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1 aat1130 2.5mhz 400ma ste p -down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 general description the aat1130 switchreg? is a member of skyworks' total power management ic? product family. the converter uses a predictive on-time, current-mode step-down con- trol scheme that provides a fixed 2.5mhz switching fre- quency (under steady state conditions). it allows the control circuit to react nearly instantly in order to improve transient response and to enhance stability with the lc components as small as 1.0 h. the unique architecture improves transient response while allowing tiny passive lc filter components. the high switching frequency (up to 2.5mhz) keeps output voltage ripple low. the aat1130 delivers up to 400ma of output current, while consuming only 60 a of quiescent current. the aat1130 regulates an output voltage between 0.6v and 1.8v from an input voltage of 2.7v to 5.5v. the aat1130's output voltage is set by an external resistive voltage divider circuit. internal mosfet switches reduce the over- all solution size while maintaining high efficiency over a wide load current range. the aat1130 is available in a space-saving 2.0x2.2mm sc70jw-10 package and is rated over the -40c to 85c temperature range. features ? 2.5mhz switching frequency ? fast transient response with small lc output filter components ? input voltage range: 2.7v to 5.5v ? output voltage range: 0.6v to 1.8v ? high 92% peak efficiency (v in = 3.6v, v out = 1.8v) ? low 60 a quiescent current ? 400ma maximum continuous output current ? internal 150 s soft-start feedback ramp ? over-temperature protection ? anti-ringing switch to reduce emi during discontinuous conduction mode operation ? valley current limit protection ? sc70jw-10 package ? -40c to 85c temperature range applications ? microprocessor/dsp core and i/o ? mobile phones ? pdas and handheld computers ? digital cameras ? portable music players ? handheld games ? handheld instruments typical application v in 2.4v to 5.5v vp vcc gnd lx en 4 3 5 6 out 2 7-10 on off aat1130 c in 4.7f 0603 6v x5r c out 4.7f 0603 6v x5r l 1.0h fb 1 r2 100k 0603 1% r1 150k 0603 1% 1.0v v out 400ma c3 100pf time ( 5 s/div ) output voltage (top) (v) output current (bottom) (a) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 100ma 400ma
2 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 pin descriptions pin # symbol function 1fb output voltage feedback input. fb senses the output voltage through a resistor voltage divider circuit. connect the voltage divider from the output voltage to fb. the feedback threshold is 0.6v. 2 vout output voltage sense input. vout senses the output voltage. connect vout to the output voltage node for proper on-time calculation. 3 vcc input supply voltage. connect vcc to the input supply voltage. 4vp power input supply voltage. connect vp to the vcc pin, and to the input supply voltage. bypass vp to gnd with a 2.2 f or greater ceramic capacitor. 5lx switching node. connect the lc lter between lx and the load. lx is internally connected to the drain of the p-channel mosfet switch and n-channel mosfet synchronous recti er. 6 en enable input. active logic high. 7, 8, 9, 10 gnd ground. pin configuration sc70jw-10 (top view) 1 2 3 4 5 10 9 8 7 6 fb vout vcc vp lx gnd gnd gnd gnd en
3 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 absolute maximum ratings 1 symbol description value units v vcc , v vp vcc, vp to gnd 6.0 v v lx lx voltage to gnd -0.3 to v vcc \v vp +0.3 v v fb fb voltage to gnd -0.3 to v vcc \v vp +0.3 v v en en voltage to gnd -0.3 to v vcc \v vp +0.3 v t j operating junction temperature range -40 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c thermal information symbol description value units p d maximum power dissipation 625 mw ? ja thermal resistance 2 160 c/w 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at c onditions other than the operating conditions specified is not implied. only one absolute maximum rating should be applied at any one time. 2. mounted on a fr4 board.
