 value that is too small degrades the device? ability to provide sufficient current drive, which leads to a loss of output voltage. increasing the value of c1 reduces the charge-pump out- put resistance to an extent. above 1f, 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 max9702? charge-pump switching tran- sients. bypass cpv dd with c3 to pgnd and place it physically close to the cpv dd and pgnd. use a value for c3 that is equal to c1. supply bypassing, 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 pgnd and gnd together at a single point on the pc board. route all traces that carry switching transients away from gnd and the traces/components in the audio signal path. connect all of the power-supply inputs (cpv dd , v dd , and pv dd ) together. bypass pv dd with a 0.1? capaci- tor to pgnd and cpv dd with a 1? capacitor to pgnd. bypass v dd with 1? capacitor to gnd. place the bypass capacitors as close to the max9702 as possi- ble. place a bulk capacitor between pv dd and pgnd, if needed. 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. large output, supply, and gnd traces allow more heat to move from the max9702 to the air, decreasing the thermal impedance of the circuit if possible or connect to v ss . the max9702 thin qfn-ep package features an exposed thermal pad on its underside. this pad lowers the package? thermal impedance by providing a direct- heat conduction path from the die to the printed circuit board. the exposed pad is internally connected to v ss . connect the exposed thermal pad to an isolated plane. 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 26 ______________________________________________________________________________________ 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 8. suggested capacitor manufacturers
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 27 functional diagram/typical operating circuit hps inm cpv dd c1p c1n cpv ss v ss gnd pgnd c1 1 f c in 1 f c in 1 f c2 1 f c3 1 f cpgnd inl 19 (22) 7 (10) 8 (11) 10 (13) 9 (12) 11 (14) 12 (15) 16 (19) 25, 26 (1, 28) 18 (21) v dd sync 6 (9) 5 (8) 2 (5) 28 (3) 15 (18) 18 (21) 23 (26) 24 (27) 20 (23) 13 (16) 14 (17) hpl hpr max9702 1 f10 f* 0.1 f c bias 1 f bias sync_out inr shdn sda baseband processor scl c in 1 f 17 (20) 21 (24) outr+ outr- charge pump bias generator input mux i 2 c oscillator and sawtooth class d modulator and h-bridge outl+ 2.5v to 6.5v v dd 1, 22 (4, 25) pv dd outl- ( ) tssop pin *bulk capacitance if needed v dd v dd class d modulator and h-bridge 4 (7) 3 (6)
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 28 ______________________________________________________________________________________ system diagram codec/ baseband processor c max4063 aux_in v dd bias in+ in- out out max9702 inm inl inr c2 1 f 1 f 0.1 f 0.1 f 0.1 f 2.2k ? 2.2k ? c1 1 f c1p c1n sync 4.7k ? outl+ outl- bias pv dd v ss cpv ss outr+ sync_out outr- hps hpl hpr v dd v dd pv dd cpv dd 0.1 f 1 f *c bulk 10 f *bulk capacitance if needed 4.7k ? 1 f 0.1 f
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 29 pin configurations 21 20 19 18 17 16 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 max9702 thin qfn top view outr+ pv dd outr- pgnd pgnd outl- outl+ shdn hps inm inl inr gnd v dd hpr hpl v ss cpv ss c1n cpgnd c1p cpv dd sync bias sda scl sync_out pv dd 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 pgnd outr- outr+ pv dd shdn hps v ss inm inl inr gnd v dd hpr hpl cpv ss c1n cpgnd c1p cpv dd sync bias sda scl sync_out pv dd outl+ outl- pgnd tssop max9702 chip information transistor count: 10,435 process: bicmos
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 30 ______________________________________________________________________________________ pa cka ge 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 e2/2 e2 0.10 m c a b pin # 1 i.d. b 0.35x45 d/2 d2/2 l c l c e e l c c l k l l detail b l l1 e xxxxx marking h 1 2 21-0140 package outline, 16, 20, 28, 32, 40l thin qfn, 5x5x0.8mm -drawing not to scale- l e/2
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier ______________________________________________________________________________________ 31 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 .) 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 yes 3.35 3.15 t2855n-1 3.25 3.15 3.25 3.35 no 3.35 3.15 t2855-8 3.25 3.15 3.25 3.35 yes 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. h 2 2 21-0140 package outline, 16, 20, 28, 32, 40l thin qfn, 5x5x0.8mm -drawing not to scale- 12. number of leads shown are for reference only. 3.30 t4055-1 3.20 3.40 3.20 3.30 3.40 ** yes 0.05 00.02 0.60 0.40 0.50 10 ----- 0.30 40 10 0.40 0.50 5.10 4.90 5.00 0.25 0.35 0.45 0.40 bsc. 0.15 4.90 0.25 0.20 5.00 5.10 0.20 ref. 0.70 min. 0.75 0.80 nom. 40l 5x5 max. 13. lead centerlines to be at true position as defined by basic dimension "e", 0.05. the max9702 thin qfn-ep package features an exposed thermal pad on its underside. this pad lowers the package? thermal impedance by providing a direct-heat conduction path from the die to the printed circuit board. the exposed pad is internally connected to v ss . connect the exposed thermal pad to an isolated plane.
max9702 1.8w, filterless, stereo, class d audio power amplifier and directdrive stereo headphone amplifier 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. 32 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2005 maxim integrated products printed usa 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 .) tssop4.40mm.eps package outline, tssop 4.40mm body 21-0066 1 1 g

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