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general description the MAX9877 combines a high-efficiency class d audio power amplifier with a stereo class ab capacitor- less directdrive headphone amplifier. maxim? 3rd generation, filterless class d amplifier with active emis- sions limiting technology provides class ab perfor- mance with class d efficiency. the MAX9877 delivers up to 725mw from a 3.7v supply into an 8 load with 87% efficiency to extend battery life. the filterless modulation scheme combined with active emissions limiting circuitry and spread-spectrum modu- lation greatly reduces emi while eliminating the need for output filtering used in traditional class d devices. the stereo class ab headphone amplifier in the MAX9877 uses maxim? patented directdrive architec- ture, that produces a ground-referenced output from a single supply, eliminating the need for large dc-blocking capacitors, saving cost, space, and component height. the device utilizes a user-defined input architecture, three preamplifier gain settings, an input mixer, volume control, comprehensive click-and-pop suppression, and i 2 c control. a bypass mode feature disables the integrat- ed class d amplifier and utilizes an internal dpst switch to allow an external amplifier to drive the speaker that is connected at the outputs of the MAX9877. the MAX9877 is available in a thermally efficient, space-saving 20-bump wlp package. applications cell phones portable multimedia players features ? low emissions, filterless class d amplifier achieves better than 10db margin under en55022 class b limits ? low rf susceptibility design rejects tdma noise from gsm radios ? input mixer with user-defined input mode ? 725mw speaker output (r spk = 8 , pv dd = 3.7v) ? 53mw headphone output (r hp = 16 , v dd = 3.7v) ? low 0.05% thd+n at 1khz (class d power amplifier) ? low 0.016% thd+n at 1khz (headphone amplifier) ? 87% efficiency (r spk = 8 , p out = 750mw) ? 1.6 analog switch for speaker amplifier bypass ? high speaker amplifier psrr (72db at 217hz) ? high headphone amplifier psrr (84db at 217hz) ? i 2 c control ? hardware and software shutdown mode ? click-and-pop suppression ? current-limit and thermal protection ? available in a space-saving, 2.5mm x 2.0mm wlp package MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ________________________________________________________________ maxim integrated products 1 mixer/mux preamplifier single supply 2.7v to 5.25v i 2 c interface volume control volume control bypass MAX9877 simplified block diagram wlp hpl v ss c1n hpr 1 a b c d 2 3 4 c1p bias sda rxin+ v dd out+ inb1 scl pgnd inb2 pv dd ina1 gnd rxin- ina2 out- 5 top view (bump side down) pin configuration 19-4076; rev 0; 7/08 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available ordering information part temp range pin - pa c k a g e MAX9877ewp+tg45 -40? to +85? 20 wlp (5x4) + denotes a lead-free package. t = tape and reel. g45 indicates protective die coating.
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. sda and scl pullup voltage = 3.3v. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 3) 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. note 1: hpr and hpl should be limited to no more than 9v above v ss , or above pv dd + 0.3v, whichever limits first. note 2: hpr and hpl should be limited to no more than 9v below pv dd , or below v ss - 0.3v, whichever limits first. v dd , pv dd to pgnd ..............................................-0.3v to +5.5v v dd to pv dd ..........................................................-0.3v to +0.3v v ss to pgnd .........................................................-5.5v to +0.3v c1n to pgnd..............................................(v ss - 0.3v) to +0.3v c1p to pgnd ...........................................-0.3v to (pv dd + 0.3v) hpl, hpr to v ss (note 1) ......-0.3v to the lower of (pv dd - (v ss + 0.3v)) or +9v hpl, hpr to pv dd (note 2) ......+0.3v to the higher of (v ss - (pv dd - 0.3v)) or -9v gnd to pgnd.....................................................................?.3v ina1, ina2, inb1, inb2, bias..................................-0.3v to +4v sda, scl...............................................................-0.3v to +5.5v all other pins to gnd...............................-0.3v to (pv dd + 0.3v) continuous current in/out of pv dd , pgnd, out_.........?00ma continuous current in/out of hpr and hpl .....................140ma continuous current in/out of rxin+ and rxin- ...............150ma continuous input current v ss ...........................................100ma continuous input current (all other pins) .........................?0ma duration of out_ short circuit to gnd or pv dd ........continuous duration of short circuit between out+ and out- ..continuous duration of hp_ short circuit to gnd or pv dd ..........continuous continuous power dissipation (t a = +70?) 20-bump wlp, 5 x 4, multilayer board (derate 13.0mw/? above +70?) ..................................1.04w junction temperature ......................................................+150? operating temperature range ...........................-40? to +85? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units supply voltage range v dd , pv dd guaranteed by psrr test 2.7 5.25 v osc = 00 5.6 9.0 hp mode, outmode = 2 osc = 10 5.5 osc = 00 6.6 11.0 spk mode, outmode = 7 osc = 10 5.7 osc = 00 10.4 16.0 quiescent current i dd spk + hp mode, outmode = 9 osc = 10 9.3 ma shutdown current i shdn i shdn = i vdd + i pvdd ; shdn = 0; v sda = v scl = logic-high; t a = +25? 10 22 ? osc = 00 10 osc = 01 10 turn-on time t on time from shutdown to full operation osc = 10 17.5 ms bias release time t br after forcing bias low, time from bias released to i 2 c reset 25 80 ms t a = +25?, preamp gain = 0db or +9db 11 21 31 input resistance r in t a = +25c, preamp gain = +20db 3 5.5 8 k preamp = 0db 2.30 preamp = +9db 0.820 maximum input signal swing preamp = +20db 0.230 v p-p
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units preamp = 0db 47 preamp = +9db 49 common-mode rejection ratio cmrr f in = 1khz (differential input mode) preamp = +20db 42 db input dc voltage in_ inputs 1.22 1.3 1.38 v bias voltage v bias 1.13 1.2 1.27 v speaker amplifier (outmode = 1) t a = +25? (volume at mute) ?.5 ? output offset voltage v os t a = +25? (volume at 0db, outmode = 1, in_ = 0) ?.5 mv into shutdown -70 click-and-pop level k cp peak voltage, t a = +25?, a-weighted, 32 samples per second, volume at mute (note 4) out of shutdown -70 dbv pv dd = v dd = 2.7v to 5.5v 50 76 f = 217hz, 100mv p-p ripple 72 f = 1khz, 100mv p-p ripple 68 power-supply rejection ratio (note 4) psrr t a = +25?, pv dd = v dd f = 20khz, 100mv p-p ripple 55 db z spk = 8 + 68?, v dd = 3.7v 725 z spk = 8 + 68?, v dd = 3.3v 560 z spk = 8 + 68?, v dd = 3.0v 465 z spk = 4 + 33?, v dd = 3.7v 825 output power (note 5) p out thd+n 1% z spk = 4 + 33?, v dd = 3.0v 770 mw total harmonic distortion plus noise thd+n f = 1khz, p out = 350mw, t a = +25?, z spk = 8 ? + 68? 0.05 % in_ = 0 (single-ended) 92 a-weighted, outmode = 1, 3, 4, 6 in_ = 1 (differential) 94 in_ = 0 (single-ended) 88 signal-to-noise ratio snr a-weighted, outmode = 7, 9 in_ = 1 (differential) 92 db electrical characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. sda and scl pullup voltage = 3.3v. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 3)