4 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 electrical characteristics 1 v in = 3.6v, c in = c out = 4.7 f, l = 1.5 h. t a = -40c to 85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units v in input voltage 2.7 5.5 v v out output voltage range 0.6 1.8 v v uvlo uvlo threshold v in rising 2.65 v hysteresis 100 mv i q quiescent current not switching 60 90 a i shdn shutdown current en = gnd 1.0 a v fb_acc feedback voltage accuracy t a = 25c, no load 0.59 0.6 0.61 v i lim valley current limit t a = 25c 500 650 ma r ds(on)h high side switch on-resistance 0.35 r ds(on)l low side switch on-resistance 0.25 f on switch on-time v in = 3.6v, v out = 1.2v 120 ns t off(min) minimum off-time 75 ns i lxleak lx leakage current v in = 5.5, v lx = 0 to v in 1 a i fbleak fb leakage current v fb = 5.5v, v en = 0v, adj only 0.2 a t s startup time from en asserted to output regulation 150 s f s switching frequency v out = 1.2v, 400ma load 2.5 mhz t sd over-temperature shutdown threshold 140 c t hys over-temperature shutdown hysteresis 15 c v en(l) enable threshold low 0.6 v v en(h) enable threshold high 1.4 v i en enable pin current v in = v fb =5.5v -1.0 1.0 a 1. the aat1130 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.
5 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 typical characteristics efficiency vs. load current (v out = 1v) load current (a) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 0.0001 0.001 0.01 0.1 1 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5v v in = 5.5v output voltage error vs. load current (v out = 1v) load current (a) output voltage error (%) -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 0.0001 0.001 0.01 0.1 1 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5v v in = 5.5v line regulation (v out = 1v) input voltage (v) output voltage error (%) -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 2.7 3.2 3.7 4.2 4.7 5.2 5.7 i out = 1ma i out = 10ma i out = 100ma i out = 300ma i out = 500ma efficiency vs. load current (v out = 1.8v) load current (a) efficiency (%) 0.0001 0.001 0.01 0.1 1 0 10 20 30 40 50 60 70 80 90 100 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5v v in = 5.5v output voltage error vs. load current (v out = 1.8v) load current (a) output voltage error (%) 0.0001 0.001 0.01 0.1 1 -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5v v in = 5.5v line regulation (v out = 1.8v) input voltage (v) output voltage difference (%) 2.7 3.2 3.7 4.2 4.7 5.2 5.7 -1 -0.75 -0.5 -0.25 0 0.25 0.5 0.75 1 i out = 1ma i out = 10ma i out = 100ma i out = 300ma
6 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 typical characteristics supply current vs. supply voltage (switching) supply voltage (v) ) supply current (a) 60 65 70 75 80 85 90 95 100 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 switching frequency vs. input voltage (v out = 1v; c in = c out = 2.2f; l = 1h) input voltage (v ) switching frequency (mhz) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 on-time vs. input voltage (v out = 1v; c in = c out = 2.2f; l = 1h)) input voltage (v ) on-time (ns) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 0 50 100 150 200 250 switching frequency vs. input voltage (v out = 1.8v; c in = c out = 2.2f; l = 1.5h)) input voltage (v ) switching frequency (mhz) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 1 1.25 1.5 1.75 2 2.25 2.5 2.75 3 on-time vs. input voltage (v out = 1.8v; c in = c out = 2.2f; l = 1.5h)) input voltage (v ) on-time (ns) 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 0 50 100 150 200 250 300 350 400 switching frequency variation vs. load current load current (ma) switching frequency variation (%) 200 250 300 350 400 450 500 550 600 -20 -15 -10 -5 0 5 10 15 20 v in = 2.7v v in = 3.3v v in = 3.6v v in = 4.2v v in = 5v v in = 5.5v
7 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 typical characteristics supply current vs. temperature temperature (v) supply current (a) -40 -15 10 35 60 85 20 30 40 50 60 70 80 90 100 output voltage error vs. temperature temperature (c) output voltage error (%) -0.5 -0.4 -0.3 -0.2 -0.1 0 0.1 0.2 -40 -15 10 35 60 85 r ds(on) vs. temperature temperature (c) r ds(on) (m ) -40 -15 10 35 60 85 0 50 100 150 200 250 300 350 400 450 pmos nmos switching frequency vs. output voltage (i out = 500ma) output voltage (v ) switching frequency (mhz) 0.6 0.9 1.2 1.5 1.8 1.25 1.75 2.25 2.75 3.25 3.75 load transient (v out = 1.8v; v in = 3.6v; c out = 4.7f; c ff = 100pf; l = 1.5h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 1.75 1.80 1.85 1.90 1.55 1.55 1.60 1.65 1.70 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100ma 300ma load transient (v out = 1.8v; v in = 3.6v; c out = 4.7f; l = 1.5h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 100ma 300ma
