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aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 1 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 general description the aat2510 is a member of skyworks' total power management ic (tpmic?) product family. it is com- prised of two 1mhz step-down converters designed to minimize external component size and cost. the input voltage ranges from 2.7v to 5.5v. the output voltage ranges from 0.6v to the maximum applied input voltage and is either fixed or externally adjustable. peak current mode control with internal compensation provides a stable converter with low esr ceramic output capacitors for extremely low output ripple. each channel has a low 25 a quiescent operating current, which is critical for maintaining high efficiency at light load. for maximum battery life, each converter?s high-side p-channel mosfet conducts continuously when the input voltage approaches dropout (100% duty cycle operation). both regulators have independent input and enable inputs. the aat2510 is available in a thermally-enhanced 12-pin tdfn33 package, and is rated over the -40c to +85c temperature range. features ? up to 96% efficiency ? 25 a quiescent current per channel ? v in range: 2.7v to 5.5v ? fixed v out range: 0.6v to v in ? adjustable v out range: 0.6v to 2.5v ? output current: 400ma ? low r ds(on) 0.4 ? integrated power switches ? low drop out 100% duty cycle ? 1.0mhz switching frequency ? shutdown current <1 a ? current mode operation ? internal reference soft start ? short-circuit protection ? over-temperature protection ? 3mm x 3mm, < 1mm high ? tdfn33-12 package ? -40c to +85c temperature range applications ? cellular phones ? digital cameras ? handheld instruments ? microprocessor/dsp core/io power ? pdas and handheld computers ? portable media players typical application 4.7 h l1 4.7 f c1 2.5v at 400ma 4.7 h l2 4.7 f c2 1.8v at 400ma 10 f c3 v in = 2.7 - 5.5v 0.1 f c8 fb1 2 en1 1 lx1 11 gnd2 7 lx2 8 gnd1 10 sgnd1 3 vin1 12 vin2 9 sgnd2 6 fb2 5 en2 4 aat2510 u1 l1,l2 sumida cdrh3d16-4r7 c1,c2 murata grm219r61a475ke1 9 c3 murata grm21br60j106ke19 aat2510 efficiency load current (ma) efficiency (%) 60 65 70 75 80 85 90 95 100 0.1 1 10 100 1000 2.5v 1.8v v in = 3.3v with unloaded output disabled
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 2 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 pin descriptions pin # symbol function 1, 4 en1, en2 converter enable input. a logic high enables the converter channel. a logic low forces the channel into shutdown mode, reducing the channel supply current to less than 1 a. this pin should not be left oating. when not actively controlled, this pin can be tied directly to the source voltage (vin1, vin2). 2, 5 fb1, fb2 feedback input pin. for xed output voltage versions, this pin is connected to the converter out- put, forcing the converter to regulate to the speci ed voltage. for adjustable versions, an external resistive divider ties to this point and programs the output voltage to the desired value. 3, 6 sgnd1, sgnd2 signal ground. for external feedback, return the feedback resistive divider to this ground. for internal xed version, tie to the point of load return. see section on pcb layout guidelines and evaluation board layout diagram. 7, 10 gnd2, gnd1 main power ground return. connect to the input and output capacitor return. see section on pcb layout guidelines and evaluation board layout diagram. 8, 11 lx2, lx1 output switching node that connects to the respective output inductor. 9, 12 vin2, vin1 input supply voltage. must be closely decoupled to the respective power gnd. ep exposed paddle (bottom). use properly sized vias for thermal coupling to the ground plane. see section on pcb layout guidelines. pin configuration tdfn33-12 (top view) en1 fb1 sgnd1 1 en2 fb2 sgnd2 vin1 lx1 gnd1 vin2 lx2 gnd2 2 3 4 5 6 12 11 10 9 8 7
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 3 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 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 an fr4 board with exposed paddle connected to ground plane. absolute maximum ratings 1 symbol description value units v in vin1, vin2 to sgnd1, sgnd2, gnd1, and gnd2 6.0 v v lx lx1, lx2 to gnd1, gnd2 -0.3 to v p + 0.3 v v fb fb1 and fb2 to sgnd1, sgnd2, gnd1, and gnd2 -0.3 to v p + 0.3 v v en en1 and en2 to sgnd1, sgnd2, gnd1, and gnd2 -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 information symbol description value units p d maximum power dissipation 2 w ? ja thermal resistance 2 50 c/w
