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general description the max9723 stereo directdrive headphone amplifier with bassmax and volume control is ideal for portable audio applications where space is at a premium and per- formance is essential. the max9723 operates from a sin- gle 1.8v to 3.6v power supply and includes features that reduce external component count, system cost, board space, and improves audio reproduction. the headphone amplifier uses maxim? patented directdrive architecture that produces a ground-refer- enced output from a single supply, eliminating the need for large dc-blocking capacitors. the headphone ampli- fiers deliver 62mw into a 16 ? l oad, feature l ow 0.006% thd+n, and high 90db psrr. the max9723 features maxim? industry-leading click-and-pop suppression. the bassmax feature boosts the bass response of the amplifier, improving audio reproduction when using inexpensive headphones. the integrated volume con- trol features 32 discrete volume levels, eliminating the need for an external potentiometer. bassmax and the volume control are enabled through the i 2 c*/smbus- compatible interface. shutdown is controlled through either the hardware or software interfaces. the max9723 consumes only 3.7ma of supply current at 1.8v, provides short-circuit and thermal-overload protection, and is fully specified over the extended -40? to +85? temperature range. the max9723 is available in a tiny (2mm x 2mm x 0.62mm) 16-bump chip-scale package (ucsp) or 16-pin thin qfn (4mm x 4mm x 0.8mm) package. applications features ? 62mw, directdrive headphone amplifier eliminates bulky dc-blocking capacitors ? 1.8v to 3.6v single-supply operation ? integrated 32-level volume control ? high 90db psrr at 1khz ? low 0.006% thd+n ? industry-leading click-and-pop suppression ? 8kv hbm esd-protected headphone outputs ? short-circuit and thermal-overload protection ? low-power shutdown mode (5a) ? software-enabled bass boost (bassmax) ? i 2 c/smbus-compatible interface ? available in space-saving, thermally efficient packages: 16-bump ucsp (2mm x 2mm x 0.62mm) 16-pin thin qfn (4mm x 4mm x 0.8mm) max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c ________________________________________________________________ maxim integrated products 1 i 2 c interface volume control bassmax bassmax 1.8v to 3.6v supply scl bbl outl bbr outr sda inl inr max9723 block diagram ordering information 19-3509; rev 1; 11/05 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. part** temp range pin- package pkg code max9723_ebe-t* -40? to +85? 16 ucsp-16 b16-1 max9723_ete+ -40? to +85? 16 tqfn t1644-4 * purchase of i 2 c components from maxim integrated products, inc. or one of its sublicensed associated companies, conveys a license under the philips i 2 c patent rights to use these com- ponents in an i 2 c system, provided that the system conforms to the i 2 c standard specification as defined by philips. smbus is a trademark of intel corp. ucsp is a trademark of maxim integrated products, inc. ** replace the ??with the one-letter code that denotes the slave address and maximum programmable gain. see the selector guide. + denotes lead-free package. * future product?ontact factory for availability. pin configurations appear at end of data sheet. pda audio portable cd players mini disc players automotive multimedia mp3-enabled cellular phones mp3 players part slave address maximum gain (db) max9723a 1001100 0 max9723b 1001101 0 max9723c 1001100 +6 max9723d 1001101 +6 selector guide
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 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. sgnd to pgnd .....................................................-0.3v to +0.3v v dd to pgnd............................................................-0.3v to +4v pv ss to sv ss .........................................................-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 , sv ss to pgnd ................................................+0.3v to -4v in_ to sgnd ..................................(sv ss - 0.3v) to (v dd + 0.3v) sda, scl to pgnd ..................................................-0.3v to +4v shdn to pgnd ..........................................-0.3v to (v dd + 0.3v) out_ to sgnd ............................................................-3v to +3v bb_ to sgnd...............................................................-2v to +2v duration of out_ short circuit to _gnd ....................continuous continuous current into/out of: v dd , c1p, pgnd, c1n, pv ss , sv ss , or out_ ..............?.85a any other pin.................................................................?0ma continuous power dissipation (t a = +70?) 4 x 4 ucsp (derate 8.2mw/? above +70?) ...........659.2mw 16-pin thin qfn (derate 16.9mw/? above +70?) ....1349mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? bump temperature (soldering) reflow ...........................................................................+230? lead temperature (soldering, 10s) .................................+300? electrical characteristics (v dd = shdn = 3v, pgnd = sgnd = 0v, c1 = c2 = 1f, bb_ = 0v. gain = 0db, maximum volume, bassmax disabled. load connect- ed between out_ and sgnd where specified. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units general supply voltage range v dd 1.8 3.6 v quiescent supply current i dd no load 4 6.5 ma shutdown supply current i dd_shdn v shdn = 0v 5 8.5 ? turn-on time t on 200 ? turn-off time t off 35 ? thermal shutdown threshold t thres +143 c thermal shutdown hysteresis t hyst 12 c headphone amplifier gain = 0db, max9723a/ max9723b 0.7 4.5 output offset voltage v os m easur ed b etw een ou t_ and s gn d ( n ote 2) gain = +6db, max9723c/ max9723d 0.8 5 mv input resistance r in all volume levels 10 17 27 k ? bbr, bbl input bias current i bias_bb 10 100 na dc, v dd = 1.8v to 3.6v 73 90 f = 217hz, 100mv p-p ripple, v dd = 3.0v 87 f = 1khz, 100mv p-p ripple, v dd = 3.0v 86 power-supply rejection ratio psrr (note 2) f = 20khz, 100mv p-p ripple, v dd = 3.0v 61 db
