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dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 1 PT5322_ds rev en_1.0 PT5322 general description the PT5322 is a dual bridge-connected audio power amplifier which, when connected to a 5v supply, will deliver 2.1w to a 4 ? load or 2.4w to a 3 ? load with less than 1.0% thd+n. in addition, the headphone input pin allows the amplifiers to operate in single-ended mode when driving stereo headphones. the PT5322 has a hp (headphone) enable input, which activates the single ended headphone mode and disables the btl output mode. the hp_sense input is for use with a normal stereo headphone jack. the PT5322 features a low-power consumption shutdown mode and thermal shutdown protection. it also utilizes circuitry to reduce ?pop and click? during device turn-on. the PT5322 is available in a 16 or 20 pin tssop package. features z p o @1% thd+n: 3 ? , 4 ? loads: 2.2w (typ), 2.0w (typ) 8 ? load: 1.3w (typ) z se mode thd+n@75mw into 32 ? : 0.01%(max) z shutdown current: 0.7a (typ) z supply voltage range: 2.5v to 5.5v z psrr@217hz: 80db (typ) z stereo headphone amplifier mode z ?click and pop? suppression circuitry z unity-gain stable z thermal shutdown protection circuitry z tssop and sop packages applications z cell phones z multimedia monitors z portable and desktop computers z portable audio systems ordering information package temperature range ordering part number transport media marking tape and reel, 3000 units tssop-16 -40 o c to +85 o c PT5322tsop tube, 60 units PT5322 xxxxxx sop-16 -40 o c to +85 o c PT5322 esop tube, 45 units PT5322 xxxxxx note: typical application -ina -inb +inb vdd shdn -outa +outa -outb +outb gnd hp_sense c1 r1 20k 0.22uf c2 r2 20k 0.22uf c3 r11 100uf 1k r13 r12 100k 100k c4 r10 100uf 1k c5 1uf ina bnc inb bnc phone jack (stereo) v dd v cc +ina bypass c b 0.33uf r3 20k r4 20k + + + + xxxxxx assembly factory code lot number figure 1. typical audio amplifier application circuit
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 2 PT5322_ds rev en_1.0 PT5322 pin assignment pin descriptions tssop-16/ sop-16 pin name description 2,7,15 gnd ground 3 +outa the non-inverting output of channel-a 4,13 vdd power supply 5 -outa the inverting output of channel-a 6 -ina the inverting input of channel-a 8 +ina the non-inverting input of channel-a 9 +inb the non-inverting input of channel-b 11 -inb the inverting input of channel-b 10 bypass tap to voltage divider for internal mid-supply bias supply. connect to a 0.1uf to 1uf low esr capacitor for best performance. 12 -outb the inverting output of channel-b 14 +outb the non-inverting output of channel-b 16 hp_sense the hp_sense input is for use with a normal stereo headphone jack to select the operational output mode. 1 shdn puts the device in shutdown mode when held high. shdn -outa vdd +outa gnd gnd -ina +ina hp_sense gnd +outb vdd -outb bypass -inb +inb tssop-16 / sop-16 6 5 4 3 2 1 8 7 11 12 13 14 15 16 9 10
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 3 PT5322_ds rev en_1.0 PT5322 absolute maximum ratings (note1) symbol parameter value unit v dd supply voltage 6.0 v t stg storage temperature -65~+150 o c v input input voltage -0.3~v dd +0.3 v p max power dissipation (note 2) internally limited w esd (hbm) (note 3) 2 kv t j junction temperature 150 o c t solder solder temperature 220 o c tssop-16 105 ja thermal resistance sop-16 80 o c/w recommended operating range symbol parameter value unit v dd supply voltage 2.5~5.5 v t opt operational temperature -40~+85 o c note 1: absolute maximum ratings indicate lim its beyond which damage to the device may occur. operating range indicate conditions for which the device is functional, but do not guarantee specific performance limits. electrical characteristics sta te dc and ac electrical specifications under particular test conditi ons which guarantee specific performance limits. this assumes tha t the device is within the operating range. speci fications are not guaranteed for parameters where no limit is given, however, the ty pical value is a good indication of device performance. note 2: the maximum power dissipation mu st be derated at elevated temperatures and is dictated by t jmax , ja , and the ambient temperature t a . the