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 4 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 1. the aat2510 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. 2. for adjustable version with higher than 2.5v output, please consult your skyworks representative. electrical characteristics 1 t a = -40c to 85c, unless otherwise noted. typical values are t a = 25c, v in = 3.6v. symbol description conditions min typ max units step-down converter channels v in input voltage 2.7 5.5 v v uvlo uvlo threshold v in rising 2.6 v hysteresis 100 mv v in falling 1.8 v v out output voltage tolerance i out = 0 to 400ma, v in = 2.7 - 5.5v -3.0 +3.0 % v out output voltage range fixed output version 0.6 4.0 v i q quiescent current adjustable output version 2 0.6 2.5 no load, 0.6v adjustable version, per channel 25 50 a i shdn shutdown current en = sgnd = gnd 1.0 a i lim p-channel current limit 600 ma r ds(on)h high side switch on resistance 0.45 ? r ds(on)l low side switch on resistance 0.4 ? i lxlk lx leakage current v in = 5.5v, v lx = 0 to v in , en = sgnd = gnd 1 a ? v linereg line regulation v in = 2.7v to 5.5v 0.2 %/v v fb fb threshold voltage accuracy 0.6v output, no load, t a = 25c 597 600 615 mv i fb fb leakage current 0.6v output 0.2 a r fb fb impedance >0.6v output 250 k ? f osc oscillator frequency t a = 25c 0.7 1.0 1.5 mhz t sd over-temperature shutdown threshold 140 c t hys over-temperature shutdown hysteresis 15 c en v en(l) enable threshold low 0.6 v v en(h) enable threshold high 1.4 v i en input low current v in = v fb = 5.5v -1.0 1.0 a
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 5 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical channel characteristics efficiency vs. load (v out = 2.5v; l = 4.7 h) output current (ma) efficiency (%) 60 70 80 90 100 0.1 1.0 10 100 1000 v in = 3.3v v in = 3.6v v in = 3.0v load regulation (v out = 2.5v; l = 4.7 h) output current (ma) output error (%) -2.0 -1.0 0.0 1.0 2.0 0.1 1.0 10 100 1000 v in = 3.0v v in = 3.3v v in = 3.6v efficiency vs. load (v out = 1.8v; l = 4.7 h) output current (ma) efficiency (%) 50 60 70 80 90 100 0.1 1.0 10 100 1000 v in = 2.7v v in = 3.6v v in = 4.2v dc regulation (v out = 1.8v; l = 4.7 h) output current (ma) output error (%) -2.0 -1.0 0.0 1.0 2.0 0.1 1.0 10 100 1000 v in = 2.7v v in = 3.6v v in = 4.2v frequency vs. input voltage (v out = 1.8v) input voltage (v) frequency variation (%) -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 output voltage error vs. temperature (v in = 3.6v; v o = 1.5v) temperature ( c) output error (%) -2.0 -1.0 0.0 1.0 2.0 -40 -20 0 20 40 60 80 100
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 6 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical channel characteristics switching frequency vs. temperature (v in = 3.6v; v o = 1.5v) temperature ( c) variation (%) -0.20 -0.10 0.00 0.10 0.20 -40 -20 0 20 40 60 80 100 quiescent current vs. input voltage (v o = 1.8v) input voltage (v) supply current ( a) 85 c 25 c -40 c 15 20 25 30 35 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 p-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 300 350 400 450 500 550 600 650 700 750 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 25 c 120 c 100 c 85 c load transient response (30ma - 300ma; v in = 3.6v; v out = 1.8v; c1 = 10 f) output voltage (top) (v) load and inductor current (200ma/div) (bottom) time (25 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 300ma 30ma n-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 300 350 400 450 500 550 600 650 700 750 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 25 c 120 c 100 c 85 c load transient response (30ma - 300ma; v in = 3.6v; v out = 1.8v; c1 = 10 f; c4 = 100pf; see figure 2) output voltage (ac coupled) (top) (v) load and inductor current (200ma/div) (bottom) time (25 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.1 0.0 1.2 1.4 0.8 0.6 1.0 0.2 0.4 -0.2 0.0 300ma 30ma
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 7 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 typical channel characteristics load transient response (30ma - 300ma; v in = 3.6v; v out = 1.8v; c1 = 4.7 f) output voltage (top) (v) load and inductor current (200ma/div) (bottom) time (25 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 300ma 30ma line transient (v out = 1.8v @ 400ma) output voltage (top) (v) input voltage (bottom) (v) time (25 s/div) 1.50 1.55 1.60 1.65 1.70 1.75 1.80 1.85 1.90 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6.5 7.0 line regulation (v out = 1.8v) input voltage (v) accuracy (%) -0.35 -0.3 -0.25 -0.2 -0.15 -0.1 -0.05 0 0.05 0.1 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 i out = 400ma i out = 100ma i out = 10ma soft