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c _______________________________________________________________________________________ 3 electrical characteristics (continued) (v dd = shdn = 3v, pgnd = sgnd = 0v, c1 = c2 = 1f, bb_ = 0v. gain = 0db, maximum volume, bassmax disabled. load connect- ed between out_ and sgnd where specified. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) (note 1) parameter symbol conditions min typ max units r l = 32 ? 59 output power p out thd+n = 1%, f in = 1khz r l = 16 ? (note 5) 38 60 mw r l = 16 ? , p out = 35mw, f in = 1khz 0.006 total harmonic distortion plus noise thd+n r l = 32 ? , p out = 45mw, f in = 1khz 0.004 % gain range bit 5 = 1 0 max9723a/ max9723b gain range bit 5 = 0 -5 db gain range bit 5 = 1 +6 maximum gain a max max9723c/ max9723d gain range bit 5 = 0 +1 db bw = 22hz to 22khz 99 signal-to-noise ratio snr r l = 32 ? , v out = 1v rms a-weighted 100 db slew rate sr 0.35 v/? capacitive drive no sustained oscillations 300 pf output resistance in shutdown r out_shdn v shdn = 0v, measured from out_ to sgnd 20 k ? shdn = 0v, measured from out_ to sgnd 60 pf into shutdown -69 max9723a/ max9723b out of shutdown -71 into shutdown -70 click/pop level k cp r l = 32 ? , peak voltage, a-weighted, 32 samples per second (notes 2, 4) max9723c/ max9723d out of shutdown -69 db charge-pump switching frequency f cp 505 600 700 khz crosstalk xtalk l to r or r to l, f = 10khz, v out = 1v p-p , r l = 32 ? , both channels loaded 80 db digital inputs ( shdn , sda, scl) input high voltage v ih 0.7 x v dd v input low voltage v il 0.3 x v dd v input leakage current 1a digital outputs (sda) output low voltage v ol i ol = 3ma 0.4 v output high current i oh v sda = v dd 1a
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 4 _______________________________________________________________________________________ timing characteristics (v dd = shdn = 3v, pgnd = sgnd = 0v, c1 = c2 = 1f, bb_ = 0v, gain = 0db, maximum volume, bassmax disabled. load connect- ed between out_ and sgnd where specified. t a = t min to t max , unless otherwise noted. typical values are at t a = +25?, see timing diagram.) (notes 1, 3) parameter symbol conditions min typ max units serial clock frequency f scl 0 400 khz bus free time between a stop and a start condition t buf 1.3 ? start condition hold time t hd:sta 0.6 ? low period of the scl clock t low 1.3 ? high period of the scl clock t high 0.6 ? setup time for a repeated start condition t su:sta 0.6 ? data hold time t hd:dat 0 0.9 ? data setup time t su:dat 100 ns maximum rise time of sda and scl signals t r 300 ns maximum fall time of sda and scl signals t f 300 ns setup time for stop condition t su:sto 0.6 ? pulse width of suppressed spike t sp 100 ns maximum capacitive load for each bus line c l_bus 400 pf note 1: all specifications are 100% tested at t a = +25?. temperature limits are guaranteed by design. note 2: inputs ac-coupled to sgnd. note 3: guaranteed by design. note 4: headphone mode testing performed with a 32 ? resistive load connected to gnd. mode transitions are controlled by shdn . the k cp level is calculated as: 20 x log [(level peak voltage during mode transition, no input signal)/(peak voltage under normal operation at rated power)]. units are expressed in db. note 5: output power min is specified at t a = +25?.
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c _______________________________________________________________________________________ 5 total harmonic distortion plus noise vs. frequency max9723 toc01 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 0.001 10 100k v dd = 2.4v r l = 16 ? p out = 10mw p out = 25mw total harmonic distortion plus noise vs. frequency max9723 toc02 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 0.001 10 100k v dd = 2.4v r l = 32 ? p out = 23mw p out = 10mw total harmonic distortion plus noise vs. frequency max9723 toc03 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 0.001 10 100k v dd = 3v r l = 16 ? p out = 37mw p out = 20mw total harmonic distortion plus noise vs. frequency max9723 toc04 frequency (hz) thd+n (%) 10k 1k 100 0.01 0.1 1 0.001 10 100k v dd = 3v r l = 32 ? p out = 30mw p out = 10mw total harmonic distortion plus noise vs. output power max9723 toc05 output power (mw) thd+n (%) 40 20 0.01 0.1 1 10 100 0.001 060 v dd = 2.4v r l = 16 ? f in = 1khz f in = 20hz f in = 10khz total harmonic distortion plus noise vs. output power max9723 toc06 output power (mw) thd+n (%) 40 20 0.01 0.1 1 10 100 0.001 060 v dd = 2.4v r l = 32 ? f in = 1khz f in = 10khz f in = 20hz total harmonic distortion plus noise vs. output power max9723 toc07 output power (mw) thd+n (%) 80 60 40 20 0.01 0.1 1 10 100 0.001 0 100 v dd = 3v r l = 16 ? f in = 10khz f in = 1khz f in = 20hz total harmonic distortion plus noise vs. output power max9723 toc08 output power (mw) thd+n (%) 80 60 40 20 0.01 0.1 1 10 100 0.001 0100 v dd = 3v r l = 32 ? f in = 10khz f in = 1khz f in = 20hz 0 40 60 80 100 120 140 160 180 0204 06080 power dissipation vs. output power max9723 toc09 output power (mw) power dissipation (mw) 20 v dd = 2.4v f in = 1khz p out = p outl + p outr outputs in phase r l = 32 ? r l = 16 ? t ypical operating characteristics (v dd = shdn = 3v, pgnd = sgnd = 0v, c1 = c2 = 1?, bb_ = 0v, gain = 0db, maximum volume, bassmax disabled. load con- nected between out_ and sgnd where specified. outputs in phase, both channels loaded. t a = +25?, unless otherwise noted.) (see functional diagram/typical operating circuit )
