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general description the MAX9712 mono class d audio power amplifier pro- vides class ab amplifier performance with class d effi- ciency, conserving board space, and extending battery life. using a class d architecture, the MAX9712 delivers up to 500mw into an 8 ? load while offering efficiencies above 85%. a patented, low emi modulation scheme renders the traditional class d output filter unnecessary. the MAX9712 offers two modulation schemes: a fixed- frequency (ffm) mode, and a spread-spectrum (ssm) mode that reduces emi-radiated emissions due to the modulation frequency. furthermore, the MAX9712 oscil- lator can be synchronized to an external clock through the sync input, allowing the switching frequency to be user defined. the sync input also allows multiple MAX9712s to be cascaded and frequency locked, mini- mizing interference due to clock intermodulation. the device utilizes a fully differential architecture, a full- bridged output, and comprehensive click-and-pop sup- pression. the gain is internally set to +4v/v, further reducing external component count. the MAX9712 features high 72db psrr, a low 0.01% thd+n, and snr in excess of 90db. short-circuit and thermal-overload protection prevent the device from damage during a fault condition. the MAX9712 is avail- able in 10-pin tdfn (3mm ? 3mm ? 0.8mm), 10-pin ?ax, and 12-bump ucsp (1.5mm ? 2mm ? 0.6mm) packages. the MAX9712 is specified over the extended -40? to +85? temperature range. applications features filterless amplifier passes fcc radiated emissions standards with 100mm of cable unique spread-spectrum mode offers 5db emissions improvement over conventional methods optional external sync input simple master-slave setup for stereo operation 85% efficiency up to 500mw into 8 ? low 0.01% thd+n high psrr (72db at 217hz) integrated click-and-pop suppression low quiescent current (4ma) low-power shutdown mode (0.1a) short-circuit and thermal-overload protection available in thermally efficient, space-saving packages 10-pin tdfn (3mm ? 3mm ? 0.8mm) 10-pin max 12-bump ucsp (1.5mm ? 2mm ? 0.6mm) MAX9712 500mw, low emi, filterless, class d audio amplifier ________________________________________________________________ maxim integrated products 1 1 2 3 4 5 10 9 8 7 6 pv dd out- out+ pgnd gnd in- in+ v dd MAX9712 tdfn/ max top view sync shdn pin configurations ordering information MAX9712 differential audio input sync input v dd oscillator modulator and h-bridge simplified block diagram 19-2917; rev 0; 8/03 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. cellular phones pdas mp3 players portable audio part temp range pin/bump- package top mark MAX9712etb -40 c to +85 c 10 tdfn aai MAX9712eub -40 c to +85 c 10 max MAX9712ebc-t* -40 c to +85 c 12 ucsp-12 abn pin configurations continued at end of data sheet. ucsp is a trademark of maxim integrated products, inc. * future product?ontact factory for availability.