start (v in = 3.6v; v out = 1.8v; 400ma) enable and output voltage (top) (v) inductor current (bottom) (a) 250 s/div -4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 output ripple (v in = 3.6v; v out = 1.8v; 400ma) output voltage (ac coupled) (top) (mv) inductor current (bottom) (a) time (250ns/div) -120 -100 -80 -60 -40 -20 0 20 40 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 8 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 functional block diagram en1 lx1 err. amp. dh dl gnd1 vin1 fb1 sgnd2 voltage reference control logic en2 lx2 err. amp. dh dl gnd2 comp. logic logic control logic vin2 fb2 sgnd1 voltage reference comp. see note see note note: internal resistor divider included for 1.2v versions. for low voltage versions, the feedback pin is tied directly to the error amplifier input. operation device summary the aat2510 is a constant frequency peak current mode pwm converter with internal compensation. each chan- nel has independent input, enable, feedback, and ground pins with non-synchronized 1mhz clocks. both converters are designed to operate with an input voltage range of 2.7v to 5.5v. the output voltage ranges from 0.6v to the input voltage for the internally fixed version and up to 2.5v for the externally adjustable ver- sion. the 0.6v fixed model shown in figure 1 is also the adjustable version and is externally programmable with a resistive divider as shown in figure 2. the converter mosfet power stage is sized for 400ma load capability with up to 96% efficiency. light load efficiency exceeds 80% at a 500 a load. soft start the aat2510 soft-start control prevents output voltage overshoot and limits inrush current when either the input power or the enable input is applied. when pulled low, the enable input forces the converter into a low-power, non- switching state with a bias current of less than 1 a.
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 9 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 low dropout operation for conditions where the input voltage drops to the out- put voltage level, the converter duty cycle increases to 100%. as 100% duty cycle is approached, the minimum off-time initially forces the high side on-time to exceed the 1mhz clock cycle and reduce the effective switching frequency. once the input drops below the level where the output can be regulated, the high side p-channel mosfet is turned on continuously for 100% duty cycle. at 100% duty cycle, the output voltage tracks the input voltage minus the i*r drop of the high side p-channel mosfet r ds(on) . low supply the under-voltage lockout (uvlo) feature guarantees sufficient v in bias and proper operation of all internal circuitry prior to activation. fault protection for overload conditions, the peak inductor current is lim- ited. thermal protection disables switching when the internal dissipation or ambient temperature becomes excessive. the junction over-temperature threshold is 140c with 15c of hysteresis. applications information inductor selection the step-down converter uses peak current mode con- trol with slope compensation to maintain stability for duty cycles greater than 50%. the output inductor value must be selected so the inductor current down slope meets the internal slope compensation requirements. the internal slope compensation for the adjustable and low-voltage fixed versions of the aat2510 is 0.24a/ sec. this equates to a slope compensation that is 75% of the inductor current down slope for a 1.5v output and 4.7 h inductor. 0.75 ? v o m = = = 0.24 l 0.75 ? 1.5v 4.7 h a sec this is the internal slope compensation for the adjust- able (0.6v) version or low-voltage fixed version. when externally programming the 0.6v version to a 2.5v out- put, the calculated inductance would be 7.5 h. 0.75 ? v o l = = 3 ? v o = 3 ? 2.5v = 7.5 h m 0.75v 0.24a / sec sec a sec a in this case, a standard 10 h value is selected. for high-voltage fixed versions (2.5v and above), m = 0.48a/ sec. table 1 displays inductor values for the aat2510 fixed and adjustable options. 4.7 h l1 4.7 f c1 2.5v at 400ma 4.7 h l2 4.7 f c2 1.8v at 400ma 10 f c3 v in = 2.7 - 5.5v 0.1 f c8 fb1 2 en1 1 lx1 11 gnd2 7 lx2 8 gnd1 10 sgnd1 3 vin1 12 vin2 9 sgnd2 6 fb2 5 en2 4 aat2510 u1 l1, l2 sumida cdrh3d16-4r7 c1, c2 murata grm219r61a475ke1 9 c3 murata grm21br60j106ke19 4.7 h l1 10 f c1 1.8v 118k r1 59.0k r2 100pf c4 10 h l2 10 f c2 2.5v 59.0k r4 100pf c5 10 f c3 v in 187k r3 fb1 2 en1 1 lx1 11 gnd2 7 lx2 8 gnd1 10 sgnd1 3 vin1 12 vin2 9 sgnd2 6 fb2 5 en2 4 aat2510 u1 0.1 f c8 figure 1: aat2510 fixed output. figure 2: aat2510 adjustable output with enhanced transient response.
