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general description the MAX13330/max13331 stereo headphone amplifiers are designed for automotive applications requiring out- put short-circuit and esd protection to battery/ground with diagnostics. these devices use maxim? 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 board space and component height. the gain of the amplifier is set internally (-1.5v/v) on the MAX13330 or adjusted externally with resistors on the max13331. the MAX13330/max13331 deliver 120mw per channel into a 16 load or 135mw into a 32 load and have a low 0.01% thd+n. low output impedance and the effi- cient integrated charge pump allows the device to drive loads as low as 8 , enabling the use of small loud- speakers. an 80db at 217hz psrr allows these devices to operate from noisy digital supplies without an additional linear regulator. these devices include ?5kv human body model esd protection and short- circuit protection up to +45v at the headphone outputs. comprehensive click-and-pop circuitry suppresses audible clicks and pops on startup and shutdown. a low-power shutdown mode reduces the supply current to 3? (typ). the MAX13330/max13331 are specified from -40? to +105? aec-q100 level 2 automotive temperature range and are available in a 16-pin qsop package. applications automotive entertainment systems automotive rear seat entertainment systems features ? 4v to 5.5v single-supply operation ? 2mhz charge pump prevents am radio interference ? ground-referenced outputs eliminate bulky dc- blocking capacitors ? short-to-ground and battery (v bat up to +45v) output protection, load dump protection ? short-circuit diagnostic output ? adjustable gain (max13331) or fixed -1.5v/v gain (MAX13330) ? 135mw per channel into 32 at 1% thd+n ? low 0.01% thd+n ? integrated click-and-pop suppression ? high psrr eliminates ldo ? no degradation of low-frequency response due to output capacitors ? ?5kv human body model esd protection for output pins MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics ________________________________________________________________ maxim integrated products 1 MAX13330 max13331 outr v ss pgnd outl 13 14 15 16 4 3 2 1 sgnd diag 12 5 v dd inr sgnd inl qsop + pgnd c1n cpvss 9 10 11 8 7 6 c1p cpvdd shdn pin configuration click-and-pop suppression output protection & diagnostics right-channel audio in left-channel audio in MAX13330 diagnostics output shdn simplified block diagram 19-4341; rev 0; 10/08 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. directdrive is a registered trademark of maxim integrated products, inc. ? u.s. patent #7,061,327 ordering information + denotes a lead-free/rohs-compliant package. t = tape-and-reel. /v denotes an automotive qualified part. typical application circuits appear at end of data sheet. part gain temp range pin- package m a x1 3 3 3 0 ge e /v + t -1.5v/v - 40c to + 105c 16 qsop m a x1 3 3 3 1 ge e /v + t e xter nal l y set - 40c to + 105c 16 qsop
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = v cpvdd = +5v, v sgnd = v pgnd = 0, shdn = v dd , c1 = c2 = 1?, r l = , resistive load referenced to ground, for MAX13330 gain = -1.5v/v (internally set), for max13331 gain = -1.5v/v (r in = 30k , r fb = 45k ), t a = t j = -40? to +105?, unless otherwise noted. typical values are at t a = +25?, unless otherwise noted.) (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. note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations, refer to http://www.maxim-ic.com/thermal-tutorial . v dd , cpvdd to sgnd..............................................-0.3v to +6v v ss , cpvss to sgnd ...............................................+0.3v to -6v v dd , cpvdd ............................................................-0.3v to 0.3v v ss , cpvss..............................................................-0.3v to 0.3v shdn , diag to sgnd................................-0.3v to (v dd + 0.3v) out_ to pgnd.......................................(v cpvss - 0.3v) to +45v in_ to sgnd (MAX13330)................(v ss - 0.3v) to (v dd + 0.3v) in_ to sgnd (max13331) ..........................-0.3v to (v dd + 0.3v) c1p to pgnd.........................................-0.3v to (v cpvdd +0.3v) c1n to pgnd.............................................(v ss - 0.3v) to + 0.3v output short-circuit duration.....................................continuous continuous power dissipation (t a = +70?) 16-pin qsop (derate 8.3mw/? above +70?)) ......666.7mw junction-to-case thermal resistance ( jc ) (note 1) jc ............................................................................... 