maximum allowable power dissipation is p dmax = (t jmax - t a )/ ja or the number given in absolute maximum ratings, whichever is lower. note 3: human body model, 100pf discharged through a 1.5k ? resistor. electrical characteristics (vdd = 5v) (note 4,5,9) symbol parameter conditions min typ max unit v dd supply voltage 2.5 5.5 v i dd quiescent powersupply current v in =0, i o =0a, btl mode v in =0, i o =0a, se mode 5.5 2.6 10 6 ma i sd shutdown current v shdn =v dd 0.1 1 ua v ih headphone sense high input voltage 4 3.7 v v il headphone sense low input voltage 2.6 0.8 v v ihsd shutdown high input voltage 1.4 1.2 v v ilsd shutdown low input voltage 1 0.4 v t wu turn on time 1uf bypass cap 200 ms
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 4 PT5322_ds rev en_1.0 PT5322 electrical characteristics for btl mode opteration (note 4,5,9) symbol parameter conditions min typ max unit v os output offset voltage v in =0v 5 25 mv thd+n=1%, f=1khz, r l =3 ? thd+n=1%, f=1khz, r l =4 ? thd+n=1%, f=1khz, r l =8 ? 1.0 2.2 2.0 1.3 p o output power (note 7, 8) thd+n=10%, f=1khz, r l =3 ? thd+n=10%, f=1khz, r l =4 ? thd+n=10%, f=1khz, r l =8 ? 2.7 2.4 1.6 w thd+n total harmonic distortion + noise 1khz, a vd =2, r l =4 ? , p o =1w 1khz, a vd =2, r l =8 ? , p o =1w 0.10 0.06 % input unterminated,217hz, v ripple =200mv p-p ,c b =1uf,r l =8 ? 80 db input unterminated,1khz, v ripple =200mv p-p ,c b =1uf, r l =8 ? 80 db input grounded, 217hz , v ripple =200mv p-p ,c b =1uf, r l =8 ? 65 db psrr power supply rejection ratio input grounded, 1khz, v ripple =200mv p-p ,c b =1uf, r l =8 ? 65 db x talk channel separation f=1khz, cb=1uf 80 db v no output noise voltage 1khz, a-weighted 20 uv electrical characteristics for single-ended mode operation (note 4,5,9) symbol parameter conditions min typ max unit p o output power (note 7) thd+n=0.05%, f=1khz, r l =32 ? 75 85 mw thd+n total harmonic distortion + noise 1khz, r l =32 ? , p o =20mw 0.02 % input unterminated,217hz, v ripple =200mv p-p ,c b =1uf, r l =32 ? 70 db input unterminated,1khz, v ripple =200mv p-p ,c b =1uf, r l =32 ? 72 db input grounded, 217hz, v ripple =200mv p-p ,c b =1uf, r l =32 ? 65 db psrr power supply rejection ratio input grounded, 1khz, v ripple =200mv p-p ,c b =1uf, r l =32 ? 70 db x talk channel separation f=1khz, cb=1uf, 3d_control = low 75 db v no output noise voltage 1khz, a-weighted 10 uv
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 5 PT5322_ds rev en_1.0 PT5322 electrical characteristics (vdd = 3v) (note 4,5,9) symbol parameter conditions min typ max unit i dd quiescent power supply current v in =0, i o =0a, btl mode v in =0, i o =0a, se mode 4.5 2.5 ma i sd shutdown current v shdn =v dd 0.1 1 ua v ih headphone sense high input voltage 2.2 v v il headphone sense low input voltage 1.5 v v ihsd shutdown high input voltage 1.4 1 v v ilsd shutdown low input voltage 0.8 0.4 v t wu turn on time 1uf bypass cap 200 ms electrical characteristics for btl mode operation (note 4,5,9) symbol parameter conditions min typ max unit v os output offset voltage v in =0v 5 mv thd+n=1%, f=1khz, r l =3 ? thd+n=1%, f=1khz, r l =4 ? thd+n=1%, f=1khz, r l =8 ? 0.82 0.70 0.43 p o output power (note 7, 8) thd+n=10%, f=1khz, r l =3 ? thd+n=10%, f=1khz, r l =4 ? thd+n=10%, f=1khz, r l =8 ? 1.0 0.85 0.53 w thd+n total harmonic distortion + noise 1khz, r l =4 ? , p o =280mw 1khz, r l =8 ? , p o =200mw 0.10 0.05 % input unterminated,217hz, v ripple =200mv p-p ,c b =1uf, r l =8 ? 80 db input unterminated,1khz, v ripple =200mv p-p ,c b =1uf, r l =8 ? 80 db input grounded, 217hz,v ripple =200mv p-p , c b =1uf, r l =8 ? 65 db psrr power supply rejection ratio input grounded, 1khz, v ripple =200mv p-p , c b =1uf, r l =8 ? 70 db x talk channel separation f=1khz, cb=1uf, 3d_control = low 80 db v no output noise voltage 1khz, a-weighted 20 uv