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 6 _______________________________________________________________________________________ 0 100 50 200 150 250 300 04060 20 80 100 120 power dissipation vs. output power max9723 toc10 output power (mw) power dissipation (mw) r l = 16 ? v dd = 3v f in = 1khz p out = p outl + p outr outputs in phase r l = 32 ? output power vs. load resistance max9723 toc11 load resistance ( ? ) output power (mw) 100 10 20 30 40 50 60 70 80 0 10 1k v dd = 2.4v f in = 1khz thd+n = 10% thd+n = 1% output power vs. load resistance max9723 toc12 load resistance ( ? ) output power (mw) 100 10 20 30 40 50 60 70 80 90 100 0 10 1k v dd = 3v f in = 1khz thd+n = 10% thd+n = 1% output power vs. supply voltage max9723 toc13 supply voltage (v) output power (mw) 3.4 3.2 2.8 3.0 2.2 2.4 2.6 2.0 10 20 30 40 50 60 70 80 90 100 0 1.8 3.6 thd+n = 10% thd+n = 1% f in = 1khz r l = 16 ? 20 40 60 80 100 120 140 0 output power vs. supply voltage max9723 toc14 supply voltage (v) output power (mw) 3.4 3.2 2.8 3.0 2.2 2.4 2.6 2.0 1.8 3.6 thd+n = 10% thd+n = 1% f in = 1khz r l = 32 ? power-supply rejection ratio vs. frequency max9723 toc15 frequency (hz) psrr (db) 10k 1k 100 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 -100 10 100k r l = 32 ? t ypical operating characteristics (continued) (v dd = shdn = 3v, pgnd = sgnd = 0v, c1 = c2 = 1?, bb_ = 0v, gain = 0db, maximum volume, bassmax disabled. load con- nected between out_ and sgnd where specified. outputs in phase, both channels loaded. t a = +25?, unless otherwise noted.) (see functional diagram/typical operating circuit )
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c _______________________________________________________________________________________ 7 crosstalk vs. frequency -100 -80 -60 -40 -20 0 -120 max9723 toc16 frequency (hz) crosstalk (db) 10k 1k 100 10 100k v in = 1v p-p r l = 32 ? a = 0db left to right a = 0db right to left a = 0db crosstalk vs. frequency -100 -80 -60 -40 -20 0 -120 max9723 toc17 frequency (hz) crosstalk (db) 10k 1k 100 10 100k v in = 1v p-p r l = 32 ? a = -10db left to right a = -10db right to left a = -10db bass boost frequency response -5 0 5 10 15 20 -10 max9723 toc18 frequency (hz) amplitude (db) 10k 1k 100 10 100k no load r1 = 47k ? bassmax disabled r2 = 36k ? c3 = 0.068 f r2 = 22k ? c3 = 0.1 f r2 = 10k ? c3 = 0.22 f gain flatness vs. frequency -6 -5 -4 -3 -2 -1 0 1 -7 max9723 toc19 frequency (hz) amplitude (db) 10k 1k 100 10 100k output spectrum vs. frequency max9723 toc20 frequency (khz) amplitude (dbv) 15 10 5 -130 -120 -110 -100 -90 -80 -70 -60 -50 -40 -140 020 r l = 32 ? v dd = 3v f in = 1khz charge-pump output voltage vs. output current max9723 toc21 output current (ma) output voltage (v) 175 150 125 100 75 50 25 -3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0 -3.5 0200 no headphone load charge-pump load connected between pv ss and pgnd t ypical operating characteristics (continued) (v dd = shdn = 3v, pgnd = sgnd = 0v, c1 = c2 = 1?, bb_ = 0v, gain = 0db, maximum volume, bassmax disabled. load con- nected between out_ and sgnd where specified. outputs in phase, both channels loaded. t a = +25?, unless otherwise noted.) (see functional diagram/typical operating circuit )
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 8 _______________________________________________________________________________________ t ypical operating characteristics (continued) (v dd = shdn = 3v, pgnd = sgnd = 0v, c1 = c2 = 1?, bb_ = 0v, gain = 0db, maximum volume, bassmax disabled. load con- nected between out_ and sgnd where specified. outputs in phase, both channels loaded. t a = +25?, unless otherwise noted.) (see functional diagram/typical operating circuit ) output power vs. charge-pump capacitance and load resistance max9723 toc22 load resistance ( ? ) output power (mw) 40 30 20 40 45 50 55 60 65 70 75 35 10 50 c1 = c2 = 2.2 f c1 = c2 = 0.68 f c1 = c2 = 1 f v dd = 3v f in = 1khz thd+n = 1% power-up/power-down waveform max9723 toc23 20ms/div v dd 2v/div v out 10mv/div exiting shutdown max9723 toc24 40 s/div v out_ 200mv/div v shdn 2v/div entering shutdown max9723 toc25 20 s/div v out_ 200mv/div v shdn 2v/div supply current vs. supply voltage max9723 toc26 supply voltage (v) supply current (ma) 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 2.5 3.0 3.5 4.0 4.5 2.0 1.8 3.6 no load inputs grounded shutdown current vs. supply voltage shutdown current ( a) 1 2 3 4 5 6 7 8 0 max9723 toc27 supply voltage (v) 3.4 3.2 3.0 2.8 2.6 2.4 2.2 2.0 1.8 3.6 no load inputs grounded
detailed description the max9723 stereo headphone amplifier features maxim? patented directdrive architecture, eliminating the large output-coupling capacitors required by con- ventional single-supply headphone amplifiers. the max9723 consists of two 62mw class ab headphone amplifiers, hardware/software shutdown control, inverting charge pump, integrated 32-level volume control, bassmax circuitry, comprehensive click-and-pop sup- pression circuitry, and an i 2 c-compatible interface (see the functional diagram/typical operating circuit ). a negative power supply (pv ss ) is created internally by inverting the positive supply (v dd ). powering the ampli- fiers from v dd and pv ss increases the dynamic range of the amplifiers to almost twice that of other single-supply amplifiers, increasing the total available output power. the max9723 directdrive outputs are biased at sgnd (see figure 1). the benefit of this 0v bias is that the amplifier outputs do not have a dc component, elimi- nating the need for large dc-blocking capacitors. eliminating the dc-blocking capacitors on the output saves board space, system cost, and improves low-fre- quency response. an i 2 c-compatible interface allows serial communica- tion between the max9723 and a microcontroller. the max9723 is available with two different i 2 c addresses allowing two max9723 ics to share the same bus (see table 1). the internal command register controls the shutdown status of the max9723, enables the bassmax circuitry, sets the maximum gain of the amplifier, and sets the volume level (see table 2). the max9723? bassmax circuitry improves audio reproduction by boosting the bass response of the amplifier, compen- sating for any low-frequency attenuation introduced by max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c _______________________________________________________________________________________ 9 pin description pin bump thin qfn ucsp name function 1d1v dd power-supply input. bypass v dd to pgnd with a 1? capacitor. 