37?/w junction-to-ambient thermal resistance ( ja ) (note 1) ja ............................................................................. 120?/w operating temperature range .........................-40? to +105? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units general amplifier supply voltage range v dd 4.0 5.5 v charge-pump supply voltage range v cpvdd 4.0 5.5 v charge-pump output voltage v cpvss -v dd v quiescent supply current i dd r l = 10 ma shutdown supply current i shdn 10 ? shdn input-logic high v ih 2v shdn input-logic low v il 0.8 v shdn input leakage current -1 +1 ? shdn to full operation time t son 100 ? diagnostics no fault 0.02 x v dd outr short to sgnd 0.22 x v dd 0.25 x v dd 0.28 x v dd outl short to sgnd 0.47 x v dd 0.50 x v dd 0.53 x v dd outr short to v bat 0.72 x v dd 0.75 x v dd 0.78 x v dd diagnostic output voltage v diag r diag = , t a = +25? outl short to v bat 0.97 x v dd v short-to-sgnd threshold 130 ma short-to-v bat threshold 130 ma
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dd = v cpvdd = +5v, v sgnd = v pgnd = 0, shdn = v dd , c1 = c2 = 1?, r l = , resistive load referenced to ground, for MAX13330 gain = -1.5v/v (internally set), for max13331 gain = -1.5v/v (r in = 30k , r fb = 45k ), t a = t j = -40? to +105?, unless otherwise noted. typical values are at t a = +25?, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units amplifiers voltage gain a v MAX13330 -1.48 -1.5 -1.52 v/v gain matching MAX13330 ?.2 % input offset voltage ? ? mv input bias current v in_ = 0 50 na input impedance r in MAX13330 20 30 k dc, v dd = 4.0v to 5.5v, input referred -86 db power-supply rejection ratio psrr f =1khz, v ripple = 100mv p-p -80 db r l = 8 75 r l = 16 2 v rms output impedance in shutdown 14 k r l = 16 , p out = 100mw, f = 1khz 0.03 % total harmonic distortion plus noise thd+n r l = 32 , p out = 125mw, f = 1khz 0.01 % signal-to-noise ratio snr r l = 32 , p ou t = 135m w , f = 22h z to 22kh z 100 db noise v n f = 22hz to 22khz bandwidth; inputs ac-coupled to grounded 6 ? rms slew rate sr 0.3 v/? maximum capacitive load c l no sustained oscillation 3000 pf into shutdown -80 click-and-pop level k cp peak voltage, t a = +25?, a-weighted, 32 samples per second; inputs ac- coupled to ground out of shutdown -60 v charge-pump oscillator frequency f osc 1.9 2.2 2.5 mhz crosstalk r l = 32 , v in = 200mv p-p , f = 10khz -75 db thermal-shutdown temperature +155 ? thermal-shutdown hysteresis 10 ? esd protection human body model (outr and outl) ?5 kv note 2: all devices are 100% tested at t a = +25?; specifications over temperature limits are guaranteed by design and qa sampling.
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics 4 _______________________________________________________________________________________ total harmonic distortion plus noise vs. frequency MAX13330/31 toc01 frequency (khz) thd+n (%) 0.1 1 10 0.01 0.1 1 0.001 0.01 100 v dd = 4v r l = 8 p out = 25mw p out = 45mw total harmonic distortion plus noise vs. frequency MAX13330/31 toc02 frequency (khz) thd+n (%) 0.1 1 10 0.01 0.1 1 0.001 0.01 100 v dd = 5v r l = 8 p out = 25mw p out = 60mw total harmonic distortion plus noise vs. frequency MAX13330/31 toc03 frequency (khz) thd+n (%) 0.1 1 10 0.01 0.1 1 0.001 0.01 100 v dd = 4v r l = 16 p out = 25mw p out = 75mw total harmonic distortion plus noise vs. frequency MAX13330/31 toc04 frequency (khz) thd+n (%) 0.1 1 10 0.01 0.1 1 0.001 0.01 100 v dd = 5v r l = 16 p out = 50mw p out = 100mw total harmonic distortion plus noise vs. frequency MAX13330/31 toc05 frequency (khz) thd+n (%) 0.1 1 10 0.01 0.1 1 0.001 0.01 100 v dd = 4v r l = 32 p out = 25mw p out = 70mw total harmonic distortion plus noise vs. frequency MAX13330/31 toc06 frequency (khz) thd+n (%) 0.1 1 10 0.01 0.1 1 0.001 0.01 100 v dd = 5v r l = 32 p out = 50mw p out = 125mw total harmonic distortion plus noise vs. output power MAX13330/31 toc07 output power (mw) thd+n (%) 50 25 0.1 1 10 0.01 0 75 v dd = 4v r l = 8 f in = 10khz f in = 1khz f in = 100hz total harmonic distortion plus noise vs. output power MAX13330/31 toc08 output power (mw) thd+n (%) 50 100 25 75 0.1 1 10 0.01 0 125 v dd = 5v r l = 8 f in = 10khz f in = 1khz f in = 100hz total harmonic distortion plus noise vs. output power MAX13330/31 toc09 output power (mw) thd+n (%) 50 100 25 75 0.01 0.1 1 10 0.001 0 125 v dd = 4v r l = 16 f in = 10khz f in = 1khz f in = 100hz typical operating characteristics (v dd = v cpvdd = 5v, v sgnd = v pgnd = 0, c1 = c2 = 1?, r l = , gain = -1.5v/v, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted.)
