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1 aat1276 data sheet boost converter with usb power switch skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 general description the aat1276 switchreg is a 2mhz, 500ma synchronous boost converter with an integrated current-limiting load switch controlled output. the aat1276?s unique peak inductor current controlled architecture eliminates audi- ble noise during light load operation. the aat1276 operates from a single-cell lithium-ion/ polymer battery source and provides a regulated 5v, cur- rent limit controlled output to support usb port v bus applications in portable consumer electronic products. the aat1276 can support both usb 2.0 host port and usb on-the-go operation, as well as general purpose applications where a 5v supply with a user programma- ble current limit is needed. the high efficiency boost converter section of the aat1276 is typically set for a 5v output and can deliver up to 500ma load current to support usb v bus operation from an input supply as low as 2.7v. the high boost converter switching frequency (up to 2.0mhz) provides fast load transient and allows the use of small external components. fully integrated control circuitry simplifies system design and reduces total solution size. the integrated, programmable current limiting load switch provides usb port protection for portable devices allowing the aat1276 to supply a 5v usb v bus up to 500ma. the load switch provides an active low fault flag to alert the system in the event of an over-current condi- tion applied to the aat1276 output. the aat1276 is available in the pb-free, space-saving 12-pin tsopjw and 16-pin tdfn34 packages and is rated over the -40c to +85c operating temperature range. features ? audible noise reduction circuitry during light load operation ? high frequency boost with 5v / 500ma output capability from a single-cell lithium-ion/polymer battery ? input voltage range: 2.7v to 5v ? v out1 adjustable ? >90% efficiency ? 20khz to 2mhz switching frequency to avoid audible noise ? true load disconnect ? load switch with programmable current limit ? over-temperature, over-current protection ? inrush current limit ? fault report ? low shutdown current < 1 a typical ? -40c to +85c temperature range ? tsopjw-12 and tdfn34-16 packages applications ? usb on-the-go ? cell phones ? digital still cameras ? pdas and portable media players ? smart phones ? other hand-held devices typical application aat1276 in out1 lin sw fb out2 gnd 10k vcc flt en set c in 4.7f c out1 4.7f c out2 1f r fb2 59k r set v in r fb1 432k l1 2.2h v bus outpu t enable fault
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 2 aat1276 data sheet boost converter with usb power switch pin descriptions pin # tsopjw-12 tdfn34-16 symbol description 1 1, 16 lin switched power input. connect an inductor between this pin and the sw pin. 2 3, 15 in supply input. connect to vcc for proper operation. 3 13, 14 pgnd power ground. 4 11, 12 sw switch pin. boost inductor is connected between sw and lin. 5 10 out1 boost converter output. 6 9 out2 load switch output. 7 8 set load switch current limit programming pin. connect a set resistor between this pin and ground. 8 7 flt load switch over-current or over-temperature fault ag. active low, open-drain output. a 10k ? external pull-up resistor is recommended. 9 6 fb boost converter voltage feedback pin. 10 5 gnd ground. 11 4 vcc bias supply for the internal circuitry. connect to in for proper operation. 12 2 en enable pin, active high. ep exposed paddle (bottom); connect to ground directly beneath the package. pin configuration tsopjw-12 tdfn34-16 (top view) (top view) 1 2 3 4 5 6 12 11 10 9 8 7 lin in pgnd sw out1 out2 en vcc gnd fb flt set in vcc gnd lin en 3 fb flt set pgnd pgnd sw lin in sw out1 out2 4 5 1 2 6 7 8 14 13 12 16 15 11 10 9
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 3 aat1276 data sheet boost converter with usb power switch absolute maximum ratings symbol description value units vcc, in, out in, outx to gnd 6.0 v sw sw to gnd -0.3 to v out + 0.3 v lin, fb lin, fb to gnd -0.3 to v in + 0.3 v en, set, flt en, set, flt to gnd -0.3 to 6.0 v t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c thermal characteristics 1 symbol description value units ? ja maximum thermal resistance tsopjw-12 110 c/w tdfn34-16 50 p d maximum power dissipation @ t a = 25c tsopjw-12 909 mw tdfn34-16 2.0 w 1. mounted on an fr4 board.