500mw, low emi, filterless, class d audio amplifier 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v dd = pv dd = shdn = 3.3v, gnd = pgnd = 0v, sync = gnd (ffm), r l = 8 ? , r l connected between out+ and out-, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) (notes 1, 2) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v dd to gnd..............................................................................6v pv dd to pgnd .........................................................................6v gnd to pgnd .......................................................-0.3v to +0.3v all other pins to gnd.................................-0.3v to (v dd + 0.3v) continuous current into/out of pv dd /pgnd/out_ ........ 600ma continuous input current (all other pins).......................... 20ma duration of out_ short circuit to gnd or pv dd ........continuous duration of short circuit between out+ and out- ..continuous continuous power dissipation (t a = +70 c) 10-pin tdfn (derate 24.4mw/ c above +70 c) .....1951.2mw 10-pin max (derate 5.6mw/ o c above +70 c) .........444.4mw 12-bump ucsp (derate 6.1mw/ c above +70 c)........484mw junction temperature ......................................................+150 c operating temperature range ...........................-40 c to +85 c storage temperature range .............................-65 c to +150 c lead temperature (soldering, 10s) .................................+300 c bump temperature (soldering) reflow ..........................................................................+235 c MAX9712 parameter symbol conditions min typ max units general supply voltage range v dd inferred from psrr test 2.5 5.5 v quiescent current i dd 4 5.2 ma shutdown current i shdn 0.1 5 a turn-on time t on 30 ms input resistance r in t a = +25 c1420k ? input bias voltage v bias either input 0.73 0.83 0.93 v voltage gain a v 3.8 4 4.2 v/v t a = +25 c 11 40 output offset voltage v os t min t a t max 65 mv common-mode rejection ratio cmrr f in = 1khz, input referred 72 db v dd = 2.5v to 5.5v 50 70 f ripple = 217hz 72 power-supply rejection ratio (note 3) psrr 200mv p-p ripple f ripple = 20khz 55 db r l = 16 ? , v dd = 5v 700 r l = 8 ? 450 output power p out thd+n = 1% r l = 6 ? 250 mw r l = 8 ? , p out = 125mw 0.01 total harmonic distortion plus noise thd+n f in = 1khz, either ffm or ssm r l = 6 ? , p out = 125mw 0.01 % ffm 88 bw = 22hz to 22khz ssm 86 ffm 91 signal-to-noise ratio snr v out = 1.8v rms a-weighted ssm 89 db
MAX9712 500mw, low emi, filterless, class d audio amplifier _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dd = pv dd = shdn = 3.3v, gnd = pgnd = 0v, sync = gnd (ffm), r l = 8 ? , r l connected between out+ and out-, t a = t min to t max , unless otherwise noted. typical values are at t a = +25 c.) (notes 1, 2) note 1: all devices are 100% production tested at +25 c. all temperature limits are guaranteed by design. note 2: testing performed with a resistive load in series with an inductor to simulate an actual speaker load. for r l = 6 ? , l = 47h. for r l = 8 ? , l = 68h. for r l = 16 ? , l = 136h. note 3: psrr is specified with the amplifier inputs connected to gnd through c in . parameter symbol conditions min typ max units sync = gnd 980 1100 1220 sync = float 1280 1450 1620 oscillator frequency f osc sync = v dd (ssm mode) 1220 120 khz sync frequency lock range 800 2000 khz efficiency p out = 300mw, f in = 1khz 85 % digital inputs ( shdn , sync) v ih 2 input thresholds v il 0.8 v shdn input leakage current 1a sync input current 5a typical operating characteristics (v dd = 3.3v, v sync = gnd, t a = +25 c, unless otherwise noted.) 0.001 10 100k 10k 100 1k total harmonic distortion plus noise vs. frequency 1 0.1 0.01 MAX9712 toc01 frequency (hz) thd+n (%) v dd = +5v r l = 8 ? p out = 300mw p out = 125mw 0.001 10 100k 10k 100 1k total harmonic distortion plus noise vs. frequency 1 0.1 0.01 MAX9712 toc02 frequency (hz) thd+n (%) v dd = +3.3v r l = 8 ? p out = 300mw p out = 125mw 0.001 10 100k 10k 100 1k total harmonic distortion plus noise vs. frequency 1 0.1 0.01 MAX9712 toc03 frequency (hz) thd+n (%) v dd = +3.3v r l = 8 ? p out = 125mw ssm mode ffm mode