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics _______________________________________________________________________________________ 5 total harmonic distortion plus noise vs. output power MAX13330/31 toc10 output power (mw) thd+n (%) 125 50 150 25 0.01 0.1 1 10 0.001 0 100 75 175 v dd = 5v r l = 16 f in = 10khz f in = 1khz f in = 100hz total harmonic distortion plus noise vs. output power MAX13330/31 toc11 output power (mw) thd+n (%) 50 100 25 75 0.01 0.1 1 10 0.001 0 125 v dd = 4v r l = 32 f in = 10khz f in = 1khz f in = 100hz total harmonic distortion plus noise vs. output power MAX13330/31 toc12 output power (mw) thd+n (%) 125 50 150 25 0.01 0.1 1 10 0.001 0 100 75 175 v dd = 5v r l = 32 f in = 10khz f in = 1khz f in = 100hz total harmonic distortion plus noise vs. frequency MAX13330/31 toc13 frequency (khz) thd+n (%) 0.1 1 10 0.001 0.01 0.1 1 0.0001 0.01 100 v dd = 5v r l = 1k v out_ = 2v rms v out_ = 1v rms output power vs. supply voltage MAX13330/31 toc14 supply voltage (v) output power (mw) 5.25 4.75 4.50 5.00 4.25 60 120 180 40 100 160 20 80 140 0 4.00 5.50 f in = 1khz 1% thd+n r l = 32 r l = 16 r l = 8 output power vs. load resistance MAX13330/31 toc15 load resistance ( ) output power (mw) 10 100 60 120 200 40 100 160 180 20 80 140 0 0 1000 f in = 1khz 10% thd+n v dd = 4v 1% thd+n v dd = 4v 1% thd+n v dd = 5v 10% thd+n v dd = 5v power dissipation vs. output power per channel MAX13330/31 toc16 output power per channel (mw) power dissipation (mw) 100 60 40 80 20 300 600 800 200 500 100 400 700 0 0 120 v dd = 4v f in = 1khz r l = 32 r l = 16 r l = 8 power dissipation vs. output power per channel MAX13330/31 toc17 output power per channel (mw) power dissipation (mw) 80 140 60 120 160 20 100 40 400 800 1200 200 600 1000 0 0 180 v dd = 5v f in = 1khz r l = 32 r l = 16 r l = 8 typical operating characteristics (continued) (v dd = v cpvdd = 5v, v sgnd = v pgnd = 0, c1 = c2 = 1?, r l = , gain = -1.5v/v, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted.)