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 6 PT5322_ds rev en_1.0 PT5322 electrical characteristics for single-ended mode operation (note 4,5,9) symbol parameter conditions min typ max unit p o output power (note 7) thd+n=0.05%, f=1khz, r l =32 ? 35 mw thd+n total harmonic distortion + noise 1khz, r l =32 ? , p o =20mw 0.02 % input unterminated,217hz, v ripple =200mv p-p ,c b =1uf, r l =32 ? 71 db input unterminated,1khz, v ripple =200mv p-p ,c b =1uf, r l =32 ? 72 db input grounded, 217hz, v ripple =200mv p-p ,c b =1uf, r l =32 ? 65 db psrr power supply rejection ratio input grounded, 1khz, v ripple =200mv p-p , c b =1uf, r l =32 ? 72 db x talk channel separation f=1khz, cb=1uf, 3d_control = low 75 db v no output noise voltage 1khz, a-weighted 10 uv note 4: typicals are measured at 25 ? c and represent the parametric norm. note 5: datasheet min/max specification limits are guaranteed by design, test, or statistical analysis. note 6: the quiescent power supply curren t depends on the offset voltage when a practical load is connected to the amplifier. note 7: output power is measured at the device terminals. note 8: when driving 3 ? or 4 ? loads and operating on a 5v supply, the ja of PT5322 must be below 150 o c note 9: all measurements taken from applications diagram ( figure 1 ). simplified block diagram ampb1 ampa2 ampa1 ampb2 -ina +ina -inb +inb vdd gnd -outa +outa -outb +outb enable shdn headphone control hp_sense pop&click vdd 2 bypass tsd - + - + - + - +
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 7 PT5322_ds rev en_1.0 PT5322 typical performance characteristics 0 200 400 600 800 1000 1200 1400 1600 1800 2000 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power btl mode v dd = 5 v r l = 8 ohm f = 1k hz 0 400 800 1200 1600 2000 2400 2800 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power btl mode v dd = 5 v r l = 4 ohm f = 1k hz 0. 0001 10 0. 001 0. 01 0.1 1 frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k thd+n (%) thd+n vs. frequency btl mode v dd = 5 v r l = 8 ohm p o = 1w channel a channel b 0. 10 0. 001 0. 01 0.1 1 frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k thd+n (%) thd+n vs. frequency se mode v dd = 5 v r l = 16 ohm p o = 150 mw 0001 channel a channel b 0. 0001 10 0. 001 0. 01 0.1 1 thd+n (%) frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k thd+n vs. frequency se mode v dd = 5 v r l = 32 ohm p o = 75 mw channel a channel b 10 0. 001 0. 01 0.1 1 frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k thd+n (%) thd+n vs. frequency btl mode v dd = 3.3 v r l = 4 ohm p o = 750 mw channel a channel b
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 8 PT5322_ds rev en_1.0 PT5322 typical performance char acteristics (continued) 0 400 800 1200 1600 2000 2400 2800 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power btl mode v dd = 5 v r l = 3 ohm f = 1k hz 0 40 80 120 160 200 240 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power btl mode v dd = 5 v r l = 32 ohm f = 1k hz 0 200 400 600 800 1000 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power btl mode v dd = 3.3 v r l = 8 ohm f = 1k hz 0 200 400 600 800 1000 1200 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power btl mode v dd = 3.3 v r l = 4 ohm f = 1k hz 0 200 400 600 800 1000 1200 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power btl mode v dd = 3.3 v r l = 3 ohm f = 1k hz 0 40 80 120 160 200 240 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power se mode v dd = 5 v r l = 16 ohm f = 1k hz
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 9 PT5322_ds rev en_1.0 PT5322 typical performance char acteristics (continued) 0 20 40 60 80 100 120 140 0.01 0.1 1 10 thd + n (%) output power (mw) thd+n vs. output power se mode v dd = 5 v r l = 32 ohm f = 1k hz 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 btl mode v dd = 5v r l = 32 ohm r l = 16 ohm power dissipation (w) output power (w) power dissipation vs. output power r l = 8 ohm 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50 0.00 0.05 0.10 0.15 0.20 se mode v dd = 5 v r l = 32 ohm r l = 16 ohm power dissipation (w) output power (w) power dissipation vs. output power r l = 8 ohm 2.02.53.03.54.04.55.05.5 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 btl mode v dd = 5 v r l = 8 ohm thd+n = 1% thd+n =10% output powr (w) supply voltage (v) output power vs. supply voltage frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k 1u 10m 10u 100u 1m output noise (v) noise floor btl mode v dd = 5 v r l = 8 ohm a-weighted filter -100 +0 -80 -60 -40 -20 20 20k 50 100 200 500 1k 2k 5k 10k frequency (hz) output level (db) crosstalk vs. frequency btl mode v dd = 5 v r l = 8 ohm