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 10 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 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. the 4.7 h cdrh3d16 series inductor selected from sumida has a 105m ? dcr and a 900ma dc current rat- ing. at full load, the inductor dc loss is 17mw which gives a 2.8% loss in efficiency for a 400ma 1.5v output. input capacitor select a 4.7 f to 10 f x7r or x5r ceramic capacitor for the input. to estimate the required input capacitor size, determine the acceptable input ripple level (v pp ) and solve for c. the calculated value varies with input voltage and is a maximum when v in is double the output voltage. ?? ? 1 - ?? v o v in c in = v o v in ?? - esr ? f s ?? v pp i o this equation provides an estimate for the input capaci- tor required for a single channel. con guration output voltage inductor slope compensation 0.6v adjustable with external resistive divider 0.6v to 2.0v 4.7 h 0.24a/ sec 2.5v 10 h 0.24a/ sec fixed output 0.6v to 2.0v 4.7 h 0.24a/ sec 2.5v to 3.3v 4.7 h 0.48a/ sec table 1: inductor values. the equation below solves for input capacitor size for both channels. it makes the worst-case assumptions that both converters are operating at 50% duty cycle and are synchronized. c in = 1 ?? - esr ? 4 ? f s ?? v pp i o1 + i o2 because the aat2510 channels will generally operate at different duty cycles and are not synchronized, the actu- al ripple will vary and be less than the ripple (v pp ) used to solve for the input capacitor in the equation above. always examine the ceramic capacitor dc voltage coef- ficient characteristics when selecting the proper value. for example, the capacitance of a 10 f 6.3v x5r ceram- ic capacitor with 5v dc applied is actually about 6 f. the maximum input capacitor rms current is: ?? i rms = i o1 1 - + i o2 1 - ?? v o1 v in v o1 v in ?? ?? v o2 v in v o2 v in ?? ?? ?? ?? the input capacitor rms ripple current varies with the input and output voltage and will always be less than or equal to half of the total dc load current of both convert- ers combined. i o1(max) + i o2(max) rms(max) i 2 = this equation also makes the worst-case assumption that both converters are operating at 50% duty cycle and are synchronized. since the converters are not syn- chronized and are not both operating at 50% duty cycle, the actual rms current will always be less than this. losses associated with the input ceramic capacitor are typically minimal. the term ?? 1 - ?? v o v in v o v in appears in both the input voltage ripple and input capacitor rms current equations. it is a maximum when v o is twice v in . this is why the input voltage ripple and the input capacitor rms current ripple are a maximum at 50% duty cycle. the input capacitor provides a low impedance loop for the edges of pulsed current drawn by the aat2510. low esr/ esl x7r and x5r ceramic capacitors are ideal for this function. to minimize the stray inductance, the capacitor 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 (c3 and c8) can be seen in the evaluation board layout in figure 4. since decoupling must be as close to the input pins as possible, it is necessary to use two decoupling capaci- tors. c3 provides the bulk capacitance required for both converters, while c8 is a high frequency bypass capaci- tor for the second channel (see c3 and c8 placement in figure 4).
