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general description the MAX9742 stereo class d audio power amplifier delivers up to 2 x 16w into 4 ? loads. the MAX9742 features high-power efficiency (92% with 8 ? loads), eliminating the need for a bulky heatsink and conserv- ing power. the MAX9742 operates from a 20v to 40v single supply or a ?0v to ?0v dual supply. features include fully differential inputs, comprehensive click- and-pop suppression, low-power shutdown mode, and an externally adjustable gain. short-circuit and thermal- overload protection prevent the device from being damaged during a fault condition. the MAX9742 is available in a thermally efficient 36-pin tqfn (6mm x 6mm x 0.8mm) package and is specified over the -40? to +85? extended temperature range. applications crt tvs flat-panel display tvs audio docking stations multimedia monitors features 2 x 16w output power (r l = 4 ? , thd+n = 10%) high efficiency: up to 92% with r l = 8 ? mute and shutdown modes differential inputs suppress common-mode noise adjustable gain integrated click-and-pop suppression low 0.06% thd+n at 3.5w, r l = 8 ? output short-circuit and thermal protection available in space-saving, 6mm x 6mm, 36-pin tqfn package MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ________________________________________________________________ maxim integrated products 1 l f c f class d modulator and half-bridge r f2 r f2 c fbr c zbl r zbl c in r in1 MAX9742 c in r in2 inl- inl+ c in r in2 c in r in1 inr+ mid inr- c fbl fbl fbr sft c out c fbl c fbr class d modulator and half-bridge control logic/ power-up sequencing l f c f c zbl r zbl c out r f1 r f1 shdn outr left positive audio input left negative audio input right positive audio input right negative audio input single-supply configuration outl 20v to 40v v ss v dd v dd 2 c sft on off simplified block diagrams 19-0731; rev 0; 1/07 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. evaluation kit available pin configuration located at end of data sheet. ordering information + denotes lead-free package. * ep = exposed paddle. part temp range pin-package pkg code MAX9742etx+ -40? to +85? 36 tqfn-ep* t3666-3 simplified block diagrams continued at end of data sheet. free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics?ingle-supply, single-ended output (v dd = 24v, v ss = v sub = lgnd = 0v, v shdn = 3.3v, v mid = 12v, c vdd = 660?, c mid1 = 10?, c mid2 = 10?, r1 = r2 = r3 = 10k ? , c sft = 0.47?, c out = 1000?, c fb_1 = 150pf, c fb_2 = 10pf, c boot = 0.1?, c regp = c regm = 1?, r in_ = 30.1k ? , r f1a = 121k ? , r f1b = 562k ? , r f2 = 681k ? , r ref = 68k ? , r l = , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 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 v ss , nsense ..............................................-0.3v to +45v mid, lgnd, lv dd , regm, regp, outr, outl to v ss .......................................................-0.3v to +45v mid, lgnd, lv dd , regm, regp, outr, outl to v dd .......................................................-45v to +0.3v regls to v ss .........................................................-0.3v to +12v mid to regp, regm...............(v regm - 0.3v) to (v regp + 0.3v) regp to regm.......................................................-0.3v to +12v lv dd to lgnd ..........................................................-0.3v to +6v shdn to lgnd.........................................................-0.3v to +4v sft to lgnd ............................................................-0.3v to +6v fb_, in_+, in_-, refcur to regp, regm..................................(v regm - 0.3v) to (v regp + 0.3v) bootr to outr ....................................................-0.3v to +12v bootl to outl .....................................................-0.3v to +12v outr, outl shorted to lgnd..................................continuous continuous power dissipation (t a = +70?) (note 1) single-layer board: 36-pin tqfn (derate 26.3mw/? above +70?) ...........2.11w multilayer board: 36-pin tqfn (derate 35.7mw/? above +70?) ...........2.86w junction-to-ambient thermal resistance ( ja ) single-layer board: 36-pin tqfn.................................................................38?/w multilayer board: 36-pin tqfn.................................................................28?/w junction-to-case thermal resistance ( jc ) ...................1.4?/w operating temperature range ...........................-40? to +85? maximum junction temperature .....................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units supply voltage range v dd (note 3) 20 40 v supply current i dd no load, output filter removed 15 ma mute mode supply current no load, v sft = 0v (outputs not switching) 8 ma shutdown current no load, v shdn = 0v 0.8 1.3 ma switching frequency f sw 300 khz power-supply rejection ratio (note 4) psrr v dd = 24v + 500mv p-p , f = 1khz 68 db crosstalk (notes 5 and 6) l to r, r to l, r l = 8 ? , p out = 1w, f = 1khz -78 db r l = 8 ? , f in = 1khz, thd+n = 10% 9.5 r l = 8 ? , f in = 1khz, thd+n = 10%, v dd = 35v 20.5 continuous output power (notes 5, 6, and 7) p out r l = 4 ? , f in = 1khz, thd+n = 10% 16 w efficiency (notes 5, 6, and 7) r l = 8 ? , p out = 9.5w, thd+n = 10% 92 % note 1: actual power capabilities are dependent on pcb layout. see the thermal considerations section. free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units r l = 8 ? , p out = 3.5w 0.06 total harmonic distortion plus noise thd+n f in = 1khz, bw = 22hz to 22khz (notes 5, 6, and 7) r l = 4 ? , p out = 5w 0.08 % unweighted 88 signal-to-noise ratio snr p out = 9.5w, r l = 8 ? , bw = 22hz to 22khz (notes 5 and 6) a-weighted 93 db half-bridge switch on-resistance r ds ( on ) 0.4 0.7 ? switch rise and fall times no load (note 4) 50 ns in_ input bias current -1 +1 ? mid input bias current i mid v dd = 24v, no load 50 ? shutdown-to-full operation t son 68 ms power-on to full operation t pu v shdn = 3.3v 1.5 s thermal-overload threshold temperature t sh junction temperature 150 o c short-circuit output current i sc out_ shorted to v dd or v ss 2.9 4.5 a into shutdown -38 click-and-pop k cp p eak vol tag e, 32- sam p l es p er second , a- w ei g hted ( n otes 4 and 8) out of shutdown -40 dbv digital inputs ( shdn ) (note 9) logic-input low voltage v il 0.4 v logic-input high voltage v ih 2.4 v input leakage current -1 +1 ? electrical characteristics?ingle-supply, single-ended output (continued) (v dd = 24v, v ss = v sub = lgnd = 0v, v shdn = 3.3v, v mid = 12v, c vdd = 660?, c mid1 = 10?, c mid2 = 10?, r1 = r2 = r3 = 10k ? , c sft = 0.47?, c out = 1000?, c fb_1 = 150pf, c fb_2 = 10pf, c boot = 0.1?, c regp = c regm = 1?, r in_ = 30.1k ? , r f1a = 121k ? , r f1b = 562k ? , r f2 = 681k ? , r ref = 68k ? , r l = , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 2) electrical characteristics?ual supplies (v dd = 15v, v ss = v sub = -15v, v shdn = 3.3v, v mid = lgnd = 0v, c vdd = c vss = 1000?, c byp = 1?, c sft = 0.22?, c fb_1 = 150pf, c fb_2 = 10pf, c boot = 0.1?, c regp = c regm = 1?, r in_ = 30.1k ? , r f1a = 121k ? , r f1b = 562k ? , r f2 = 681k ? , r ref = 68k ? , r l = , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 2) parameter symbol conditions min typ max units p osi ti ve s up p l y v ol tag e rang ev dd (note 3) 10 20 v n eg ati ve s up p l y v ol tag e rang e v ss (note 3) -20 -10 v positive supply mute mode current no load, v sft = 0v (outputs not switching) 8 11 ma negative supply mute mode current no load, v sft = 0v (outputs not switching) -12 -8 ma free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 4 _______________________________________________________________________________________ electrical characteristics?ual supplies (continued) (v dd = 15v, v ss = v sub = -15v, v shdn = 3.3v, v mid = lgnd = 0v, c vdd = c vss = 1000?, c byp = 1?, c sft = 0.22?, c fb_1 = 150pf, c fb_2 = 10pf, c boot = 0.1?, c regp = c regm = 1?, r in_ = 30.1k ? , r f1a = 121k ? , r f1b = 562k ? , r f2 = 681k ? , r ref = 68k ? , r l = , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 2) parameter symbol conditions min typ max units positive supply current i dd no load, output filter removed 23 36 ma negative supply current i ss no load, output filter removed -36 -23 ma positive supply shutdown current no load, v shdn = 0v 0.001 1 a negative supply shutdown current no load, v shdn = 0v -1 -0.03 a output offset voltage output referred, affected by r in_ and r f_ tolerances (note 4) 530mv in_ input bias current -1 +1 ? v dd = 10v to 20v 97 v ss = -10v to -20v 100 v dd = 15v + 500mv p-p , f = 1khz 67 power-supply rejection ratio (note 4) psrr v ss = -15v + 500mv p-p , f = 1khz 64 db crosstalk (notes 5 and 6) l to r, r to l, r l = 8 ? , p out = 1w, f = 1khz -61 db r l = 8 ? 