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics 6 _______________________________________________________________________________________ crosstalk vs. frequency MAX13330/31 toc19 frequency (khz) crosstalk (db) 0.1 1 10 -80 -60 -40 -90 -70 -50 -100 0.01 100 v in = 200mv p-p r l = 32 right to left left to right gain flatness vs. frequency MAX13330/31 toc20 frequency (khz) gain (db) 100 0.1 10 1 3.2 3.4 3.5 3.1 3.3 3.0 0.01 1000 MAX13330 v in = 100mv p-p outl outr typical operating characteristics (continued) (v dd = v cpvdd = 5v, v sgnd = v pgnd = 0, c1 = c2 = 1?, r l = , gain = -1.5v/v, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted.) power-supply rejection ratio vs. frequency MAX13330/31 toc18 frequency (khz) psrr (db) 10 0.1 1 -100 -40 -110 -80 -60 -50 -90 -70 -120 0.01 100 v dd = 5v outr v dd = 5v outl v ripple = 100mv p-p r l = 32 v dd = 4v outr v dd = 4v outl supply current vs. supply voltage MAX13330/31 toc22 supply voltage (v) supply current (ma) 5.25 4.75 5.00 4.50 5 7 10 2 1 6 9 4 3 8 0 4.00 4.25 5.50 supply current vs. temperature MAX13330/31 toc23 temperature ( c) supply current (ma) 075 -25 100 6 10 12 4 2 8 0 -50 50 25 125 output fft MAX13330/31 toc21 frequency (khz) amplitude (dbv) 10 15 r l = 32 -40 -20 0 -100 -120 -60 -80 -140 05 20 shutdown current vs. supply voltage MAX13330/31 toc25 supply voltage (v) shutdown current ( a) 5.00 4.25 4.75 4.50 4 5 3 2 1 0 4.00 5.25 5.50 exiting shutdown transient MAX13330/31 toc26 200 shutdown current vs. temperature MAX13330/31 toc24 temperature ( c) shutdown current ( a) 075 -25 100 2.0 3.5 4.0 1.5 1.0 3.0 0.5 2.5 0 -50 50 25 125
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics _______________________________________________________________________________________ 7 pin description typical operating characteristics (continued) (v dd = v cpvdd = 5v, v sgnd = v pgnd = 0, c1 = c2 = 1?, r l = , gain = -1.5v/v, thd+n measurement bandwidth = 22hz to 22khz, t a = +25?, unless otherwise noted.) pin name function 1 inl inverting left-channel audio input 2, 4 sgnd amplifier signal ground. the noninverting inputs of the amplifiers are connected to the amplifier signal ground. connect both to the signal ground plane. 3 inr inverting right-channel audio input 5v dd amplifier positive-power supply. connect to positive supply. bypass with a 1? capacitor to sgnd as close to the pin as possible. 6 shdn active-low shutdown input 7 cpvdd charge-pump power supply. powers charge-pump inverter, charge-pump logic, and oscillator. connect to positive supply. bypass with a 1? capacitor to pgnd as close to the pin as possible. 8 c1p flying-capacitor positive terminal. connect a 1? capacitor between c1p and c1n. 9, 15 pgnd power ground. connect both to the power ground plane. 10 c1n flying-capacitor negative terminal. connect a 1? capacitor between c1p and c1n. 11 cpvss charge-pump output. connect to v ss and bypass with a 1? capacitor to pgnd. 12 diag diagnostic voltage output 13 outr right-channel output 14 v ss amplifier negative power supply. connect to cpvss. 16 outl left-channel output entering shutdown transient MAX13330/31 toc27 200 power-up/-down transient MAX13330/31 toc28 10ms/div outl 1v/div outr 1v/div shdn 5v/div
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics 8 _______________________________________________________________________________________ detailed description the MAX13330/max13331 headphone amplifiers fea- ture maxim? patented directdrive architecture, eliminating the large output-coupling capacitors required by conventional single-supply headphone amplifiers. the devices consists of two class ab head- phone amplifiers, undervoltage lockout (uvlo), low- power shutdown control, comprehensive click-and-pop suppression, output short-circuit/esd protection and output short-circuit diagnostics. these devices can drive loads as low as 8 , and deliv- er up to 120mw per channel into 16 and 135mw into 32 . the MAX13330 features a fixed gain of -1.5v/v, and the max13331 features a programmable gain con- figured with external resistors. the headphone outputs feature ?5kv human body model esd protection, and enhanced short-circuit protection to ground or battery (v bat up to +45v). an integrated short-circuit diagnos- tic output provides the status of the MAX13330/ max13331 during operation as a fraction of the analog supply voltage. 