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 4 _______________________________________________________________________________________ electrical characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. sda and scl pullup voltage = 3.3v. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 3) parameter symbol conditions min typ max units spread-spectrum modulation mode, osc = 00 1176 ?0 fixed-frequency mode, osc = 01 1100 output frequency fixed-frequency mode, osc = 10 700 khz current limit 1.5 a efficiency p out = 600mw, f = 1khz 87 % speaker gain a v 11.5 12.0 12.5 db output noise a-weighted, outmode = 1, in_ = 0 (note 4) 63 ? rms headphone amplifiers (outmode = 2) t a = +25? (volume at mute) ?.15 ?.6 output offset voltage v os t a = +25? (volume at 0db) ?.6 mv into shutdown -80 click-and-pop level k cp peak voltage, t a = +25?, a-weighted, 32 samples per second. volume at mute (note 4) out of shutdown -80 dbv pv dd = v dd = 2.7v to 5.25v 70 85 f = 217hz, v ripple = 100mv p-p 84 f = 1khz, v ripple = 100mv p-p 80 power-supply rejection ratio (note 4) psrr t a = +25?, pv dd = v dd f = 20khz, v ripple = 100mv p-p 62 db r hp = 16 53 output power p out thd+n 1% r hp = 32 27 mw headphone gain a v -0.4 0 +0.4 db channel-to-channel gain tracking t a = +25?, hpl to hpr, volume at 0db, outmode = 2, 5; in_ = 0 ?.3 ?.5 % r hp = 32 (p out = 10mw, f = 1khz) 0.016 total harmonic distortion plus noise thd+n r hp = 16 (p out = 10mw, f = 1khz), t a = +25? 0.03 % in_ = 0 (single-ended) 98 a-weighted, outmode = 2, 3, 5, 6; r hp = 16 ? in_ = 1 (differential) 98 in_ = 0 (single-ended) 96 signal-to-noise ratio snr a-weighted, r hp = 16 ?, outmode = 8, 9 in_ = 1 (differential) 96 db
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier _______________________________________________________________________________________ 5 electrical characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. sda and scl pullup voltage = 3.3v. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 3) parameter symbol conditions min typ max units slew rate sr 0.35 v/? capacitive drive c l 100 pf crosstalk hpl to hpr, hpr to hpl, f = 20hz to 20khz 65 db spread-spectrum modulation mode, osc = 00 588 ?0 fixed-frequency mode, osc = 01 430 550 670 charge-pump frequency fixed-frequency mode, osc = 10 220 350 500 khz volume control minimum setting _vol = 1 -75 db maximum setting _vol = 31 0 db pgain_ = 00 0 pgain_ = 01 9 preamp gain input a or b pgain_ = 10 20 db speaker 100 mute attenuation f = 1khz, _vol = 0 headphone 110 db zero-crossing detection timeout zcd = 1 60 ms analog switch t a = +25? 1.6 4.5 on-resistance r on i rxin_ = 20ma, rxin_ = 0v and v dd, bypass = 1 t a = t min to t max 5.2 series resistance is 9.1 per switch 0.05 0.25 total harmonic distortion v dif = 2v p-p , v cm = v dd /2, f = 1khz, bypass = 1, t a = +25? no series resistors 0.3 % off-isolation bypass = 0, rxin+ and rxin- to gnd = 50 ? , z spk = 8 ? + 68?, f = 10khz, referred to speaker output signal 88 db digital inputs input-voltage high (sda, scl) v h 1.4 v input-voltage low (sda, scl) v l 0.4 v input-voltage low (bias) v bl 0.15 v input hysteresis (sda, scl) v hys 80 mv sda, scl input capacitance c in 4pf input leakage current i in sda, scl; t a = +25? ?.0 ? bias pullup current i bias 94 ? digital outputs (sda open drain) output low voltage sda v ol i sink = 3ma 0.4 v output fall time sda t of v h(min) to v l(max) bus capacitance = 10pf to 400pf, i sink = 3ma 250 ns
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 6 _______________________________________________________________________________________ electrical characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. sda and scl pullup voltage = 3.3v. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 3) parameter symbol conditions min typ max units 2-wire interface timing external pullup voltage range: sda and scl 1.7 3.6 v serial clock frequency f scl dc 400 khz bus free time between stop and start conditions t buf 1.3 ? start condition hold t hd:sta 0.6 ? start condition setup time t su:sta 0.6 ? clock low period t low 1.3 ? clock high period t high 0.6 ? data setup time t su:dat 100 ns data hold time t hd:dat 0 900 ns maximum receive scl/sda rise time t r 300 ns maximum receive scl/sda fall time t f 300 ns setup time for stop condition t su:sto 0.6 ? capacitive load for each bus line c b 400 pf note 3: all devices are 100% production tested at room temperature. all temperature limits are guaranteed by design. note 4: amplifier inputs are ac-coupled to gnd. note 5: output levels higher than 825mw are not recommended for extended durations. production tested with z spk = 8 + 68? only.
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier _______________________________________________________________________________________ 7 supply current vs. supply voltage MAX9877 toc01 supply voltage (v) supply current (ma) 5.0 4.5 4.0 3.5 3.0 5 6 7 8 9 4 2.5 5.5 headphone only inputs ac-coupled to gnd outmode = 8 v sda = v scl = 3.3v f osc = 1176khz sread-spectrum mode f osc = 1100khz f osc = 700khz supply current vs. supply voltage MAX9877 toc02 supply voltage (v) supply current (ma) 5.0 4.5 4.0 3.5 3.0 6 5 7 8 9 10 4 2.5 5.5 speaker only inputs ac-coupled to gnd outmode = 7 v sda = v scl = 3.3v f osc = 1176khz spread-spectrum mode f osc = 1100khz f osc = 700khz supply current vs. supply voltage MAX9877 toc03 supply voltage (v) supply current (ma) 5.0 4.5 4.0 3.5 3.0 10 9 8 11 12 13 7 2.5 5.5 f osc = 1176khz spread-spectrum mode f osc = 1100khz f osc = 700khz headphone and speaker inputs ac-coupled to gnd outmode = 9 v sda = v scl = 3.3v shutdown current vs. supply voltage MAX9877 toc04 supply voltage (v) shutdown current ( a) 5.0 4.5 4.0 3.5 3.0 10 9 8 11 12 13 14 7 2.5 5.5 inputs ac-coupled to gnd v sda = v scl = 3.3v volume attenuation vs. _vol control code MAX9877 toc05 _vol control code volume attenuation (db) 5 15 10 20 25 30 -60 -80 -100 -40 -20 0 20 -120 35 0 f in = 1khz measured at hpl and hpr typical operating characteristics (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) general