14 r l = 8 ? , v dd = 18v, v ss = -18v 21 continuous output power p out f in = 1khz, thd+n = 10% (notes 5, 6, and 7) r l = 4 ? , v dd = 12v, v ss = -12v 9.5 w efficiency (notes 5, 6, and 7) r l = 8 ? , p out = 15w, thd+n = 10% 93 % r l = 8 ? , p out = 5w 0.06 total harmonic distortion plus noise thd+n f in = 1khz, bw = 22hz to 22khz (notes 5, 6, and 7) r l = 4 ? , p out = 10w 0.08 % unweighted 89 signal-to-noise ratio snr p out = 14w, r l = 8 ? , bw = 22hz to 22khz (notes 5 and 6) a-weighted 94 db shutdown-to-full operation t son 68 ms short-circuit output current i sc out_ shorted to v dd or v ss 2.9 4.5 a into shutdown -36 click-and-pop k cp p eak vol tag e, 32- sam p l es p er second , a- w ei g hted ( n otes 4 and 8) out of shutdown -36 dbv free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs _______________________________________________________________________________________ 5 note 2: all devices are 100% production tested at +25?. all temperature limits are guaranteed by design. note 3: supply pumping may occur at high output powers with low audio frequencies. use proper supply bypassing to prevent the device from entering overvoltage protection due to supply pumping. see the supply pumping effects and the supply undervoltage and overvoltage protection sections. note 4: amplifier inputs ac-coupled to ground. note 5: for r l = 4 ? , l f = 22? and c f = 0.68?. for r l = 6 ? , l f = 33? and c f = 0.47?. for r l = 8 ? , l f = 47? and c f = 0.33?. note 6: testing performed with four-layer pcb. note 7: both channels driven in phase. note 8: testing performed with an 8 ? resistor connected between lc filter output and ground. mode transitions are controlled by shdn . k cp level is calculated as 20log[(peak voltage during mode transition, no input signal) / 1v rms ]. note 9: digital input specifications apply to both single-supply and dual-supply operation. note 10: channels driven 180 out-of-phase. load connected between lc filter outputs. note 11: l f = 22? and c f = 0.68?. note 12: testing performed with an 8 ? resistor connected between lc filter outputs. mode transitions are controlled by shdn . k cp level is calculated as 20log[(peak voltage during mode transition, no input signal) / 1v rms ]. electrical characteristics?ingle-supply, btl configuration (v dd = 24v, v ss = v sub = lgnd = 0v, v shdn = 3.3v, v mid = 12v, c vdd = 660?, c mid1 = 10?, c mid2 = 10?, r1 = r2 = r3 = 10k ? , c sft = 0.47?, c out = 1000?, c fb_1 = 150pf, c fb_2 = 10pf, c boot = 0.1?, c regp = c regm = 1?, r in_ = 30.1k ? , r f1a = 121k ? , r f1b = 562k ? , r f2 = 681k ? , r ref = 68k ? , r l = , t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 2) parameter symbol conditions min typ max units output offset voltage (note 4) 7 mv v dd = 20v to 40v 88 power-supply rejection ratio (note 4) psrr v dd = 24v + 500mv p-p , f = 1khz 77 db continuous output power p out r l = 8 ? , f in = 1khz, thd+n = 10%, (notes 6, 10, and 11) 32 w efficiency r l = 8 ? , p out = 10w, thd+n = 10%, (notes 5 and 6) 83 % total harmonic distortion plus noise (notes 6, 10, and 11) thd+n f in = 1khz, bw = 22hz to 22khz, r l = 8 ? , p out = 10w 0.08 % unweighted 90 signal-to-noise ratio snr p out = 32w, r l = 8 ? , bw = 22hz to 22khz (notes 6, 10, and 11) a-weighted 96 db shutdown-to-full operation t son 68 ms into shutdown -47 click-and-pop k cp p eak vol tag e, 32- sam p l es p er second , a- w ei g hted ( n otes 4, 11, and 12) out of shutdown -32 dbv free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 6 _______________________________________________________________________________________ typical operating characteristics (24v single-supply mode, ?5v dual-supply mode, both channels driven in phase, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted. see figure 1 for test circuits, see typical application circuits/functional diagrams for test circuit component values.) total harmonic distortion plus noise vs. output power MAX9742 toc01 output power per channel (w) thd+n (%) 15 10 5 0.1 1 10 100 0.01 020 single supply v dd = 24v f = 1khz r l = 8 ? r l = 6 ? r l = 4 ? total harmonic distortion plus noise vs. output power MAX9742 toc02 output power per channel (w) thd+n (%) 30 20 10 0.1 1 10 100 0.01 040 single supply v dd = 32v f = 1khz r l = 8 ? r l = 6 ? thermally limited r l = 4 ? total harmonic distortion plus noise vs. output power MAX9742 toc03 output power per channel (w) thd+n (%) 30 20 10 0.1 1 10 100 0.01 040 single supply v dd = 36v f = 1khz r l = 8 ? r l = 6 ? thermally limited r l = 4 ? total harmonic distortion plus noise vs. output power MAX9742 toc04 output power per channel (w) thd+n (%) 30 20 10 0.1 1 10 100 0.01 040 single supply v dd = 40v f = 1khz r l = 8 ? r l = 6 ? thermally limited r l = 4 ? total harmonic distortion plus noise vs. output power MAX9742 toc05 output power (w) thd+n (%) 30 20 10 0.1 1 10 100 0.01 050 40 btl configuration v dd = 24v r l = 8 ? f = 1khz v dd = 24v v dd = 36v thermally limited total harmonic distortion plus noise vs. output power MAX9742 toc06 output power per channel (w) thd+n (%) 15 10 5 0.1 1 10 100 0.01 020 dual supply r l = 8 ? f = 1khz f = 100hz total harmonic distortion plus noise vs. output power MAX9742 toc07 output power per channel (w) thd+n (%) 20 10 0.1 1 10 100 0.01 030 15 525 dual supply r l = 4 ? f = 1khz f = 100hz thermally limited total harmonic distortion plus noise vs. output power MAX9742 toc08 output power per channel (w) thd+n (%) 10 5 0.1 1 10 100 0.01 015 single supply v dd = 24v r l = 8 ? f = 1khz f = 100hz total harmonic distortion plus noise vs. output power MAX9742 toc09 output power per channel (w) thd+n (%) 10 5 0.1 1 10 100 0.01 020 15 single supply v dd = 24v r l = 4 ? f = 1khz f = 100hz free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs _______________________________________________________________________________________ 7 total harmonic distortion plus noise vs. output power MAX9742 toc10 output power (w) thd+n (%) 20 10 0.1 0.01 1 10 100 0.001 040 30 btl configuration v dd = 24v r l = 8 ? f = 1khz f = 100hz total harmonic distortion plus noise vs. output power MAX9742 toc11 output power per channel (w) thd+n (%) 10 5 0.1 1 10 100 0.01 015 f = 1khz f = 100hz single supply v dd = 24v r l = 8 ? t a = 40 c total harmonic distortion plus noise vs. output power MAX9742 toc12 output power per channel (w) thd+n (%) 10 5 0.1 1 10 100 0.01 020 15 f = 1khz f = 100hz single supply v dd = 24v r l = 8 ? t a = 40 c total harmonic distortion plus noise vs. output power MAX9742 toc13 output power (w) thd+n (%) 20 10 0.1 1 10 100 0.001 0.01 040 30 f = 1khz f = 100hz btl configuration v dd = 24v r l = 8 ? t a = 40 c total harmonic distortion plus noise vs. frequency MAX9742 toc14 frequency (hz) thd+n (%) 10k 1k 0.1 1 10 100 0.01 100 100k dual supply r l = 8 ? p out = 8w p out = 4w total harmonic distortion plus noise vs. frequency MAX9742 toc15 frequency (hz) thd+n (%) 10k 1k 0.1 1 10 100 0.01 100 100k dual supply r l = 4 ? p out = 13w p out = 8w total harmonic distortion plus noise vs. frequency MAX9742 toc16 frequency (hz) thd+n (%) 10k 1k 0.1 1 10 100 0.001 0.01 100 100k single supply v dd = 24v r l = 8 ? p out = 5w p out = 3w total harmonic distortion plus noise vs. frequency MAX9742 toc17 frequency (hz) thd+n (%) 10k 1k 0.1 1 10 100 0.001 0.01 100 100k single supply v dd = 24v r l = 4 ? p out = 9w p out = 5w total harmonic distortion plus noise vs. frequency MAX9742 toc18 frequency (hz) thd+n (%) 10k 1k 0.1 1 10 100 0.001 0.01 100 100k btl configuration v dd = 24v r l = 8 ? p out = 17w p out = 12w typical operating characteristics (continued) (24v single-supply mode, ?5v dual-supply mode, both channels driven in phase, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted. see figure 1 for test circuits, see typical application circuits/functional diagrams for test circuit component values.) free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 8 _______________________________________________________________________________________ total harmonic distortion plus noise vs. frequency MAX9742 toc19 frequency (hz) thd+n (%) 10k 1k 0.1 1 10 0.01 100 100k single supply v dd = 24v r l = 8 ? p out = 50mw total harmonic distortion plus noise vs. frequency MAX9742 toc20 frequency (hz) thd+n (%) 10k 1k 0.1 1 10 0.01 100 100k single supply v dd = 24v r l = 4 ? p out = 50mw total harmonic distortion plus noise vs. output power with and without t-network MAX9742 toc21 output power per channel (w) thd+n (%) 0.1 0.01 10 1 0.1 1 10 100 0.01 0.001 100 without t-network with t-network single supply v dd = 24v r l = 8 ? f = 1khz efficiency and power dissipation vs. output power MAX9742 toc22 output power per channel (w) efficiency (%) 510 90 80 70 60 50 40 30 20 10 100 0 power dissipation (w) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 5.0 0 015 system power dissipation efficiency single supply v dd = 30v r l = 8 ? f in = 1khz efficiency and power dissipation vs. output power MAX9742 toc23 output power per channel (w) efficiency (%) 51015 90 80 70 60 50 40 30 20 10 100 0 power dissipation (w) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 5.0 0 020 system power dissipation efficiency dual supply r l = 8 ? f in = 1khz efficiency and power dissipation vs. output power MAX9742 toc24 output power per channel (w) efficiency (%) 510 90 80 70 60 50 40 30 20 10 100 0 power dissipation (w) 2.0 1.5 1.0 0.5 2.5 0 015 system power dissipation efficiency single supply v dd = 24v r l = 8 ? f in = 1khz efficiency and power dissipation vs. output power MAX9742 toc25 output power per channel (w) efficiency (%) 5101520 80 70 60 50 40 30 20 10 90 0 power dissipation (w) 8 7 6 5 4 3 2 1 9 0 025 system power dissipation efficiency single supply v dd = 24v r l = 4 ? f in = 1khz typical operating characteristics (continued) (24v single-supply mode, ?5v dual-supply mode, both channels driven in phase, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted. see figure 1 for test circuits, see typical application circuits/functional diagrams for test circuit component values.) free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs _______________________________________________________________________________________ 9 efficiency and power dissipation vs. output power MAX9742 toc26 output power (w) efficiency (%) 10 20 30 40 90 80 70 60 50 40 30 20 10 100 0 power dissipation (w) 8 6 4 2 1 9 7 5 3 10 0 050 system power dissipation efficiency btl configuration v dd = 24v r l = 8 ? f in = 1khz output power vs. supply voltage MAX9742 toc27 supply voltage (v) output power per channel (w) 14 12 15 20 25 30 0 10 5 10 20 18 16 dual supply r l = 8 ? 10% thd+n 1% thd+n output power vs. supply voltage MAX9742 toc28 supply voltage (v) output power per channel (w) 14 12 15 20 25 0 10 5 10 20 18 16 dual supply r l = 4 ? 10% thd+n 1% thd+n output power vs. supply voltage MAX9742 toc29 supply voltage (v) output power per channel (w) 30 25 20 25 30 0 15 10 5 20 40 35 single supply r l = 8 ? 10% thd+n 1% thd+n output power vs. supply voltage MAX9742 toc30 supply voltage (v) output power per channel (w) 30 25 20 25 30 0 15 10 5 20 40 35 single supply r l = 4 ? 10% thd+n 1% thd+n output power vs. supply voltage MAX9742 toc31 supply voltage (v) output power (w) 26 22 40 45 0 30 20 10 35 25 15 5 20 30 28 24 btl configuration r l = 8 ? 