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general description the max9724a/max9724b stereo headphone ampli- fiers are designed for portable equipment where board space is at a premium. these devices use a unique, patented ? directdrive architecture to produce a ground-referenced output from a single supply, elimi- nating the need for large dc-blocking capacitors, sav- ing cost, board space, and component height. the max9724 suppresses rf radiation received by input and supply traces acting as antennas and prevents the amplifer from demodulating the coupled noise. the max9724a offers an externally adjustable gain while the max9724b has an internally preset gain of -1.5v/v. the max9724a/max9724b deliver up to 60mw per channel into a 32 load and have low 0.02% thd+n. an 80db at 1khz power-supply rejection ratio (psrr) allows these devices to operate from noisy digital sup- plies without an additional linear regulator. comprehensive click-and-pop circuitry suppresses audible clicks and pops on startup and shutdown. the max9724a/max9724b operate from a single 2.7v to 5.5v supply, consume only 3.5ma of supply current, feature short-circuit and thermal-overload protection, and are specified over the extended -40? to +85? temperature range. the devices are available in tiny 12- bump ucsp (1.5mm x 2mm) and 12-pin thin qfn (3mm x 3mm x 0.8mm) packages. applications features ? improved rf noise rejection (up to 67db over typical amplifiers) ? no bulky dc-blocking capacitors required ? low-power shutdown mode, < 0.1 a ? adjustable gain (max9724a) or fixed -1.5v/v gain (max9724b) ? low 0.02% thd+n ? high psrr (80db at 1khz) eliminates ldo ? integrated click-and-pop suppression ? 2.7v to 5.5v single-supply operation ? low quiescent current (3.5ma) ? available in space-saving packages: 12-bump ucsp (1.5mm x 2mm) 12-pin thin qfn (3mm x 3mm x 0.8mm) max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown ________________________________________________________________ maxim integrated products 1 ordering information 19-3597; rev 5; 3/08 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 part gain (v/v) pin- package pkg code top mark max9724aebc+t adj. 12 ucsp-12 b12-1 +adh max9724aetc+ adj. 12 tqfn-ep* t1233-1 +aat max9724bebc+t -1.5 12 ucsp-12 b12-1 +adi max9724betc+ -1.5 12 tqfn-ep* t1233-1 +aau note: all devices specified over the -40? to +85? operating range. + denotes lead-free package. t = tape and reel. * ep = exposed paddle. cellular phones mp3 players notebook pcs handheld gaming consoles left audio input right audio input shdn max9724a left audio input right audio input max9724b shdn directdrive outputs eliminate dc-blocking capacitors directdrive outputs eliminate dc-blocking capacitors fixed gain eliminates external resistor network block diagrams pin configurations appear at end of data sheet. dvd players smart phones pdas ? u.s. patent# 7,061,327 ucsp is a trademark of maxim integrated products, inc.
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v dd to gnd ..............................................................-0.3v to +6v pv ss to sv ss .........................................................-0.3v to +0.3v pgnd to sgnd .....................................................-0.3v to +0.3v c1p to pgnd..............................................-0.3v to (v dd + 0.3v) c1n to pgnd............................................(pv ss - 0.3v) to +0.3v pv ss and sv ss to pgnd..........................................-6v to +0.3v in_ to sgnd (max9724a)..........................-0.3v to (v dd + 0.3v) in_ to sgnd (max9724b) .............(sv ss - 0.3v) to (v dd + 0.3v) out_ to sv ss (note 1) ....-0.3v to min (v dd - sv ss + 0.3v, +9v) out_ to v dd (note 2) ......+0.3v to max (sv ss - v dd - 0.3v, -9v) shdn to _gnd.........................................................-0.3v to +6v out_ short circuit to gnd ........................................continuous short circuit between outl and outr ....................continuous continuous input current into pv ss ..................................260ma continuous input current (any other pin) .........................?0ma continuous power dissipation (t a = +70?, multilayer board) 12-bump ucsp (derate 6.5mw/? above +70?) ........519mw ja ................................................................................154 c/w 12-pin tqfn (derate 16.7mw/? above +70?) .........1333mw ja ..................................................................................60?/w jc ..................................................................................11?/w operating temperature range ...........................-40? to +85? storage temperature range .............................-65? to +150? junction temperature ......................................................+150? lead temperature (soldering, 10s) .................................+300? bump temperature (soldering) reflow............................+235? electrical characteristics ( v dd = 5v , pgnd = sgnd, shdn = 5v, c1 = c2 = 1?, r l = , resistive load reference to ground; for max9724a gain = -1.5v/v (r in = 20k , r f = 30k ); for max9724b gain = -1.5v/v (internally set), t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?, unless otherwise noted.) (note 3) parameter symbol conditions min typ max units general supply voltage range v dd guaranteed by psrr test 2.7 5.5 v quiescent current i cc 3.5 5.5 ma shutdown current i shdn shdn = sgnd = pgnd 0.1 1 a shutdown to full operation t son 180 ? input impedance r in max9724b, measured at in_ 12 19 28 k output offset voltage v os (note 4) ?.5 ?0 mv v dd = 2.7v to 5.5v, t a = +25? 69 86 f = 1khz, 100mv p-p (note 4) 80 power-supply rejection ratio psrr f = 20khz, 100mv p-p (note 4) 65 db r l = 32 , thd+n = 1% 30 63 output power (tqfn) p out r l = 16 , thd+n = 1% 42 mw r l = 32 , thd+n = 1% 25 45 output power (ucsp) p out r l = 16 , thd+n = 1% 35 mw voltage gain a v max9724b (note 5) -1.52 -1.5 -1.48 v/v channel-to-channel gain tracking max9724b ?.15 % r l = 1k , v out = 2v rms , f in = 1khz 0.003 r l = 32 , p out = 50mw, f in = 1khz 0.02 total harmonic distortion plus noise (tqfn) (note 6) thd+n r l = 16 , p out = 35mw, f in = 1khz 0.04 % r l = 1k , v out = 2v rms , f in = 1khz 0.003 r l = 32 , p out = 45mw, f in = 1khz 0.03 total harmonic distortion plus noise (ucsp) (note 6) thd+n r l = 16 , p out = 32mw, f in = 1khz 0.05 % bw = 22hz to 22khz 102 r l = 1k , v out = 2v rms a-weighted 105 bw = 22hz to 22khz 98 signal-to-noise ratio snr r l = 32 , p out = 50mw a-weighted 101 db note 1: outr and outl should be limited to no more than 9v above sv ss , or above v dd + 0.3v, whichever limits first. note 2: outr and outl should be limited to no more than 9v below v dd , or below sv ss - 0.3v, whichever limits first.