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 11 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 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 during load tran- sients. errors in the loop phase and gain measurements can also result. since the inductance of a short printed circuit board 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 induc- tance cannot be reduced to a level that does not affect converter performance, a high esr tantalum or alumi- num electrolytic capacitor should be placed in parallel with the low esr, esl bypass ceramic capacitor. this dampens the high q network and stabilizes the system. 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 output voltage droop due to a load transient is dominated by the capacitance of the ceramic output capacitor. during a step increase in load current the ceramic output capacitor alone supplies the load current until the loop responds. as the loop responds, the induc- tor current increases to match the load current demand. this typically takes two to three switching cycles and can be estimated by: c out = 3 i load v droop f s once the average inductor current increases to the dc load level, the output voltage recovers. the above equa- tion establishes a limit on the minimum value for the output capacitor with respect to load transients. 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. the maximum output capacitor rms ripple current is given by: 1 23 v out (v in(max) - v out ) rms(max) i l f v in(max) = dissipation due to the rms current in the ceramic output capacitor esr is typically minimal, resulting in less than a few degrees rise in hot spot temperature. adjustable output resistor selection for applications requiring an adjustable output voltage, the 0.6v version can be programmed externally. resistors r1 through r4 of figure 2 program the output to regu- late at a voltage higher than 0.6v. to limit the bias cur- rent required for the external feedback resistor string, the minimum suggested value for r2 and r4 is 59k ? . although a larger value will reduce the quiescent cur- rent, it will also increase the impedance of the feedback node, making it more sensitive to external noise and interference. table 2 summarizes the resistor values for various output voltages with r2 and r4 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 ref ?? ?? 1.5v 0.6v the adjustable version of the aat2510 in combination with an external feedforward capacitor (c4 and c5 of figure 2) delivers enhanced transient response for extreme pulsed load applications. the addition of the feedforward capacitor typically requires a larger output capacitor (c1 and c2) for stability.
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 12 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 v out (v) r2, r4 = 59k ? r1, r3 (k ? ) r2, r4 = 221k ? r1, r3 (k ? ) 0.8 19.6 75 0.9 29.4 113 1.0 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 1.85 124 464 2.0 137 523 2.5 187 715 table 2: adjustable resistor values for use with 0.6v version. thermal calculations there are three types of losses associated with the aat2510 converter: switching losses, conduction losses, and quiescent current losses. conduction losses are associated with the r ds(on) characteristics of the power output switching devices. switching losses are dominat- ed by the gate charge of the power output switching devices. at full load, assuming continuous conduction mode (ccm), a simplified form of the dual converter losses is given by: p total i o1 2 (r dson(hs) v o1 + r dson(ls) [v in -v o1 ]) v in = + + (t sw f [i o1 + i o2 ] + 2 i q ) v in i o2 2 (r dson(hs) v o2 + r dson(ls) [v in -v o2 ]) v in i q is the aat2510 quiescent current for one channel and t sw is used to estimate the full load switching losses. for the condition where channel one is in dropout at 100% duty cycle, the total device dissipation reduces to: p total = i o1 2 r dson(hs) + + (t sw f i o2 + 2 i q ) v in i o2 2 (r dson(hs) v o2 + r dson(ls) [v in -v o2 ]) 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 tempera- ture can be derived from the ? ja for the tdfn33-12 pack- age which is 50c/w. t j(max) = p total ? ja + t am b pcb layout the following guidelines should be used to insure a proper layout. 1. due to the pin placement of v in for both converters, proper decoupling is not possible with just one input capacitor. the large input capacitor c3 should con- nect as closely as possible to v p and gnd, as shown in figure 4. the additional input bypass capacitor c8 is necessary for proper high frequency decoupling of the second converter. 2. the output capacitor and inductor should be con- nected as closely as possible. the connection of the inductor to the lx pin should also be as short as pos- sible. 3. the feedback trace 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. this prevents noise from being coupled into the high impedance feedback node. 4. the resistance of the trace from the load return to gnd should be kept to a minimum. this will help to minimize any error in dc regulation due to differ- ences in the potential of the internal signal ground and the power ground. 5. for good thermal coupling, pcb vias are required from the pad for the tdfn paddle to the ground plane. the via diameter should be 0.3mm to 0.33mm and positioned on a 1.2 mm grid.