10% thd+n 1% thd+n supply current vs. supply voltage MAX9742 toc32 supply voltage (v) supply current (ma) 16 12 15 20 -20 5 -5 -15 10 0 -10 10 20 18 14 dual supply output filter removed no load connected v dd = |v ss | i ss i dd supply current vs. supply voltage MAX9742 toc33 supply voltage (v) supply current (ma) 35 25 17 18 12 15 13 16 14 20 40 30 single supply output filter removed inputs grounded no load connected shutdown supply current vs. supply voltage MAX9742 toc34 supply voltage (v) supply current (na) 14 0 10 -60 -20 -40 -10 -30 -50 10 22 18 20 12 16 dual supply v dd = |v ss | output filter removed inputs grounded no load connected i ss i dd typical operating characteristics (continued) (24v single-supply mode, ?5v dual-supply mode, both channels driven in phase, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted. see figure 1 for test circuits, see typical application circuits/functional diagrams for test circuit component values.) free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 10 ______________________________________________________________________________________ shutdown supply current vs. supply voltage MAX9742 toc35 supply voltage (v) supply current (ma) 30 0.8 1.0 0 0.4 0.6 0.2 20 40 25 35 single supply inputs ac grounded no load connected wideband output spectrum MAX9742 toc36 frequency (mhz) output amplitude (dbv) 10 -20 0 -120 -60 -40 -100 -80 0.1 100 1.0 rbw = 10khz measured at single- ended filter output inputs ac grounded output spectrum fft MAX9742 toc37 frequency (hz) output amplitude (dbv) 10k 15k -20 0 -120 -60 -40 -100 -80 0 20k 5k single supply r l = 8 ? f in = 1khz v out_ = -60dbv power-supply rejection ratio vs. frequency MAX9742 toc38 frequency (hz) psrr (db) 1k 10k -10 0 -80 -30 -20 -50 -60 -70 -40 10 100k 100 dual supply r l = 8 ? v dd = 15v + 500mv p-p v ss = -15v + 500mv p-p power-supply rejection ratio vs. frequency MAX9742 toc39 frequency (hz) psrr (db) 10k 1k 100 -100 -80 -60 -40 -20 0 20 -120 10 100k out_ psrr single supply v dd = 24v + 500mv p-p r l = 8 ? mid psrr power-supply rejection ratio vs. frequency MAX9742 toc40 frequency (hz) psrr (db) 1k 10k 0 -100 -20 -60 -90 -40 -10 -50 -80 -70 -30 10 100k 100 btl v dd = 24v + 500mv p-p r l = 8 ? crosstalk vs. frequency MAX9742 toc41 frequency (hz) crosstalk (db) 1k 10k 0 -90 -20 -60 -80 -40 -10 -50 -70 -30 10 100k 100 l into r r into l dual supply r l = 8 ? p out = 1w crosstalk vs. frequency MAX9742 toc42 frequency (hz) crosstalk (db) 10k 1k 100 -100 -80 -60 -40 -20 0 20 -120 10 100k r into l l into r single supply r l = 8 ? p out = 1w exiting shutdown (dual supply) MAX9742 toc43 20ms/div v out_ 20v/div v shdn 2v/div filtered v out_ 5v/div dual supply r l = 8 ? typical operating characteristics (continued) (24v single-supply mode, ?5v dual-supply mode, both channels driven in phase, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted. see figure 1 for test circuits, see typical application circuits/functional diagrams for test circuit component values.) free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 11 entering shutdown MAX9742 toc44 10ms/div v out_ 20v/div v shdn 2v/div filtered v out_ 5v/div dual supply r l = 8 ? exiting shutdown MAX9742 toc45 20ms/div v out_ 10v/div v shdn 2v/div filtered v out_ 5v/div single supply r l = 8 ? entering shutdown (single supply) MAX9742 toc46 10ms/div v out_ 10v/div v shdn 2v/div filtered v out_ 5v/div single supply r l = 8 ? case temperature vs. output power MAX9742 toc47 output power per channel (w) case temperature ( c) 810 50 0 30 10 40 20 012 46 2 single supply v dd = 24v r l = 8 ? 4-layer pcb case temperature vs. output power MAX9742 toc48 output power per channel (w) case temperature ( c) 10 15 120 0 80 40 20 100 60 020 5 single supply v dd = 24v r l = 4 ? 4-layer pcb output waveform MAX9742 toc49 1 s/div v out 10v/div v outr 10v/div single supply, v dd = 24v inputs ac grounded emi amplitude vs. frequency MAX9742 toc50 frequency (mhz) amplitude (db v/m) 100 40 5 30 10 20 35 15 25 30 1000 9.4db v/m below limit 18.1db v/m below limit en55022b limit 12.8db v/m below limit single supply r l = 8 ? , p out = 1.25w speaker cable lenth = 1m emi amplitude vs. frequency MAX9742 toc51 frequency (mhz) amplitude (db v/m) 100 40 5 30 10 20 35 15 25 30 1000 single supply r l = 4 ? , p out_ = 1.25w speaker cable lenth = 1m 11.3db v/m below limit 3.6db v/m below limit 7.8db v/m below limit 7db v/m below limit 5.8db v/m below limit en55022b limit typical operating characteristics (continued) (24v single-supply mode, ?5v dual-supply mode, both channels driven in phase, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted. see figure 1 for test circuits, see typical application circuits/functional diagrams for test circuit component values.) free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 12 ______________________________________________________________________________________ 12 ______________________________________________________________________________________ pin description pin name function 1, 6, 18, 27, 28, 36 n.c. no connection. not internally connected. 2, 3 outl left speaker output 4 sub device substrate. connect sub to v ss . 5 bootl left-channel bootstrap capacitor terminal. connect a 0.1? capacitor between bootl and outl. 7 inl+ left-channel positive input 8 inl- left-channel negative input. connect an external feedback capacitor between inl- and fbl. see the feedback capacitor (c fb_ ) section. 9 fbl left-channel feedback capacitor terminal. connect an external feedback capacitor between fbl and inl-. see the feedback capacitor (c fb_ ) section. 10 regm -5v internal regulator output. regulator output voltage is with respect to mid. bypass regm with a 1? capacitor to signal ground plane (sgnd). see the supply bypassing/layout section. 11 mid midsupply bias voltage input. the mid input biases the internal preamplifiers to the average value of the v dd and v ss supply inputs. for dual-supply operation, connect to the signal ground plane (sgnd). for single-supply operation, apply a voltage to mid equal to 0.5 x v dd through an external resistive voltage- divider and decoupling network (see the setting v mid section). see the typical application circuits / functional diagrams and supply bypassing/layout sections. 12 regp 5v internal regulator output. regulator output voltage is with respect to mid. bypass regp with a 1? capacitor to the signal ground plane (sgnd). see the supply bypassing/layout section. 13 refcur reference current resistor terminal. connect an external resistor from refcur to regp to set the switching frequency and output short-circuit current-limit value. use resistor values greater than or equal to 58k ? and less than or equal to 75k ? . see the setting the switching frequency and output current limit (r ref ) section. 14 sft soft-start capacitor terminal/mute input. connect a 0.22? capacitor between sft and pgnd to utilize the soft-start power-up sequence. drive sft low to mute the outputs. 15 lgnd logic ground. connect lgnd to signal ground (sgnd) and power ground (pgnd) planes. see the supply bypassing/layout section. 16 lv dd internal 5v logic supply. bypass lv dd to lgnd with a 0.1? capacitor. 17 shdn active-low shutdown input. drive shdn high for normal operation. drive shdn low to place the device into shutdown mode. 19 fbr right-channel feedback capacitor terminal. connect an external feedback capacitor between fbr and inr-. see the feedback capacitor (c fb_ ) section. 20 inr- right-channel negative input. connect an external feedback capacitor between inr- and fbr. see the feedback capacitor (c fb_ ) section. 21 inr+ right-channel positive input 22 nsense negative supply sense input. nsense is internally connected to v ss . connect a 1? bypass capacitor between nsense and regls. 23 regls 7v internal regulator output. regls output voltage is with respect to v ss . bypass regls with a 1? capacitor to nsense. free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 13 detailed description the MAX9742 is a two-channel, single-ended class d stereo amplifier capable of providing 16w of output power on each channel into 4 ? loads in single- or dual- supply operation. the amplifier can also provide 32w of output power in a mono bridge-tied-load (btl) con- figuration. the device offers class ab audio perfor- mance with class d efficiency. the differential input architecture reduces common- mode noise pickup. the device can also be configured for single-ended input signals. the connection of external feedback components allows custom gain settings. class d operation and efficiency class d amplifiers are switch-mode devices capable of significantly higher power efficiencies in comparison to linear amplifiers. the output stage of the MAX9742 con- sists of a half-bridge speaker driver (see figure 2). the high efficiency of a class d amplifier is attributed to the region of operation of the output stage transistors. in a class d amplifier, the output transistors act as current- steering switches by switching the output between v dd and v ss (ground for single-supply operation). 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 ______________________________________________________________________________________ 13 pin description (continued) pin name function 24 bootr right-channel bootstrap capacitor. connect a 0.1? capacitor between bootr and outr. 25, 26 outr right speaker output 29, 30, 34, 35 v dd positive power-supply input. bypass v dd to lgnd with a 0.1? plus additional bulk capacitance. see the supply pumping effects section. 