MAX9712 500mw, low emi, filterless, class d audio amplifier 4 _______________________________________________________________________________________ typical operating characteristics (continued) (v dd = 3.3v, v sync = gnd, t a = +25 c, unless otherwise noted.) 100 0 0.1 0.2 0.3 0.4 0.5 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power MAX9712 toc04 output power (w) thd+n (%) v dd = 3.3v r l = 8 ? f = 10khz f = 1khz f = 100hz 100 0 0.2 0.4 0.6 0.8 1.0 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power MAX9712 toc05 output power (w) thd+n (%) v dd = 5v r l = 16 ? f = 10khz f = 1khz f = 100hz 100 0 0.1 0.2 0.3 0.4 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power MAX9712 toc06 output power (w) thd+n (%) v dd = 3.3v r l = 6 ? f = 1khz f = 100hz f = 10khz 100 0 0.1 0.2 0.3 0.4 0.5 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power MAX9712 toc07 output power (w) thd+n (%) v dd = 2.5v r l = 8 ? v cm = 1.25v no input capacitors differential input single-ended 100 0 0.1 0.2 0.3 0.4 0.5 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power MAX9712 toc08 output power (w) thd+n (%) v dd = 3.3v r l = 8 ? ffm (sync floating) ffm (sync = gnd) ssm (sync = v dd ) 100 0 0.1 0.2 0.3 0.4 0.5 0.6 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power MAX9712 toc09 output power (w) thd+n (%) v dd = 3.3v r l = 8 ? sync = 3.3v p-p 50% duty cycle square wave f sync = 1.4mhz f sync = 2mhz f sync = 800khz 10 0 0.5 1.0 1.5 2.0 2.5 3.0 1 0.1 0.01 total harmonic distortion plus noise vs. common-mode voltage MAX9712 toc10 common-mode voltage (v) thd+n (%) v dd = 3.3v r l = 8 ? f = 1khz p out = 300mw differential input 0 30 20 10 50 40 90 80 70 60 100 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 efficiency vs. output power MAX9712toc11 output power (w) efficiency (%) r l = 8 ? v dd = 5v f = 1khz r l = 16 ? 0 30 20 10 50 40 90 80 70 60 100 0 0.1 0.2 0.3 0.4 0.5 efficiency vs. output power MAX9712toc12 output power (w) efficiency (%) r l = 8 ? r l = 6 ? v dd = 3.3v f = 1khz r l = 16 ?
MAX9712 500mw, low emi, filterless, class d audio amplifier _______________________________________________________________________________________ 5 0 30 20 10 50 40 90 80 70 60 100 2.5 3.0 3.5 4.0 4.5 5.0 5.5 efficiency vs. supply voltage MAX9712toc13 supply voltage (v) efficiency (%) r l = 8 ? f = 1khz r l = 6 ? r l = 16 ? 0 30 20 10 50 40 90 80 70 60 100 800 1000 1200 1400 1800 1600 2000 efficiency vs. sync input frequency MAX9712toc14 sync frequency (khz) efficiency (%) r l = 8 ? v dd = 3.3v f = 1khz p out = 300mw 0 500 400 200 100 300 700 600 900 800 1000 2.5 3.1 3.7 4.3 4.9 5.5 output power vs. supply voltage MAX9712toc15 supply voltage (v) output power (mw) f = 1khz r l = 6 ? r l = 8 ? r l = 16 ? 0 300 200 100 500 400 900 800 700 600 1000 01020 40 30 80 70 60 50 100 90 output power vs. load resistance MAX9712toc16 load resistance ( ? ) output power (mw) v dd = 5v v dd = 3.3v f = 1khz thd+n = 1% 0 -100 10 100 1k 10k 100k common-mode rejection ratio vs. frequency -80 max1972toc17 frequency (hz) cmrr (db) -60 -40 -20 -30 -50 -70 -90 -10 input referred v in = 200mv p-p 0 -100 10 100 1k 10k 100k power-supply rejection ratio vs. frequency -80 max1972toc18 frequency (hz) psrr (db) -60 -40 -20 -30 -50 -70 -90 -10 output referred inputs ac grounded v dd = 3.3v gsm power-supply rejection MAX9712toc19 MAX9712 output v dd 100 v/div 500mv/div 2ms/div f = 217hz input low = 3v input high = 3.5v duty cycle = 88% r l = 8 ? -140 -100 -120 -60 -80 -20 -40 0 output frequency spectrum MAX9712toc20 frequency (hz) output magnitude (dbv) 0 5k 10k 15k 20k ffm mode v out = -60dbv f = 1khz r l = 8 ? unweighted typical operating characteristics (continued) (v dd = 3.3v, v sync = gnd, t a = +25 c, unless otherwise noted.)