8 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 typical characteristics load transient (v out = 1.8v; v in = 3.6v; c out = 4.7f; c ff = 100pf; l = 1.5h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10ma 500ma load transient (v out = 1.5v; v in = 3.6v; c out = 4.7f; c ff = 100pf; l = 1.5h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10ma 500ma load transient (v out = 1.5v; v in = 3.6v; c out = 4.7f; l = 1.5h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 1.20 1.25 1.30 1.35 1.40 1.45 1.50 1.55 1.60 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 300ma 100ma load transient (v out = 1v; v in = 3.6v; c out = 4.7f; c ff = 100pf; l = 1h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 100ma 400ma load transient (v out = 1v; v in = 3.6v; c out = 4.7f; l = 1h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 100ma 400ma load transient (v out = 1v; v in = 3.6v; c out = 4.7f; c ff = 100pf; l = 1h) time (5s/div) output voltage (top) (v) output current (bottom) (a) 0.70 0.75 0.80 0.85 0.90 0.95 1.00 1.05 1.10 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 10ma 500ma
9 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 typical characteristics soft-start (v out = 1.8v; v in = 3.6v; c out = 4.7f; l = 1.5h) time (100s/div) enable voltage (top) (v) output voltage (middle) (v) output current (bottom) (a) 200ma 0ma 0v 0v (100ma/div) 1.8v (1v/div) 3.6v (2v/div) line transient (v out = 1.8v; c out = 4.7f; l = 1.5h) time (10s/div) output voltage (top) (v) output voltage (bottom) (v) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 2.6 3.1 3.6 4.1 4.6 5.1 5.6 6.1 6.6
10 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 functional description the aat1130 is a high performance 400ma 2.5mhz (maximum switching frequency during steady-state operation) monolithic step-down converter. it minimizes external component size, enabling the use of a tiny 0603 inductor that is only 1mm tall, and optimizes efficiency over the complete load range. apart from the small bypass input capacitor, only a small l-c filter is required at the output. typically, a 1 h inductor and a 4.7 f ceramic capacitor are recommended for <1.2v output voltage applications (see table of values). only three external power components (c in , c out , and l) are required. output voltage is programmed with exter- nal feedback resistors, ranging from 0.6v to 1.8v. an additional feed-forward capacitor can also be added to the external feedback to provide improved transient response (see figure 1). the input voltage range is 2.7v to 5.5v. the converter efficiency has been optimized for all load conditions, ranging from no load to 400ma. the internal error comparator and incorporated compen- sation provide excellent transient response, load, and line regulation. soft-start eliminates any output voltage over- shoot when the enable or the input voltage is applied. control loop the aat1130 uses a current-mode control scheme that allows it to operate at very high switching frequencies. the current-mode control scheme operates with a pre- dicted on-time for a given output to input voltage ratio. the on-time varies inversely proportional to the input voltage and proportional to the output voltage giving the regulator a fixed switching frequency when in steady- state. this allows the use of very small external inductor and capacitor. the small size coupled with the low quies- functional block diagram shoot through protection error comparator + - current limit comparator en current sense amplifier soft-start control and fet driver logic circuitry vout fb vcc vp v ref v ilim gnd gnd lx
11 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 cent current and automatic transition to variable switch- ing frequency mode makes it ideal for small battery operated applications. light load operation the aat1130 monitors the synchronous rectifier current and when the current drops to zero, it turns off the syn- chronous rectifier to emulate an actual rectifier. this allows the regulator to operate in discontinuous conduc- tion mode. in this mode the on-time remains the same as it is in continuous conduction mode, and therefore the inductor ripple current remains the same in both modes. but reduced load current requires more time for the out- put capacitor to discharge to the regulation voltage reducing the switching frequency. this has the added benefit of reducing the switching transition losses improving efficiency at light loads. stability the aat1130 requires no additional compensation com- ponents to guarantee stability. the only requirement for stability is to choose the appropriate output capacitor. current-mode control simplifies compensation by control- ling the inductor current to regulate the output voltage. this approximates a single pole response in the loop gain even though a complex pole pair exists due to the lc fil- ter. therefore the crossover frequency is approximated as the dc loop gain multiplied by the single pole. the aat1130 dc loop gain is a function of the 60m current sense resistor and is determined by the equation: a loop(dc) = v out 0.6v r load 60m and the dominant pole frequency is: f p = 1 2 r load c out therefore the crossover frequency is: f c = a loop(dc) f p = v out 2 0.6v 60m c out the only requirement for stability is that the crossover frequency be much less