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 4 aat1276 data sheet boost converter with usb power switch electrical characteristics 1 v cc = v in = 3.6v, v out1 = 5v, t a = -40c to +85c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units v in , v cc operating input voltage range 2.7 5.0 v v outx maximum output voltage range 5.5 v v uvlo under-voltage lockout 2.7 v i q quiescent supply current no load, switching 100 a no load, not switching, v fb = 1.5v 45 90 i shdn shutdown current en = gnd 1.0 a boost converter i o continuous output current 3v < v in < 5v, v o = 5v 500 ma i limit input switch current limit 2.5 a v fb fb pin regulation no load, t a = 25c 0.591 0.6 0.609 v v out output voltage tolerance i load = 0 to 500ma, v in = 2.7v to 5v -3 3 % v out (v out * v in) load regulation i load = 0 to 500ma 0.005 %/ma v out /v out line regulation v in = 2.7v to 5v 0.2 %/v r ds(on)h high side switch on resistance v out1 = 5v, i out1 = 500ma 200 m r ds(on)l low side switch on resistance v out1 = 5v, i out1 = 500ma 170 m r ds(on)_in input disconnect switch v out1 = 5v, i out1 = 500ma 170 m t ss soft-start time from enable to output regulation 300 s ef ciency i out1 = 250ma, l = 2.2 h, v in = 3.6v, v out1 = 5v 90 % f osc switching frequency t a = 25c, i out1 = 500ma, v in = 3.6v, v out1 = 5v 2.0 mhz load switch r ds(on) current limit switch on resistance v out1 = 5v, t a = 25c 0.2 i lim current limit r set = 16.9k 500 625 ma i lim(min) minimum current limit r set = 40k 100 ma t resp current limit response time v out1 = 5v 0.4 s t on turn-on delay time v out1 = 5v, r l = 10 4ms t off turn-off delay time v out1 = 5v, r l = 10 10 s v flt_low flt logic output low i sink = 1ma 0.4 v i flt flt logic output high leakage cur- rent v fault = 5v 0.5 1 a t blank fault blanking time rising and falling edge 4 ms control v th-l en threshold low 0.4 v v th-h en threshold high 1.4 v i en en input leakage v en = 5v, v in = 5v -1 1 a t j-th tj thermal shutdown threshold 140 c t j-hys tj thermal shutdown hysteresis 15 c 1. the aat1276 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correla- tion with statistical process controls.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 5 aat1276 data sheet boost converter with usb power switch typical characteristics efficiency vs. load output current (ma) efficiency (%) 0 20 40 60 80 100 0.1 1 10 100 1000 v in = 2.7v v in = 3.6v v in = 4.2v dc regulation (v out = 5.0v) output current (ma) output error (%) -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 0.1 1 10 100 100 0 v in = 2.7v v in = 3.6v v in = 4.2v line regulation (i out = 300ma) input voltage (v) output voltage accuracy (%) 4.940 4.942 4.944 4.946 4.948 4.950 4.952 4.954 4.956 4.958 4.960 3.6 3.7 3.8 3.9 4.0 4.1 4.2 output voltage vs. temperature (v in = 3.6v; 50 load) temperature ( -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 0.1 -50 -25 0 25 50 75 100 no load current vs. supply voltage supply voltage (v) no load current (a) 0 20 40 60 80 100 120 140 2.7 2.9 3.2 3.4 3.6 3.9 4.1 4.3 4.5 4.8 5. 0 -40 c 25 c 85 c no load current vs. temperature (v in = 3.6v; v out = 5.0v) temperature ( c) no load current (a) 0 20 40 60 80 100 120 140 -50 0 50 100 15 0
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 6 aat1276 data sheet boost converter with usb power switch typical characteristics light load switching waveform (v in = 3.6v; v out = 5.0v; 10ma load) time (5s/div) v out2 (25mv/div) i lx (500ma/div) v out1 (25mv/div) v lx (2v/div) heavy load switching waveform (v in = 3.6v; v out = 5.0v; 500ma load) time (500ns/div) v out2 (100mv/div) i lx (500ma/div) v out1 (100mv/div) v lx (2v/div) load transient response (v in = 3.6v; v out = 5.0v) time (100s/div) v out (100mv/div) i out (400ma/div) 5.062v 4.87v 500ma 1ma load transient response (v in = 3.6v; v out = 5.0v) time (100s/div) v out (50mv/div) i out (200ma/div) 5.0v 4.92v 500ma 250ma line transient response (16 load) time (100s/div) v in (500mv/div) v out (200mv/div) 3.6v 5.064v 4.752v 4.2v load switch r ds(on) vs. input voltage supply voltage (v) r ds(on) (m ) 0 50 100 150 200 250 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 -40 c 25 c 85 c 120 c
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 7 aat1276 data sheet boost converter with usb power switch typical characteristics p-channel r ds(on) vs. supply voltage supply voltage (v) r ds(on) (m ) 160 180 200 220 240 260 280 300 320 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4. 5 25 c 85 c 100 c 125 c n-channel r ds(on) vs. supply voltage supply voltage (v) r ds(on) (m ) 100 150 200 250 300 350 2.5 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 4.3 4.5 25 c 85 c 100 c 125 c enable soft start (v in = 3.6v; 500ma load) time (1ms/div) en (2v/div) v out2 (2v/div) i in (500ma/div) v out1 (2v/div) enable soft start (v in = 4.2v; 500ma load) time (1ms/div) en (2v/div) v out2 (2v/div) i in (500ma/div) v out1 (2v/div) enable soft start (v in = 3.6v; c vout2 = 120f; 16 load) time (100s/div) en (2v/div) v out2 (2v/div) v out1 (2v/div) shutdown (v in = 3.6v; c vout2 = 120f; 16 load) time (50ms/div) en (2v/div) v out2 (2v/div) v out1 (1v/div)