31, 32, 33 v ss negative power-supply input. for dual-supply operation, connect to negative power-supply voltage and bypass v ss to lgnd with a 0.1? plus additional bulk capacitance. for single-supply operation, connect to lgnd. ep ep exposed paddle. ep is internally connected to device substrate. connect ep to v ss through a large section of copper to maximize power dissipation. outl outr c f l f r l aux-0025 filter audio analyzer single-ended configuration btl configuration MAX9742 c f l f r l outl + - + - + - + - + - + - outr c f l f r l aux-0025 filter audio analyzer MAX9742 c f l f note: single-ended configuration is ac-coupled in single-supply mode. figure 1. test circuits for single-ended and btl configurations test circuits free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 14 ______________________________________________________________________________________ efficiency of a linear amplifier is 78%; however, that effi- ciency is only exhibited at peak output powers. under normal operating levels (typical music reproduction lev- els), efficiency falls below 30%, whereas the MAX9742 still exhibits 80% efficiency under the same conditions. since the output transistors switch the output to either v dd or v ss (ground for single-supply operation), the resulting output of a class d amplifier is a high-fre- quency square wave. this square wave is pulse-width- modulated by the audio input signal. in the MAX9742, the pulse-width modulation (pwm) is accomplished by comparing the input audio signal to an internally gener- ated triangle wave oscillator. the resulting duty cycle of the square wave is proportional to the level of the input signal. when the input signal is at 0v, the duty cycle of the MAX9742 output is equal to 50%. to extract the amplified audio signal from this pwm waveform, the output of the MAX9742 is fed to an external lc lowpass filter (see the single-ended lc output filter design (l f and c f ) section). the lc filter works as an averaging circuit for the pwm output voltage waveform. the resulting averaged output voltage is equal to the ampli- fied audio signal. figure 3a illustrates the resulting pwm output waveform due to the varying input signal level, and figure 3b shows the recovered amplified input signal after filtering. l f c f out_ v dd v ss v ss dual-supply configuration shown 7v regulator (with respect to v ss ) gate drive logic c boot 0.1 f d boot 1n4148 regls c regls 1 f v regls nsense (internally connected to v ss ) MAX9742 figure 2. simplified block diagram of the MAX9742 output stage free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 15 internal triangle wave oscillator input signal v out_ v dd v dd + v ss 2 v ss 1 f sw note: for clarity, signal periods are not shown to actual scale. figure 3a. MAX9742 output with an applied input signal v out_ v dd v dd + v ss 2 v ss note: for clarity, signal periods are not shown to actual scale. average value of v out_ figure 3b. MAX9742 output with resulting output after filtering free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 16 ______________________________________________________________________________________ shutdown mode the MAX9742 features a low-power shutdown mode that reduces quiescent current consumption to less than 0.5ma in single-supply mode and less than 1? in dual-supply mode. drive shdn low to place the device into shutdown mode. connect shdn to a logic-high for normal operation. the maximum voltage that may be applied to the shdn input is 4v (see the absolute maximum ratings sec- tion). if the shdn input must be controlled by a 5v logic signal, limit the maximum voltage that can be applied to the shdn input to 4v through an external resistive divider. click-and-pop suppression the MAX9742 features comprehensive click-and-pop suppression that minimizes audible transients on start- up and shutdown. while in shutdown, the half-bridge output transistor switches are turned off, causing each output to go high impedance. during startup, or power- up, the input amplifiers are muted and an internal loop sets the modulator bias voltages to the correct levels, minimizing audible clicks and pops when the output half-bridge is enabled. the value of the soft-start capacitor, c sft , affects the click-and-pop performance and startup time of the MAX9742 (see the soft-start capacitor (c sft) section). to maximize click-and-pop suppression when powering up an audio system, drive shdn or sft (see the mute function section) to 0v until the rest of the circuitry in the system has had enough time to stabilize. this ensures the MAX9742 is the last device to be activated in the system and pre- vents transients caused by circuitry preceding the MAX9742 from being amplified at the outputs. mute function the MAX9742 features a clickless/popless mute mode. when the device is muted, the outputs stop switching, muting the speaker. the mute function only affects the output stage and does not shutdown the device. to mute the MAX9742, drive sft to ground. figure 4 shows how an external transistor (mosfet or bjt) can be used to easily mute the MAX9742. thermal-overload protection thermal-overload protection limits total power dissipa- tion in the MAX9742. when the junction temperature exceeds approximately +160?, the thermal protection circuitry disables the amplifier output stage. the ampli- fiers are enabled once the junction temperature cools by approximately 15?. this results in a pulsing output under continuous thermal-overload conditions. supply undervoltage and overvoltage protection the MAX9742 features an undervoltage protection function that prevents the device from operating if v dd is less than +7v with respect to v mid input or if v ss is greater than -7v with respect to v mid . this feature pre- vents improper operation when insufficient supply volt- ages are present. once the supply voltage exceeds the undervoltage threshold, the MAX9742 is turned on and the amplifiers are powered, provided that shdn is high and the outputs are unmuted. the MAX9742 also features an overvoltage protection function that prevents the device from operating if the potential difference between v dd and v ss exceeds +46v. this feature prevents the MAX9742 from damag- ing itself due to excessive supply pumping effects (see the supply pumping effects section). the device returns to normal operation once the potential differ- ence between v dd and v ss drops below +46v. applications information output dynamic range dynamic range is the difference between the noise floor of the system and the output level at 10% thd+n. it is essential that a system? dynamic range be known before setting the maximum output gain. output clip- ping occurs if the output signal is greater than the dynamic range of the system. use the thd+n vs. output power graph in typical operating characteristics to identify the system? dynamic range. given the system? supply voltage, find the output power that causes 10% thd+n for a given load. use the following equation to determine the peak- sft c sft control logic/power-up sequencing to output stage mute un-mute 10k ? MAX9742 figure 4. MAX9742 mute circuit free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 17 to-peak output voltage that causes 10% thd+n for a given load. where p out_10% is the output power that causes 10% thd+n, r l is the load resistance, and v out_p-p is the peak-to-peak output voltage. determine the voltage gain (a v ) necessary to attain this output voltage based on the maximum peak-to-peak input voltage (v in_p-p ): set the closed-loop voltage gain of the MAX9742 less than or equal to a v to prevent clipping of the output, unless audible clipping is acceptable for the application. input amplifier the external feedback networks of the MAX9742 input amplifiers allow custom gain settings while maximizing dynamic range. the input amplifiers also accommodate a variety of standard amplifier configurations including differential input, single-ended input, and summing amplifiers. due to the output current limitations of the internal input amplifiers, always select feedback resistors (r f1 , see the typical application circuits/functional diagrams ) with values greater than or equal to 400k ? . to preserve gain accuracy, avoid using feedback resistors with values greater than 1m ? . for proper operation, limit common-mode input voltages to ?v. differential input configuration the typical application circuits/functional diagrams show each channel of the MAX9742 configured as dif- ferential input amplifiers. a differential input offers improved noise immunity over a single-ended input. in systems that include high-speed digital circuitry, high- frequency noise can couple into the amplifier? input traces. the signals appear at the amplifier? inputs as common-mode noise. a differential input amplifier amplifies the difference of the two inputs, and signals common to both inputs are subtracted out. when con- figured for differential inputs, the voltage gain of the MAX9742 is set by: where a v is the desired voltage gain in v/v. r in1 should be equal to r in2 , and r f1 should be equal to r f2 . when using the differential input configuration, the common-mode rejection ratio (cmrr) is primarily limit- ed by the external resistor tolerances. ideally, to achieve the highest possible cmrr, the resistors should be perfectly matched and the following condi- tion should be met: to ensure the MAX9742 input amplifiers operate as fully differential integrators, connect a capacitor between in_+ and mid whose value is equal to c f (see the feedback capacitor (cfb_) section). single-ended input each channel of the MAX9742 can be configured as a single-ended input amplifier by connecting in_+ to mid (through an external resistor, r os ) and driving in_- with the input source (see figure 5). in this configuration, the MAX9742 is configured as a single-ended amplifier whose voltage gain is equal to: where a v is the desired voltage gain in v/v. to minimize output offset voltages due to input bias cur- rents, connect a resistor, r os , (see figure 5) between in_+ and mid. select the value of r os so that the dc resistances looking out of inputs of the amplifier (in_+ and in_-) are equal. for example, when using the dual- supply configuration with a dc-coupled input source, the value of r os should be equal to r f ||r in . a r r v f in (/) = ? vv r r r r f1 in1 f2 in2 = a r r v f1 in1 = ( / ) vv a v v v out_p p in_p p (/) = ? ? vv v2 2pr out_p p out_10% l ? = () () v out_ v in c in r in r os MAX9742 mid to class d modulator r f in_- in_+ c fb_ fb_ figure 5. single-ended input configuration free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 18 ______________________________________________________________________________________ summing configuration (audio mixer) figure 6 shows the MAX9742 configured as a summing amplifier, which allows multiple audio sources to be lin- early mixed together. using this configuration, the out- put of the MAX9742 is equal to the weighted sum of the input signals: as shown in the above equation, the