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 13 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 design example specifications v o1 = 2.5v @ 400ma (adjustable using 0.6v version), pulsed load ? i load = 300ma v o2 = 1.8v @ 400ma (adjustable using 0.6v version), pulsed load ? i load = 300ma v in = 2.7v to 4.2v (3.6v nominal) f s = 1.0 mhz t amb = 85c 2.5v v o1 output inductor l1 = 3 ? v o1 = 3 ? 2.5v = 7.5 h sec a sec a (see table 1) for sumida inductor cdrh3d16, 10 h, dcr = 210m ? . v o v o1 2.5 v 2.5v i1 = ? 1 - = ? 1 - = 100ma l1 ? f v in 10 h ? 1.0mhz 4.2v i pk1 = i o1 + i1 = 0.4a + 0.05a = 0.45a 2 p l1 = i o1 2 ? dcr = 0.4a 2 ? 210m = 34mw ? ? ? ? ? ? ? ? 1.8v v o2 output inductor l2 = 3 ? v o2 = 3 ? 1.8v = 5.4 h sec a sec a (see table 1) for sumida inductor cdrh3d16, 4.7 h, dcr = 105m ? . v o2 v o2 1.8 v 1.8v i2 = ? 1 - = ? 1 - = 218ma l ? f v in 4.7 h ? 1.0mhz 4.2v i pk2 = i o2 + i2 = 0.4a + 0.11a = 0.51a 2 p l2 = i o2 2 ? dcr = 0.4a 2 ? 105m = 17mw ? ? ? ? ? ? ? ?
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 14 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 2.5v output capacitor 1 23 1 2.5v (4.2v - 2.5v) 10 h 1mhz 4.2v 23 rms(max) i l f v in(max) = 3 i load v droop f s 3 0.3a 0.2v 1mhz c out = = = 4.5 f = 29marms (v out ) (v in(max) - v out ) = p esr = esr i rms 2 = 5m (29ma) 2 = 4.2 w 1.8v output capacitor 1 23 1 1.8v (4.2v - 1.8v) 4.7 h 1.0mhz 4.2v 23 rms(max) i l f v in(max) = 3 i load v droop f s 3 0.3a 0.2v 1mhz c out = = = 4.5 f = 63marms (v out ) (v in(max) - v out ) = p esr = esr i rms 2 = 5m (63ma) 2 = 20 w input capacitor input ripple v pp = 25mv. c in = = = 9.5 f 1 ?? - esr ? 4 ? f s ?? v pp i o1 + i o2 1 ?? - 5m ? 4 ? 1mhz ?? 25mv 0.8a i o1 + i o2 rms(max) i p = esr i rms 2 = 5m (0.4a) 2 = 0.8mw 2 = = 0.4arms
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 15 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 aat2510 losses the maximum dissipation occurs at dropout where v in = 2.7v. all values assume an ambient temperature of 85c and a junction temperature of 120c. p total + (t sw f i o2 + 2 i q ) v in i o1 2 (r dson(hs) v o1 + r dson(ls) (v in -v o1 )) + i o2 2 (r dson(hs) v o2 + r dson(ls) (v in -v o2 )) v in = = + 5ns 1mhz 0.4a + 60 a) 2.7v = 240mw 0.4 2 (0.725 2.5v + 0.7 (2.7v - 2.5v)) + 0.4 2 (0.725 1.8v + 0.7 (2.7v - 1.8v)) 2.7v t j(max) = t amb + ja ? p loss = 85 c + (50 c/w) ? 240mw = 97 c
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 16 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 1. for enhanced transient configuration c5, c4 = 100pf and c1, c2 = 10 f. see table 3 l2 4.7 f c2 1 v o1 gnd see table 3 r1 59.0k r2 c4 1 fb1 2 en1 1 lx1 11 gnd2 7 lx2 8 gnd1 10 sgnd1 3 vin1 12 vin2 9 sgnd2 6 fb2 5 en2 4 aat2510 u1 10 f c3 see table 3 l1 v o2 gnd lx2 see table 3 r3 59.0k r4 c5 1 4.7 f c1 1 lx1 123 output 1 enable 321 output 2 enable v in 0.01 f c7 0.01 f c6 0.1 f c8 figure 3: aat2510 evaluation board schematic. figure 4: aat2510 evaluation board top side. figure 5: aat2510 evaluation board bottom side.