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 8 aat1276 data sheet boost converter with usb power switch typical characteristics current limit vs. r set current limit (ma) r set (k ) 10 100 100 100 0 current limit vs. temperature (r set = 20.3k ) temperature ( -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 -50 -25 0 25 50 75 10 0 switching frequency vs. input voltage (24w load; l = 2.2h) input voltage (v) f s (khz) 0 200 400 600 800 1000 3.0 3.2 3.4 3.6 3.8 4.0 4.2 switching frequency vs. temperature (v in = 3.6v; 16.5 load; l = 2.2h) temperature ( 820 840 860 880 900 920 940 -50 -25 0 25 50 75 100
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 9 aat1276 data sheet boost converter with usb power switch functional description the aat1276 is a 500ma synchronous boost converter with a current-limited load switch targeted for single-cell lithium-ion/polymer devices acting as a portable host for usb power. the aat1276 has integrated control and synchronous mosfets, minimizing the cost and the number of exter- nal components. additional features include a soft-start function which allows the load voltage to ramp up in a controlled manner, eliminating output voltage overshoot and minimizing inrush current. typical soft-start time for the boost converter is approximately 300 s. the aat1276 also has a load switch with user-program- mable current limiting. the load switch reports over- current and over-temperature conditions through an open-drain fault reporting signal (flt). the fault report- ing signal has a 4ms turn-on delay. control scheme the control circuit uses hysteretic current mode control with internal inductor current sensing for very high effi- ciency over a wide output current range. for heavy load, the boost converter operates in continuous conduction mode (ccm). this minimizes the rms current and opti- mizes the efficiency at load conditions where the losses are dominated by the power mosfet r ds(on) . this also keeps the ripple current to a minimum and minimizes the output voltage ripple and the output capacitor size. a zero current comparator senses the inductor current and prevents reverse current flow for optimum light load efficiency. the aat1276 also has peak inductor current control to eliminate audible noise below 20khz during light load operation. functional block diagram en in flt lin sw out1 out2 boost regulator control fb load switch control vcc gnd set
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 10 aat1276 data sheet boost converter with usb power switch step-up converter application information the aat1276 step-up converter provides the benefits of current mode control with a simple hysteretic feedback loop. the device maintains exceptional dc regulation, transient response, and cycle-by-cycle current limit with- out additional compensation components. the aat1276 modulates the power mosfet switching current in response to changes in output voltage. the voltage loop programs the required inductor current in response to changes in the output load and input voltage. the switching cycle initiates when the n-channel mosfet is turned on and the inductor current ramps up. the on interval is terminated when the inductor current reaches the programmed peak current level. during the off interval, the input current decays until the lower thresh- old, or zero inductor current is reached. the lower cur- rent is equal to the peak current minus a preset hyster- esis threshold, which determines the inductor ripple current. the peak current is adjusted by the controller until the output current requirement is met. the magnitude of the feedback error signal determines the average input current. therefore, the aat1276 boost controller implements a programmed current source connected to the output capacitor and load resistor. there is no right-half plane zero, and loop stability is achieved with no additional external compensation com- ponents. at light load, the inductor off interval current goes to zero and the boost converter enters discontinuous mode operation. further reduction in the load results in a cor- responding