than the 2.5mhz switching fre- quency. the crossover frequency can be as high as 1/2 of the switching frequency, or 1.25mhz. therefore calcu- late the output capacitor by the equation: c out > v out 2 0.6v 60m 1.25mhz example: given that v out = 1.5v, then c out > 5.3 f, therefore a 4.7 f capacitor is the closest standard value that can be used for 1.2v to 1.5v output. due to the unique control method, the ?inside? current control loop does not have the inherent instability that plagues most fixed frequency current-mode dc-dc reg- ulators. soft-start when the aat1130 is enabled, it enters soft-start mode. in this mode, the output voltage slowly rises over 150 s allowing the output capacitor to charge without drawing excessive input current. this feature prevents over- stressing the battery or other input power source. valley current limit the aat1130 includes a cycle-by-cycle, valley current limit to prevent damage to itself or the external compo- nents. the valley current limit uses the low-side-n- channel synchronous rectifier to monitor the inductor current. if the measured current exceeds the valley cur- rent limit, the aat1130 keeps the low-side synchronous rectifier on until the current drops below the current limit. along with the predictive on-time control scheme, the valley current limit protection allows the converter to control and limit the inductor current, even with output overload or short-circuit fault condition. since the aat1130 uses a predictive on-time architec- ture (constant on-time with input feed-forward), the actual output current capability is a function of the inductor ripple current ( i l ) and the current limit com- parator delay (see figure 1): i out_max = i lim_valley + t delay - ?i l 2 v out l i out_max = i lim_valley + t delay t sw - v in - v out 2l v out v in v out l
12 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 where t sw is the switching period constant (typically 360ns) as defined by the on-time specification in the electrical characteristics table, and t delay is the current- limit comparator delay (typically 150ns). t on t delay i limit i out(max) i l figure 1: output current to valley current-limit relationship anti-ringing switch the aat1130 includes an anti-ringing switch that dissi- pates any energy left in the inductor when the current is approximately zero. the anti-ringing switch turns on when both the p-channel switch and n-channel synchro- nous rectifier are off and the inductor current is approx- imately zero. the switch shorts the lx and vout nodes together, effectively shorting the inductor. the low on- resistance of the anti-ringing switch dissipates any energy left in the inductor preventing ringing at light loads. when either the switch or synchronous rectifier are on, the anti-ringing switch remains off. over-temperature the aat1130 includes thermal protection that automati- cally turns off the regulator when the die temperature exceeds a safe level. the thermal protection turns on at a die temperature of 140c and has a 15c hysteresis. applications information inductor selection the step-down converter uses a predictive on-time con- trol scheme with internal slope and current compensa- tion. the internal current compensation eliminates the "minimum, output capacitor esr" stability requirement commonly required with this control architecture. however, the current compensation requires that the inductor cur- rent down slope to maintain a sufficient signal-to-noise ratio. the inductor current down-slope is defined by: = v out l di dt resulting in an inductor recommendation to keep the inductance value equal to the output voltage l = v out h v to maintain the appropriate di dt . manufacturer?s specifications list both the inductor dc current rating, which is a thermal limitation, and the peak current rating, which is determined by the satura- tion characteristics. the inductor should not show any appreciable saturation under normal load conditions. some inductors may meet the peak and average current ratings yet result in excessive losses due to a high dcr. always consider the losses associated with the dcr and its effect on the total converter efficiency when selecting an inductor. see table 2 for suggested inductor values and vendors. input capacitor select a 4.7 f to 10 f x7r or x5r ceramic capacitor for the input. always examine the ceramic capacitor dc voltage coefficient characteristics when selecting the proper value. for example, the capacitance of a 10 f, 6.3v, x5r ceramic capacitor with 5.0v dc applied is actually about 6 f. the input capacitor provides a low impedance loop for the edges of pulsed current drawn by the aat1130. low esr/esl x7r and x5r ceramic capacitors are ideal for this function. to minimize stray inductance, the capaci- tor should be placed as closely as possible to the ic. this keeps the high frequency content of the input current localized, minimizing emi and input voltage ripple. the proper placement of the input capacitor (c1) can be seen in the evaluation board layouts in figures 4 and 5.