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 17 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 1. for reduced quiescent current, r2 and r4 = 221k ? . adjustable version (0.6v device) v out (v) r2, r4 = 59k ? r1, r3 (k ? ) r2, r4 = 221k ? 1 r1, r3 (k ? ) l1, l2 ( h) 0.8 19.6 75.0 4.7 0.9 29.4 113 4.7 1.0 39.2 150 4.7 1.1 49.9 187 4.7 1.2 59.0 221 4.7 1.3 68.1 261 4.7 1.4 78.7 301 4.7 1.5 88.7 332 4.7 1.8 118 442 4.7 1.85 124 464 4.7 2.0 137 523 4.7 or 6.8 2.5 187 715 10 fixed version v out (v) r2, r4 not used r1, r3 (k ? ) l1, l2 ( h) 0.6-3.3v 0 4.7 table 3: evaluation board component values. manufacturer part number inductance ( h) max dc current (a) dcr ( ? ) size (mm) lxwxh type sumida cdrh3d16-4r7 4.7 0.90 0.11 3.8x3.8x1.8 shielded sumida cdrh3d16-100 10 0.55 0.21 3.8x3.8x1.8 shielded murata lqh32cn4r7m23 4.7 0.45 0.20 2.5x3.2x2.0 non-shielded murata lqh32cn4r7m33 4.7 0.65 0.15 2.5x3.2x2.0 non-shielded murata lqh32cn4r7m53 4.7 0.65 0.15 2.5x3.2x1.55 non-shielded coilcraft lpo6610-472 4.7 1.10 0.20 5.5x6.6x1.0 1mm coilcraft lpo3310-472 4.7 0.80 0.27 3.3x3.3x1.0 1mm coiltronics sdrc10-4r7 4.7 1.53 0.117 4.5x3.6x1.0 1mm shielded coiltronics sdr10-4r7 4.7 1.30 0.122 5.7x4.4x1.0 1mm shielded coiltronics sd3118-4r7 4.7 0.98 0.122 3.1x3.1x1.85 shielded coiltronics sd18-4r7 4.7 1.77 0.082 5.2x5.2x1.8 shielded table 4: typical surface mount inductors. manufacturer part number value voltage temp. co. case murata grm219r61a475ke19 4.7 f 10v x5r 0805 murata grm21br60j106ke19 10uf 6.3v x5r 0805 murata grm21br60j226me39 22uf 6.3v x5r 0805 table 5: surface mount capacitors.
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 18 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 2013 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . ordering information package voltage marking 1 part number (tape and reel) 2 channel 1 channel 2 tdfn33-12 0.6v 0.6v obxyy AAT2510IWP-AA-T1 tdfn33-12 0.6v 3.3v pnxyy aat2510iwp-aw-t1 tdfn33-12 1.8v 1.2v pexyy aat2510iwp-ie-t1 tdfn33-12 1.8v 1.5v otxyy aat2510iwp-ig-t1 tdfn33-12 1.8v 1.6v qjxyy aat2510iwp-ih-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. legend voltage code adjustable (0.6v) a 0.9 b 1.2 e 1.5 g 1.8 i 1.9 y 2.5 n 2.6 o 2.7 p 2.8 q 2.85 r 2.9 s 3.0 t 3.3 w 4.2 c
aat2510 dual 400ma, 1mhz step-down dc/dc converter data sheet 19 skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202020b ? skyworks proprietary information ? products and product information are subject to change without notice. ? mar ch 19, 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. 1. 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 c onnection. package information tdfn33-12 1 top view bottom view detail "a" side view 3.00 0.05 index area detail "a" 1.70 0.05 3.00 0.05 0.05 0.05 0.23 0.05 0.75 0.05 2.40 0.05 pin 1 indicator (optional) 0.40 0.05 0.45 0.05 0.23 0.05 0.1 ref c0.3 all dimensions in millimeters.

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