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 10 PT5322_ds rev en_1.0 PT5322 typical performance char acteristics (continued) -100 +0 -80 -60 -40 -20 output level (db) 20 20k 50 100 200 500 1k 2k 5k 10k frequency (hz) crosstalk vs. frequency se mode v dd = 5 v r l = 32 ohm psrr vs. frequency -80 +0 -70 -60 -50 -40 -30 -20 -10 btl mode v dd = 5 v r l = 8 ohm channel a psrr (db) frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k psrr vs. frequency -80 +0 -70 -60 -50 -40 -30 -20 -10 psrr (db) 20 20k 50 100 200 500 1k 2k 5k 10k frequency (hz) btl mode v dd = 5 v r l = 8 ohm channel b -80 +0 -60 -40 -20 psrr (db) frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k psrr vs. frequency se mode v dd = 5 v r l = 16 ohm channel a channel b -80 +0 -60 -40 -20 psrr (db) frequency (hz) 20 20k 50 100 200 500 1k 2k 5k 10k psrr vs. frequency se mode v dd = 5 v r l = 8 ohm channel a channel b
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 11 PT5322_ds rev en_1.0 PT5322 application information bridge configuration explanation as shown in figure1, the PT5322 has two internal operational amplifiers per cha nnel. the first amplifier?s gain is externally configurable, while the second amplifier is internally fixed in a unity-gain, inverting configuration. the closed-loop gain of the first amplifier is set by selecting the ratio of r f to r i while the second amplifier?s gain is fixed by the two internal 20k ? resistors. figure1shows that the output of amplifier one serves as the input to amplif ier two which results in both amplifiers producing signals identical in magnitude, but out of phase by 180 ? . consequently, the differential gain for the ic is a vd = 2 * ( r f /ri ) or a vd = 2 * ( r3/r1 ) (1) or a vd = 2 * ( r4/r2 ) by driving the load differentially through outputs +outa and ?outa (or +outb, -outb), an amplifier configuration commonly referred to as ?bridged mode? is established. bridged mode operation is different from the classical single-ended amplifier configuration where one side of the load is connected to ground. a bridge amplifier design has a few distinct advantages over the single-ended configuration, as it provides differential drive to the load, thus doubling output swing for a specified supply voltage. four times the output power is possible as compared to a single-ended amplifier under the same conditions. this increase in attainable output power assumes that the amplifier is not current limited or clipped. in order to choose an amplifier?s closed-loop gain without causing excessive clipping, please refer to the audio power amplifier design section. a bridge configuration, such as the one used in PT5322, also creates a second advantage over single-ended amplifiers. since the differential outputs, +outa and ?outa (or +outb, -outb), ar e biased at half-supply, no net dc voltage exists across the load. this eliminates the need for an output coupling capacitor which is required in a single supply, single-ended amplifier configuration. without an output coupling capacitor, the half-supply bias across the load would result in both increased internal ic power dissipation and also possible loudspeaker damage. power dissipation power dissipation is a major concern when designing a successful amplifier, whether the amplifier is bridged or single-ended. equation (2) states the maximum power dissipation point for a single-ended amplifier operating at a given supply voltage and driving a specified output load. p dmax = (v dd ) 2 /(2 2 r l ) single-ended (2) a direct consequence of th e increased power delivered to the load by a bridge amplifier is an increase in internal power dissipation. since the PT5322 has two operational amplifiers per channel in one package, the maximum internal power dissipation is 4 times that of a single-ended amplifier. the maximum power dissipation for a given application can be derived from the power dissipation graphs or from equation 3. p dmax = 4*(v dd ) 2 /(2 2 r l ) bridge mode (3) the PT5322?s power dissipation is twice that given by equation (2) or equation (3) when operating in the single-ended mode or bridge mode, respectively. twice the maximum power dissipation point given by equation (3) must not exceed the pow er dissipation given by equation (4): p dmax ' = (t jmax ? t a )/ ja (4) the PT5322?s t jmax = 150c. the ja of PT5322 in the tssop-16 package is 105c/w, and the ja of PT5322 in the sop-16 package is 80c/w. at any given ambient temperature t a , use equation (4) to find the maximum internal power dissipation supported by the ic packaging. rearranging equation (4) and substituting p dmax for p dmax ' results in equation (5). this equation gives the maximum ambient temperature that still allows maximum stereo power dissipation without violating the PT5322?s maximum junction temperature. t a = t jmax ? 