13 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 a laboratory test set-up typically consists of two long wires running from the bench power supply to the evalu- ation board input voltage pins. the inductance of these wires, along with the low-esr ceramic input capacitor, can create a high q network that may affect converter performance. this problem often becomes apparent in the form of excessive ringing in the output voltage dur- ing load transients. errors in the loop phase and gain measurements can also result. since the inductance of a short pcb trace feeding the input voltage is significantly lower than the power leads from the bench power supply, most applications do not exhibit this problem. in applications where the input power source lead inductance cannot be reduced to a level that does not affect the converter performance, a high esr tantalum or aluminum electrolytic should be placed in parallel with the low esr, esl bypass ceramic. this dampens the high q network and stabilizes the sys- tem. output capacitor the output capacitor limits the output ripple and pro- vides holdup during large load transitions. a 4.7 f to 10 f x5r or x7r ceramic capacitor typically provides sufficient bulk capacitance to stabilize the output during large load transitions and has the esr and esl charac- teristics necessary for low output ripple. the internal voltage loop compensation also limits the minimum output capacitor value to 4.7 f. this is due to its effect on the loop crossover frequency (bandwidth), phase margin, and gain margin. increased output capac- itance will reduce the crossover frequency with greater phase margin. fb r1 r2 c ff figure 2: aat1130 external resistor output voltage programming. feedback resistor selection resistors r1 and r2 of figure 2 program the output to regulate at a voltage higher than 0.6v. to limit the bias current required for the external feedback resistor string while maintaining good noise immunity, the minimum suggested value for r2 is 59k . although a larger value will further reduce quiescent current, it will also increase the impedance of the feedback node, making it more sensitive to external noise and interference. table 1 summarizes the resistor values for various output volt- ages with r2 set to either 59k for good noise immunity or 221k for reduced no load input current. r1 = -1 r2 = - 1 59k = 88.5k v out v fb 1.5v 0.6v the aat1130, combined with an external feedforward capacitor (c3 in figure 2), delivers enhanced transient response for extreme pulsed load applications. the addi- tion of the feedforward capacitor typically requires a larger output capacitor c1 for stability. v out (v) r2 = 59k r1 (k ) r2 = 221k r1 (k ) 0.9 29.4 113 1 39.2 150 1.1 49.9 187 1.2 59.0 221 1.3 68.1 261 1.4 78.7 301 1.5 88.7 332 1.8 118 442 table 1: feedback resistor values. thermal calculations there are three types of losses associated with the aat1130 step-down converter: switching losses, conduc- tion losses, and quiescent current losses. conduction losses are associated with the r ds(on) characteristics of the power output switching devices. switching losses are dominated by the gate charge of the power output switching devices. at full load, assuming continuous con- duction mode (ccm), a simplified form of the losses is given by: p total i o 2 (r ds(on)h v o + r ds(on)l [v in - v o ]) v in = + (t sw f s i o + i q ) v in