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 8 _______________________________________________________________________________________ total harmonic distortion plus noise vs. frequency MAX9877 toc10 frequency (hz) thd+n (%) 10k 1k 100 1 0.1 0.01 10 100k v dd = pv dd = 3.7v p out = 200mw z spk = 8 + 68 h f osc = 700khz f osc = 1176khz f osc = 1100khz total harmonic distortion plus noise vs. output power MAX9877 toc11 output power (w) thd+n (%) 1.5 1.0 0.5 0.1 1 10 0.01 0 2.0 f in = 20hz f in = 1khz f in = 6khz v dd = pv dd = 5v z spk = 8 + 68 h total harmonic distortion plus noise vs. output power MAX9877 toc12 output power (w) thd+n (%) 1.5 0.1 1 10 0.01 0 2.5 1.0 3.0 0.5 2.0 v dd = pv dd = 5v z spk = 4 + 33 h dashed lines are limited by the abs. max ratings f in = 6khz f in = 20hz f in = 1khz total harmonic distortion plus noise vs. output power MAX9877 toc13 output power (mw) thd+n (%) 0.1 1 10 0.01 0 1000 600 400 800 200 f in = 6khz f in = 20hz f in = 1khz v dd = pv dd = 3.7v z spk = 8 + 68 h typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) speaker amplifier total harmonic distortion plus noise vs. frequency MAX9877 toc06 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k v dd = pv dd = 3.7v z spk = 8 + 68 h p out = 200mw p out = 675mw total harmonic distortion plus noise vs. frequency MAX9877 toc07 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k v dd = pv dd = 3.7v z spk = 4 + 33 h dashed lines are limited by the abs. max ratings p out = 1100mw p out = 650mw total harmonic distortion plus noise vs. frequency MAX9877 toc08 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k p out = 425mw p out = 200mw v dd = pv dd = 3v z spk = 8 + 68 h total harmonic distortion plus noise vs. frequency MAX9877 toc09 frequency (hz) thd+n (%) 10k 1k 100 0.1 1 10 0.01 10 100k p out = 700mw p out = 250mw v dd = pv dd = 3v z spk = 4 + 33 h
MAX9877 efficiency vs. output power MAX9877 toc19 output power (w) efficiency (%) 1.5 100 0 50 60 10 80 30 70 20 90 40 0 3.0 0.5 2.0 1.0 2.5 v dd = pv dd = 5v f in = 1khz dashed lines are limited by the abs. max ratings z spk = 8 + 68 h z spk = 4 + 33 h efficiency vs. output power MAX9877 toc20 output power (w) efficiency (%) 100 0 50 60 10 80 30 70 20 90 40 0 2.0 1.5 1.0 0.5 v dd = pv dd = 3.7v f in = 1khz dashed lines are limited by the abs. max ratings z spk = 8 + 68 h z spk = 4 + 33 h efficiency vs. output power MAX9877 toc21 output power (mw) efficiency (%) 100 0 50 60 10 80 30 70 20 90 40 0 1000 600 200 800 400 v dd = pv dd = 3.7v f in = 1khz z spk = 8 + 68 h f osc = 700khz f osc = 1176khz and 1100khz typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) low rf susceptibility, mono audio subsystem with directdrive headphone amplifier _______________________________________________________________________________________ 9 total harmonic distortion plus noise vs. output power MAX9877 toc14 output power (w) thd+n (%) 0.1 1 10 0.01 0 1.5 1.0 0.5 v dd = pv dd = 3.7v z spk = 4 + 33 h dashed lines are limited by the abs. max ratings f in = 6khz f in = 20hz f in = 1khz total harmonic distortion plus noise vs. output power MAX9877 toc15 output power (mw) thd+n (%) 0.1 1 10 0.01 0 600 400 200 f in = 6khz f in = 20hz f in = 1khz v dd = pv dd = 3v z spk = 8 + 68 h total harmonic distortion plus noise vs. output power MAX9877 toc16 output power (w) thd+n (%) 0.1 1 10 0.01 0 1.2 0.8 0.4 1.0 0.6 0.2 v dd = pv dd = 3v z spk = 4 + 33 h dashed lines are limited by the abs. max ratings f in = 6khz f in = 20hz f in = 1khz total harmonic distortion plus noise vs. output power MAX9877 toc17 output power (mw) thd+n (%) 600 400 200 1 0.01 0.1 0 800 v dd = pv dd = 3.7v f in = 1khz z spk = 8 + 68 h f osc = 1176khz ssm f osc = 700khz f osc = 1100khz total harmonic distortion plus noise vs. output power MAX9877 toc18 output power (mw) thd+n (%) 600 400 200 1 0.01 0.1 0 800 v dd = pv dd = 3.7v f in = 6khz z spk = 8 + 68 h f osc = 1176khz ssm f osc = 700khz f osc = 1100khz
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 10 ______________________________________________________________________________________ typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) in-band output spectrum MAX9877 toc28 frequency (khz) amplitude (dbv) 15 10 5 0 -140 -80 -40 -120 -20 -60 -100 020 f osc = 1100khz f in = 1khz in-band output spectrum MAX9877 toc29 frequency (khz) amplitude (dbv) 15 10 5 0 -140 -80 -40 -120 -20 -60 -100 020 f osc = 700khz f in = 1khz efficiency vs. output power MAX9877 toc22 output power (mw) efficiency (%) 100 0 50 60 10 80 30 70 20 90 40 0 1000 600 400 800 200 v dd = pv dd = 3v f in = 1khz dashed lines are limited by the abs. max ratings z spk = 8 + 68 h z spk = 4 + 33 h output power vs. supply voltage MAX9877 toc23 supply voltage (v) output power (w) 5.0 4.5 4.0 3.5 3.0 2.0 2.5 0.5 1.0 1.5 3.0 3.5 0 2.5 5.5 10% thd+n 1% thd+n v dd = pv dd z spk = 4 + 33 h dashed lines are limited by the abs. max ratings output power vs. supply voltage MAX9877 toc24 supply voltage (v) output power (w) 5.0 4.5 4.0 3.5 3.0 2.0 0.2 0.8 0.6 1.2 1.0 1.6 0.4 1.8 1.4 0 2.5 5.5 v dd = pv dd z spk = 8 + 68 h 10% thd+n 1% thd+n output power vs. load resistance MAX9877 toc25 load resistance ( ) output power (w) 1.8 0.2 0.8 0.6 1.2 1.0 1.6 0.4 1.4 0 0 100 70 40 10 80 50 20 90 60 30 v dd = pv dd = 3.7v f in = 1khz z spk = load + 68 h 10% thd+n 1% thd+n output power vs. load resistance MAX9877 toc26 load resistance ( ) output power (w) 1.2 0.2 0.8 0.6 1.0 0.4 0 0 100 70 40 10 80 50 20 90 60 30 v dd = pv dd = 3v f in = 1khz z spk = load + 68 h 10% thd+n 1% thd+n power-supply rejection ratio vs. frequency MAX9877 toc27 frequency (hz) psrr (db) 10k 1k 100 -90 -70 -60 -40 -30 -10 -80 -50 -20 0 -100 10 100k v dd = pv dd = 3.7v v ripple = 100mv p-p inputs ac-coupled to gnd
MAX9877 typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 11 in-band output spectrum MAX9877 toc30 frequency (khz) amplitude (dbv) 15 10 5 0 -140 -80 -40 -120 -20 -60 -100 020 f osc = 1176khz f in = 1khz wideband output spectrum MAX9877 toc31 frequency (mhz) amplitude (dbv) 0 -70 -40 -50 -20 -80 -60 -90 -30 -10 -100 0.1 10 100 1 f osc = 1100khz inputs ac-coupled to gnd wideband output spectrum MAX9877 toc32 frequency (mhz) amplitude (dbv) 0 -70 -40 -50 -20 -80 -60 -90 -30 -10 -100 0.1 10 100 1 f osc = 700khz inputs ac-coupled to gnd wideband output spectrum MAX9877 toc33 frequency (mhz) amplitude (dbv) 0 -70 -40 -50 -20 -80 -60 -90 -30 -10 -100 0.1 10 100 1 f osc = 1176khz inputs ac-coupled to gnd hardware shutdown response MAX9877 toc34 v bias 500mv/div 20ms/div out+ - out- 1v/div software shutdown on- and off-response MAX9877 toc35 v sda 2v/div 20ms/div out+ - out- 1v/div
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 12 ______________________________________________________________________________________ typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) headphone amplifier total harmonic distortion plus noise vs. frequency MAX9877 toc36 frequency (hz) thd+n (%) 0 0.001 0.01 0.1 10 100 1k 10k 100k v dd = pv dd = 3.7v r hp = 32 p out = 10mw p out = 20mw total harmonic distortion plus noise vs. frequency MAX9877 toc37 frequency (hz) thd+n (%) 1 0.001 0.01 0.1 10 100 1k 10k 100k v dd = pv dd = 3.7v r hp = 16 p out = 20mw p out = 40mw total harmonic distortion plus noise vs. frequency MAX9877 toc38 frequency (hz) thd+n (%) 1 0.001 0.01 0.1 10 100 1k 10k 100k v dd = pv dd = 3v r hp = 32 p out = 10mw p out = 20mw total harmonic distortion plus noise vs. frequency MAX9877 toc39 frequency (hz) thd+n (%) 1 0.001 0.01 0.1 10 100 1k 10k 100k v dd = pv dd = 3v r hp = 16 p out = 15mw p out = 30mw total harmonic distortion plus noise vs. output power MAX9877 toc40 output power (mw) thd+n (%) 30 20 10 0.01 0.1 1 10 0.001 040 v dd = pv dd = 3.7v r hp = 32 f in = 20hz f in = 1khz f in = 6khz total harmonic distortion plus noise vs. output power MAX9877 toc41 output power (mw) thd+n (%) 0.01 0.1 1 10 0.001 0 204060 10 30 50 70 v dd = pv dd = 3.7v r hp = 16 f in = 20hz and 1khz f in = 6khz total harmonic distortion plus noise vs. output power MAX9877 toc42 output power (mw) thd+n (%) 30 20 10 0.01 0.1 1 10 0.001 040 v dd = pv dd = 3v r hp = 32 f in = 20hz f in = 1khz f in = 6khz total harmonic distortion plus noise vs. output power MAX9877 toc43 output power (mw) thd+n (%) 0.01 0.1 1 10 0.001 02040 10 30 50 60 v dd = pv dd = 3v r hp = 16 f in = 20hz and 1khz f in = 6khz