2c 1 c1p charge-pump flying capacitor positive terminal 3b 1 pgnd power ground. connect to sgnd. 4a 1 c1n charge-pump flying capacitor negative terminal 5b 2 scl serial clock input. connect a 10k ? pullup resistor from scl to v dd . 6a2pv ss charge-pump output. connect to sv ss . bypass pv ss with a 1? capacitor to pgnd. 7a 3 sda serial-data input. connect a 10k ? pullup resistor from sda to v dd . 8b3 shdn shutdown. drive shdn low to disable the max9723. connect shdn to v dd while bit 7 is high for normal operation (see the command register section). 9a 4 sgnd signal ground. connect to pgnd. 10 b4 inl left-channel input 11 c4 inr right-channel input 12 d4 sv ss headphone amplifier negative power-supply input. connect to pv ss . 13 c3 bbr right bassmax input. connect an external lowpass filter between outr and bbr to apply bass boost to the right-channel output. connect bbr to sgnd if bassmax is not used (see the bassmax (bass boost) section). 14 d3 outr right headphone output 15 d2 outl left headphone output 16 c2 bbl left bassmax input. connect an external lowpass filter between outl and bbl to apply bass boost to the right-channel output. connect bbl to sgnd if bassmax is not used (see the bassmax (bass boost) section). ep ep exposed paddle. connect ep to sv ss or leave unconnected.
max9723 the headphone. the max9723a and max9723b have a maximum amplifier gain of 0db while the max9723c and max9723d have a maximum gain of +6db. amplifier volume is digitally programmable to any one of 32 levels. directdrive traditional single-supply headphone amplifiers have their outputs biased at a nominal dc voltage, typically half the supply, for maximum dynamic range. large cou- pling capacitors are needed to block this dc bias from the headphone. without these capacitors, a significant amount of dc current flows to the headphone, resulting in unnecessary power dissipation and possible damage to both headphone and headphone amplifier. maxim? patented directdrive architecture uses a charge pump to create an internal negative supply voltage. this allows the max9723 headphone amplifier outputs to be biased at 0v, almost doubling the dynamic range while operating from a single supply. with no dc component, there is no need for the large dc-blocking capacitors. instead of two large (typically 220?) tantalum capaci- tors, the max9723 charge pump requires only two small 1? ceramic capacitors, thereby conserving board space, reducing cost, and improving the low-frequency response of the headphone amplifier. see the output power vs. charge-pump capacitance and load resistance graph in the typical operating characteris- tics for details of the possible capacitor sizes. in addition to the cost and size disadvantages, the dc- blocking capacitors required by conventional head- phone amplifiers limit low-frequency response and can distort the audio signal. previous attempts at eliminating the output-coupling capacitors involved biasing the headphone return (sleeve) to the dc bias voltage of the headphone amplifiers. this method raises some issues: 1) the sleeve is typically grounded to the chassis. using the midrail biasing approach, the sleeve must be isolated from system ground, complicating prod- uct design. the directdrive output biasing scheme allows the sleeve to be grounded. 2) during an esd strike, the amplifier? esd structure is the only path to system ground. the amplifier must be able to withstand the full esd strike. the max9723 headphone outputs can withstand an ?kv esd strike (hbm). 3) when using the headphone jack as a line out to other equipment, the bias voltage on the sleeve may conflict with the ground potential from other equip- ment, resulting in possible damage to the amplifiers. the directdrive outputs of the max9723 can be directly coupled to other ground-biased equipment. charge pump the max9723 features a low-noise charge pump. the 600khz switching frequency is well beyond the audio range, and does not interfere with the audio signals. this enables the max9723 to achieve a 99db snr. the switch drivers feature a controlled switching speed that minimizes noise generated by turn-on and turn-off tran- sients. limiting the switching speed of the charge pump minimizes di/dt noise caused by the parasitic bond wire and trace inductance. although not typically required, additional high-frequency noise attenuation can be achieved by increasing the size of c2 (see the functional diagram/typical operating circuit ). shutdown the max9723 features a 5?, low-power shutdown mode that reduces quiescent current consumption and extends battery life. shutdown is controlled by a hard- ware or software interface. driving shdn low disables the drive amplifiers, bias circuitry, charge pump, and sets the headphone amplifier output impedance to 20k ? . similarly, the max9723 enters shutdown when bit seven (b7) in the control register is reset. shdn and b7 must be high to enable the max9723. the i 2 c interface is active and the contents of the command register are not affected when in shutdown. this allows the master to write to the max9723 while in shutdown. stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 10 ______________________________________________________________________________________ v dd +v dd -v dd v dd /2 gnd sgnd conventional amplifier biasing scheme directdrive biasing scheme figure 1. traditional amplifier output vs. max9723 directdrive output