reduction in the switching frequency, which reduces switching losses and maintains high efficiency at light loads. the operating frequency varies with changes in the input voltage, output voltage, and inductor size. once the boost converter has reached continuous mode, increas- ing the output load will not significantly change the oper- ating frequency. a small 2.2 h ( 20%) inductor is selected to maintain high frequency operation for the 5v usb output voltage. output voltage programming the output voltage is programmed through a resistor divider network located from the out1 output capacitor to the fb pin to ground. soft start / enable the input disconnect switch is activated when a valid input voltage is present and the en pin is pulled high. the slew rate control on the p-channel mosfet ensures minimal inrush current as the output voltage is charged to the input voltage prior to switching of the n-channel power mosfet. the soft-start circuitry guarantees monotonic turn-on and eliminates output voltage over- shoot across the full input voltage range for all load conditions. input current limit and over-temperature protection the switching of the n-channel mosfet terminates when input current limit of 2.5a (typical) is exceeded. this minimizes the power dissipation and component stresses under overload and short-circuit conditions. switching resumes when the current decays below the limit. thermal protection disables the aat1276 boost con- verter when the internal power dissipation becomes excessive. the junction over-temperature threshold is 140c with 15c of temperature hysteresis. the output voltage automatically recovers when the over-tempera- ture or over-current fault condition is removed. shutdown and output disconnect a typical synchronous step-up (boost) converter has a conduction path from the input to the output via the body diode of the p-channel mosfet. the aat1276 design disconnects this body diode from the output and eliminates this conduction path. this enables the aat1276 to provide true load disconnect during shutdown and inrush current limit at turn-on. short-circuit protection the p-channel synchronous mosfet body diode discon- nect feature also gives the aat1276 the ability to pro- vide output short-circuit current limit protection. under-voltage lockout under-voltage lockout (uvlo) guarantees sufficient v in bias and proper operation of all internal circuitry prior to soft start. internal bias of all circuits is controlled via the vcc input, which is connected to v in .
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 11 aat1276 data sheet boost converter with usb power switch selecting the boost inductor the aat1276 boost controller utilizes hysteretic control and the switching frequency varies with output load and input voltage. the value of the inductor determines the maximum switching frequency of the boost converter. increasing output inductance decreases the switching frequency, resulting in higher peak currents and increased output voltage ripple. to maintain the 2mhz switching frequency and stable operation, an output inductor sized from 1.5 h to 2.7 h is recommended. manufacturer?s specifications list both the inductor dc current rating, which is a thermal limitation, and peak inductor current rating, which is a function of the satu- ration characteristics. measure the inductor current at full load and high ambi- ent temperature to ensure that the inductor does not saturate or exhibit excessive temperature rise. select the output inductor (l) to avoid saturation at the mini- mum input voltage and maximum load. the rms current flowing through the boost inductor is equal to the dc plus ac ripple components. the maximum inductor rms current occurs at the minimum input voltage and the maximum load. use the following equations to calculate the maximum peak and rms current: v o - v in(min) v o d max = v in(min) d l f s i pp = i o 1 - d i p = i pp 2 i pk = i p + i v = i p - i pp i rms = i pk 2 + i pk i v + i v 2 3 p loss(inductor) = i 2 rms dcr at light load and low output voltage, the controller reduces the operating frequency to maintain maximum efficiency. as a result, further reduction in output load does not reduce the peak current. the minimum peak current ranges from 0.5a to 0.75a. compare the rms current values with the manufactur- er?s temperature rise, or thermal derating guidelines. for a given inductor type, smaller inductor size leads to an increase in dcr winding resistance and, in most cases, increased thermal impedance. winding resistance degrades