MAX9877 typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 13 output power vs. supply voltage MAX9877 toc46 supply voltage (v) output power (mw) 5.0 4.5 4.0 3.5 3.0 50 0 10 20 30 40 45 5 15 25 35 2.5 5.5 f in = 1khz r hp = 32 10% thd+n 1% thd+n output power vs. supply voltage MAX9877 toc47 supply voltage (v) output power (mw) 5.0 4.5 4.0 3.5 3.0 100 0 20 40 60 80 90 10 30 50 70 2.5 5.5 f in = 1khz r hp = 16 10% thd+n 1% thd+n output power vs. load resistance MAX9877 toc48 load resistance ( ) output power (mw) 100 0 20 40 60 80 90 10 30 50 70 10 40 70 100 20 50 80 30 60 90 v dd = pv dd = 3.7v f in = 1khz 10% thd+n 1% thd+n output power vs. load resistance MAX9877 toc49 load resistance ( ) output power (mw) 100 0 20 40 60 80 90 10 30 50 70 10 40 70 100 20 50 80 30 60 90 v dd = pv dd = 3v f in = 1khz 10% thd+n 1% thd+n output power vs. load resistance MAX9877 toc50 load resistance ( ) output power (mw) 100 0 20 40 60 80 90 10 30 50 70 10 40 70 100 20 50 80 30 60 90 v dd = pv dd = 3v osc = 10 f in = 1khz 1% thd+n c1 = c2 = 2.2 f c1 = c2 = 0.47 f power-supply rejection ratio vs. frequency MAX9877 toc51 frequency (hz) psrr (db) 0 -120 -80 -60 -40 -20 -10 -90 -100 -110 -70 -50 -30 10 100 1k 10k 100k v dd = pv dd = 3.7v v ripple = 100mv p-p r hp = 32 inputs ac-coupled to gnd hpr hpl power dissipation vs. output power MAX9877 toc44 output power (mw) power dissipation (mw) 350 0 250 50 150 300 100 200 0 150 100 50 v dd = pv dd = 3.7v f in = 1khz p out = p hpl + p hpr r hp = 32 r hp = 16 power dissipation vs. output power MAX9877 toc45 output power (mw) power dissipation (mw) 250 0 50 150 100 200 0 150 100 50 v dd = pv dd = 3v f in = 1khz p out = p hpl + p hpr r hp = 32 r hp = 16
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 14 ______________________________________________________________________________________ typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) common-mode rejection ratio vs. frequency MAX9877 toc55 frequency (hz) cmrr (db) 80 0 20 40 60 10 70 30 50 10 100k 10k 1k 100 v dd = pv dd = 3.7v cmrr = 20log(a dm /a cm ) +9db +20db 0db hardware shutdown response MAX9877 toc56 v bias 500mv/div hpl 500mv/div 20ms/div hpr 500mv/div software shutdown on- and off-repsonse MAX9877 toc57 v bias 500mv/div hpl 500mv/div 20ms/div hpr 500mv/div output spectrum MAX9877 toc52 frequency (khz) amplitude (dbv) 0 -140 -100 -60 -20 -120 -80 -40 020 15 10 5 v dd = pv dd = 3.7v f in = 1khz r hp = 32 output spectrum MAX9877 toc53 frequency (khz) amplitude (dbv) 0 -140 -100 -60 -20 -120 -80 -40 020 15 10 5 v dd = pv dd = 3.7v f in = 1khz r hp = 16 crosstalk vs. frequency MAX9877 toc54 frequency (hz) crosstalk (db) 0 -120 -30 -10 -50 -90 -60 -100 -110 -70 -20 -40 -80 10 100k 10k 1k 100 v dd = pv dd = 3.7v v ina_ = 1v p-p r hp = 16 hpr to hpl hpl to hpr
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 15 typical operating characteristics (continued) (v dd = pv dd = 3.7v, v gnd = v pgnd = 0v. single-ended inputs, preamp gain = 0db, volume controls = 0db, osc = 00, bypass = 0, shdn = 1. speaker loads (z spk ) connected between out+ and out-. headphone loads (r hp ) connected from hpl or hpr to gnd. z spk = , r hp = . c1 = c2 = c bias = 1?. t a = +25?, unless otherwise noted.) analog switch total harmonic distortion plus noise vs. output power MAX9877 toc58 output power (mw) thd+n (%) 10 0.01 0.1 1 0 100 75 50 25 external class ab amplifier connected directly to rxin+ and rxin- f = 6khz f = 20hz f = 1khz total harmonic distortion plus noise vs. output power MAX9877 toc59 output power (mw) thd+n (%) 10 0.001 1 0.1 0.01 080 60 40 20 70 50 30 10 external class ab amplifier connected with 9 resistors in series with rxin+ and rxin- f = 6khz f = 20hz and 1khz
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 16 ______________________________________________________________________________________ pin description pin name function a1 hpr right headphone output a2 hpl left headphone output a3 v ss headphone amplifier negative power supply. bypass with a 1? capacitor to pgnd. a4 c1n charge-pump flying capacitor negative terminal. connect a 1? capacitor between c1p and c1n. a5 c1p charge-pump flying capacitor positive terminal. connect a 1? capacitor between c1p and c1n. b1 v dd analog supply. connect to pv dd . bypass with a 1? capacitor to gnd. b2 bias common-mode bias. bypass to gnd with a 1? capacitor. pulse low to reset the part and place in shutdown (see the typical application circuit ). b3 sda serial-data input. connect a pullup resistor from sda to a 1.7v to 3.6v supply. b4 rxin+ receiver bypass positive input b5 out+ positive speaker output c1 inb2 input b2. right input or positive input (see the differential input configuration ( in_) section). c2 inb1 input b1. left input or negative input (see the differential input configuration ( in_) section). c3 scl serial-clock input. connect a pullup resistor from scl to a 1.7v to 3.6v supply. c4 pgnd power ground c5 pv dd class d and charge-pump power supply. bypass with a 1? capacitor to pgnd. d1 ina2 input a2. right input or positive input (see the differential input configuration ( in_) section). d2 ina1 input a1. left input or negative input (see the differential input configuration ( in_) section). d3 gnd analog ground d4 rxin- receiver bypass negative input d5 out- negative speaker output detailed description signal path the MAX9877 signal path consists of flexible inputs, signal mixing, volume control, and output amplifiers (figure 1). the inputs can be configured for single-ended or differ- ential signals (figure 2). the internal preamplifiers fea- ture three programmable gain settings of 0db, +9db, and +20db. following preamplification, the input sig- nals are mixed, volume adjusted, and routed to the headphone and speaker amplifiers based on the out- put mode configuration (see table 7). the volume con- trol stages provide up to 75db attenuation. the headphone amplifier is configured as a unity-gain buffer while the speaker amplifier provides +12db of additional gain. when an input is configured as mono differential it can be routed to the speaker or to both headphones. when an input is stereo, it is mixed to mono without attenuation for the speaker and kept stereo for the headphones. when the application does not require the use of both ina_ and inb_, the snr of the MAX9877 is improved by deselecting the unused input through the i 2 c output mode register and ac-coupling the unused inputs to ground with a 330pf capacitor. the 330pf capacitor and the input resistance to the MAX9877 form a high- pass filter preventing audible noise from coupling into the outputs.