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 the headphone and the head- phone amplifier. maxim? patented directdrive architecture uses a charge pump to create an internal negative-supply volt- age, allowing the MAX13330/max13331 outputs to be biased about sgnd (figure 1). with no dc component, there is no need for the large dc-blocking capacitors. instead of two large (220?, typ) tantalum capacitors, the MAX13330/max13331 charge pump requires two small ceramic capacitors, conserving board space, reducing cost, and improving the frequency response of the headphone amplifier. see the output power vs. load resistance graph in the typical operating characteristics for details of the possible capacitor sizes. there is a low dc voltage on the amplifier out- puts due to amplifier offset. however, the output offset of the MAX13330 is typically ?.5mv which, when com- bined with a 32 load, results in less than ?8? of dc current flow to the headphones. previous attempts to eliminate the output-coupling capacitors involved bias- ing the headphone return (sleeve) to the dc-bias volt- age of the headphone amplifiers. this method raises some issues: the sleeve is typically grounded to the chassis. using this biasing approach, the sleeve must be isolated from system ground, complicating product design. during an esd strike, the amplifier? esd structures are the only path to system ground. thus, the ampli- fier must be able to withstand the full esd strike. when using the headphone jack as a line out to other equipment, the bias voltage on the sleeve may conflict with the ground potential from other equipment, resulting in possible damage to the amplifiers. v dd v ss gnd v out conventional driver-biasing scheme directdrive biasing scheme v dd /2 v dd gnd v out figure 1. conventional driver output waveform vs. MAX13330/ max13331 output waveform
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics _______________________________________________________________________________________ 9 low-frequency response in addition to the cost and size disadvantages of the dc- blocking capacitors required by conventional head- phone amplifiers, these capacitors limit the amplifier? low-frequency response and can distort the audio signal: 1) the impedance of the headphone load and the dc- blocking capacitor form a highpass filter with the -3db point set by: where r l is the impedance of the headphone and c out is the value of the dc-blocking capacitor. the highpass filter is required by conventional single- ended, single power-supply headphone amplifiers to block the midrail dc-bias component of the audio sig- nal from the headphones. the drawback to the filter is that it can attenuate low-frequency signals. larger val- ues of c out reduce this effect but result in physically larger, more expensive capacitors. figure 2 shows the relationship between the size of c out and the resulting low-frequency attenuation. note that the -3db point for a 16 headphone with a 100? blocking capacitor is 100hz, well within the normal audio band, resulting in low-frequency attenuation of the reproduced signal. 2) the voltage coefficient of the dc-blocking capacitor contributes distortion to the reproduced audio signal as the capacitance value varies and the function of the voltage across the capacitor changes. the reactance of the capacitor dominates at frequencies below the -3db point and the voltage coefficient appears as fre- quency-dependent distortion. figure 3 shows the thd+n introduced by two different capacitor dielectric types. note that below 100hz, thd+n increases rapid- ly. the combination of low-frequency attenuation and frequency-dependent distortion compromises audio reproduction in portable audio equipment that empha- sizes low-frequency effects such as in multimedia lap- tops, mp3, cd, and dvd players. by eliminating the dc-blocking capacitors through directdrive technolo- gy, these capacitor-related deficiencies are eliminated. charge pump the MAX13330/max13331 feature a low-noise charge pump. the 2.2mhz (typ) switching frequency is well beyond the audio range. it does not interfere with the audio signals and avoids am band interference. the switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off tran- sients. by limiting the switching speed of the charge pump, the di/dt noise caused by the parasitic bond wire and trace inductance is minimized. although not typically required, additional high-frequency noise attenuation can be achieved by increasing the value of c2 (see the typical application circuits ). f rc hz db lout ? = () 3 1 2 0 -30 10 100 1k 10k 100k low-frequency rolloff (r l = 16 ) -24 -27 -12 -15 -18 -21 -6 -9 -3 frequency (hz) attenuation (db) directdrive 330 f 220 f 100 f 33 f figure 2. low-frequency attenuation for common dc-blocking capacitor values additional thd+n due to dc-blocking capacitors frequency (hz) thd+n (%) 10k 1k 100 0.001 0.01 0.1 1 10 0.0001 10 100k tantalum alum/elec figure 3. distortion contributed by dc-blocking capacitors