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown _______________________________________________________________________________________ 3 electrical characteristics (continued) ( v dd = 5v , pgnd = sgnd, shdn = 5v, c1 = c2 = 1?, r l = , resistive load reference to ground; for max9724a gain = -1.5v/v (r in = 20k , r f = 30k ); for max9724b gain = -1.5v/v (internally set), t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?, unless otherwise noted.) (note 3) parameter symbol conditions min typ max units slew rate sr 0.5 v/? capacitive drive c l no sustained oscillations 100 pf crosstalk l to r, r to l, f = 10khz, r l = 16 , p out = 15mw -70 db charge-pump oscillator frequency f osc 190 270 400 khz into shutdown -67 click-and-pop level k cp r l = 32 , peak voltage, a-weighted, 32 samples per second (notes 4, 7) out of shutdown -64 db digital inputs ( shdn ) input-voltage high v inh (tqfn only) 2 v input-voltage low v inl (tqfn only) 0.8 v input-voltage high v inh (ucsp only) 1.4 v input-voltage low v inl (ucsp only) 0.9 v input leakage current ? ? electrical characteristics ( v dd = 3v , pgnd = sgnd, shdn = 3v, c1 = c2 = 1?, r l = , resistive load reference to ground; for max9724a gain = -1.5v/v (r in = 20k , r f = 30k ); for max9724b gain = -1.5v/v (internally set), t a = -40? to +85?, unless otherwise noted. typical values are at t a = +25?, unless otherwise noted.) (note 3) parameter symbol conditions min typ max units quiescent current i cc 3.0 ma shutdown current i shdn shdn = sgnd = pgnd 0.1 ? f = 1khz, 100mv p-p 80 power-supply rejection ratio (note 4) psrr f = 20khz, 100mv p-p 65 db r l = 32 , thd+n = 1% 20 output power (tqfn) p out r l = 16 , thd+n = 1% 14 mw r l = 32 , thd+n = 1% 17 output power (ucsp) p out r l = 16 , thd+n = 1% 12 mw r l = 1k , v out = 2v rms , f in = 1khz 0.05 r l = 32 , p out = 15mw, f in = 1khz 0.03 total harmonic distortion plus noise (tqfn) (note 6) thd+n r l = 16 , p out = 10mw, f in = 1khz 0.06 % r l = 1k , v out = 2v rms , f in = 1khz 0.003 r l = 32 , p out = 15mw, f in = 1khz 0.04 total harmonic distortion plus noise (ucsp) (note 6) thd+n r l = 16 , p out = 10mw, f in = 1khz 0.06 % note 3: all specifications are 100% tested at t a = +25?; temperature limits are guaranteed by design. note 4: the amplifier inputs are ac-coupled to gnd. note 5: gain for the max9724a is adjustable. note 6: measurement bandwidth is 22hz to 22khz. note 7: test performed with a 32 resistive load connected to gnd. mode transitions are controlled by shdn . k cp level is calculated as 20log[(peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power level)]. units are expressed in db.