MAX9877 mixer and mux input a 0db/+9db/+20db ina2 ina1 input b 0db/+9db/+20db inb2 inb1 -75db to 0db 0db hpr -75db to 0db 0db hpl -75db to 0db +12db out+ out- figure 1. signal path in_2 (r) r l in_1 (l) stereo single-ended to mixer in_2 (+) in_1 (-) differential to mixer figure 2. differential and stereo single-ended input configurations low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 17
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 18 ______________________________________________________________________________________ volume control and mute the MAX9877 features three volume control registers (see table 4) allowing independent volume control of mono speaker and stereo headphone amplifier outputs. each volume control register has 31 steps providing 0 to 75db (typ) of attenuation and a mute function. class d speaker amplifier the MAX9877 integrates a filterless class d amplifier that offers much higher efficiency than class ab with- out the typical disadvantages. the high 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 out- put 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 power. under normal operating levels (typical music reproduction levels), efficiency falls below 30%, whereas the MAX9877 still exhibits 70% efficiency under the same conditions (figure 3). ultra-low emi filterless output stage in traditional class d amplifiers, the high dv/dt of the rising and falling edge transitions results in increased emi emissions, which requires the use of external lc filters or shielding to meet en55022 electromagnetic- interference (emi) regulation standards. limiting the dv/dt normally results in decreased efficiency. maxim? active emissions limiting circuitry actively limits the dv/dt of the rising and falling edge transitions, provid- ing reduced emi emissions, while maintaining up to 87% efficiency. in addition to active emission limiting, the MAX9877 features a patented spread-spectrum modulation mode that flattens the wideband spectral components. proprietary techniques ensure that the cycle-to-cycle variation of the switching period does not degrade audio reproduction or efficiency (see the typical operating characteristics ). select spread-spectrum modulation mode through the i 2 c interface (table 6). in spread-spectrum modulation mode, the switching fre- quency varies randomly by ?0khz around the center frequency (1.176mhz). the effect is to reduce the peak energy at harmonics of the switching frequency. above 10mhz, the wideband spectrum looks like white noise for emi purposes (see figure 4). speaker current limit most applications will not enter current limit unless the output is short circuited or connected incorrectly. when the output current of the speaker amplifier exceeds the current limit (1.5a, typ) the MAX9877 dis- ables the outputs for approximately 250?. at the end of 250?, the outputs are re-enabled, if the fault condition still exists, the MAX9877 will continue to disable and re- enable the outputs until the fault condition is removed. bypass mode the integrated dpst analog audio switch allows the MAX9877? class d amplifier to be bypassed. in bypass mode, the class d amplifier is automatically disabled allowing an external amplifier to drive the speaker connected between out+ and out- through rxin+ and rxin- (see the typical application circuit ). the bypass switch is enabled at startup. the switch can be opened or closed even when the MAX9877 is in soft- ware shutdown (see the i 2 c register description section). unlike discrete solutions, the switch design reduces coupling of class d switching noise to the rxin_ inputs. this eliminates the need for a costly t-switch. the bypass switch is typically used with two 9.1 resis- tors connected to each input. these resistors, in combi- nation with the switch on-resistance and an 8 load, approximate the 32 load expected by the external amplifier. although not required, using the resistors optimizes thd+n. drive rxin+ and rxin- with a low-impedance source to minimize noise on the pins. in applications that do not require the bypass mode, leave rxin+ and rxin- unconnected. MAX9877 efficiency vs. ideal class efficiency MAX9877 fig03 output power (w) efficiency (%) 0.75 0.50 0.25 10 20 30 40 50 60 70 80 90 100 0 0 1.00 MAX9877 ideal class ab v dd = pv dd = 3.7v (MAX9877) v supply = 3.7v (ideal class ab) figure 3. MAX9877 efficiency vs. class ab efficiency
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 19 directdrive headphone amplifier traditional single-supply headphone amplifiers have outputs biased at a nominal dc voltage (typically half the supply). large coupling 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 dissi- pation and possible damage to both the 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 MAX9877 to be biased at gnd while operating from a single supply (figure 5). without a dc component, there is no need for the large dc-blocking capacitors. instead of two large (220?, typ) capacitors, the MAX9877 charge pump requires two small ceramic capacitors, conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. see the output power vs. load resistance graph in the typical operating characteristics for details of the pos- sible capacitor sizes. there is a low dc voltage on the amplifier outputs due to amplifier offset. however, the offset of the MAX9877 is typically ?.15mv, which, when combined with a 32 load, results in less than 10? 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: frequency (mhz) amplitude (db v/m) 160 140 120 100 80 60 10 15 20 25 30 35 40 test limit MAX9877 output MAX9877 output test limit 5 30 180 200 240 260 280 300 220 frequency (mhz) amplitude (db v/m) 600 550 500 450 400 350 15 20 25 35 40 10 300 650 700 800 850 900 1000 950 750 figure 4. emi with 152mm of speaker cable
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 20 ______________________________________________________________________________________ 1) the sleeve is typically grounded to the chassis. using the midrail 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. thus, the amplifier must be able to withstand the full energy from an 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 possible damage to the amplifiers. the MAX9877 features a low-noise charge pump. the switching frequency of the charge pump is 1 / 2 of the class d switching frequency, regardless of the operating mode. when the class d amplifiers are operated in spread-spectrum mode, the charge pump also switches with a spread-spectrum pattern. the nominal switching frequency is well beyond the audio range, and thus does not interfere with audio signals. the switch drivers fea- ture 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 trace inductance is minimized. although not typically required, additional high-frequen- cy noise attenuation can be achieved by increasing the size of c2 (see the typical application circuit ). the charge pump is active only in headphone modes. headphone current limit the headphone amplifier current is limited to 140ma (typ). the current limit clamps the output current, which appears as clipping when the maximum current is exceeded. shutdown mode the MAX9877 features two ways of entering low-power shutdown. the hardware shutdown function is controlled by pulsing bias low for 1ms. while bias is low the ampli- fiers are shut down. following an 80ms reset period, the MAX9877 reverts to its power-on-reset condition. pull bias low using an open-drain output that is not pulled up with a resistor (see the typical application circuit ) . the open-drain output leakage must not exceed 100na and must be able to sink at least 1ma. the device can also be placed in shutdown mode by writing to the shdn bit in the output control register. click-and-pop suppression the MAX9877 features click-and-pop suppression that eliminates audible transients from occurring at startup and shutdown. use the following procedure to start up the MAX9877: 1) configure the desired output mode and pream- plifier gain. 2) set the shdn bit to 1 to start up the amplifier. 