weighting or amount of gain applied to each input signal source is determined by the ratio of r f and the respective input resistor (r in1 , r in2 , r in3 ) connected to each signal source. select r f and r in_ so that the dynamic range of the MAX9742 is not exceeded when the input signals are at their maximum values and in phase with each other (see the output dynamic range section). to minimize output offset voltages due to input bias currents, connect a resistor, r os , (see figure 6) between in_+ and mid. select the value of r os such that the dc resistances looking out of inputs of the amplifier (in_+ and in_-) are equal. for example, when using the dual-supply configuration with a dc-coupled input source, the value of r os should be equal to r f ||r in1 ||r in2 || ||r inn . mono bridge-tied-load (btl) configuration the MAX9742 also accommodates a mono bridge-tied- load (btl) configuration that can be used in single- supply and dual-supply applications. in the btl configuration, the speaker load is driven differentially by connecting the half-bridge outputs as a full h-bridge driver. to drive the speaker differentially, the inputs of both channels must be driven by the same audio signal with one channel 180 out-of-phase with the other channel. figure 7 shows the connections required for btl operation. the advantages of btl operation include reduced component count due to the elimination of the output- coupling capacitors when using single-supply opera- tion, a 6db increase in gain due to the load being driven differentially, increased output power into a sin- gle load, and the minimization of the supply-pumping since each half bridge is driven 180 out-of-phase (see the supply pumping effects section). for single-supply applications, the output-coupling capacitors are not needed for btl operation since the dc voltage present at each half-bridge output is equal in value and applies to each side of the load. this means no dc voltage appears across the load, and therefore, no dc current flows into the speaker. v (v r r v r r v r r ) out_ in1 f in1 in2 f in2 in3 f in3 = ? ++ out_ v in2 c in r in2 r os MAX9742 v in1 c in r in1 v in3 c in r in3 mid to class d modulator r f in_- in_+ c fb_ fb_ v out_ (v in1 r f v in2 r f v in3 r f ) r in1 r in2 r in3 figure 6. summing amplifier configuration free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 19 since each half-bridge output stage is only capable of driving loads as small as 4 ? and each half-bridge sees half of the differential load resistance when configured for btl, only use the btl configuration with loads greater than or equal to 8 ? . the MAX9742 may be ther- mally limited when using the btl configuration with high supply voltages due to the decreased load resis- tance seen by each half bridge. for optimum perfor- mance, the pcb should be thermally optimized to achieve the continuous output powers required for the application (see the thermal considerations section). component selection feedback capacitor (c fb_ ) to maximize dynamic range, an external feedback capacitor (c fb_ ) is needed to generate an error signal for the class d modulator. the feedback capacitor con- figures the input amplifier stage as an integrator whose output is equal to an error signal consisting of the sum of the integrated input audio and pwm output signals. the integrator provides a noise-shaping function for the closed-loop response of the amplifier. a v_btl = 2 r f_ r in_ r in1 = r in2 , r f1 = r f2 mid class d modulator and gate drive r f2 l f l f r f2 c fbr r f1 c zbl c zbl r zbl r zbl c in r in1 MAX9742 c in r in2 r f1 inl- inl+ c in r in2 c in r in1 inr+ inr- c fbl differential audio input fbl fbr c f outl v dd v ss c f c f c f class d modulator and gate drive outr v dd v ss v out_p-p v dd /2 v dd /2 v out_p-p 2 x v out_p-p 0v figure 7. input signal source and load connections for btl operation free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 20 ______________________________________________________________________________________ to guarantee stability and minimize distortion, select the external feedback resistor (r f_ ) and capacitor (c fb_ ) so that the following conditions are met: where f sw is the output switching frequency deter- mined by r ref (see the setting the switching frequency and output current limit (r ref ) section). setting the switching frequency and output current limit (r ref ) resistor r ref determines the output switching frequency (f sw ) and the output short-circuit current-limit value (i sc ). set f sw and i sc with the following equations: for example, selecting a 68k ? resistor for r ref results in a switching frequency of 303khz and an output short-circuit current limit of 4.5a. to prevent damage to the MAX9742 during output short-circuit conditions and to utilize its full output power capabilities, use resistor values greater than or equal to 58k ? and less than or equal to 75k ? for r ref . input-coupling capacitor the ac-coupling capacitors (c in ) and input resistors (r in_ ) form highpass filters that remove any dc bias from an input signal (see the typical application circuits/functional diagrams ). c in prevents any dc components from the input-signal source from appear- ing at the amplifier outputs. the -3db point of the high- pass filter, assuming zero source impedance due to the input signal source, is given by: choose c in so that f -3db is well below the lowest frequen- cy of interest. setting f -3db too high affects the amplifier? low-frequency response. use capacitors with low-voltage coefficient dielectrics. aluminum electrolytic, tantalum, or film dielectric capacitors are good choices for ac-cou- pling capacitors. capacitors with high-voltage coeffi- cients, such as ceramics (non-c0g dielectrics), can result in increased distortion at low frequencies. single-ended lc output filter design (l f and c f ) an lc output filter is needed to extract the amplified audio signal from the pwm output (see figure 8). the lc circuit forms an lcr lowpass filter (neglecting voice coil inductance) with the impedance of the speaker. to pro- vide a maximally flat-frequency response, the lcr filter should be designed to have a butterworth response and should be optimized for a specific speaker load. table 1 provides some recommended standard l f and c f com- ponent values for 4 ? , 6 ? , and 8 ? speaker loads. the component values given in table 1 provide an approxi- mate -3db cutoff frequency (f c ) of 40khz. the following paragraph provides information on calculating filter com- ponent values for cutoff frequencies other than 40khz and speaker loads not listed in table 1. the lcr filter has the following 2nd order transfer function: where l f is the value of the filter inductor, c f is the value of the filter capacitor, and r spkr is the dc resis- tance of the speaker. the voice coil inductance of the speaker has been neglected to simplify filter calcula- tions (see the zobel network section). the above trans- fer function is presented in the general 2nd order transfer function format given below: where w n is the natural frequency in radians/s and is the damping ratio of the 2nd order system. for an ideal butterworth response, is equal to 0.707 and c is equal to the -3db cutoff frequency, c . using the above transfer functions and converting to hertz, the -3db cut- off frequency of the filter is: f 1 2 l c c ff = () hz h s2 s (s) n 2 2 nn 2 = + + ? h 1 l c s 1 r c s 1 l c (s) ff 2 spkr f f f = + + f 1 2 r c 3db in in ? = () hz f 1 3.3 s 68k r i 3.6a 68k r sw ref sc ref = = () () ? ? hz a r c 21.5 f f_ fb_ sw > _ and r k f 400 ? free datasheet http:///
using the transfer functions and the equation for f c , the following expressions for l f and c f can be derived: since the frequency response of the output filter is dependent on the speaker resistance, it is best to opti- mize the lc filter for a particular load resistance. to calculate the component values of the lc filter for a given speaker load resistance, first select an appropri- ate cutoff frequency for the filter. the cutoff frequency should be high enough so that upper audio frequency band attenuation is kept to a minimum while providing sufficient attenuation at the switching frequency (f sw ) of the MAX9742. once the cutoff frequency is determined, calculate c f using the dc resistance of the speaker (r spkr ) and a damping ratio ( ) equal to 0.707. finally, calculate l f using the resulting c f value. when selecting c f , use capacitors with dc voltage rat- ings greater than v dd . when selecting l f , it is important to take into account the dc resistance, current capabilities, and upper fre- quency limitations of the inductor. choosing an induc- tor with minimum dc resistance minimizes i 2 r losses due to the filter inductor and therefore preserves power efficiency. the inductor current rating should be greater than the maximum peak output current to pre- vent the inductor from going into saturation. output inductor saturation introduces nonlinearities into the output signal and therefore increases distortion. the upper frequency limit of the inductor should also be taken into account. the load connected to the output of the half-bridge (lc filter and speaker) should remain inductive at the switching frequency of the MAX9742. if not, a significant amount of high-frequency energy is dissipated in the resistive load, therefore, increasing the supply current to excessive levels. to prevent this from occurring, select an output inductor whose self- resonant frequency is substantially higher than the switching frequency of the MAX9742. to minimize possible emi radiation, place the lc filter near the MAX9742 on the pcb. table 2 provides some suggested inductor manufac- turers. btl lc output filter design when using the btl configuration, optimize the output fil- ter for fully differential operation (see figure 9 and table 3). follow the design criteria provided for the single- ended filter except use half the value of the btl resis- tance for the output filter calculations. this is because each half-bridge output sees half of the btl resistance. for example, with a btl resistance of 8 ? the ideal filter component values are c f = 0.7? and l f = 22.5? for a maximally flat differential filter response with an approxi- mate cutoff frequency of 40khz. rounding to the nearest standard component values yields c f = 0.68? and l f = 22?. also connect ground-terminated zobel networks on each side of the speaker load (see the zobel network section). ground terminating the zobel networks pre- vents excessive peaking in the common-mode frequen- cy response of the filter. c 1 4 f r l 1 4 f c f c spkr f 2 c 2 f = = () () f h MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 21 table 1. recommended lc filter component values for various speaker loads (f c = 40khz) dc resistance of speaker ( ? )l f (?) c f (?) 4 22 0.68 6 33 0.47 8 47 0.33 table 2. suggested inductor manufacturers model manufacturer dimensions website do3340p coilcraft 12.95mm x 9.4mm x 11.43mm www.coilcraft.com cdrh127 sumida 12.3mm x 12.3mm x 8mm www.sumida.com 11rhbp toko 11mm x 11mm x 13.75mm www.tokoam.com slf12575 tdk 12.5mm x 12.5mm x 7.5mm www.component.tdk.com l f c f out_ r spkr single-ended output filter note: an output-coupling capacitor (c out ) is needed for single-supply, single-ended output configuration. figure 8. single-ended lc output filter free datasheet http:///