boost converter efficiency and increases the inductor?s operating temperature. shielded inductors provide decreased emi and may be required in noise sensitive applications. unshielded chip inductors provide significant space savings at a reduced cost compared to shielded inductors. in general, chip- type inductors have increased winding resistance (dcr) when compared to shielded, wound varieties. selecting the step-up converter capacitors the high output ripple inherent in the boost converter necessitates low impedance output filtering. multi-layer ceramic (mlc) capacitors provide small size, adequate capacitance, with low parasitic equivalent series resis- tance (esr) and equivalent series inductance (esl). this makes them well suited for use with the aat1276. mlc capacitors of type x7r or x5r ensure good capacitance stability over the full operating range. mlc capacitors exhibit significant capacitance reduction with an applied dc voltage. output ripple measurements can confirm that the capacitance used meets the specific ripple requirements. voltage derating minimizes this factor, but results may vary with package size and among specific manufacturers. use a 4.7 f 10v ceramic output capacitor to minimize output ripple for the 5v output. small 0805 sized ceram- ic capacitors are available which meet these require- ments. estimate the output capacitor required at the minimum switching frequency (f s ) of 800khz (worst-case). i out d max f s v out c out = the boost converter input current flows during both on and off switching intervals. the input ripple current is less than the output ripple and, as a result, less input capacitance is required. a ceramic output capacitor from 1 f to 4.7 f is recommended. minimum 6.3v rated capacitors are required at the input. ceramic capacitors sized as small as 0603 are available which meet these requirements.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 12 aat1276 data sheet boost converter with usb power switch setting the output voltage program the output voltage through a resistive divider located from the output to the fb pin to ground. the internal error amplifier reference voltage is 0.6v. a 59.0k ? programming resistor value from vfb to gnd with a 432k ? resistor from fb to the output will set the output voltage to 5v. ?? ?? v out = v ref 1 + r2 r3 ?? ?? = 0.6v 1 + = 5.0v 432k 59.0k usb load switch application information setting the load switch current limit in most applications, the variation in i lim must be taken into account when determining r set . the i lim variation is due to processing variations from part to part, as well as variations in the voltages at out1 and out2, plus the operating temperature. the typical r set value for a 300ma load is in the range of 20 to 22k ? . r set (k )i out (ma) 11 740 12 690 14 590 16 550 18 450 20 420 30 160 40 100 table 1: current limit vs.r set . operation in current limit when a heavy load is applied to out2 of the aat1276, the load current is limited to the value of i lim (deter- mined by r set ) causing a drop in the output voltage. this increases the aat1276 power dissipation and die tem- perature. when the die temperature exceeds the over- temperature limit, the aat1276 shuts down until it has cooled sufficiently, at which point it will start up again. the aat1276 will continue to cycle on and off until the load is removed, power is removed, or until a logic low level is applied to the en pin. a fault flag indicates when the out2 pin load current has exceeded the current limit level set by r set . the fault flag is an active low, open-drain pin that requires 10k ? pull- up to v in . the fault signal has a 4ms blanking time to prevent false over current indicator during the charging of the usb bus capacitor. steady-state maximum power dissipation the maximum power dissipation for the aat1276 occurs at the minimum input voltage, where it operates in con- tinuous conduction mode (ccm). the total power dissi- pation at full load is dominated by the r ds(on) losses of the power mosfet. the dissipation includes the losses in the input and output switch, as well as both synchronous switches. due to the magnitude of the inductor ripple current, it cannot be neglected when analyzing the r ds(on) power dissipation. once the ripple current has been deter- mined, the rms current during the on and the off period can be calculated. v o - v in(min) v o d max = v in(min) d max l f s i pp = i o 1 - d i p = i pp 2 i pk = i p + i v = i p - i pp i rms(on) = (i p 2 + i pk i v + i v 2 ) d max 3 i rms(off) = (i p 2 + i pk i v + i v 2 ) (1 - d max ) 3 p total = i rms(on) 2 ( r ds(on)in + r ds(on)n ) + i rms(off) 2 ( r ds(on)in + r ds(on)p + r ds(on) ) t j(max) = p total ja + t amb