click-and-pop suppression the output-coupling capacitor is a major contributor of audible clicks and pops in conventional single-supply headphone amplifiers. the amplifier charges the cou- pling capacitor to its output bias voltage at startup. during shutdown the capacitor is discharged. this charging and discharging results in a dc shift across the capacitor, which appears as an audible transient at the speaker. since the max9723 headphone amplifier does not require output-coupling capacitors, no audi- ble transients occur. additionally, the max9723 features extensive click-and- pop suppression that eliminates any audible transient sources internal to the device. the power-up/power- down waveform in the typical operating characteristics shows that there are minimal transients at the output upon startup or shutdown. in most applications, the preamplifier driving the max9723 has a dc bias of typically half the supply. the input-coupling capacitor is charged to the pream- plifier? bias voltage through the max9723? input impedance (r in ) during startup. the resulting voltage shift across the capacitor creates an audible click/pop. to avoid clicks/pops caused by the input filter, delay the rise of shdn by at least 4 time constants, 4 x r in x c in , relative to the start of the preamplifier. bassmax (bass boost) typical headphones do not have a flat-frequency response. the small physical size of the diaphragm does not allow the headphone speaker to efficiently reproduce low frequencies. this physical limitation results in attenuated bass response. the max9723 includes a bass boost feature that compensates for the headphone? poor bass response by increasing the amplifier gain at low frequencies. the directdrive output of the max9723 has more head- room than typical single-supply headphone amplifiers. this additional headroom allows boosting the bass fre- quencies without the output-signal clipping. program the bassmax gain and cutoff frequency with external components connected between out_ and bb_ (see the functional diagram/typical operating circuit ). use the i 2 c-compatible interface to program the command register to enable/disable the bassmax circuit. bb_ is connected to the noninverting input of the output amplifier when bassmax is enabled. bb_ is pulled to sgnd when bassmax is disabled. the typical application of the bassmax circuit involves feeding a lowpass version of the output signal back to the amplifier. this is realized using positive feedback from out_ to bb_. figure 2 shows the connections needed to implement bassmax. maximum gain control the max9723a and max9723b have selectable maximum gains of -5db or 0db (see table 5) while the max9723c and max9723d have selectable maxi- mum gains of +1db or +6db (see table 6). bit 5 in the command register selects between the two maximum gain settings. volume control the max9723 includes a 32-level volume control that adjusts the gain of the output amplifiers according to the code contained in the command register. volume is programmed through the command register bits [4:0]. tables 7?0 show all of the available gain settings for the max9723a?ax9723d. the mute attenuation is typically better than 100db when driving a 32 ? load. serial interface the max9723 features an i 2 c/smbus-compatible, 2-wire serial interface consisting of a serial data line (sda) and a serial clock line (scl). sda and scl facili- tate communication between the max9723 and the master at clock rates up to 400khz. figure 3 shows the 2-wire interface timing diagram. the max9723 is a receive-only slave device relying on the master to gen- erate the scl signal. the max9723 cannot write to the sda bus except to acknowledge the receipt of data max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c ______________________________________________________________________________________ 11 c3 r2 r1 r r out_ bb_ audio input max9723 bassmax enable figure 2. bassmax external connections
max9723 from the master. the master, typically a microcontroller, generates scl and initiates data transfer on the bus. a master device communicates to the max9723 by transmitting the proper address followed by the data word. each transmit sequence is framed by a start (s) or repeated start (sr) condition and a stop (p) con- dition. each word transmitted over the bus is 8 bits long and is always followed by an acknowledge clock pulse. the max9723 sda line operates as both an input and an open-drain output. a pullup resistor, greater than 500 ? , is required on the sda bus. the max9723 scl line operates as an input only. a pullup resistor, greater than 500 ? , is required on scl if there are multiple mas- ters on the bus, or if the master in a single-master sys- tem has an open-drain scl output. series resistors in line with sda and scl are optional. series resistors protect the digital inputs of the max9723 from high- voltage spikes on the bus lines, and minimize crosstalk and undershoot of the bus signals. bit transfer one data bit is transferred during each scl cycle. the data on sda must remain stable during the high period of the scl pulse. changes in sda while scl is high are control signals (see the start and stop conditions section ). sda and scl idle high when the i 2 c bus is not busy. start and stop conditions sda and scl idle high when the bus is not in use. a master device initiates communication by issuing a start condition. a start condition is a high-to-low transition on sda with scl high. a stop condition is a low-to-high transition on sda while scl is high (figure 4). a start condition from the master signals the begin- ning of transmission to the max9723. the master termi- nates transmission and frees the bus by issuing a stop condition. the bus remains active if a repeated start condition is generated instead of a stop condition. early stop conditions the max9723 recognizes a stop condition at any point during data transmission except if the stop condition occurs in the same high pulse as a start condition. slave address the max9723 is available with one of two preset slave addresses (see table 1). the address is defined as the seven most significant bits (msbs) followed by the read/ write (r/ w ) bit. the address is the first byte of information sent to the max9723 after the start condi- tion. the max9723 is a slave device only capable of being written to. the sent r/ w bit must always be a zero when configuring the max9723. the max9723 acknowledges the receipt of its address even if r/ w is set to 1. however, the max9723 will not drive sda. addressing the max9723 with r/ w set to 1 causes the master to receive all 1? regardless of the contents of the command register. acknowledge the acknowledge bit (ack) is a clocked 9th bit that the max9723 uses to handshake receipt of each byte of stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 12 ______________________________________________________________________________________ scl sda start condition stop condition repeated start condition start condition t hd, sta t su, sta t hd, sta t sp t buf t su, sto t low t su, dat t hd, dat t high t r t f figure 3. 2-wire serial-interface timing diagram