MAX9712 500mw, low emi, filterless, class d audio amplifier 6 _______________________________________________________________________________________ typical operating characteristics (continued) (v dd = 3.3v, v sync = gnd, t a = +25 c, unless otherwise noted.) -140 -100 -120 -60 -80 -20 -40 0 output frequency spectrum MAX9712toc22 frequency (khz) output magnitude (dbv) 0 5 10 15 20 ssm mode v out = -60dbv f = 1khz r l = 8 ? a-weighted 0 -100 1m 10m 100m 1g wideband output spectrum (ffm mode) -80 max1972 toc23 frequency (hz) output amplitude (db) -60 -40 -20 -30 -50 -70 -90 -10 rbw = 10khz 0 -100 1m 10m 100m 1g wideband output spectrum (ssm mode) -80 max1972toc24 frequency (hz) output amplitude (db) -60 -40 -20 -30 -50 -70 -90 -10 rbw = 10khz turn-on/turn-off response MAX9712toc25 MAX9712 output shdn 0v 250mv/div 3v 10ms/div f = 1khz r l = 8 ? 3.0 3.5 4.5 4.0 5.5 5.0 6.0 supply current vs. supply voltage MAX9712toc26 supply voltage (v) supply current (ma) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 t a = +85 c t a = +25 c t a = -40 c 0 0.06 0.04 0.02 0.10 0.08 0.14 0.12 0.16 2.5 3.0 3.5 4.0 4.5 5.0 5.5 shutdown supply current vs. supply voltage MAX9712 toc27 supply voltage (v) supply current ( a) t a = +85 c t a = -40 c t a = +25 c -140 -100 -120 -60 -80 -20 -40 0 output frequency spectrum MAX9712toc21 frequency (khz) output magnitude (dbv) 0 5 10 15 20 ssm mode v out = -60dbv f = 1khz r l = 8 ? unweighted
MAX9712 500mw, low emi, filterless, class d audio amplifier _______________________________________________________________________________________ 7 functional diagram MAX9712 2 (b4) 5 (b3) 3 (a4) 7 (b2) 10 f ( ) ucsp bump. 1 f pgnd out+ out- pv dd pgnd pgnd pv dd 4 (a5) gnd in+ v dd v dd 1 (c4) shdn in- uvlo/power management class d modulator pv dd sync 10 (b1) 6 (c2) 8 (c1) 9 (a1) click and pop suppression oscillator
MAX9712 detailed description the MAX9712 filterless, class d audio power amplifier features several improvements to switch-mode amplifier technology. the MAX9712 offers class ab performance with class d efficiency, while occupying minimal board space. a unique filterless modulation scheme, synchro- nizable switching frequency, and ssm mode create a compact, flexible, low-noise, efficient audio power amplifier. the differential input architecture reduces common-mode noise pick-up, and can be used without input-coupling capacitors. the device can also be con- figured as a single-ended input amplifier. comparators monitor the MAX9712 inputs and com- pare the complementary input voltages to the sawtooth waveform. the comparators trip when the input magni- tude of the sawtooth exceeds their corresponding input voltage. both comparators reset at a fixed time after the rising edge of the second comparator trip point, gener- ating a minimum-width pulse t on(min) at the output of the second comparator (figure 1). as the input voltage increases or decreases, the duration of the pulse at one output increases (the first comparator to trip) while the other output pulse duration remains at t on(min) . this causes the net voltage across the speaker (v out+ - v out- ) to change. operating modes fixed-frequency modulation (ffm) mode the MAX9712 features two ffm modes. the ffm modes are selected by setting sync = gnd for a 1.1mhz switching frequency, and sync = float for a 1.45mhz switching frequency. in ffm mode, the fre- quency spectrum of the class d output consists of the fundamental switching frequency and its associated harmonics (see the wideband fft graph in the typical operating characteristics ). the MAX9712 allows the switching frequency to be changed by +32%, should the frequency of one