2*p dmax * ja (5) for a typical application with a 5v power supply and an 8 load, the maximum ambient temperature that allows maximum stereo power dissi pation without exceeding the maximum junction temperature is approximately 84c or 100c for the tssop-16 or sop-16 package
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 12 PT5322_ds rev en_1.0 PT5322 respectively. t jmax = p dmax * ja + t a (6) equation (6) gives the maximum junction temperature t jmax . if the result violates the PT5322?s 150c, reduce the maximum junction temperature by reducing the power supply voltage or increasing the load resistance. further allowance should be made for increased ambient temperatures. the above examples assume that a device is a surface mount part oper ating around the maximum power dissipation point. since internal power dissipation is a function of outut power, higher ambient temperatures are allowed as output power decreases. if the result of equation (2) and equation (3) is greater than that of equation (4), then decrease the supply voltage, increase the load impedance, or reduce the ambient temperature. if these measures are insufficient, a heat sink can be added to reduce ja . power supply bypassing as with any amplifier, proper supply bypassing is critical for low noise pe rformance and high power supply rejection. the capacitor location on both the bypass and power supply pins should be as close to the device as possible. typical applications employ a 5v regulator with 10f tantalum or electrolytic capacitor and a ceramic bypass capacitor which aid in supply stability. however, their presence does not eliminate the need for bypassing the supply nodes of the PT5322. the selection of a bypass capacitor, especially c b , is dependent upon psrr requirements, click and pop performance (as explained in the section, proper selection of external components ), system cost, and size constraints. shutdown function in order to reduce power consumption while not in use, the PT5322 contains shutdown circuitry that is used to turn off the amplifier?s bias circuitry whenever the shutdown pin is put at logical ?high?. while the device may be disabled with shutdown voltages in between ground and supply, the idle current may be greater than the typical value of 0.1a. therefore, the shutdown pin should be tied to a definite voltage to avoid unwanted state changes. in many applications, a microcontroller or microprocessor output is used to control the shutdown circuitry, which provides a quick, smooth transition to shutdown. another solution is to use a single-throw switch in conjunction with an external pull-up resistor (or pull-down, depending on shutdown high or low application). this scheme guarantees that the shutdown pin will not float, thus preventing unwanted state changes. table 1. logic level truth table shdn pin hp_sense pin operational mode low high single-ended amplifiers low low bridged amplifiers high don?t care shutdown headphone logic in functions applying a logic level to the PT5322?s hp_sense headphone control pin turns off ampa2 (+outa) and ampb2 (+outb) muting a bridged-connected load. quiescent current consumption is reduced when the ic is in this single-ended mode. figure 2 shows the implementation of the PT5322?s headphone control function. with no headphones connected to the headphone jack, the r11-r13 voltage divider sets the voltage applied to the hp_sense pin (pin 20) at approximately 50mv. this 50mv enables ampa2 (+outa) and ampb2 (+outb) placing the PT5322 in bridged mode operation. while the PT5322 operates in bridged mode, the dc potential across the load is essentially 0v. therefore, even in an ideal situation, the output swing cannot cause a false single-ended trigger. connecting headphones to the headphone jack disconnects the headphone jack contact pin from ? outa and allows r13 to pull the hp_sense -outa +outa -outb +outb hp_sense c3 r11 100uf 1k r13 r12 100k 100k c4 r10 100uf 1k phone jack (stereo) v cc + + + + ampb1 ampa2 ampa1 ampb2 - + - + figure 2. headphone circuit