MAX9742 to maximize the performance of the differential output filter and minimize emi radiation, keep the ground con- nections of the c f capacitors close together on the pcb and place the filter near the MAX9742. the component ratings for c f and l f follow the same requirements mentioned in the single-ended lc output filter design (l f and c f ) section. zobel network for speaker loads that have appreciable amounts of voice coil inductance (> 33?), peaking in the frequen- cy response of the output may occur near the cutoff fre- quency of the lc filter, which may cause the device to go into current limit at high output powers. this peaking is due to the resonant circuit formed by the lc output filter and complex impedance of the speaker. to nullify the peaking in the frequency response, connect a zobel network (series rc circuit) in parallel with the speaker load as shown in figure 10. the zobel circuit reduces the peaking by dampening the reactive behav- ior of the speaker. for the single-ended output configu- ration, use the following equations to calculate the component values for the zobel network: where r zbl is the value of the zobel resistor, c zbl is the value of the zobel capacitor, r spkr is the dc resis- tance of the speaker, and f c is the cutoff frequency of the lc filter. for the btl configuration, use half of the btl resistance for the zobel network calculations. connect a ground-terminated zobel network on each side of the btl resistance to prevent excessive peak- ing in the common-mode response of the output filter. for most applications, r zbl should have a minimum power rating of 1/4w or greater. c zbl should have a voltage rating greater than or equal to v dd . r 1.2 r c 1 2r f zbl spkr zbl spkr c = = () () ? f single-/dual-supply, stereo 16w, class d amplifier with differential inputs 22 ______________________________________________________________________________________ table 3. recommended differential lc filter component values for an 8 ? btl speaker load (f c = 40khz) dc resistance of speaker ( ? )l f (?) c f (?) 8 22 0.68 l f c f c f outl l f outr r spkr bridge-tied-load (btl) output filter figure 9. btl lc output filter l f c f c f outl l f outr r spkr note: an output-coupling capacitor (c out ) is needed for single-supply, single-ended output configuration. speaker load l spkr r zbl r zbl c zbl c zbl l f c f out_ r spkr speaker load l spkr r zbl c zbl figure 10. zobel network connections for high-inductance speakers free datasheet http:///
bootstrap diode (d boot ) to provide sufficient gate drive voltage to the high-side transistor of the half-bridge output stage, an external diode (d boot ) and capacitor (c boot ) are needed for the internal bootstrapping circuitry (see figure 2). to maintain high power efficiencies and maximum output power at low audio frequencies, use fast-recovery switching diodes for d boot . silicon diodes equivalent to 1n914, bas16, or 1n4148 work well. capacitor (c boot ) for most applications, use a c boot capacitor 0.1? and 0.22?. for proper operation, use capacitors with low esr and voltage ratings greater than 7v for c boot . output-coupling capacitors (c out , single-ended, single-supply operation) the MAX9742 requires output-coupling capacitors for single-supply operation. since the MAX9742 outputs switch between v dd and ground in single-supply opera- tion, there is a dc component equal to 0.5 x v dd pre- sent at the outputs. the output-coupling capacitor blocks this dc component, preventing dc current from flowing into the load. the output capacitor and the load resistance of the speaker form a highpass filter. the -3db point of the highpass filter can be approximated by: where f -3db is the -3db cutoff frequency of the filter, r spkr is the dc resistance of the speaker, and c out is the value of the output-coupling capacitor. as with the input capacitor, choose c out such that f -3db is well below the lowest frequency of interest. setting f -3db too high affects the amplifier? low-frequency response. select capacitors with low esr to minimize power loss- es. since the output-coupling capacitor has a large amplitude ac current (resulting average output current due to the lc filter) flowing through it at high output powers, it is important to select an output-coupling capacitor that has an appropriate ripple current rating. to prevent damage to the output-coupling capacitor, use the following equation to calculate the required rms ripple current rating for c out : where i rms_ripple is the minimum required rms ripple current rating for c out and r spkr is the dc resistance of the speaker. the ripple current ratings of capacitors are frequency dependent, so be sure to select a capacitor based on its ripple current rating within the audio frequency range. select output-coupling capacitors with dc voltage rat- ings greater than v dd . in single-supply operation with single-ended outputs, the leakage current of c out can affect the startup time of the MAX9742. to minimize startup time delays due to c out , use capacitors with leakage current ratings less than 1? for c out . see the startup time considerations section for more information on optimizing the startup time of the MAX9742. setting v mid the voltage present at the mid input biases the internal amplifiers and should be set to the average value of v dd and v ss for maximum dynamic range. for dual- supply operation, connect mid to ground. for single- supply operation, set mid to 0.5 x v dd through an external resistive divider. to minimize power dissipation while providing enough input bias current for the mid input, select divider-resistors with values greater than or equal to 10k ? and less than or equal to 20k ? . connect a decoupling network between mid and the sgnd plane (see the supply bypassing/layout sec- tion) to provide a sufficient low- and high-frequency ac ground for the internal amplifiers. figure 11 shows the recommended decoupling networks for bypassing the mid input. i v 2.83 r rms_ripple dd spkr = () a f 1 2r c 3db spkr out ? = () hz MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 23 free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 24 ______________________________________________________________________________________ multiple-pole mid network vs. single-pole vmid network for increased psrr performance (single-supply operation) a multiple-pole mid network improves psrr perfor- mance over a single-pole network. since the input amplifiers of the MAX9742 are biased at v mid , any noise coupled into the mid input using the mid bias network supply appears at the outputs of the MAX9742. increasing the number of poles in the mid network pro- vides further attenuation of low-frequency noise at the mid input, and therefore, improving the ac psrr per- formance of the MAX9742. figure 11 shows the recom- mended single-pole and two-pole mid input bias networks. figure 12 illustrates the differences of the MAX9742? low-frequency ac psrr performance with the single-pole and two-pole networks shown in figure 11. soft-start capacitor (c sft ) the soft-start capacitor determines the timing for the soft-start power-up sequencing that minimizes audible clicks-and-pops during power-up/power-down transi- tions and when entering/exiting shutdown mode. connect a capacitor between sft and ground for proper operation. for optimum performance, this capacitor should equal 0.22?. using capacitor values much smaller than these values degrade click-and- pop performance and values much greater lengthen startup time. startup time considerations at the beginning of the soft-start sequence, the MAX9742 ensures v out_ is approximately equal to v mid before continuing the soft-start sequence. for sin- gle-supply operation with single-ended outputs, the output-coupling capacitors (c out ) are first gradually charged up to v mid before continuing soft-start sequencing. this gradual charging up of c out mini- mizes audible transients that may appear across the r1 10k ? r2 10k ? v dd single-pole network to mid c mid1 22 f c mid2 1 f r1 10k ? r2 10k ? v dd two-pole network to mid c mid1 10 f c mid2 10 f r3 10k ? figure 11. recommended mid input bias networks power-supply rejection ratio vs. frequency MAX9742 fg12 frequency (hz) psrr (db) 10k 1k 100 -100 -80 -60 -40 -20 0 20 -120 10 100k 1-pole mid network single supply v dd = 24v + 500mv p-p r l = 8 ? 