or more of the harmonics fall in a sensitive band. this can be done at any time and does not affect audio reproduction. spread-spectrum modulation (ssm) mode the MAX9712 features a unique, patented spread-spec- trum mode that flattens the wideband spectral compo- nents, improving emi emissions that may be radiated by the speaker and cables by 5db. proprietary techniques ensure that the cycle-to-cycle variation of the switching period does not degrade audio reproduction or efficien- cy (see the typical operating characteristics ). select ssm mode by setting sync = v dd . in ssm mode, the switching frequency varies randomly by 120khz around the center frequency (1.22mhz). the modulation scheme remains the same, but the period of the saw- tooth waveform changes from cycle to cycle (figure 2). instead of a large amount of spectral energy present at multiples of the switching frequency, the energy is now 500mw, low emi, filterless, class d audio amplifier 8 _______________________________________________________________________________________ pin description pin bump tdfn/max ucsp name function 1c4v dd analog power supply 2 b4 in+ noninverting audio input 3 a4 in- inverting audio input 4 a3 gnd analog ground 5b3 shdn active-low shutdown input. connect to v dd for normal operation. 6 c2 sync frequency select and external clock input. sync = gnd: fixed-frequency mode with f s = 1100khz. sync = float: fixed-frequency mode with f s = 1450khz. sync = v dd : spread-spectrum mode with f s = 1220khz 120khz. sync = clocked: fixed-frequency mode with f s = external clock frequency. 7 b2 pgnd power ground 8 c1 out+ amplifier output positive phase 9 a1 out- amplifier output negative phase 10 b1 pv dd h-bridge power supply
MAX9712 500mw, low emi, filterless, class d audio amplifier _______________________________________________________________________________________ 9 spread over a bandwidth that increases with frequency. above a few mhz, the wideband spectrum looks like white noise for emi purposes (figure 3). external clock mode the sync input allows the MAX9712 to be synchro- nized to a system clock (allowing a fully synchronous system), or allocating the spectral components of the switching harmonics to insensitive frequency bands. applying an external ttl clock of 800khz to 2mhz to sync synchronizes the switching frequency of the MAX9712. the period of the sync clock can be ran- domized, enabling the MAX9712 to be synchronized to another MAX9712 operating in ssm mode. filterless modulation/common-mode idle the MAX9712 uses maxim s unique, patented modula- tion scheme that eliminates the lc filter required by traditional class d amplifiers, improving efficiency, reducing component count, conserving board space and system cost. conventional class d amplifiers out- put a 50% duty cycle square wave when no signal is present. with no filter, the square wave appears across figure 1. MAX9712 outputs with an input signal applied out+ out- v in- v in+ v out+ - v out- t on(min) t sw sync input mode gnd ffm with f s = 1100khz float ffm with f s = 1450khz v dd ssm with f s = 1220khz 120khz clocked ffm with f s = external clock frequency table 1. operating modes