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 4 _______________________________________________________________________________________ typical operating characteristics (v dd = 5v, pgnd = sgnd = 0v, shdn = v dd , c1 = c2 = 1?, r l = , gain = -1.5v/v (r in = 20k , r f = 30k for the max9724a), thd+n measurement bandwidth = 22hz to 22khz, both outputs driven in phase, t a = +25?, unless otherwise noted.) 100 010203040 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (tqfn) max9724 toc01 output power (mw) thd+n (%) v dd = 3v r l = 16 f in = 1khz f in = 20hz f in = 10khz 10 0 5 15 25 10 20 30 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (ucsp) max9724 toc02 output power (mw) thd+n (%) v dd = 3v r l = 16 f in = 1khz f in = 20hz f in = 10khz 100 010 30 20 40 50 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (tqfn) max9724toc03 output power (mw) thd+n (%) v dd = 3v r l = 32 f in = 1khz f in = 20hz f in = 10khz 10 05 15 10 20 25 30 35 40 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (uscp) max9724toc04 output power (mw) thd+n (%) v dd = 3v r l = 32 f in = 1khz f in = 10khz f in = 20hz 100 020 60 40 80 100 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (tqfn) max9724 toc05 output power (mw) thd+n (%) v dd = 5v r l = 16 f in = 1khz f in = 20hz f in = 10khz 10 010 30 20 40 50 60 70 80 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (ucsp) max9724 toc06 output power (mw) thd+n (%) v dd = 5v r l = 16 f in = 1khz f in = 20hz f in = 10khz 100 020 60 40 80 120 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (tqfn) max9724 toc07 output power (mw) thd+n (%) 100 v dd = 5v r l = 32 f in = 1khz f in = 20hz f in = 10khz 10 050 25 75 100 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power (ucsp) max9724 toc08 output power (mw) thd+n (%) v dd = 5v r l = 32 f in = 1khz f in = 20hz f in = 10khz 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (tqfn) max9724 toc09 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 3v r l = 16 p out = 5mw p out = 10mw
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown _______________________________________________________________________________________ 5 typical operating characteristics (continued) (v dd = 5v, pgnd = sgnd = 0v, shdn = v dd , c1 = c2 = 1?, r l = , gain = -1.5v/v (r in = 20k , r f = 30k for the max9724a), thd+n measurement bandwidth = 22hz to 22khz, both outputs driven in phase, t a = +25?, unless otherwise noted.) 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (ucsp) max9724 toc10 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 3v r l = 16 p out = 5mw p out = 10mw 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (tqfn) max9724 toc11 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 3v r l = 32 p out = 8mw p out = 15mw 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (ucsp) max9724 toc12 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 3v r l = 32 p out = 8mw p out = 13mw 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (tqfn) max9724 toc13 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 5v r l = 16 p out = 20mw p out = 37mw 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (ucsp) max9724 toc14 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 5v r l = 16 p out = 20mw p out = 32mw 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (tqfn) max9724 toc15 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 5v r l = 32 p out = 50mw p out = 30mw 10 1k 100 10k 100k total harmonic distortion plus noise vs. frequency (ucsp) max9724 toc16 frequency (hz) thd+n (%) 1 0.1 0.001 0.01 v dd = 5v r l = 32 p out = 45mw p out = 20mw 0 20 10 40 30 60 50 70 2.5 3.5 4.0 3.0 4.5 5.0 5.5 output power vs. supply voltage (tqfn) max9724 toc17 supply voltage (v) output power (mw) f in = 1khz r l = 16 1% thd+n 10% thd+n 0 20 10 40 30 60 50 70 2.5 3.5 4.0 3.0 4.5 5.0 5.5 output power vs. supply voltage (ucsp) max9724 toc18 supply voltage (v) output power (mw) f in = 1khz r l = 16 1% thd+n 10% thd+n