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics 10 ______________________________________________________________________________________ diagnostic output the MAX13330/max13331 provides an analog diag- nostic output as a fraction of the analog supply voltage v dd . the voltage at diag will correspond to the fault condition with the highest priority that is present in the system, as shown in table 1. when simultaneous fault conditions occur on both headphone outputs, the diag- nostic output will only report the fault condition at outr until it is cleared or removed. only then will the fault condition at outl be reported at diag. connect diag to a high-impedance input. for both headphone outputs, short circuits to v bat are dynamic and v diag will be automatically cleared as soon as the fault condition is removed. short circuits to gnd occurring when a positive output voltage is pre- sent on outl or outr, will result in v diag being latched until the fault condition is cleared. when v diag is latched, it can be cleared by either tog- gling shdn low for less than 5? or initiating a full reset of the MAX13330/max13331. toggling shdn low for less than 5? will cause the fault to ground to be cleared without shutting down the device or interrupting the output state of the amplifiers. a full reset requires shdn to be pulled low for more than 50?. the amplifi- er outputs will enter high impedance and remain in that state until the device exits shutdown. click-and-pop suppression in conventional single-supply audio amplifiers, the out- put-coupling capacitor is a major contributor of audible 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 to sgnd. this results in a dc shift across the capacitor which appears as an audible transient at the speaker. since the MAX13330/max13331 does not require output-coupling capacitors, this problem does not arise. additionally, the MAX13330/max13331 feature exten- sive click-and-pop suppression that eliminates any audible transient sources internal to the device. the power-up/-down transient graph in the typical operating characteristic s shows that there is minimal dc shift and no spurious transients at the output upon startup or shutdown. in most applications, the output of the preamplifier dri- ving the MAX13330/max13331 has a dc bias of typi- cally half the supply. at startup, the input-coupling capacitor is charged to the preamplifier? dc-bias volt- age through the feedback resistor of the MAX13330/ max13331, resulting in a dc shift across the capacitor and an audible click/pop. delaying the rise of shdn 4 to 5 time constants (80ms to 100ms) based on r in and c in relative to the startup of the preamplifier, eliminates this click/pop caused by the input filter. shutdown the MAX13330/max13331 feature shutdown control allowing audio signals to be shut down or muted. driving shdn low disables the amplifiers and the charge pump, sets the amplifier output impedance to 14k (typ), and reduces the supply current. in shut- down mode, the supply current is reduced to 2?. the charge pump is 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 contin- uous power dissipation or can be calculated by the following equation: where t j(max) is +145?, t a is the ambient tempera- ture, and ja is the reciprocal of the derating factor in ?/w as specified in the absolute maximum ratings section. the thermal resistance ja of the qsop pack- age is 120?/w. the MAX13330/max13331 have two power dissipation sources: the charge pump and two amplifiers. if power dissipation for a given application exceeds the maxi- mum allowed for a particular package, either reduce v dd , increase load impedance, decrease the ambient temperature, or add heatsinking to the device. large output, supply, and ground traces improve the maxi- mum power dissipation in the package. p tt disspkg max jmax a ja () () () = ? v diag state priority v dd outl short to v bat 3 3/4 v dd outr short to v bat 1 1/2 v dd outl short to sgnd 4 1/4 v dd outr short to sgnd 2 0 no fault 5 three state shutdown table 1. MAX13330/max13331 diagnostic priority
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics ______________________________________________________________________________________ 11 thermal-overload protection limits total power dissipa- tion in the MAX13330/max13331. when the junction temperature exceeds +145? (typ), the thermal-protec- tion circuitry disables the amplifier output stage. the amplifiers are enabled once the junction temperature cools by 5?. this results in a pulsing output under continuous thermal-overload conditions. output power the device has been specified for the worst-case sce- nario, when both inputs are in-phase. under this condi- tion, the amplifiers simultaneously draw current from the charge pump, leading to a proportional reduction in v ss headroom. in typical stereo audio applications, the left and right signals have differences in both magni- tude and phase, subsequently leading to an increase in the maximum attainable output power. figure 4 shows the two extreme cases for in- and out-of-phase. in reali- ty, the available power lies between these extremes. uvlo the MAX13330/max13331 feature a uvlo function that prevents the device from operating if the supply voltage is less than 3.6v (typ). this feature ensures proper operation during brownout conditions and prevents deep battery discharge. once the supply voltage reaches the uvlo threshold, the charge-pump is turned on and the amplifiers are powered. component selection gain-setting resistors (max13331 only) the gain of the MAX13330 is internally set at -1.5v/v. all gain-setting resistors are integrated