data (see figure 5). the max9723 pulls down sda dur- ing the master-generated 9th clock pulse. the sda line must remain stable and low during the high period of the acknowledge clock pulse. monitoring ack allows for detection of unsuccessful data transfers. an unsuc- cessful data transfer occurs if a receiving device is busy or if a system fault has occurred. in the event of an unsuccessful data transfer, the bus master may reattempt communication. write data format a write to the max9723 includes transmission of a start condition, the slave address with the r/ w bit reset to 0 (see table 1), one byte of data to configure the command register, and a stop condition. figure 6 illustrates the proper format for one frame. the max9723 only accepts write data, but it acknowl- edges the receipt of its address byte with the r/ w bit set high. the max9723 does not write to the sda bus in the event that the r/ w bit is set high. subsequently, the master reads all 1? from the max9723. always reset the r/ w bit to 0 to avoid this situation. command register the max9723 has one command register that is used to enable/disable shutdown, enable/disable bassmax, and set the maximum gain and volume. table 2 describes the function of the bits contained in the com- mand register. reset b7 to 0 to shut down the max9723. the max9723 wakes up from shutdown when b7 is set to 1 provided shdn is high. shdn must be high and b7 must be set to 1 for the max9723 to operate normally (see table 3). set b6 to 1 to enable bassmax (see table 4). the output signal? low-frequency response will be boosted accord- ing to the external components connected between out_ and bb_. see the bassmax gain-setting components section in the applications information sec- tion for details on choosing the external components. max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c ______________________________________________________________________________________ 13 scl sda ssrp figure 4. start, stop, and repeated start conditions 1 scl start condition sda 289 clock pulse for acknowledgment acknowledge not acknowledge figure 5. acknowledge max9723 slave address part a6 a5 a4 a3 a2 a1 a0 r/ w max9723a 1001100 0 max9723b 1001101 0 max9723c 1001100 0 max9723d 1001101 0 table 1. max9723 address map b7 b6 b5 b4 b3 b2 b1 b0 shutdown bassmax enable maximum gain volume table 2. max9723 command register mode b7 max9723 disabled 0 max9723 enabled 1 table 3. shutdown control, shdn = 1 mode b6 bassmax disabled 0 bassmax enabled 1 table 4. bassmax control
max9723 the max9723a and max9723b have a maximum gain setting of -5db or 0db, while the max9723c and max9723d have a maximum gain setting of +1db or +6db. b5 in the command register programs the maxi- mum gain (see tables 5 and 6). adjust the max9723? amplifier gain with the volume control bits [4:0]. the gain is adjustable to one of 32 steps ranging from full mute to the maximum gain pro- grammed by b5. tables 7?0 list all the possible gain settings for the max9723. figures 7?0 show the vol- ume control transfer functions for the max9723. power-on reset the contents of the max9723? command register at power-on are shown in table 11. applications information power dissipation and heat sinking linear power amplifiers can dissipate a significant amount of power under normal operating conditions. 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 ?/w as specified in the absolute maximum ratings section. for example, ja for the thin qfn package is +59?/w. the max9723 has two power dissipation sources, the charge pump and the two output amplifiers. if the power dissipation exceeds the rated package dissipa- tion, reduce v dd , increase load impedance, decrease the ambient temperature, or add heatsinking. large output, supply, and ground traces decrease ja , allow- ing more heat to be transferred from the package to surrounding air. output dynamic range dynamic range is the difference between the noise floor of the system and the output level at 1% thd+n. it is essential that a system? dynamic range be known before setting the maximum output gain. output clip- ping will occur if the output signal is greater than the dynamic range of the system. the directdrive architec- ture of the max9723 has increased dynamic range compared to other single-supply amplifiers. use the thd+n vs. output power in the typical operating characteristics to identify the system? dynamic range. find the output power that causes 1% thd+n for a given load. this point will indicate what output power causes the output to begin to clip. use the following equation to determine the peak output voltage that causes 1% thd+n for a given load. where p out_1% is the output power that causes 1% thd+n, r l is the load resistance, and v out_(p-p) is the peak output voltage. after v out_(p-p) is identified, determine the peak input voltage that can be amplified without clipping: where v in_(p-p) is the largest peak voltage that can be amplified without clipping, and a v is the voltage gain of v v in p p out p p a v _( ) _( ) ? ? ? ? ? ? ? ? = 10 20 vpr out p p out l _( ) _ % () ? = 22 1 p tt d max j max a ja () () = ? stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 14 ______________________________________________________________________________________ s ack 0 acknowledge from max9723 r/w acknowledge from max9723 b7 b6 b5 b4 b3 b2 command byte is stored on receipt of stop condition ack p b1 b0 slave address command byte figure 6. write data format example maximum gain (db) b5 -5 0 01 table 5. max9723a and max9723b maximum gain control maximum gain (db) b5 +1 0 +6 1 table 6. max9723c and max9723d maximum range control