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 6 _______________________________________________________________________________________ typical operating characteristics (continued) (v dd = 5v, pgnd = sgnd = 0v, shdn = v dd , c1 = c2 = 1?, r l = , gain = -1.5v/v (r in = 20k , r f = 30k for the max9724a), thd+n measurement bandwidth = 22hz to 22khz, both outputs driven in phase, t a = +25?, unless otherwise noted.) 0 40 20 80 60 100 120 2.5 3.5 4.0 3.0 4.5 5.0 5.5 output power vs. supply voltage (tqfn) max9724 toc19 supply voltage (v) output power (mw) f in = 1khz r l = 32 1% thd+n 10% thd+n 0 40 20 80 60 100 120 2.5 3.5 4.0 3.0 4.5 5.0 5.5 output power vs. supply voltage (ucsp) max9724 toc20 supply voltage (v) output power (mw) f in = 1khz r l = 32 1% thd+n 10% thd+n 35 0 10 100 1000 output power vs. load resistance (tqfn) 5 max9724 toc21 load resistance ( ) output power (mw) 15 10 20 25 30 v dd = 3v f in = 1khz 1% thd+n 10% thd+n 35 0 10 100 1000 output power vs. load resistance (ucsp) 5 max9724 toc22 load resistance ( ) output power (mw) 15 10 20 25 30 v dd = 3v f in = 1khz thd+n = 1% thd+n = 10% 100 0 10 100 output power vs. load resistance (tqfn) 10 max9724 toc23 load resistance ( ) output power (mw) 30 20 50 70 90 40 60 80 thd+n = 1% v dd = 5v f in = 1khz thd+n = 10% 100 0 10 100 output power vs. load resistance (ucsp) 10 max9724 toc24 load resistance ( ) output power (mw) 30 20 50 70 90 40 60 80 thd+n = 1% v dd = 5v f in = 1khz thd+n = 10% 0 50 150 100 200 250 power dissipation vs. output power (tqfn) max9724t oc25 output power (mw) power dissipation (mw) 040 20 60 80 v dd = 3v f in = 1khz p out = p outl + p outr outputs in phase r l = 16 r l = 32 0 20 100 80 60 40 120 140 160 power dissipation vs. output power (ucsp) max9724t oc26 output power (mw) power dissipation (mw) 01015202530 54045 35 50 v dd = 3v f in = 1khz p out = p outl + p outr outputs in phase r l = 16 r l = 32 0 -120 10 100 10k 100k power-supply rejection ratio vs. frequency -100 -80 -40 -60 -20 max9724 toc27 frequency (hz) psrr (db) 1k v dd = 5v v dd = 3v r l = 32
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown _______________________________________________________________________________________ 7 0 -120 10 100 10k 100k crosstalk vs. frequency -100 -80 -40 -60 -20 max9724 toc28 frequency (hz) crosstalk (db) 1k right to left left to right p out = 15mw r l = 16 20 40 30 60 50 70 80 0 100 150 50 output power vs. load resistance and charge-pump capacitor size (tqfn) max9724 toc29 load resistance ( ) output power (mw) v dd = 5v f in = 1khz thd+n = 1% c1 = c2 = 2.2 f c1 = c2 = 1 f c1 = c2 = 0.47 f 0 40 30 20 10 60 50 70 80 0 100 150 50 output power vs. load resistance and charge-pump capacitor size (ucsp) max9724 toc30 load resistance ( ) output power (mw) v dd = 5v f in = 1khz thd+n = 1% c1 = c2 = 2.2 f c1 = c2 = 1 f c1 = c2 = 0.47 f -140 -110 -130 -70 -90 -50 -120 -80 -100 -60 -40 0 5 10 15 20 output spectrum vs. frequency max9724 toc31 frequency (khz) amplitude (dbv) r l = 32 v dd = 3v f in = 1khz v out = -60dbv 2.8 3.1 2.9 3.3 3.0 3.4 3.2 3.5 2.5 3.0 4.0 3.5 4.5 5.0 5.5 supply current vs. supply voltage max9724 toc32 supply voltage (v) supply current (ma) no load inputs ground shutdown current vs. supply voltage (tqfn) max9724 toc33 supply voltage (v) shutdown current (na) 5.0 4.5 4.0 3.5 3.0 20 40 60 80 100 120 140 0 2.5 5.5 no load inputs gnd typical operating characteristics (continued) (v dd = 5v, pgnd = sgnd = 0v, shdn = v dd , c1 = c2 = 1?, r l = , gain = -1.5v/v (r in = 20k , r f = 30k for the max9724a), thd+n measurement bandwidth = 22hz to 22khz, both outputs driven in phase, t a = +25?, unless otherwise noted.)
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 8 _______________________________________________________________________________________ pin description pin tqfn ucsp name function 1 c1 c1p flying capacitor positive terminal. connect a 1? ceramic capacitor from c1p to c1n. 2c2 pgnd power ground. connect to sgnd. 3 c3 c1n flying capacitor negative terminal. connect a 1? ceramic capacitor from c1p to c1n. 4c4pv ss charge-pump output. connect to sv ss and bypass with a 1? ceramic capacitor to pgnd. 5a2 shdn active-low shutdown input 6 b3 inl left-channel input 7a1 sgnd signal ground. connect to pgnd. 8 b2 inr right-channel input 9b4sv ss amplifier negative supply. connect to pv ss . 10 a3 outr right-channel output 11 a4 outl left-channel output 12 b1 v dd positive power-supply input. bypass with a 1? capacitor to pgnd. ep ep exposed paddle. internally connected to sv ss . connect to sv ss or leave unconnected. exiting shutdown max9724 toc34 v shdn 5v/div v out_ 500mv/div v in_ 1v/div 40 s/div entering shutdown max9724 toc35 v shdn 5v/div v out_ 500mv/div v in_ 1v/div 20 s/div typical operating characteristics (continued) (v dd = 5v, pgnd = sgnd = 0v, shdn = v dd , c1 = c2 = 1?, r l = , gain = -1.5v/v (r in = 20k , r f = 30k for the max9724a), thd+n measurement bandwidth = 22hz to 22khz, both outputs driven in phase, t a = +25?, unless otherwise noted.)