3) wait 10ms for the startup time to pass. 4) increase the output volume to the desired level. to disable the device simply set shdn to 0. during the startup period, the MAX9877 precharges the input capacitors to prevent clicks and pops. if the output amplifiers have been programmed to be active they are held in shutdown until the precharge period is complete. when power is initially applied to the MAX9877, the power-on-reset state of all three volume control registers is mute. for most applications, the volume can be set to the desired level once the device is active. if the click- and-pop is too high, step through intermediate volume settings with zero-crossing detection disabled. stepping through higher volume settings has a greater impact on click-and-pop than lower volume settings. for the lowest possible click-and-pop, start up the device at minimum volume and then step through each volume setting until the desired setting is reached. disable zero- crossing detection if no input signal is expected. v dd v dd /2 gnd conventional amplifier biasing scheme directdrive amplifier biasing scheme +v dd gnd -v dd (v ss ) figure 5. traditional amplifier output vs. MAX9877 directdrive output
MAX9877 i 2 c register description zero-crossing detection (zcd) zero-crossing detection limits distortion in the output signal during volume transitions by delaying the transi- tion until the mixer output crosses the internal bias volt- age. a timeout period (typically 60ms) forces the volume transition if the mixer output signal does not cross the bias voltage. 1 = zero-crossing detection is enabled. 0 = zero-crossing detection is disabled. differential input configuration ( in_) the inputs ina_ and inb_ can be configured for mono differential or stereo single-ended operation. 1 = in_ is configured as a mono differential input with in_2 as the positive and in_1 as the negative input. 0 = in_ is configured as a stereo single-ended input with in_2 as the right and in_1 as the left input. preamplifier gain (pgain_) the preamplifier gain of ina_ and inb_ can be pro- grammed by writing to pgain_. 00 = 0db 01 = +9db 10 = +20db 11 = reserved the MAX9877 is controlled through five i 2 c program- mable registers. table 1 shows the MAX9877? com- plete register map. tables 2, 3, and 5 show the individual registers. i 2 c address the slave address of the MAX9877 is 1001101r/( w ). table 1. register map register register address por state b7 b6 b5 b4 b3 b2 b1 b0 input mode control 0x00 0x40 0 zcd ina inb pgaina pgainb speaker volume control 0x01 0x00 0 0 0 svol (table 4) left headphone volume control 0x02 0x00 0 0 0 hplvol (table 4) right headphone volume control 0x03 0x00 0 0 0 hprvol (table 4) output mode control 0x04 0x49 shdn bypass osc (table 6) outmode (table 7) table 2. input mode control register b7 b6 b5 b4 b3 b2 b1 b0 0x00 0 zcd ina inb pgaina pgainb i 2 c interface low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 21
shutdown ( s s h h d d n n ) 1 = MAX9877 operational. 0 = MAX9877 in low-power shutdown mode. shdn is an active-low shutdown bit that overrides all settings and places the entire device in low-power shut- down mode. the i 2 c interface is fully active in this shut- down mode and bypass mode remains operational. all register settings are preserved while in shutdown. MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 22 ______________________________________________________________________________________ volume control the device has a separate volume control for left head- phone, right headphone, and speaker amplifiers. the total system gain is a combination of the input gain, the volume control, and the output amplifier gain. table 4 shows the volume settings for each volume control. table 4. volume control settings _vol code b4 b3 b2 b1 b0 gain (db) 0 0 0 0 0 0 mute 1 0 0 0 0 1 -75 2 0 0 0 1 0 -71 3 0 0 0 1 1 -67 4 0 0 1 0 0 -63 5 0 0 1 0 1 -59 6 0 0 1 1 0 -55 7 0 0 1 1 1 -51 8 0 1 0 0 0 -47 9 0 1 0 0 1 -44 10 0 1 0 1 0 -41 11 0 1 0 1 1 -38 12 0 1 1 0 0 -35 13 0 1 1 0 1 -32 14 0 1 1 1 0 -29 15 0 1 1 1 1 -26 _vol code b4 b3 b2 b1 b0 gain (db) 16 1 0 0 0 0 -23 17 1 0 0 0 1 -21 18 1 0 0 1 0 -19 19 1 0 0 1 1 -17 20 1 0 1 0 0 -15 21 1 0 1 0 1 -13 22 1 0 1 1 0 -11 23 1 0 1 1 1 -9 24 1 1 0 0 0 -7 25 1 1 0 0 1 -6 26 1 1 0 1 0 -5 27 1 1 0 1 1 -4 28 1 1 1 0 0 -3 29 1 1 1 0 1 -2 30 1 1 1 1 0 -1 31 1 1 1 1 1 0 table 5. output mode control register b7 b6 b5 b4 b3 b2 b1 b0 0x04 shdn bypass osc (table 6 ) outmode (table 7) table 3. speaker/left headphone/right headphone volume control register b7 b6 b5 b4 b3 b2 b1 b0 0x01 0 0 0 svol (table 4) 0x02 0 0 0 hplvol (table 4) 0x03 0 0 0 hprvol (table 4)
MAX9877 table 6. oscillator modes osc b1 b0 class d oscillator mode (khz) charge-pump oscillator mode (khz) 0 0 1176, spread spectrum 588, spread spectrum 0 1 1100, fixed frequency 550, fixed frequency 1 0 700, fixed frequency 350, fixed frequency 1 1 reserved table 7. output modes outmode in_ = 0 (the single-ended input signals are defined as in_1 = left and in_2 = right) in_ = 1 (the differential input signal is defined as in_ = in_2 - in_1) mode b3 b2 b1 b0 spk left hp right hp spk left hp right hp 0 0000 reserved reserved 1 0001 ina1+ina2 ina 2 0010 ina1 ina2 ina ina 3 0011 ina1+ina2 ina1 ina2 ina ina ina 4 0100 inb1+inb2 inb 5 0101 inb1 inb2 inb inb 6 0110 inb1+inb2 inb1 inb2 inb inb inb 7 0111 ina1+ina2 +inb1+inb2 ina +inb 8 1000 ina1+inb1 ina2+inb2 ina +inb ina +inb 9 1001 ina1+ina2 +inb1+inb2 ina1+inb1 ina2+inb2 ina +inb ina +inb _ ina +inb 10?5 reserved reserved ?= amplifier off low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 23 bypass mode (bypass) 1 = MAX9877 bypass switches are closed and the class d amplifier is disabled. 0 = bypass mode disabled. this mode does not control headphone operation. output configuration (outmode) the MAX9877 has a stereo directdrive headphone ampli- fier and a mono class d amplifier. table 7 shows how each of the output amplifiers can be configured and con- nected to the input signals. for simplicity, not all possible combinations of ina and inb are shown.