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 13 aat1276 data sheet boost converter with usb power switch r ds(on)in is the input disconnect switch, r ds(on)n is the high- side synchronous switch, r ds(on)p is the low-side synchro- nous switch, and r ds(on) is the current limit load switch. pcb layout guidelines the step-up converter performance can be adversely affected by poor layout. possible impact includes high input and output voltage ripple, poor emi performance, and reduced operating efficiency. every attempt should be made to optimize the layout in order to minimize parasitic pcb effects (stray resistance, capacitance, inductance) and emi coupling from the high frequency sw node. a suggested pcb layout for the aat1276 is shown in figures 1 and 2. the following pcb layout guidelines should be considered: 1. minimize the distance from capacitors c2 and c3 to the ic. this is especially true for the output capaci- tor c2, which conducts high ripple current associated with the step-up converter output capacitor. 2. place the feedback resistor close to the output termi- nals. route the output pin directly to resistor r2 to maintain good output regulation. r3 should be routed close to the output gnd pin and should not share a significant return path with output capacitor c2. 3. minimize the distance between l1 and the switching pin sw; minimize the size of the pcb area connected to the sw pin. 4. maintain a ground plane and connect to the ic rtn pin(s), as well as the gnd terminals of c1 and c2. figure 1: aat1276 evaluation board figure 2: aat1276 evaluation board top side layout. bottom side layout.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 14 aat1276 data sheet boost converter with usb power switch manufacturer part number value voltage temp. co. case murata grm21br61a475ka73l 4.7 f 10v x5r 0805 murata grm18br60j475ke19d 4.7 f 6.3v x5r 0603 murata grm21br60j106ke19 10 f 6.3v x5r 0805 murata grm21br60j226me39 22 f 6.3v x5r 0805 table 2: typical surface mount capacitors. manufacturer part number inductance ( h) max dc current (a) dcr ( ? ) size (mm) lxwxh type sumida cdrh2d14-2r2 2.2 1.6 0.094 3.2x3.2x1.55 shielded sumida cdrh4d11/hp-2r4 2.4 1.7 0.105 4.8x4.8x1.2 shielded coiltronics sd3112-2r2 2.2 1.12 0.140 3.1x3.1x1.2 shielded coiltronics sd3114-2r2 2.2 1.48 0.086 3.1x3.1x1.4 shielded table 3: typical surface mount inductors. lin 1 vin 2 pgnd 3 sw 4 out1 5 out2 6 set 7 flt 8 fb 9 gnd 10 vcc 11 en 12 aat1276 u1 432 k r2 59 k r3 10 k r1 r4 16.9k l1 2.2h c2 4.7f 10v c3 4.7f 10v c6 120f ccase c1 4.7f flt v in gnd 1 2 3 enable v in v in v o2 v o1 j5 gnd gnd figure 3: aat1276 evaluation board schematic.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 15 aat1276 data sheet boost converter with usb power switch step-up converter design example specifications v out = 5v i out = 300ma v in = 2.7v to 4.2v (3.6v nominal) t amb = 50c output inductor v out - v in(min) v out d max = 5v - 2.7v 5v = = 0.46 from the characterization curves, the switching frequency at room temperature with a 300ma load and 2.2 h inductor is about 800khz. v in(min) d max l f s i pp = i o 1 - d i p = i pp 2 i pk = i p + i v = i p - i pp i v = i p - i pp = 0.9a - 0.7a = 0.20a i rms = i pk 2 + i pk i v + i v 2 3 = = 0.59a 0.9a 2 + 0.9a 0.2a + 0.2a 2 3 for the sumida cdrh2d14-2r2 inductor, i sat = 1.0a, i dc(max) = 1.6a and dcr = 94m ? . p loss(inductor) = i 2 rms dcr = (590ma) 2 94m = 32mw 5v output capacitor v out = 0.05v i out d max f s v out c out(min) = 0.3a 0.46 800khz 0.05v = = 3.0f; use 4.7f 10v mlc
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 16 aat1276 data sheet boost converter with usb power switch aat1276 losses i rms(on) = (i pk 2 + i pk i v + i v 2 ) d max 3 = = 0.4 a (0.9a 2 + 0.9a 0.2a + 0.2a 2 ) 0.46 3 i rms(off) = (i pk 2 + i pk i v + i v 2 ) (1 - d max ) 3 = = 0.43 a (0.9a 2 + 0.9a 0.2a + 0.2a 2 ) (1 - 0.46) 3 p total = i rms(on) 2 ( r ds(on)in + r ds(on)n ) + i rms(off) 2 ( r ds(on)in + r ds(on)p + r ds(on) ) = 0.4a 2 ( 0.25 + 0.3 ) + 0.42 2 ( 0.25 + 0.3 + 0.2 ) = 0.22w t j(max) = p total ja + t amb = 0.22w + 85c = 109c 110c w