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown _______________________________________________________________________________________ 9 detailed description the max9724a/max9724b stereo headphone ampli- fiers feature maxim? patented directdrive architecture, eliminating the large output-coupling capacitors required by conventional single-supply headphone amplifiers. the device consists of two 60mw class ab headphone amplifiers, undervoltage lockout (uvlo)/shutdown control, charge pump, and compre- hensive click-and-pop suppression circuitry (see the functional diagram/typical operating circuits ). the charge pump inverts the positive supply (v dd ), creat- ing a negative supply (pv ss ). the headphone ampli- fiers operate from these bipolar supplies with their outputs biased about pgnd (figure 1). the benefit of this pgnd bias is that the amplifier outputs do not have a dc component. the large dc-blocking capacitors required with conventional headphone amplifiers are unnecessary, conserving board space, reducing sys- tem cost, and improving frequency response. the max9724a/max9724b feature an undervoltage lockout that prevents operation from an insufficient power sup- ply and click-and-pop suppression that eliminates audi- ble transients on startup and shutdown. the max9724a/max9724b also feature thermal-overload and short-circuit protection. directdrive conventional single-supply headphone amplifiers have their outputs biased about a nominal dc voltage (typi- cally half the supply) for maximum dynamic range. large-coupling capacitors are needed to block this dc bias from the headphone. without these capacitors, a significant amount of dc current flows to the head- phone, resulting in unnecessary power dissipation and possible damage to both headphone and headphone amplifier. maxim? patented directdrive architecture uses a charge pump to create an internal negative supply volt- age, allowing the max9724a/max9724b outputs to be biased about gnd. with no dc component, there is no need for the large dc-blocking capacitors. the max9724a/max9724b charge pumps require 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 and charge-pump capacitor size graph in the typical operating characteristics for details of the possible capacitor sizes. there is a low dc voltage on the amplifier outputs due to amplifier off- set. however, the offsets of the max9724a/max9724b are typically 1.5mv, which, when combined with a 32 load, results in less than 47? of dc current flow to the headphones. charge pump the max9724a/max9724b feature a low-noise charge pump. the 270khz switching frequency is well beyond the audio range and does not interfere with audio sig- nals. the switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off transients. the di/dt noise caused by the para- sitic bond wire and trace inductance is minimized by limiting the switching speed of the charge pump. although not typically required, additional high-fre- quency noise attenuation can be achieved by increas- ing the value of c2 (see the functional diagram/typical operating circuits ). rf susceptibility modern audio systems are often subject to rf radiation from sources like wireless networks and cellular phone networks. although the rf radiation is out of the audio band, many signals, in particular gsm signals, contain bursts or modulation at audible frequencies. most ana- log amplifiers demodulate the low-frequency envelope, adding noise to the audio signal. the architecture of v dd -v dd gnd v out conventional driver-biasing scheme directdrive biasing scheme v dd /2 v dd v dd gnd v out 2v dd figure 1. conventional driver output waveform vs. max9724a/max9724b output waveform
max9724a/max9724b the max9724 addresses the problem of the rf suscep- tibility by rejecting rf noise and preventing it from cou- pling into the audio band. the rf susceptibility of an amplifier can be measured by placing the amplifier in an isolated chamber and sub- jecting it to an electric field of known strength. if the electric field is modulated with an audio band signal, a percentage of the modulated signal will be demodulat- ed and amplified by the device in the chamber. figure 2 shows the signal level at the outputs of an unoptimized amplifier and the max9724. the test conditions are shown in table 1. click-and-pop suppression in conventional single-supply audio amplifiers, the out- put-coupling capacitor contributes significantly to audi- ble clicks and pops. upon startup, the amplifier charges the coupling capacitor to its bias voltage, typically half the supply. likewise, on shutdown, the capacitor is dis- charged. this results in a dc shift across the capacitor, which appears as an audible transient at the speaker. since the max9724a/ max9724b do not require output- coupling capacitors, this problem does not arise. additionally, the max9724a/max9724b feature exten- sive click-and-pop suppression that eliminates any audi- ble transient sources internal to the device. typically, the output of the device driving the max9724a/max9724b has a dc bias of half the supply voltage. at startup, the input-coupling capacitor, c in , is charged to the preamplifier? dc bias voltage through the max9724a/max9724b input resistor, r in , and a series 15k resistor. this dc shift across the capacitor results in an audible click-and-pop. delay the rise of shdn 4 to 5 time constants based on r in x 15k x c in to eliminate clicks-and-pops caused by the input filter. shutdown the max9724a/max9724b feature a <0.1?, low- power shutdown mode that reduces quiescent current consumption and extends battery life for portable appli- cations. drive shdn low to disable the amplifiers and the charge pump. in shutdown mode, the amplifier out- put impedance is set to 14k ||r f (r f is 30k for the max9724b). the amplifiers and charge pump are enabled once shdn is driven high. applications information power dissipation under normal operating conditions, linear power ampli- fiers can dissipate a significant amount of power. the maximum power dissipation for each package is given in the absolute maximum ratings section under continuous power dissipation or can be calculated by the following equation: where t j(max) is +150?, t a is the ambient tempera- ture, and ja is the reciprocal of the derating factor in p tt disspkg max j max a ja () () = ? 