14 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 i q is the step-down converter quiescent current. the term t sw is used to estimate the full load step-down con- verter switching losses. for the condition where the step-down converter is in dropout at 100% duty cycle, the total device dissipation reduces to: p total = i o 2 r ds(on)h + i q v in since r ds(on) , quiescent current, and switching losses all vary with input voltage, the total losses should be inves- tigated over the complete input voltage range. given the total losses, the maximum junction temperature can be derived from the ja for the sc70jw-10 package which is 160c/w. t j(max) = p total ja + t amb layout the suggested pcb layout for the aat1130 is shown in figures 4 and 5. the following guidelines should be used to help ensure a proper layout: 1. the input capacitor (c1) should connect as closely as possible to the vcc/vp and gnd pins. 2. c1 and l1 should be connected as closely as possi- ble. the connection of l1 to the lx pin should be as short as possible. 3. the feedback trace or fb pin for adjustable output voltage should be separate from any power trace and connect as closely as possible to the load point. sensing along a high current load trace will degrade dc load regulation. if external feedback resistors are used, they should be placed as closely as possible to the fb pin for adjustable output voltage to minimize the length of the high impedance feedback trace. 4. the resistance of the trace from the load return to the gnd pins should be kept to a minimum. this will help to minimize any error in dc regulation due to differences in the potential of the internal signal ground and the power ground.
15 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 4.7f c1 4.7f c2 1. 5 h l1 a 1 b 2 c 3 header j1 vin gnd vout fb 1 vout 2 vcc 3 vp 4 lx 5 en 6 gnd 7 gnd 8 gnd 9 gnd 10 aat1130_ adj u1 vout gnd vin c3 100pf 59k r2 r1 1.5v 1v 1h 1.8v 1.8h, 2.2h l1 v out u1 aat1130 analogic technologies, 2.5mhz, 400ma buck converter c1, c2 cap, mlc, 4.7f/6.3v, 0805 c3 cap, mlc, 100pf/6.3v, 0402 (optional) r1 carbon film resistor, 0402 (adjust to output voltage) r2 carbon film resistor, 59k, 0402 l1 lqm2hp-go, 1.5h, murata, i sat = 1.5a, dcr = 70m; or vlf3010a, 1.5h, tdk, i sat = 1.2a, dcr = 68m figure 3: aat1130 evaluation board schematic. figure 4: aat1130 evaluation board figure 5: aat1130 evaluation board top side pcb layout. bottom side pcb layout.
16 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 manufacturer part number/type inductance ( h) rated current (ma) dcr (m ) (typ) size (mm) lxwxh murata lqm2hp_g0 1 1600 55 2.5x2x1 1.5 1500 70 2.2 1300 80 lqh32p_n0 1 2050 45 3.2x2.5x1.6 1.5 1750 57 2.2 1600 76 tdk glc2518 1 2.8 20 2.5x1.8x1.8 2.2 2.45 25 vlf3010a 1.5 1200 68 2.8x2.6x1 2.2 1000 100 vlf3010s 1 1700 41 3.0x2.8x1 2.2 1100 77 table 2: suggested inductor components. manufacturer part number value voltage temp. co. case avx 0603zd225k 2.2 f 10 x5r 0603 tdk c1608x5r1c225k 2.2 f16 x5r 0603 c1608x5r1a475k 4.7 f10 c2012x5r1a106k 10 f 10 0805 c3216x5r1a226k 22 f 10 1206 murata grm188r61a225k 2.2 f10 x5r 0603 grm219r61a106k 10 f 10 0805 grm31cr71a226k 22 f 10 x7r 1206 taiyo yuden lmk107bj475ka 4.7 f 10 x5r 0603 table 3: suggested capacitor components.
17 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 ordering information output voltage package marking 1 part number (tape and reel) 2 adjustable sc70jw-10 2vxxy aat1130ijq-0.6-t1 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. package information sc70jw-10 0.45 all dimensions in millimeters. 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold
18 aat1130 2.5mhz 400ma step-down dc/dc converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 201977b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 15, 2013 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.

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