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 13 PT5322_ds rev en_1.0 PT5322 pin up to vdd. this enables the headphone function, turns off ampa2 (+outa) and ampb2 (+outb) which mutes the bridged speaker. the amplifier then drives the headphones, whose impedance is in parallel with resistors r10 and r11. these resistors have negligible effect on the PT5322?s output drive capability since the typical impedance of headphones is 32 ? . figure 2 also shows the suggested headphone jack electrical connections. the jack is designed to mate with a three wire plug. the plug?s tip and ring should each carry one of the two stereo output signals, whereas the sleeve should carry the ground return. a headphone jack with one control pin contact is sufficient to drive the hp sense pin when connecting headphones. proper selection of external components proper selection of external components in applications using integrated power amplifiers is critical to optimize device and system performance. while the PT5322 is tolerant of external component combinations, consideration to component values must be used to maximize overall system quality. the PT5322 is unity-gain stable which gives the designer maximum system flexibility. the PT5322 should be used in low gain configurations to minimize thd+n values, and maximize the signal to noise ratio. low gain configurations require large input signals to obtain a given output power. input signals equal to or greater than 1vrms are available from sources such as audio codecs. please refer to the section, audio power amplifier design , for a more complete explanation of proper gain selection. input capacitor value selection besides gain, one of the major considerations is the closed loop bandwidth of the amplifier. to a large extent, the bandwidth is dictated by the choice of external components shown in figure1 . the input resistors (r1, r2) coupling capacitor, c i (c1, c2), forms a first order high pass filter which limits low frequency response. this value should be chosen based on needed frequency response for a few distinct reasons. large input capacitors are both expensive and space hungry for portable designs. clearly, a certain sized capacitor is needed to couple in low frequencies without severe attenuation. but in many cases the speakers used in portable systems, whether internal or external, have little ability to reproduce signals below 100hz to 150hz. thus, using a large input capacitor may not increase actual system performance. eq uation (7) states the -3db cutoff frequency of the input high pass filter. 1 1 2 1 2 1 3 c r rici f db = = ? (7) in addition to system cost and size, click and pop performance is affected by the size of the input coupling capacitor, c i (c1, c2). a larger input coupling capacitor requires more charge to reach its quiescent dc voltage (nominally v dd /2). the amplifier?s output charges the input capacitor through the feedback resistors, r2 and r8. thus, pops can be minimized by selecting an input capacitor value that is no higher than necessary to meet the desired ? 3db frequency. bypass capacitor value selection besides minimizing the input capacitor size, careful consideration should be pa id to the bypass capacitor value. bypass capacitor, c b , is the most critical component to minimize turn-on pops since it determines how fast the PT5322 turns on. the slower the PT5322?s outputs ramp to their quiescent dc voltage (nominally v dd /2), the smaller the turn-on pop. choosing c b equal to 1.0f along with a small value of c i (in the range of 0.1f to 0.39f), should produce a virtually pop&click free shutdown function. while the device will function properly, (no oscillations or motorboating), with c b equal to 0.1f, the device will be much more susceptible to turn-on clicks and pops. thus, a value of c b equal to 1.0f is recommended in all but the most cost sensitive designs. audio power amplifier design a 1w/8 audio amplifier given: power output: 1w rms load impedance: 8 ? input level: 1v rms input impedance: 20k ? bandwidth: 100hz?20khz 0.25db 5v is a standard voltage in most applications, it is chosen for the supply rail. extra supply voltage creates headroom that allows the pt 5322 to reproduce peaks in excess of 1w without producing audible distortion. at this time, the designer must make sure that the power supply choice along with the output impedance does not violate the conditions explained in the power