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 24 ______________________________________________________________________________________ scl sda start condition stop condition repeated start condition start condition t hd:sta t su:sta t su:sta t buf t su:sto t low t su:dat t hd:dat t high t r t f figure 6. 2-wire interface timing diagram scl sda ssrp figure 7. start, stop, and repeated start conditions smbus is a trademark of intel corp. i 2 c interface specification the MAX9877 features an i 2 c/smbus-compatible, 2- wire serial interface consisting of a serial-data line (sda) and a serial-clock line (scl). sda and scl facil- itate communication between the MAX9877 and the master at clock rates up to 400khz. figure 6 shows the 2-wire interface timing diagram. the master generates scl and initiates data transfer on the bus. the master device writes data to the MAX9877 by transmitting the proper slave address followed by the register address and then the data word. each transmit sequence is framed by a start (s) or repeated start (sr) con- dition and a stop (p) condition. each word transmitted to the MAX9877 is 8 bits long and is followed by an acknowledge clock pulse. a master reading data from the MAX9877 transmits the proper slave address fol- lowed by a series of nine scl pulses. the MAX9877 transmits data on sda in sync with the master-generat- ed scl pulses. the master acknowledges receipt of each byte of data. each read sequence is framed by a start (s) or repeated start (sr) condition, a not acknowledge, and a stop (p) condition. sda operates as both an input and an open-drain output. a pullup resistor, typically greater than 500 , is required on sda. scl operates only as an input. a pullup resistor, typically greater than 500 , is required on scl if there are multiple masters on the bus, or if the single master has an open-drain scl output. series resistors in line with sda and scl are optional. series resistors protect the digital inputs of the MAX9877 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). start and stop conditions sda and scl idle high when the bus is not in use. a master initiates communication by issuing a start con- dition. 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 7). a start condition from the master signals the beginning of a transmission to the MAX9877. the master terminates transmission, and frees the bus, by issuing a stop con- dition. the bus remains active if a repeated start condition is generated instead of a stop condition.
MAX9877 a 0 slave address register address data byte acknowledge from MAX9877 r/w 1 byte autoincrement internal register address pointer acknowledge from MAX9877 acknowledge from MAX9877 b1 b0 b3 b2 b5 b4 b7 b6 s a a p figure 9. writing one byte of data to the MAX9877 1 scl start condition sda 289 clock pulse for acknowledgment acknowledge not acknowledge figure 8. acknowledge low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 25 early stop conditions the MAX9877 recognizes a stop condition at any point during data transmission except if the stop con- dition occurs in the same high pulse as a start condi- tion. for proper operation, do not send a stop condition during the same scl high pulse as the start condition. slave address the MAX9877 is preprogrammed with a slave address of 1001101r/( w ). the address is defined as the seven most significant bits (msbs) followed by the read/write bit. setting the read/write bit to 1 configures the MAX9877 for read mode. setting the read/write bit to 0 configures the MAX9877 for write mode. the address is the first byte of information sent to the MAX9877 after the start condition. acknowledge the acknowledge bit (ack) is a clocked 9th bit that the MAX9877 uses to handshake receipt each byte of data when in write mode (see figure 8). the MAX9877 pulls down sda during the entire master-generated 9th clock pulse if the previous byte is successfully received. monitoring ack allows for detection of unsuc- cessful data transfers. an unsuccessful 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 retry communication. the master pulls down sda during the ninth clock cycle to acknowledge receipt of data when the MAX9877 is in read mode. an acknowledge is sent by the master after each read byte to allow data transfer to continue. a not acknowledge is sent when the master reads the final byte of data from the MAX9877, followed by a stop condition. write data format a write to the MAX9877 includes transmission of a start condition, the slave address with the r/ w bit set to 0, one byte of data to configure the internal register address pointer, one or more bytes of data, and a stop condition. figure 9 illustrates the proper frame format for writing one byte of data to the MAX9877. figure 10 illustrates the frame format for writing n-bytes of data to the MAX9877. the slave address with the r/ w bit set to 0 indicates that the master intends to write data to the MAX9877. the MAX9877 acknowledges receipt of the address byte during the master-generated 9th scl pulse.
MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 26 ______________________________________________________________________________________ acknowledge from MAX9877 1 byte autoincrement internal register address pointer acknowledge from MAX9877 not acknowledge from master a a p a 0 acknowledge from MAX9877 r/w sa r/w repeated start sr 1 slave address register address slave address data byte figure 11. reading one indexed byte of data from the MAX9877 1 byte autoincrement internal register address pointer acknowledge from MAX9877 acknowledge from MAX9877 b1 b0 b3 b2 b5 b4 b7 b6 a a 0 acknowledge from MAX9877 r/w s a 1 byte acknowledge from MAX9877 b1 b0 b3 b2 b5 b4 b7 b6 p a slave address register address data byte 1 data byte n figure 10. writing n-bytes of data to the MAX9877 the second byte transmitted from the master config- ures the MAX9877? internal register address pointer. the pointer tells the MAX9877 where to write the next byte of data. an acknowledge pulse is sent by the MAX9877 upon receipt of the address pointer data. the third byte sent to the MAX9877 contains the data that will be written to the chosen register. an acknowl- edge pulse from the MAX9877 signals receipt of the data byte. the address pointer autoincrements to the next register address after each received data byte. this autoincrement feature allows a master to write to sequential registers within one continuous frame. figure 10 illustrates how to write to multiple registers with one frame. the master signals the end of transmission by issuing a stop condition. register addresses greater than 0x04 are reserved. do not write to these addresses. read data format send the slave address with the r/ w bit set to 1 to initiate a read operation. the MAX9877 acknowledges receipt of its slave address by pulling sda low during the 9th scl clock pulse. a start command followed by a read command resets the address pointer to register 0x00. the first byte transmitted from the MAX9877 will be the contents of register 0x00. transmitted data is valid on the rising edge of scl. the address pointer autoincrements after each read data byte. this autoincrement feature allows all registers to be read sequentially within one continuous frame. a stop condition can be issued after any number of read data bytes. if a stop condition is issued followed by another read operation, the first data byte to be read will be from register 0x00. the address pointer can be preset to a specific register before a read command is issued. the master presets the address pointer by first sending the MAX9877? slave address with the r/ w bit set to 0 followed by the register address. a repeated start condition is then sent followed by the slave address with the r/ w bit set to 1. the MAX9877 then transmits the contents of the specified register. the address pointer autoincrements after transmitting the first byte. the master acknowl- edges receipt of each read byte during the acknowl- edge clock pulse. the master must acknowledge all correctly received bytes except the last byte. the final byte must be followed by a not acknowledge from the master and then a stop condition. figure 11 illustrates the frame format for reading one byte from the MAX9877. figure 12 illustrates the frame format for reading multiple bytes from the MAX9877.