the amplifier in db determined by the maximum gain set- ting (bit 5) or the combination of the maximum gain set- ting plus bass boost (see the bassmax gain-setting components section). component selection input-coupling capacitor the ac-coupling capacitor (c in ) and internal gain-set- ting resistor form a highpass filter that removes any dc bias from an input signal (see the functional diagram/ typical operating circuit ). c in allows the max9723 to bias the signal to an optimum dc level. the -3db point max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c ______________________________________________________________________________________ 15 b4 b3 b2 b1 b0 ( lsb) gain (db) 11111 0 11110 -0.5 11101 -1 11100 -1.5 11011 -2 11010 -2.5 11001 -3 11000 -4 10111 -5 10110 -6 10101 -7 10100 -9 1001 1 -11 1001 0 -13 1000 1 -15 1000 0 -17 0111 1 -19 0111 0 -21 0110 1 -23 0110 0 -25 0101 1 -27 0101 0 -29 0100 1 -31 0100 0 -33 0011 1 -35 0011 0 -37 0010 1 -39 0010 0 -41 0001 1 -43 0001 0 -45 0000 1 -47 00 00 0 mute table 7. max9723a and max9723b gain settings (bit 5 = 1, max gain = 0db) b4 b3 b2 b1 b0 (lsb) gain (db) 1 1111 -5 1 1110 -6 1 1101 -7 1 1100 -9 1 1011 -11 11010-13 1 1001 -15 11000-17 1 0111 -19 1 0110 -21 1 0101 -23 1 0100 -25 1 0011 -27 1 0010 -29 1 0001 -31 1 0000 -33 0 1111 -35 0 1110 -37 01101-39 0 1100 -41 01011-43 0 1010 -45 0 1001 -47 0 1000 -51 0 0111 -55 0 0110 -59 0 0101 -63 0 0100 -67 0 0011 -71 00010-75 0 0001 -79 00000 mute table 8. max9723a and max9723b gain settings (b5 = 0, max gain = -5db)
max9723 of the highpass filter, assuming zero-source imped- ance, is given by: f rc db in in ? = 3 1 2 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 16 ______________________________________________________________________________________ b4 b3 b2 b1 b0 (lsb) gain (db) 111111 111100 11101-1 11100-3 11011-5 11010-7 11001-9 11000-11 10111-13 10110-15 10101-17 10100-19 10011-21 10010-23 10001-25 10000-27 01111-29 01110-31 01101-33 01100-35 01011-37 01010-39 01001-41 01000-45 00111-49 00110-53 00101-57 00100-61 00011-65 00010-69 00001-73 00000 mute table 10. max9723c and max9723d gain settings (b5 = 0, max gain = +1db) mode b7 b6 b5 b4 b3 b2 b1 b0 power-on reset 1 111111 1 table 11. initial power-up command register status b4 b3 b2 b1 b0 (lsb) gain (db) 111116 111105.5 111015 111004.5 110114 110103.5 110013 110002 101111 101100 10101-1 10100-3 10011-5 10010-7 10001-9 10000-11 01111-13 01110-15 01101-17 01100-19 01011-21 01010-23 01001-25 01000-27 00111-29 00110-31 00101-33 00100-35 00011-37 00010-39 00001-41 00000 mute table 9. max9723c and max9723d gain settings (b5 = 1, max gain = +6db)
where r in is a minimum of 10k ? . choose c in such that f -3db is well below the lowest frequency of interest. setting f -3db too high affects the amplifier? low-frequen- cy response. use capacitors with low-voltage coefficient dielectrics. film or c0g dielectric capacitors are good choices for ac-coupling capacitors. capacitors with high-voltage coefficients, such as ceramics, can result in increased distortion at low frequencies. charge-pump flying capacitor the charge-pump flying capacitor connected between c1n and c1p affects the charge pump? load regula- tion and output impedance. choosing a flying capacitor that is too small degrades the max9723? ability to pro- vide sufficient current drive and leads to a loss of out- put voltage. increasing the value of the flying capacitor improves load regulation and reduces the charge- pump output impedance. see the output power vs. max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c ______________________________________________________________________________________ 17 max9723a and max9723b transfer function (bit 5 = 1) code gain (db) -20 -30 -40 10 0 -10 -50 0612 18 24 30 figure 7. max9723a/max9723b transfer function with bit 5 = 1 max9723a and max9723b transfer function (bit 5 = 0) code gain (db) -40 -50 -60 -70 -80 0 -10 -30 -20 -90 0612 18 24 30 figure 8. max9723a/max9723b transfer function with bit 5 = 0 max9723c and max9723d transfer function (bit 5 = 1) code 0612 18 24 30 gain (db) -30 -40 -50 -60 -70 10 0 -20 -10 -80 figure 9. max9723c/max9723d transfer function with bit 5 = 1 max9723c and max9723d transfer function (bit 5 = 0) code gain (db) -30 -40 10 0 -20 -10 -50 0612 18 24 30 figure 10. max9723c/max9723d transfer function with bit 5 = 0
max9723 charge-pump capacitance and load impedance graph in the typical operating characteristics . charge-pump hold capacitor the hold capacitor? value and esr directly affect the ripple at pv ss . ripple is reduced by increasing the value of the hold capacitor. choosing a capacitor with lower esr reduces ripple and output impedance. lower capacitance values can be used in systems with low maximum output power levels. see the output power vs. charge-pump capacitance and load impedance graph in the typical operating characteristics . bassmax gain-setting components the bass-boost low-frequency response, when bassmax is enabled, is set by the ratio of r1 to r2 by the following equation (see figure 2): where a v_boost is the voltage gain boost in db at low frequencies. a v_boost is added to the gain realized by the volume setting. the absolute gain at low frequen- cies is equal to: where a v_vol is the gain due to the volume setting, and a v_total is the absolute gain at low frequencies. to maintain circuit stability, the ratio: r 2 /(r 1 + r 2 ) must not exceed 1/2. a ratio equaling 1/3 is recom- mended. the switch that shorts bb_ to sgnd, when bassmax is disabled, can have an on-resistance as high as 300 ? . choose a value for r1 that is greater than 40k ? to ensure that positive feedback is negligible when bassmax is disabled. table 12 contains a list of r2 values, with r1 = 47k ? , and the corresponding low- frequency gain. the low-frequency boost attained by the bassmax cir- cuit is added to the gain realized by the volume