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 10 ______________________________________________________________________________________ test parameter setting rf field strength 50v/m rf modulation type sine wave rf modulation index 100% rf modulation frequency 1khz table 1. rf susceptibility test conditions max9724 fig02 rf carrier frequency (mhz) amplifier output amplitude (dbv) 1600 2100 1100 600 -80 -60 -40 -20 0 20 40 rf susceptible amplifier max9724 62db improvement at 850mhz 39db improvement at 900mhz 67db improvement at 1800mhz 49db improvement at 1900mhz -100 100 2600 figure 2. rf susceptibility of the max9724 and a typical headphone amplifier
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown ______________________________________________________________________________________ 11 ?/w as specified in the absolute maximum ratings section. for example, ja of the thin qfn package is +68?/w, and 154.2?/w for the ucsp package. the max9724a/max9724b have two power dissipation sources; a charge pump and the two output amplifiers. if power dissipation for a given application exceeds the maximum allowed for a particular package, reduce v dd , increase load impedance, decrease the ambient temperature, or add heatsinking to the device. large output, supply, and ground traces decrease ja , allow- ing more heat to be transferred from the package to the surrounding air. thermal-overload protection limits total power dissipa- tion in the max9724a/max9724b. when the junction temperature exceeds +150?, the thermal protection circuitry disables the amplifier output stage. the ampli- fiers are enabled once the junction temperature cools by approximately 12?. this results in a pulsing output under continuous thermal-overload conditions. output dynamic range dynamic range is the difference between the noise floor of the system and the output level at 1% thd+n. determine the system? dynamic range before setting the maximum output gain. output clipping occurs if the out- put signal is greater than the dynamic range of the sys- tem. the directdrive architecture of the max9724a/ max9724b has increased the dynamic range compared to other single-supply amplifiers. maximum output swing v dd < 4.35v if the output load impedance is greater than 1k , the max9724a/max9724b can swing within a few millivolts of their supply rail. for example, with a 3.3v supply, the output swing is 2v rms , or 2.83v peak while maintaining a low 0.003% thd+n. if the supply voltage drops to 3v, the same 2.83v peak has only 0.05% thd+n. v dd > 4.35v internal device structures limit the maximum voltage swing of the max9724a/max9724b when operated at supply voltages greater than 4.35v. the output must not be driven such that the peak output voltage exceeds the opposite supply voltage by 9v. for example, if v dd = 5v, the charge pump sets pv ss = -5v. therefore, the peak output swing must be less than ?v to prevent exceeding the absolute maximum ratings. uvlo the max9724a/max9724b feature an undervoltage lockout (uvlo) function that prevents the device from operating if the supply voltage is less than 2.7v. this fea- ture ensures proper operation during brownout condi- tions and prevents deep battery discharge. once the supply voltage exceeds the uvlo threshold, the max9724a/max9724b charge pump is turned on and the amplifiers are powered, provided that shdn is high. component selection input-coupling capacitor the input capacitor (c in ), in conjunction with the input resistor (r in ), forms a highpass filter that removes the dc bias from an incoming signal (see the functional diagram/typical operating circuits ). the ac-coupling capacitor allows the device to bias the signal to an opti- mum dc level. assuming zero-source impedance, the - 3db point of the highpass filter is given by: choose the c in such that f -3db is well below the lowest frequency of interest. setting f -3db too high affects the device? low-frequency response. use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or aluminum electrolytic. capacitors with high-voltage coefficients, such as ceramics, can result in increased distortion at low frequencies. charge-pump capacitor selection use ceramic capacitors with a low esr for optimum performance. for optimal performance over the extend- ed temperature range, select capacitors with an x7r dielectric. table 2 lists suggested manufacturers. flying capacitor (c1) the value of the flying capacitor (see the functional diagram/typical operating circuits ) affects the charge f rc db in in ? = 3 1 2 supplier phone fax website taiyo yuden 800-348-2496 847-925-0899 www.t-yuden.com tdk 847-803-6100 847-390-4405 www.component.tdk.com murata 770-436-1300 770-436-3030 www.murata.com table 2. suggested capacitor manufacturers