MAX9712 500mw, low emi, filterless, class d audio amplifier 10 ______________________________________________________________________________________ the load as a dc voltage, resulting in finite load current, increasing power consumption. when no signal is pre- sent at the input of the MAX9712, the outputs switch as shown in figure 4. because the MAX9712 drives the speaker differentially, the two outputs cancel each other, resulting in no net idle mode voltage across the speaker, minimizing power consumption. efficiency efficiency of a class d amplifier is attributed to the region of operation of the output stage transistors. in a class d amplifier, the output transistors act as current- steering switches and consume negligible additional power. any power loss associated with the class d out- put stage is mostly due to the i ? r loss of the mosfet on-resistance, and quiescent current overhead. the theoretical best efficiency of a linear amplifier is 78%, however, that efficiency is only exhibited at peak output powers. under normal operating levels (typical music reproduction levels), efficiency falls below 30%, whereas the MAX9712 still exhibits >80% efficiencies under the same conditions (figure 5). figure 2. MAX9712 output with an input signal applied (ssm mode) v out+ - v out- t sw t sw t sw t sw v in- v in+ out+ out- t on(min)
MAX9712 500mw, low emi, filterless, class d audio amplifier ______________________________________________________________________________________ 11 shutdown the MAX9712 has a shutdown mode that reduces power consumption and extends battery life. driving shdn low places the MAX9712 in a low-power (0.1a) shutdown mode. connect shdn to v dd for normal operation. click-and-pop suppression the MAX9712 features comprehensive click-and-pop suppression that eliminates audible transients on start- up and shutdown. while in shutdown, the h-bridge is in a high-impedance state. during startup, or power-up, the input amplifiers are muted and an internal loop sets the modulator bias voltages to the correct levels, pre- venting clicks and pops when the h-bridge is subse- quently enabled. for 35ms following startup, a soft-start function gradually unmutes the input amplifiers. applications information filterless operation traditional class d amplifiers require an output filter to recover the audio signal from the amplifier s output. the filters add cost, increase the solution size of the amplifi- er, and can decrease efficiency. the traditional pwm scheme uses large differential output swings (2 x v dd peak-to-peak) and causes large ripple currents. any parasitic resistance in the filter components results in a loss of power, lowering the efficiency. the MAX9712 does not require an output filter. the device relies on the inherent inductance of the speaker coil and the natural filtering of both the speaker and the human ear to recover the audio component of the square-wave output. eliminating the output filter results in a smaller, less costly, more efficient solution. because the frequency of the MAX9712 output is well beyond the bandwidth of most speakers, voice coil movement due to the square-wave frequency is very small. although this movement is small, a speaker not designed to handle the additional power may be dam- aged. for optimum results, use a speaker with a series inductance >10h. typical 8 ? speakers exhibit series inductances in the range of 20h to 100h. power conversion efficiency unlike a class ab amplifier, the output offset voltage of a class d amplifier does not noticeably increase quies- cent current draw when a load is applied. this is due to figure 3. MAX9712 with 76mm of speaker cable 30.0 60.0 80.0 100.0 120.0 140.0 160.0 180.0 280.0 300.0 220.0 200.0 240.0 260.0 10.0 15.0 20.0 25.0 30.0 35.0 40.0 45.0 50.0 amplitude (db v/m) frequency (mhz) figure 4. MAX9712 outputs with no input signal v in = 0v out- out+ v out+ - v out- = 0v figure 5. MAX9712 efficiency vs. class ab efficiency 0 30 20 10 50 40 90 80 70 60 100 0 0.1 0.2 0.3 0.4 0.5 efficiency vs. output power output power (w) efficiency (%) MAX9712 class ab v dd = 3.3v f = 1khz r l - 8 ?