setting. select the bassmax gain so that the output signal will remain within the dynamic range of the max9723. output signal clipping will occur at low frequencies if the bassmax gain boost is excessively large (see the output dynamic range section). capacitor c3 forms a pole and a zero according to the following equations: f pole is the frequency at which the gain boost begins to roll off. f zero is the frequency at which the bass- boost gain no longer affects the transfer function and the volume-control gain dominates. table 13 contains a list of capacitor values and the corresponding poles and zeros for a given dc gain. see figure 11 for an example of a gain profile using bassmax. custom maximum gain setting using bassmax the circuit in figure 12 uses the bassmax function to increase the maximum gain of the max9723. the gain boost created with the circuit in figure 12 is added to the maximum gain selected by bit 5 in the command register. set the maximum gain with ra and rb using the following equation: where a v_vol is the gain due to the volume setting, and a v_total is the absolute passband gain in db. capacitor ca blocks any dc offset from being gained, but allows higher frequencies to pass. ca creates a pole that indicates the low-frequency point of the pass band. choose ca so that the lowest frequencies of aa ra rb ra rb v total v vol __ log =+ + ? ? ? ? ? ? ? 20 f rr crr f rr crr pole zero = ? = + 12 2312 12 2312 aaa v total v vol v boost ___ =+ a rr rr v boost _ log = + ? 20 12 12 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 18 ______________________________________________________________________________________ gain profile with and without bassmax frequency (hz) a v (db) 1k 100 10 -8 -6 -4 -2 0 2 4 6 8 10 -10 1 10k max9723a cmd register code = 0xff r1 = 47k ? r2 = 22k ? c3 = 0.1 f f pole f zero with bassmax without bassmax figure 11. bassmax, gain profile example
interest are not attenuated. for a typical application, set f pole equal to or below 20hz. figure 13 shows the frequency response of the circuit in figure 12. with ra = 47k ? , rb = 22k ? , and ca = 0.33?, the passband gain is set to 8.8db. 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 to pgnd. bypass v dd to pgnd with a 1? capacitor. place the power-supply bypass capacitor and the charge-pump capacitors as close to the max9723 as possible. route pgnd and all traces that carry switching transients away from sgnd and the audio signal path. route digital signal traces away from the audio signal path. make traces perpen- dicular to each other when routing digital signals over or under audio signals. 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 when the board layout dictates that the exposed paddle cannot be left floating. ca frarb pole () = ? 1 2 max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c ______________________________________________________________________________________ 19 ca rb ra r r out_ bb_ audio input max9723 bassmax enable figure 12. using bassmax to increase max9723? maximum gain r2 (k ? )a v gain (db) 39 20.6 33 15.1 27 11.3 22 8.8 15 5.7 10 3.7 table 12. bassmax gain examples (r1 = 47k ? ) c3 (nf) f pole (hz) f zero (hz) 100 38 106 82 47 130 68 56 156 56 68 190 47 81 230 22 174 490 10 384 1060 table 13. bassmax pole and zero examples for a gain boost of 8.8db (r1 = 47k ? , r2 = 22k ? ) frequency response of figure 12 frequency (hz) a v (db) 1k 100 10 1 1 2 3 4 5 6 7 8 9 10 0 0.1 10k max9723a cmd register code = 0xff ra = 47k ? rb = 22k ? ca = 0.33 f figure 13. increasing the maximum gain using bassmax
max9723 ucsp applications information for the latest application details on ucsp construction, dimensions, tape carrier information, pc board tech- niques, bump-pad layout , and recommended reflow temperature profile, as well as the latest information on reliability testing results, go to maxim? website at www.maxim-ic.com/ucsp and look up the application note: ucsp? wafer-level chip-scale package. stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 20 ______________________________________________________________________________________ functional diagram/typical operating circuit r5 10k ? r6 10k ? c in 0.47 f c4 0.1 f r4 22k ? r3 47k ? r1 47k ? c5 1 f c2 1 f c in 0.47 f c1 1 f 1.8v to 3.6v analog input i 2 c interface charge pump v dd inr sda scl v dd v dd sv ss v dd r outr rbb lbb outl r sv ss v dd sv ss v dd sv ss shdn c1p c1n sgnd pgnd pv ss sv ss c3 0.1 f r2 22k ? analog input bass boost circuit tuned for +8.8db at 106hz. max9723 r inl r chip information transistor count: 7165 process: bicmos
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c ______________________________________________________________________________________ 21 12 11 10 9 sv ss inr inl sgnd 5 6 7 8 scl pv ss sda shdn 16 15 14 13 bbl outl outr bbr 1234 v dd c1p pgnd c1n max9723_ top view top view (bump side down) thin qfn ucsp shdn c1n pv ss sda sgnd inl scl pgnd c1p v dd bbl bbr inr outl outr sv ss max9723_ 1234 a b c d r3 47k ? r4 22k ? r1 47k ? c3 0.1 f c4 0.1 f r2 22k ? outl v dd pv ss c2 1 f c5 1 f r6 10k ? r5 10k ? i 2 c master codec sv ss pgnd sgnd lbb outr rbb 1.8v to 3.6v sda scl inl inr c1p c1n c in 0.47 f c in 0.47 f c1 1 f max9723 system diagram pin configurations
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 22 ______________________________________________________________________________________ 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 .) 24l qfn thin.eps package outline, 21-0139 2 1 e 12, 16, 20, 24, 28l thin qfn, 4x4x0.8mm package outline, 21-0139 2 2 e 12, 16, 20, 24, 28l thin qfn, 4x4x0.8mm
max9723 stereo directdrive headphone amplifier with bassmax, volume control, and i 2 c 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 ____________________ 23 2005 maxim integrated products printed usa is a registered trademark of maxim integrated products, inc. 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 .) 16l,ucsp.eps h 1 1 21-0101 package outline, 4x4 ucsp

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