2-pole mid network figure 12. comparison of MAX9742 ac psrr with single-pole and two-pole mid networks free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 25 speaker loads during mode transitions. after c out is charged up to v mid , the MAX9742 concludes the soft- start sequence by precharging c regls , c boot , and c in . once the soft-start sequence is complete, the MAX9742 begins normal operation. for dual-supply operation, the startup time of the MAX9742 is primarily dependent on the value of c sft since it controls the rate of the soft-start sequencing. in single-supply operation, the overall startup time is affected by the values of c mid1 , c mid2 , c sft , c out (single-ended outputs) and the value of the resistors used to bias the mid input. this is because soft-start power-up sequencing is dependent on the charging-up of the mid input bias network and the charging rate of c out . as with dual-supply operation, the startup time is also affected by the value of c sft since it controls the rate of the soft-start sequencing. using the component values shown in figure 11 and a c sft capacitor value of 0.22? yields a typical single-supply power-up time of 1.5s. for single-supply operation with single-ended outputs, the leakage current of c out can also affect the startup time of the MAX9742. to minimize startup time delays due to c out , use capacitors with leakage current rat- ings less than 1? for c out . supply pumping effects when using the MAX9742 in the single-ended output configuration, the power-supply voltages (v dd and v ss ) may increase if the supplies cannot sink current. this ?upply pumping?is primarily due to the inductive loading of the lc filter and the voice coil inductance of the speaker. the inductive load connected to the out- put of the device prevents the output current from changing instantaneously. when the MAX9742 drives this inductive load, a continuous current flows at the output whose value is equal to the running average of the output switching currents, or in other words, the amplified audio signal. this averaged current continues to flow during both switching cycles of the half-bridge, which means that some of the current is pumped back towards the opposite power supply. if the respective supply cannot sink this current, it flows into supply bypass capacitor causing the voltage across the capacitor to increase. the amount of current pumped back into the opposite supply is proportional to the duty cycle of the switching period. for example, if the magnitude of the average (continuous) current during a single switching cycle is equal to -1a and the duty cycle of the output is equal to 25%, this means the v ss supply provides 0.75a of cur- rent while the v dd supply must sink 0.25a. since the v dd supply cannot sink this current, it flows into the bypass capacitor causing the v dd supply voltage to be pumped up. figures 13a and 13b illustrates the contin- uous output current flow that causes the supply pump- ing action. free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 26 ______________________________________________________________________________________ l f c f on off c vdd c vss i avg i avg v ss c vss v dd l f c f on off c vdd v ss v dd case 1: i avg flowing into half-bridge causing voltage across c vdd to increase (duty cycle < 50%). i avg = average (continuous) output current during one switching cycle. i pump = amount of current pumped into supply bypass capacitor. i pump = duty cycle x i avg figure 13a. continuous output current flow for positive supply pumping l f c f on off c vdd c vss i avg i avg v ss c vss v dd l f c f on off c vdd v ss v dd case 2: i avg flowing out of half-bridge causing voltage across c vss to increase (duty cycle > 50%). i avg = average (continuous) output current during one switching cycle. i pump = amount of current pumped into supply bypass capacitor. i pump = duty cycle x i avg figure 13b. continuous output current flow for negative supply pumping free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 27 a v - r f r in_ r in1 = r in2 , r f1 = r f2 dual-supply configuration mid r f2 r f2 c fbr r f1 c in r in1 MAX9742 c in r in2 r f1 inl- inl+ c in r in2 c in r in1 inr+ inr- c fbl outl + + - - + - + - c fbl c fbr outr l f c f l f c f left-channel audio input fbl fbr right-channel audio input v dd v ss figure 14. circuit configuration for minimizing supply pumping worst-case supply pumping occurs at high output pow- ers with low-frequency signals and small load resis- tances. since the period is longer for low-frequency signals, the continuous output current has more time to pump up the supply rails during each cycle of the audio signal. additionally, for most stereo audio sources the low-frequency audio content (bass) is pri- marily monophonic. this means both output channels are basically equal in magnitude and in phase at low frequencies causing twice as much pump-up current to flow into the supply bypass capacitors and therefore doubling the supply pump-up voltages. assuming purely sinusoidal output signals, the worst-case supply voltage increase due to supply pumping can be approximated using the following equation: where v pump_max is the magnitude increase of the supply rail, v supply is the nominal voltage magnitude of the respective supply, f out is the frequency of the audio signal, and c supply is the value of the respec- tive supply bypass capacitor. the above equation shows that increasing the value of the supply bypass capacitor decreases the supply voltage variations due to supply pumping. using large bypass capacitors helps minimize supply voltage variations by providing sufficient supply decoupling at low output frequencies. to prevent the MAX9742 from entering supply overvolt- age protection mode at low output frequencies (as low as 20hz), use supply bypass capacitors with values of at least 1000? for dual-supply operation and 660? for single-supply operation. alternate methods for mitigating supply pumping using the btl configuration minimizes the supply pumping effect since the outputs are driven 180 out- of-phase with each other. driving the outputs 180 out- of-phase causes each half-bridge to pump up and draw current from opposite supplies, which reduces the magnitude of the of the supply pumping. for the single-ended output configuration, the supply pumping can be minimized by driving the channels 180 out-of-phase and reversing the polarity of one speaker connection (see figure 14). reversing the polarity of one speaker minimizes any adverse affects on the audio quality by ensuring that the physical dis- placement of the speaker cones matches the physical displacement of the speakers when driven with in phase signals. v v 2 1 f r c pump_max supply 2 out spkr supply = ? ? ? ? ? ? ? ? ? ? ? ? free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 28 ______________________________________________________________________________________ t-network for low thd performance at low output powers (optional) if low thd+n performance is needed at low-output pow- ers, replace the feedback resistor (r f1 ) in each channel with the t-network shown in figure 15. the t-network provides additional attenuation of audio band noise, therefore, providing improved thd+n performance at lower output powers. use the following expressions to select r in1 , r in2 , r f1a , r f1b , and r f2 : where a v is the desired voltage gain in v/v. to maxi- mize cmrr and minimize gain mismatch between channels, use the closest 1% tolerance resistor values available for r in1 , r in2 , r f1a , r f1b , and r f2 . see the thd+n vs. output power with and without t-network plot in the typical operating characteristics for a comparison of the thd+n performance with and without the optional t-network. output limiting diodes (optional) in applications where the output can be driven to clip- ping, a pair of diodes around the feedback capacitor helps reduce distortion. clipping is most likely to hap- pen when driving high-impedance speakers with lower supply voltages, for example, 8 ? loads with a 24v sin- gle supply. diodes such as bav99, a dual series silicon switching diode, are a good choice. connect these diodes around the feedback capacitor as shown in figure 16. r rr a kk a 683k a rr rr r in1 f1a f1b vvv in1 in2 f2 f1a f1b () () () = + = + = = =+ 121 562 ?? ? ? ? ? to out_ c in r in1 MAX9742 c in r in2 to class d modulator in_- in_+ fb_ r f1a 121k ? r f1b 562k ? c fb_1 150pf c fb_2 10pf c fb_1 150pf r f2 681k ? negative audio input positive audio input to mid a v = r f1a + r f1b r in1 r f2 = r f1a + r f1b = 688k ? r in1 = r in2 figure 15. optional t-network for minimizing thd+n at low output powers c fb_ to fb_ to in_- figure 16. connection of output limiting diodes free datasheet http:///
supply bypassing/layout to maximize output power and minimize distortion, proper layout and supply bypassing is essential. to prevent ground-loop-induced noise and minimize noise due to parasitic ground inductance, use separate ground planes for input-signal ground connections (sgnd plane) and output-power ground connections (pgnd plane). for dual-supply applications, connect mid to the sgnd plane. for single-supply operation, connect mid to an external voltage-divider and bypass mid to the sgnd plane with a decoupling network (see figure 11). this provides a sufficient low- and high-fre- quency ac ground for the internal amplifiers. connect the sgnd and pgnd planes together at a single point in the pcb near the MAX9742. minimize the parasitic trace inductances and resistances associated with the v dd and v ss connections, by using wide traces of min- imal length. proper power-supply bypassing is essential to ensure low distortion operation and to prevent excessive sup- ply pumping when using the single-ended output con- figuration. for dual-supply operation, bypass v dd and v ss to pgnd with 1000? aluminum electrolytic capac- itors. v dd and v ss should also be bypassed to pgnd with 0.1? capacitors as physically close as possible to v dd and v ss pins to provide sufficient high-frequency decoupling. also, connect an additional 1? capacitor between v dd and v ss . for single-supply operation, bypass v dd to pgnd with two 330? capacitors. v dd should also be bypassed to pgnd with an additional 0.1? capacitor as physically close as possible to the v dd pin. the MAX9742 includes voltage regulators for the inter- nal amplifiers, logic circuitry, and gate-drive circuitry that require external bypassing. bypass regp and regm to the sgnd plane with 1? capacitors. bypass regls to nsense with a 1? capacitor. bypass lv dd to lgnd with a 0.1? capacitor. the voltage rating requirements of the external bypass capacitors must