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 17 aat1276 data sheet boost converter with usb power switch ordering information package marking 1 part number (tape and reel) 2 tsopjw-12 1vxyy aat1276itp-5.0-t1 tdfn34-16 1uxyy aat1276irn-5.0-t1 package information 3 tsopjw-12 0.20 + 0.10 - 0.05 0.055 0.045 0.45 0.1 5 7 nom 4 4 3.00 0.10 2.40 0.10 2.85 0.20 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.50 bsc 0.15 0.05 0.9625 0.0375 1.00 + 0.10 - 0.065 0.04 ref 0.010 2.75 0.25 all dimensions in millimeters. 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 3. the leadless package family, which includes qfn, tqfn, dfn, tdfn and stdfn, has exposed copper (unplated) at the end of the lead terminals due to the manufacturing process. a solder fillet at the exposed copper edge cannot be guaranteed and is not required to ensure a proper bottom solder connection. skyworks green? products are compliant with all applicable legislation and are halogen-free. for additional information, refer to skyworks de?ition of green , document number sq04-0074.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202061b ? skyworks proprietary information ? products and product information are subject to change without notice. ? ma rch 19, 2013 18 aat1276 data sheet boost converter with usb power switch copyright ? 2012, 2013 skyworks solutions, inc. all rights reserved. information in this document is provided in connection with skyworks solutions, inc. (?skyworks?) products or services. these m aterials, including the information contained herein, are provided by skyworks as a service to its customers and may be used for informational purposes only by the customer. skyworks assumes no responsibility fo r errors or omissions in these materials or the information contained herein. sky- works may change its documentation, products, services, speci cations or product descriptions at any time, without notice. skyworks makes no commitment to update the materials or informati on and shall have no responsibility whatsoever for con icts, incompatibilities, or other dif culties arising from any future changes. no license, whether express, implied, by estoppel or otherwise, is granted to any intellectual property rights by this document . skyworks assumes no liability for any materials, products or information provided here- under, including the sale, distribution, reproduction or use of skyworks products, information or materials, except as may be p rovided in skyworks terms and conditions of sale. the materials, products and information are provided ?as is? without warranty of any kind, whether express, implied, statutory, or otherwise, including fitness for a particular purpose or use, merchantability, performance, quality or non-infringement of any intellectual property right; all such warranti es are hereby expressly disclaimed. skyworks does not warrant the accuracy or completeness of the information, text, graphics or other items contained within these materials. sk yworks shall not be liable for any damages, in- cluding but not limited to any special, indirect, incidental, statutory, or consequential damages, including without limitation , lost revenues or lost profits that may result from the use of the materials or information, whether or not the recipient of materials has been advised of the possibility of such damage. skyworks products are not intended for use in medical, lifesaving or life-sustaining applications, or other equipment in which the failure of the skyworks products could lead to personal injury, death, physical or en- vironmental damage. skyworks customers using or selling skyworks products for use in such applications do so at their own risk and agree to fully indemnify skyworks for any damages resulting from such improper use or sale. customers are responsible for their products and applications using skyworks products, which may deviate from published speci cations as a result of design defects, errors, or operation of products outside of pub- lished parameters or design speci cations. customers should include design and operating safeguards to minimize these and other risks. skyworks assumes no liabi lity for applications assistance, customer product design, or damage to any equipment resulting from the use of skyworks products outside of stated published speci cations or parameters. skyworks, the skyworks symbol, and ?breakthrough simplicity? are trademarks or registered trademarks of skyworks solutions, inc ., in the united states and other countries. third-party brands and names are for identi cation purposes only, and are the property of their respective owners. additional information, including relevant terms and co nditions, posted at www.skyworksinc.com, are incorporated by reference. tdfn34-16 3.000 all dimensions in millimeters.

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