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 14 PT5322_ds rev en_1.0 PT5322 dissipation section. once the power dissipation equations have been addressed, the required differential gain can be determined from equation 8. () inrms orms in l o vd v v v r p a / ) /( = (8) from equation 8, the minimum a vd is 2.83. for this example, let a vd =3. the amplifier?s overall gain is set using the input (r1 and r2) and feedback resistors r3 and r4. 2 / 2 / 4 1 / 3 / vd i f a r r r r r r = = = (9) since the desired input impedance was 20k ? , with a ratio of 1.5:1 of r f to r i results in an allocation of r i = 20k ? and r f = 30k ? . the final design step is to address the bandwidth requirements which must be stated as a pair of ? 3db frequency points. five times away from a ? 3db point is 0.17db down from passband response which is better than the required 0.25db specified. f l = 100hz/5 = 20hz and f h = 20khz 5= 100khz as mentioned in the external components section, r i in conjunction with c i create a high-pass filter. find the coupling capacitor?s value using equation (10). c i 1/(2 r 1 f l ) (10) this result is ci 1/(2 *20k ? *20hz) = 0.397f use a 0.39f capacitor, th e closest standard value. the high frequency pole is determined by the product of the desired frequency pole, f h , and the differential gain, a vd . with an a vd = 3 and f h = 100k hz, the resulting the closed-loop gain bandwidth product (gbwp ) is 300k hz which is much smaller than the PT5322?s gbwp. pcb layout and supply regulation considerations for driving 3 ? and 4 ? ? loads power dissipated by a load is a function of the voltage swing across the load and the load?s impedance. as load impedance decreases, load dissipation becomes increasingly dependent on the interconnect (pcb trace and wire) resistance between the amplifier output pins and the load?s connections. residual trace resistance causes a voltage drop, which results in power dissipated in the trace and not in the load as desired. for example, 0.1 trace resistance reduces the output power dissipated by a 4 load from 2.1w to 2.0w. this problem of decreased load dissipation is exacerbated as load impedance decreases. therefore, to maintain the highest load dissipation and widest output voltage swing, pcb traces that connect the output pins to a load must be as wide as possible. poor power supply regulation adversely affects maximum output power. a poorly regulated supply?s output voltage decreases with increasing load current. reduced supply voltage causes decreased headroom, output signal clipping, and reduced output power. even with tightly regulated supp lies, trace resistance creates the same effects as poor supply regulation. therefore, making the power supply traces as wide as possible helps maintain full output voltage swing.
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 15 PT5322_ds rev en_1.0 PT5322 package information tssop-16 millimeters inches symbol min max min max d 4.900 5.100 0.193 0.201 e 4.300 4.500 0.169 0.177 b 0.190 0.300 0.007 0.012 c 0.090 0.200 0.004 0.008 e1 6.250 6.550 0.246 0.258 a 1.100 0.043 a2 0.800 1.000 0.031 0.039 a1 0.020 0.150 0.001 0.006 e 0.65 0.026 l 0.500 0.700 0.020 0.028 h 0.25 (typ) 0.01 (typ) 1 7 1 7
dual 2.2w audio amplifier plus stereo headphone function china resources powtech (shanghai) limited www.crpowtech.com page 16 PT5322_ds rev en_1.0 PT5322 package information sop-16 millimeters inches symbol min max min max a 2.30 2.70 0.090 0.106 a1 0.10 0.30 0.004 0.012 a2 2.10 2.50 0.083 0.099 d 10.10 10.50 0.398 0.414 e 7.30 7.70 0.287 0.303 e1 10.10 10.50 0.398 0.414 e 1.27 typ. 0.050 typ. l 0.60 0.80 0.0236 0.0316 0 7 0 7 d e1 e e a2 a a1 l

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