into the device, reducing external component count. the internally set gain, in combination with directdrive, results in a head- phone amplifier that requires only five tiny 1? capaci- tors to complete the amplifier circuit: two for the charge-pump, two for audio input coupling, and one for power-supply bypassing (see the typical application circuits ). the gain of the max13331 amplifier is set externally as shown in the typical application circuits , the gain is: choose feedback resistor values of 10k . values other than 10k increase output offset voltage due to the input bias current, which in turn, increases the amount of dc current flow to the load. input filtering 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 typical application circuits ). the ac-coupling capacitor allows the device to bias the signal to an optimum dc level. assuming zero source impedance, the -3db point of the highpass filter is given by: choose c in so f -3db is well below the lowest frequency of interest. for the MAX13330, use the value of r in as given in the electrical characteristics table. 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 capacitors with an esr less than 100m for opti- mum performance. low-esr ceramic capacitors mini- mize the output resistance of the charge pump. for best performance over the extended temperature range, select capacitors with an x7r dielectric. f rc hz db in in ? = 3 1 2 () a r r vv v f in =? (/) output power vs. supply voltage supply voltage (v) output power (mw) 4.25 5.00 5.25 4.75 4.50 50 100 150 200 250 0 4.00 5.50 f in = 1khz r l = 32 thd+n = 10% inputs in phase inputs 180 out of phase figure 4. output power vs. supply voltage
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics 12 ______________________________________________________________________________________ flying capacitor (c1) the value of the flying capacitor (c1) affects the charge 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 resistance to an extent. see the output power vs. load resistance graph in the typical operating characteristics . above 1?, the on-resistance of the switches and the esr of c1 and c2 dominate. holding capacitor (c2) the hold capacitor value and esr directly affect the ripple at cpvss. increasing the value of c2 reduces output ripple. likewise, decreasing the esr of c2 reduces both ripple and output resistance. lower capacitance values can be used in systems with low maximum output power levels. see the output power vs. load resistance graph in the typical operating characteristics . power-supply bypass capacitor (c3) the power-supply bypass capacitor (c3) lowers the output impedance of the power supply and reduces the impact of the MAX13330/max13331 charge-pump switching transients. bypass cpvdd with c3, the same value as c1, and place it physically close to the cpvdd and pgnd pins. layout and grounding proper layout and grounding are essential for optimum performance. connect cpvdd and v dd together at the device. connect cpvss and v ss together at the device. bypassing of both supplies is accomplished by charge-pump capacitors c2 and c3 (see the typical application circuits ). place capacitors c2 and c3 as close to the device as possible and bypass them to the pgnd plane. keep pgnd and all traces that carry switching transients as short as possible to minimize emi. route them away from sgnd, the audio signal path, and the external feedback components (max13331). connect the pgnd plane and the sgnd plane together at a single point on the pcb. refer to the MAX13330/max13331 evaluation kit for layout guidelines.
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics ______________________________________________________________________________________ 13 cpvss v ss c1p diag outr c2 1 f c1 1 f c1n click-and-pop suppression v dd v ss 45k 45k 30k 0.33 f output protection and diagnostics uvlo/ shutdown control charge pump outl cpvdd v dd inr shdn inl pgnd sgnd right channel audio in left channel audio in 4v to 5.5v c3 1 f 10nf 1nf 1nf MAX13330 v dd v ss 30k 0.33 f typical application circuits
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics 14 ______________________________________________________________________________________ typical application circuits (continued) cpvss v ss c1p diag outr c2 1 f c1 1 f c1n click-and-pop suppression v dd v ss r f 45k output protection and diagnostics uvlo/ shutdown control charge pump outl cpvdd v dd inr shdn inl pgnd sgnd right channel audio in left channel audio in 4v to 5.5v c3 1 f 10nf 1nf 1nf max13331 v dd v ss c in 0.33 f c in 0.33 r in 30k r in 30k
MAX13330/max13331 automotive directdrive headphone amplifiers with output protection and diagnostics maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ____________________ 15 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. package type package code document no. 16-qsop e16-4 21-0055 package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages .

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