MAX9712 500mw, low emi, filterless, class d audio amplifier 12 ______________________________________________________________________________________ the power conversion of the class d amplifier. for exam- ple, an 8mv dc offset across an 8 ? load results in 1ma extra current consumption in a class ab device. in the class d case, an 8mv offset into 8 ? equates to an addi- tional power drain of 8w. due to the high efficiency of the class d amplifier, this represents an additional quies- cent current draw of: 8w/(v dd /100 ), which is on the order of a few microamps. input amplifier differential input the MAX9712 features a differential input structure, making it compatible with many codecs, and offering improved noise immunity over a single-ended input amplifier. in devices such as cellular phones, high-fre- quency signals from the rf transmitter can be picked up by the amplifier s input traces. the signals appear at the amplifier s inputs as common-mode noise. a differ- ential input amplifier amplifies the difference of the two inputs, any signal common to both inputs is canceled. single-ended input the MAX9712 can be configured as a single-ended input amplifier by capacitively coupling either input to gnd, and driving the other input (figure 6). dc-coupled input the input amplifier can accept dc-coupled inputs that are biased within the amplifier s common-mode range (see the typical operating characteristics ). dc cou- pling eliminates the input-coupling capacitors, reduc- ing component count to potentially one external component (see the system diagram ). however, the low-frequency rejection of the capacitors is lost, allow- ing low-frequency signals to feedthrough to the load. component selection input filter an input capacitor, c in , in conjunction with the input impedance of the MAX9712 forms a highpass filter that removes the dc bias from an incoming signal. the ac- coupling capacitor allows the amplifier to bias the sig- nal 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. setting f -3db too high affects the low-fre- quency response of the amplifier. use capacitors whose dielectrics have low-voltage coefficients, such as tantalum or aluminum electrolytic. capacitors with high-voltage coefficients, such as ceramics, may result in increased distortion at low frequencies. other considerations when designing the input filter include the constraints of the overall system and the actual frequency band of interest. although high-fidelity audio calls for a flat-gain response between 20hz and 20khz, portable voice-reproduction devices such as cellular phones and two-way radios need only concen- trate on the frequency range of the spoken human voice (typically 300hz to 3.5khz). in addition, speakers used in portable devices typically have a poor response below 150hz. taking these two factors into considera- tion, the input filter may not need to be designed for a 20hz to 20khz response, saving both board space and cost due to the use of smaller capacitors. output filter the MAX9712 does not require an output filter. the device passes fcc emissions standards with 100mm of unshielded speaker cables. however, output filtering can be used if a design is failing radiated emissions due to board layout or cable length, or the circuit is near emi sensitive devices. use an lc filter when radi- ated emissions are a concern, or when long leads are used to connect the amplifier to the speaker. supply bypassing/layout proper power-supply bypassing ensures low distortion operation. for optimum performance, bypass vdd to gnd and pvdd to pgnd with separate 0.1f capaci- tors as close to each pin as possible. a low-imped- ance, high-current power-supply connection to pvdd is assumed. additional bulk capacitance should be added as required depending on the application and power-supply characteristics. gnd and pgnd should be star connected to system ground. refer to the MAX9712 evaluation kit for layout guidance. stereo configuration two MAX9712s can be configured as a stereo amplifier (figure 7). device u1 is the master amplifier; its unfil- ?= ? 3 1 2 db in in rc figure 6. single-ended input 1 f in+ in- 1 f single-ended audio input MAX9712