max9724a/max9724b pump? load regulation and output resistance. a c1 value that is too small degrades the device? ability to provide sufficient current drive, which leads to a loss of output voltage. increasing the value of c1 improves load regulation and reduces the charge-pump output resis- tance to an extent. see the output power vs. load resistance and charge-pump capacitor size graph in the typical operating characteristics . above 1?, the on-resistance of the switches and the esr of c1 and c2 dominate. hold capacitor (c2) the hold capacitor value (see the functional diagram/typical operating circuits ) and esr directly affect the ripple at pv 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 and charge-pump capacitor size graph in the typical operating characteristics . power-supply bypass capacitor (c3) the power-supply bypass capacitor (see the functional diagram/typical operating circuits ) lowers the output impedance of the power supply, and reduces the impact of the max9724a/max9724b? charge-pump switching transients. bypass v dd with c3, the same value as c1, and place it physically close to the v dd and pgnd pins. amplifier gain the gain of the max9724b amplifier is internally set to -1.5v/v. all gain-setting resistors are integrated into the device, reducing external component count. the inter- nally set gain, in combination with directdrive, results in a headphone amplifier that requires only five small capacitors to complete the amplifier circuit: two for the charge pump, two for audio input coupling, and one for power-supply bypassing (see the functional diagram/typical operating circuits ). the gain of the max9724a amplifier is set externally as shown in figure 3, the gain is: a v = -r f /r in (v/v) choose feedback resistor values in the tens of k range. lower values may cause excessive power dissi- pation and require impractically small values of r in for large gain settings. the high-impedance state of the outputs can also be degraded during shutdown mode if an inadequate feedback resistor is used since the equivalent output impedance during shutdown is 14k ||r f (r f is equal to 30k for the max9724b). the source resistance of the input device may also need to be taken into consideration. since the effective value of r in is equal to the sum of the source resistance of the input device and the value of the input resistor connect- ed to the inverting terminal of the headphone amplifier (20k for the max9724b), the overall closed-loop gain of the headphone amplifier can be reduced if the input resistor is not significantly larger than the source resis- tance of the input device. 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 12 ______________________________________________________________________________________ left audio input right audio input outl inl inr outr max9724a r in r in r f r f figure 3. gain setting for the max9724a
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown ______________________________________________________________________________________ 13 lineout amplifier and filter block the max9724a can be used as an audio line driver capable of providing 2v rms into 10k loads with a sin- gle 5v supply (see figure 4 for the rms output voltage vs. supply voltage plot). 2v rms is a popular audio line level, first used in cd players, but now common in dvd and set-top box (stb) interfacing standards. a 2v rms sinusoidal signal equates to approximately 5.7v p-p , which means that the audio system designer cannot simply run the lineout stage from a (typically common) 5v supply?he resulting output swing would be inade- quate. a common solution to this problem is to use op amps driven from split supplies (?v typically), or to use a high-voltage supply rail (9v to 12v). this can mean adding extra cost and complexity to the system power supply to meet this output level requirement. having the ability to derive 2v rms from a 5v supply, or even 3.3v supply, can often simplify power-supply design in some systems. when the max9724a is used as a line driver to provide outputs that feed stereo equipment (receivers, stbs, notebooks, and desktops) with a digital-to-analog con- verter (dac) used as an audio input source, it is often desirable to eliminate any high-frequency quantization noise produced by the dac output before it reaches the load. this high-frequency noise can cause the input stages of the line-in equipment to exceed slew-rate lim- itations or create excessive emi emissions on the cables between devices. left audio input right audio input outl inl inr outr max9724a 7.5k 7.5k 7.5k 7.5k 15k 10k 10k 15k 1.2nf 1.2nf 220pf 220pf line in device stereo dac 1 f 1 f figure 5. max9724a line out amplifier and filter block configuration rms output voltage vs. supply voltage supply voltage (v) rms output voltage (v) 5.0 4.5 4.0 3.5 3.0 2.0 2.5 3.0 3.5 1.5 2.5 5.5 r l = 10k 1% thd+n f in = 1khz r l = 1k 1% thd+n limited by abs. maximum ratings figure 4. rms output voltage vs. supply voltage
to suppress this noise, and to provide a 2v rms stan- dard audio output level from a single 5v supply, the max9724a can be configured as a line driver and active lowpass filter. figure 5 shows the max9724a connected as 2-pole rauch/multiple feedback filter with a passband gain of 6db and a -3db (below passband) cutoff frequency of approximately 27khz (see figure 6 for the gain vs. frequency plot). layout and grounding proper layout and grounding are essential for optimum performance. connect pgnd and sgnd together at a single point on the pc board. connect pv ss to sv ss and bypass with a 1? capacitor. place the power-sup- ply bypass capacitor and the charge-pump hold capacitor as close to the max9724 as possible. route pgnd and all traces that carry switching transients away from sgnd and the audio signal path. the thin qfn package features an exposed paddle that improves thermal efficiency. ensure that the exposed paddle is electrically isolated from pgnd, sgnd, and v dd . connect the exposed paddle to sv ss only when the board layout dictates that the exposed paddle cannot be left floating. ucsp applications information for the latest application details on ucsp construction, dimensions, tape carrier information, printed circuit board techniques, bump-pad layout, and recommend- ed reflow temperature profile, as well as the latest infor- mation on reliability testing results, refer to the application note ucsp? wafer-level chip-scale package available on maxim? website at www.maxim- ic.com/ucsp. max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 14 ______________________________________________________________________________________ max9724a active filter gain vs. frequency frequency (hz) gain (db) 100k 10k -30 -25 -20 -15 -10 -5 0 5 10 -35 1k 1m r l = 10k figure 6. frequency response of active filter of figure 4