applications information filterless class d operation traditional class d amplifiers require an output filter to recover the audio signal from the amplifier? output. the filters add cost, increase the solution size of the amplifier, and can decrease efficiency and thd+n performance. the traditional pwm scheme uses large differential out- put swings (2 x v dd(p-p) ) and causes large ripple cur- rents. any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. the MAX9877 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. eliminating the output filter results in a smaller, less costly, more efficient solution. because the frequency of the MAX9877 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 can be dam- aged. for optimum results, use a speaker with a series inductance > 10?. typical 8 speakers exhibit series inductances in the 20? to 100? range. component selection optional ferrite bead filter in applications where speaker leads exceed 20mm, additional emi suppression can be achieved by using a filter constructed from a ferrite bead and a capacitor to ground. a ferrite bead with low dc resistance, high- frequency (> 1.176mhz) impedance of 100 to 600 , and rated for at least 1a should be used. the capacitor value varies based on the ferrite bead chosen and the actual speaker lead length. select a capacitor less than 1nf based on emi performance. input capacitor an input capacitor, c in , in conjunction with the input impedance of the MAX9877 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 so 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. bias capacitor bias is the output of the internally generated dc bias volt- age. the bias bypass capacitor, c bias , reduces power supply and other noise sources at the common-mode bias node. bypass bias with a 1? capacitor to gnd. charge-pump capacitor selection use capacitors with an esr less than 100m for optimum performance. low-esr ceramic capacitors minimize 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. 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. f rc db in in ? = 3 1 2 MAX9877 MAX9877 out+ out- figure 13. optional ferrite bead filter acknowledge from MAX9877 1 byte autoincrement internal register address pointer acknowledge from MAX9877 a a ap 0 acknowledge from MAX9877 r/w sa r/w repeated start sr 1 slave address register address slave address data byte figure 12. reading n-bytes of indexed data from the MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 27
increasing the value of c1 reduces the charge-pump out- put resistance to an extent. above 1?, the on-resistance of the switches and the esr of c1 and c2 dominate. output holding capacitor (c2) the output capacitor value and esr directly affect the ripple at v 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. load resistance graph in the typical operating characteristics . pv dd bulk capacitor (c3) in addition to the recommended pv dd bypass capaci- tance, bulk capacitance equal to c3 should be used. place the bulk capacitor as close to the device as possible. supply bypassing, layout, and grounding proper layout and grounding are essential for optimum performance. use wide traces for the power-supply inputs and amplifier outputs to minimize losses due to parasitic trace resistance. wide 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 pcb. route all traces that carry switching transients away from gnd and the traces/components in the audio signal path. connect pv dd to a 2.7v to 5.25v source. bypass pv dd to the pgnd pin with a 1? ceramic capacitor. additional bulk capacitance should be used to prevent power-supply pumping. place the bypass capacitors as close to the MAX9877 as possible. connect v dd to pv dd . bypass v dd to gnd with a 1? capacitor. place the bypass capacitors as close to the MAX9877 as possible. rf susceptibility gsm radios transmit using time-division multiple access (tdma) with 217hz intervals. the result is an rf signal with strong amplitude modulation at 217hz that is easily demodulated by audio amplifiers. figure 14 shows the susceptibility of the MAX9877 to a trans- mitting gsm radio placed in close proximity. although there is measurable noise at 217hz and its harmonics, the noise is well below the threshold of hearing using typical headphones. in rf applications, improvements to both layout and component selection decreases the MAX9877? sus- ceptibility to rf noise and prevent rf signals from being demodulated into audible noise. trace lengths should be kept below 1 / 4 the wavelength of the rf fre- quency of interest. minimizing the trace lengths pre- vents them from functioning as antennas and coupling rf signals into the MAX9877. the wavelength in meters is given by: = c/f where c = 3 x 10 8 m/s, and f = the rf frequency of interest. route audio signals on middle layers of the pcb to allow ground planes above and below shield them from rf interference. ideally the top and bottom layers of the pcb should primarily be ground planes to create effec- tive shielding. additional rf immunity can also be obtained from rely- ing on the self-resonant frequency of capacitors as it exhibits the frequency response similar to a notch filter. depending on the manufacturer, 10pf to 20pf capaci- tors typically exhibit self resonance at rf frequencies. these capacitors, when placed at the input pins, can effectively shunt the rf noise at the inputs of the MAX9877. for these capacitors to be effective, they must have a low-impedance, low-inductance path to the ground plane. do not use microvias to connect to the ground plane as these vias do not conduct well at rf frequencies. MAX9877 low rf susceptibility, mono audio subsystem with directdrive headphone amplifier 28 ______________________________________________________________________________________ rf susceptibility MAX9877 fig14 frequency (hz) efficiency (db ) 10k 1k 100 -130 -110 -90 -70 -50 -30 -10 -150 10 100k threshold of hearing MAX9877 noise floor figure 14. MAX9877 susceptibility to a gsm cell phone radio
MAX9877 wlp applications information for the latest application details on wlp construction, dimensions, tape carrier information, pcb techniques, bump-pad layout, and recommended reflow tempera- ture profile, as well as the latest information on reliability testing results, refer to the application note: ucsp? wafer-level chip-scale package on maxim? website at www.maxim-ic.com/ucsp. see figure 15 for the rec- ommended pcb footprint for the MAX9877. low rf susceptibility, mono audio subsystem with directdrive headphone amplifier ______________________________________________________________________________________ 29 250 m 45 5 m figure 15. pcb footprint recommendation diagram
MAX9877 low rf susceptibility, mono audio subsystem with directdrive 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. 30 __________________ maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. typical application circuit charge pump mixer and mux class d modulator +12db input a 0db/+9db/+20db ina2 ina1 d1 d2 c1n input a input b c1p a4 a5 bias b2 b5 d5 out+ a1 hpr a2 hpl out- i 2 c control sda scl b3 c3 baseband receiver amplifier rxin+ rxin- b4 d4 -75db to 0db 0db 0db -75db to 0db -75db to 0db bypass c1 1 f 1 f 1 f input b 0db/+9db/+20db inb2 inb1 c1 c2 1 f 1 f 1 f open-drain gpio 9.1 9.1 d3 gnd c4 pgnd MAX9877 a3 v ss c2 1 f b1 v dd 1 f v batt v batt c5 pv dd c3 1 f chip information process: bicmos package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . package type package code document no. 20 wlp w202a2+2 21-0059

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