be taken into account. this is especially important when selecting the regp and regm bypass capaci- tors since the ground-referenced voltages present at these regulator outputs are dependent on the voltage applied to the mid input. the minimum required volt- age ratings for the regulator bypass capacitors are summarized in table 4. thermal considerations class d amplifiers provide much better efficiency and thermal performance than a comparable class ab amplifier. however, the system? thermal performance must be considered with realistic expectations along with its many parameters. continuous sine wave vs. music when a class d amplifier is evaluated in the lab, often a continuous sine wave is used as the signal source. while this is convenient for measurement purposes, it represents a worst-case scenario for thermal loading on the amplifier. it is not uncommon for a class d amplifier to enter thermal shutdown if driven near maxi- mum output power with a continuous sine wave. the pcb must be optimized for best dissipation (see the pcb thermal considerations section). audio content, both music and voice, has a much lower rms value rel- ative to its peak output power. therefore, while an audio signal may reach similar peaks as a continuous sine wave, the actual thermal impact on the class d amplifier is highly reduced. if the thermal performance of a system is being evaluated, it is important to use actual audio signals instead of sine waves for testing. if sine waves must be used, the thermal performance is less than the system? actual capability for real music or voice. pcb thermal considerations the exposed paddle is the primary route for conducting heat away from the ic. with a bottom-side exposed pad- dle, the pcb and its copper becomes the primary heatsink for the class d amplifier. solder the exposed paddle to a copper polygon. add as much copper as possible from this polygon to any adjacent pin on the class d amplifier as well as to any adjacent components, provided these connections are at the same potential. MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 29 table 4. minimum required voltage ratings for regulator bypass capacitors capacitor voltage rating (v) c regp v mid + 5 c regm v mid - 5 c regls 7 c lvdd 5 free datasheet http:///
MAX9742 these copper paths must be as wide as possible. each of these paths contributes to the overall thermal capa- bilities of the system. the copper polygon to which the exposed paddle is attached should have multiple vias to the opposite side of the pcb, where they connect to another copper poly- gon. make this polygon as large as possible within the system? constraints for signal routing. additional improvements are possible if all the traces from the device are made as wide as possible. although the ic pins are not the primary thermal path out of the package, they do provide a small amount. the total improvement would not exceed approximately 10%, but it could make the difference between accept- able performance and thermal problems. auxiliary heatsinking if operating in higher ambient temperatures, it is possi- ble to improve the thermal performance of a pcb with the addition of an external heatsink. the thermal resis- tance to this heatsink must be kept as low as possible to maximize its performance. with a bottom-side exposed paddle, the lowest resistance thermal path is on the bottom of the pcb. the topside of the ic is not a significant thermal path for the device, and therefore, is not a cost-effective location for a heatsink. place the inductor of the external lc output filter in close proximi- ty to the ic. this not only helps minimize emi radiation at the output traces, but also helps draw heat away from the MAX9742. single-/dual-supply, stereo 16w, class d amplifier with differential inputs 30 ______________________________________________________________________________________ chip information process: bcd 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 20 19 + MAX9742 top view tqfn (6mm 6mm 0.8mm) regm mid regp refcur sft lgnd lv dd shdn n.c. fbr inr- inr+ nsense regls bootr outr outr n.c. v dd v dd v dd v dd v ss v ss v ss n.c. n.c. outl outl sub bootl n.c. inl+ inl- fbl n.c. pin configuration free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 31 l f c f class d modulator and half-bridge r f2 r f2 c fbr c zbl r zbl c in r in1 MAX9742 c in r in2 inl- inl+ c in r in2 c in r in1 inr+ mid inr- c fbl fbl fbr sft c fbl c fbr class d modulator and half-bridge control logic/ power-up sequencing l f c f c zbl r zbl r f1 r f1 shdn outr left positive audio input left negative audio input right positive audio input right negative audio input dual supply configuration outl 10v to 20v -10v to -20v v ss v dd c sft on off simplified block diagram (continued) free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 32 ______________________________________________________________________________________ typical application circuits/functional diagrams MAX9742 - + v mid + 5v v dd v ss 20v to 40v r in1 30.1k ? r in2 30.1k ? c in 0.47 f c in 0.47 f v mid - 5v v ss v mid - 5v c fbl 150pf left positive audio input left negative audio input + - v mid + 5v c fbr1 150pf r in2 30.1k ? r3 10k ? v dd r in1 30.1k ? c in 0.47 f c in 0.47 f v mid - 5v right negative audio input right positive audio input r f2 681k ? 8 9 fbl fbr 19 shdn off on 17 sft lgnd sub 14 15 4 31, 32, 33 single-supply operation device connected for a v = 22v/v v ss 7 inl- inl+ 11 mid 21 20 inr+ inr- c fbr 150pf r f2 681k ? c mid2 10 f c mid1 10 f r1 10k ? r2 10k ? class d modulator and half-bridge v dd v ss class d modulator and half-bridge connect pgnd and sgnd to a single point on the pcb near the MAX9742 7v regulator (with respect to v ss ) current reference -5v regulator (with respect to v mid ) v mid + 5v 5v regulator (with respect to v mid ) optional 5v supply control logic/ power-up sequencing c fbl1 150pf r f1a 121k ? r f1b 562k ? 10 12 regm regp 2, 3 outl c f 0.33 f 5 bootl 13 refcur 29, 30, 34, 35 v dd c regp 1 f l f 47 h l f 47 h c out 1000 f c boot 0.1 f d boot 1n4148 r ref 68k ? c regm 1 f c fbl2 10pf c vdd 330 f c vdd 330 f 0.1 f 16 lv dd c lvdd 0.1 f 22 nsense 23 regls optional r f1a 121k ? r f1b 562k ? c fbr2 10pf c sft 0.47 f c zbl 0.47 f r zbl 10 ? 25, 26 outr c f 0.33 f 24 bootr c out 1000 f 8 ? 8 ? c boot 0.1 f c regls 1 f c zbl 0.47 f r zbl 10 ? d boot 1n4148 = sgnd = pgnd free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 33 typical application circuits/functional diagrams (continued) MAX9742 - + v mid + 5v v dd v ss v ss 10v to 20v r in1 30.1k ? r in2 30.1k ? c in 0.47 f c in 0.47 f v mid - 5v v ss v mid - 5v c fbl1 150pf left positive audio input left negative audio input + - v mid + 5v c fbr1 150pf r in2 30.1k ? r in1 30.1k ? c in 0.47 f c in 0.47 f v mid - 5v right negative audio input right positive audio input r f2 681k ? 8 9 fbl fbr 19 shdn off on 17 sft lgnd sub 14 15 4 31, 32, 33 dual-supply operation device connected for a v = 22v/v. v ss 7 inl- inl+ 11 mid 21 20 inr+ inr- c fbr1 150pf r f2 681k ? class d modulator and half-bridge v dd v ss class d modulator and half-bridge connect pgnd and sgnd to a single point on the pcb near the MAX9742 7v regulator (with respect to v ss ) current reference -5v regulator (with respect to v mid ) -10v to -20v v mid + 5v 5v regulator (with respect to v mid ) optional 5v supply control logic/ power-up sequencing c fbl1 150pf r f1a 121k ? r f1b 562k ? 10 12 regm regp 2, 3 outl c f 0.33 f 5 bootl 13 refcur 29, 30, 34, 35 v dd c regp 1 f c byp 1 f l f 47 h l f 47 h c boot 0.1 f d boot 1n4148 r ref 68k ? c regm 1 f c fbl2 10pf c vdd 1000 f 0.1 f c vdd 1000 f 0.1 f 16 lv dd c lvdd 0.1 f 22 nsense 23 regls optional r f1a 121k ? r f1b 562k ? c fbr2 10pf c sft 0.22 f c zbl 0.47 f r zbl 10 ? 25, 26 outr c f 0.33 f 24 bootr 8 ? 8 ? c boot 0.1 f c regls 0.1 f c zbl 0.47 f r zbl 10 ? d boot 1n4148 = sgnd = pgnd free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs 34 ______________________________________________________________________________________ MAX9742 - + v mid + 5v v dd v ss 20v to 40v r in1 30.1k ? r in2 30.1k ? c in 0.47 f c in 0.47 f v mid - 5v v ss v mid - 5v c fbl1 150pf positive audio input negative audio input + - v mid + 5v c fbr1 150pf r in2 30.1k ? r3 10k ? v dd r in1 30.1k ? c in 0.47 f c in 0.47 f v mid - 5v r f2 681k ? 8 9 fbl fbr 19 shdn off on 17 sft lgnd sub 14 15 4 31, 32, 33 v ss 7 inl- inl+ 11 mid 21 20 inr+ inr- c fbr1 150pf r f2 681k ? c mid2 10 f c mid1 10 f r1 10k ? r2 10k ? class d modulator and half-bridge v dd v ss class d modulator and half-bridge connect pgnd and sgnd to a single point on the pcb near the MAX9742 7v regulator (with respect to v ss ) current reference -5v regulator (with respect to v mid ) v mid + 5v 5v regulator (with respect to v mid ) optional 5v supply control logic/ power-up sequencing c fbl1 150pf r f1a 121k ? r f1b 562k ? 10 12 regm regp 2, 3 outl c f 0.68 f 5 bootl 13 refcur 29, 30, 34, 35 v dd c regp 1 f l f 22 h l f 22 h c boot 0.1 f d boot 1n4148 r ref 68k ? c regm 1 f c fbl2 10pf cv dd 330 f 0.1 f cv dd 330 f 16 lv dd c lvdd 0.1 f 22 nsense 23 regls optional r f1a 121k ? r f1b 562k ? c fbr2 10pf c sft 0.47 f c zbl 0.82 f c zbl 0.82 f r zbl 5 ? r zbl 5 ? 25, 26 outr c f 0.68 f 24 bootr 8 ? c boot 0.1 f c regls 1 f d boot 1n4148 = sgnd = pgnd bridge-tied-load (btl), single-supply operation device connected for a v = 44v/v. typical application circuits/functional diagrams (continued) free datasheet http:///
MAX9742 single-/dual-supply, stereo 16w, class d amplifier with differential inputs ______________________________________________________________________________________ 35 package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) qfn thin.eps free datasheet http:///
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 .) 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. 36 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2007 maxim integrated products is a registered trademark of maxim integrated products, inc. single-/dual-supply, stereo 16w, class d amplifier with differential inputs MAX9742 free datasheet http:///

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