MAX9712 500mw, low emi, filterless, class d audio amplifier ______________________________________________________________________________________ 13 tered output drives the sync input of the slave device (u2), synchronizing the switching frequencies of the two devices. synchronizing two MAX9712s ensures that no beat frequencies occur within the audio spectrum. this configuration works when the master device is in either ffm or ssm mode. there is excellent thd+n perfor- mance and minimal crosstalk between devices due to the sync connection (figures 8 and 9). u2 locks onto only the frequency present at sync, not the pulse width. the internal feedback loop of device u2 ensures that the audio component of u1 s output is rejected. 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 information on reliability testing results, refer to the application note: ucsp a wafer-level chip-scale package available on maxim s website at www.maxim- ic.com/ucsp. chip information transistor count: 3595 process: bicmos figure 7. master-slave stereo configuration in+ in- out+ out- sync 1 f right-channel differential audio input MAX9712 v dd v dd pv dd in+ in- out+ out- sync 1 f left-channel differential audio input MAX9712 v dd pv dd figure 8. master-slave thd 100 0 0.1 0.2 0.3 0.4 0.5 10 1 0.1 0.01 0.001 total harmonic distortion plus noise vs. output power output power (w) thd+n (%) v dd = 3.3v f = 1khz r l = 8 ? slave device figure 9. master-slave crosstalk 0 -120 -100 10 100 1k 10k 100k crosstalk vs. frequency -80 frequency (hz) crosstalk (db) -60 -40 -20 master-to-slave slave-to-master v dd = 3.3v r l = 8 ? f = 1khz v in = 500mv p-p
MAX9712 500mw, low emi, filterless, class d audio amplifier 14 ______________________________________________________________________________________ in+ in- shdn out+ out- sync 1 f MAX9712 v dd v dd v dd v dd pv dd inl c1p cin alert hps outr sv dd 1 f 1 f max9720 outl mode1 mode2 v dd pv dd inr time 1 f 1 f 220nf 100k ? 10k ? 1 f controller codec/ baseband processor out out in+ 0.1 f 2.2k ? 2.2k ? 0.1 f bias aux_in in- 0.1 f max4063 v dd system diagram MAX9712 top view (bump side down) ucsp gnd in- out- 1 a b c 234 out+ v dd sync pv dd shdn in+ pgnd pin configurations (continued)
MAX9712 500mw, low emi, filterless, class d audio amplifier ______________________________________________________________________________________ 15 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 .) 12l, ucsp 4x3.eps f 1 1 21-0104 package outline, 4x3 ucsp
MAX9712 500mw, low emi, filterless, class d audio amplifier 16 ______________________________________________________________________________________ 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 .) 6, 8, &10l, qfn thin.eps proprietary information title: approval document control no. rev. 2 1 package outline, 6, 8 & 10l, tdfn, exposed pad, 3x3x0.80 mm 21-0137 d l c l c semiconductor dallas a2 a pin 1 index area d e a1 d2 b e2 [(n/2)-1] x e ref. e k 1n 1 l e l a l pin 1 id c0.35 detail a e number of leads shown are for reference only
MAX9712 500mw, low emi, filterless, class d audio amplifier ______________________________________________________________________________________ 17 document control no. approval title: proprietary information rev. 2 2 common dimensions symbol min. max. a 0.70 0.80 d 2.90 3.10 e 2.90 3.10 a1 0.00 0.05 l 0.20 0.40 pkg. code 6 n t633-1 1.500.10 d2 2.300.10 e2 0.95 bsc e mo229 / weea jedec spec 0.400.05 b 1.90 ref [(n/2)-1] x e 1.500.10 mo229 / weec 1.95 ref 0.300.05 0.65 bsc 2.300.10 t833-1 8 package variations 21-0137 0.250.05 2.00 ref mo229 / weed-3 0.50 bsc 1.500.10 2.300.10 10 t1033-1 0.25 min. k a2 0.20 ref. d semiconductor dallas package outline, 6, 8 & 10l, tdfn, exposed pad, 3x3x0.80 mm 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 .)
MAX9712 500mw, low emi, filterless, class d audio amplifier maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 18 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2003 maxim integrated products printed usa is a registered trademark of maxim integrated products. 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 .) 10lumax.eps package outline, 10l umax/usop 1 1 21-0061 i rev. document control no. approval proprietary information title: top view front view 1 0.498 ref 0.0196 ref s 6 side view bottom view 0 0 6 0.037 ref 0.0078 max 0.006 0.043 0.118 0.120 0.199 0.0275 0.118 0.0106 0.120 0.0197 bsc inches 1 10 l1 0.0035 0.007 e c b 0.187 0.0157 0.114 h l e2 dim 0.116 0.114 0.116 0.002 d2 e1 a1 d1 min -a 0.940 ref 0.500 bsc 0.090 0.177 4.75 2.89 0.40 0.200 0.270 5.05 0.70 3.00 millimeters 0.05 2.89 2.95 2.95 - min 3.00 3.05 0.15 3.05 max 1.10 10 0.60.1 0.60.1 ? 0.500.1 h 4x s e d2 d1 b a2 a e2 e1 l l1 c gage plane a2 0.030 0.037 0.75 0.95 a1

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