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown ______________________________________________________________________________________ 15 max9710 outr+ outr- outl- outl+ inr inl bias pv dd v dd shdn 15k 15k 15k 15k v dd 0.1 f 1 f 0.1 f 1 f max9724b 0.1 f outl outr sgnd c1p c1n pgnd pv ss sv ss v dd shdn 1 f o.47 f o.47 f inl inr controller stereo dac 1 f 100k 100k v dd 1 f v dd mute pgnd gnd system diagram
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 16 ______________________________________________________________________________________ charge pump uvlo/ shutdown control click-and-pop suppression c1n c1p pv ss sv ss pgnd sgnd *r in and r f values are chosen for a gain -1.5v/v. ( ) ucsp package inr v dd shdn on off sv ss v dd sgnd inl r f * 30k r in * 20k r in * 20k outr left audio input right audio input headphone jack 5 (a2) 12 (b1) 1 (c1) 2 (c2) 3 (c3) 4 (c4) 9 (b4) 11 (a4) 6 (b3) 10 (a3) 7 (a1) c1 1 f c2 1 f 2.7v to 5.5v c3 1 f c in 0.47 f sv ss v dd outl c in 0.47 f 8 (b2) r f * 30k max9724a functional diagram/typical operating circuits
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown ______________________________________________________________________________________ 17 charge pump uvlo/ shutdown control click-and-pop suppression c1n c1p pv ss sv ss pgnd sgnd ( ) ucsp package inr v dd shdn sv ss v dd sgnd inl r f 30k r in 20k r in * 20k outr left audio input right audio input headphone jack 5 (a2) 12 (b1) 1 (c1) 2 (c2) 3 (c3) 4 (c4) 9 (b4) 11 (a4) 6 (b3) 10 (a3) 7 (a1) c1 1 f c2 1 f 2.7v to 5.5v c3 1 f c in 0.47 f v ss v dd outl c in 0.47 f 8 (b2) r f * 30k max9724b on off functional diagram/typical operating circuits (continued)
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 18 ______________________________________________________________________________________ top view 12 11 10 4 5 6 1 + 23 987 max9724a max9724b tqfn c1p pgnd c1n pv ss shdn inl sgnd inr sv ss outr outl v dd pin configurations ucsp top view (bumps on bottom) max9724a/max9724b 1234 sgnd shdn outr outl v dd inr inl sv ss c1p pgnd c1n pv ss b a c chip information transistor count: 993 process: bicmos
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown ______________________________________________________________________________________ 19 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 .) 12x16l qfn thin.eps 0.10 c 0.08 c 0.10 m c a b d d/2 e/2 e a1 a2 a e2 e2/2 l k e (nd - 1) x e (ne - 1) x e d2 d2/2 b l e l c l e c l l c l c package outline 21-0136 2 1 i 8, 12, 16l thin qfn, 3x3x0.8mm marking aaaa
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 20 ______________________________________________________________________________________ exposed pad variations codes pkg. t1233-1 min. 0.95 nom. 1.10 d2 nom. 1.10 max. 1.25 min. 0.95 max. 1.25 e2 12 n k a2 0.25 ne a1 nd 0 0.20 ref - - 3 0.02 3 0.05 l e e 0.45 2.90 b d a 0.20 2.90 0.70 0.50 bsc. 0.55 3.00 0.65 3.10 0.25 3.00 0.75 0.30 3.10 0.80 16 0.20 ref 0.25 - 0 4 0.02 4 - 0.05 0.50 bsc. 0.30 2.90 0.40 3.00 0.20 2.90 0.70 0.25 3.00 0.75 3.10 0.50 0.80 3.10 0.30 pkg ref. min. 12l 3x3 nom. max. nom. 16l 3x3 min. max. 0.35 x 45 pin id jedec weed-1 t1233-3 1.10 1.25 0.95 1.10 0.35 x 45 1.25 weed-1 0.95 t1633f-3 0.65 t1633-4 0.95 0.80 0.95 0.65 0.80 1.10 1.25 0.95 1.10 0.225 x 45 0.95 weed-2 0.35 x 45 1.25 weed-2 t1633-2 0.95 1.10 1.25 0.95 1.10 0.35 x 45 1.25 weed-2 package outline 21-0136 2 2 i 8, 12, 16l thin qfn, 3x3x0.8mm weed-1 1.25 1.10 0.95 0.35 x 45 1.25 1.10 0.95 t1233-4 t1633fh-3 0.65 0.80 0.95 0.225 x 45 0.65 0.80 0.95 weed-2 notes: 1. dimensioning & tolerancing conform to asme y14.5m-1994. 2. all dimensions are in millimeters. angles are in degrees. 3. n is the total number of terminals. 4. the terminal #1 identifier and terminal numbering convention shall conform to jesd 95-1 spp-012. details of terminal #1 identifier are optional, but must be located within the zone indicated. the terminal #1 identifier may be either a mold or marked feature. 5. dimension b applies to metallized terminal and is measured between 0.20 mm and 0.25 mm from terminal tip. 6. nd and ne refer to the number of terminals on each d and e side respectively. 7. depopulation is possible in a symmetrical fashion. 8. coplanarity applies to the exposed heat sink slug as well as the terminals . 9. drawing conforms to jedec mo220 revision c. 10. marking is for package orientation reference only. 11. number of leads shown are for reference only. 12. warpage not to exceed 0.10mm. 0.25 0.30 0.35 2 0.25 0 0.20 ref - - 0.02 0.05 0.35 8 2 0.55 0.75 2.90 2.90 3.00 3.10 0.65 bsc. 3.00 3.10 8l 3x3 min. 0.70 0.75 0.80 nom. max. tq833-1 1.25 0.25 0.70 0.35 x 45 weec 1.25 0.70 0.25 t1633-5 0.95 1.10 1.25 0.35 x 45 weed-2 0.95 1.10 1.25 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 .)
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown ______________________________________________________________________________________ 21 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 .) 12l, ucsp 4x3.eps f 1 1 21-0104 package outline, 4x3 ucsp
max9724a/max9724b 60mw, directdrive, stereo headphone amplifier with low rf susceptibility and shutdown 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. 22 ____________________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. revision history revision number revision date description pages changed 0 5/05 initial release 1 1/06 added rf immunity to general description , features , and detailed description . 1, 7 2 11/06 added ucsp package. 1?, 6, 9, 12, 14?6 3 3/07 updated electrical characteristics table and typical operating characteristics . 1?, 17, 18 4 6/07 corrected pin description , pin configuration , and functional diagrams/typical operating circuits with new ucsp information. 1?, 12, 14?6 5 3/08 updated absolute maximum ratings and click-and-pop suppression section. 2, 10

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