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1 AAT2120 500ma low-noise, step-down converter data sheet skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 general description the AAT2120 switchreg is a 1.8mhz step-down con- verter with an input voltage range of 2.7v to 5.5v and output as low as 0.6v. its low supply current, small size, and high switching frequency make the AAT2120 the ideal choice for portable applications. the AAT2120 delivers up to 500ma of load current, while maintaining a low 45 a no load quiescent current. the 1.8mhz switching frequency minimizes the size of exter- nal components, while keeping switching losses low. the AAT2120 feedback and control delivers excellent load regulation and transient response with a small output inductor and capacitor. the AAT2120 maintains high efficiency throughout the load range. the AAT2120?s unique architecture produces reduced ripple and spectral noise. over-temperature and short-circuit protection safeguard the AAT2120 and sys- tem components from damage. the AAT2120 is available in a pb-free, 8-pin, 2x2mm stdfn package and is rated over the -40c to +85c temperature range. features ? v in range: 2.7v to 5.5v ? v out range: 0.6v to v in ? up to 500ma output current ? up to 96% efficiency ? low noise light load mode ? 45 a typical quiescent current ? 1.8mhz switching frequency ? soft-start control ? over-temperature and current limit protection ? 100% duty cycle low-dropout operation ? <1 a shutdown current ? small external components ? ultra-small stdfn22-8 package ? temperature range: -40c to +85c applications ? bluetooth ? headsets ? cellular phones ? digital cameras ? handheld instruments ? micro hard disk drive ? portable music players ? usb devices typical application 3.0h l1 r 1 118k r 2 59k c 1 4.7f c 2 4.7f en fb vp vin lx pgnd gnd AAT2120 v in v o = 1.8v 500m a
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 2 AAT2120 500ma low-noise, step-down converter data sheet pin descriptions pin # symbol function 1 vp input power pin; connected to the source of the p-channel mosfet. connect to the input capacitor. 2 vin input bias voltage for the converter. 3 gnd non-power signal ground pin. 4 fb feedback input pin. connect this pin to an external resistive divider for adjustable output. 5 n/c no connect. 6 en enable pin. a logic high enables normal operation. a logic low shuts down the converter. 7lx switching node. connect the inductor to this pin. it is connected internally to the drain of both high- and low-side mosfets. 8 pgnd input power return pin; connected to the source of the n-channel mosfet. connect to the output and input capacitor return. ep exposed paddle (bottom); connect to ground directly beneath the package. pin configuration stdfn22-8 (top view) gnd fb vp vin en n/c pgnd lx 3 4 1 2 6 5 8 7
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 3 AAT2120 500ma low-noise, step-down converter data sheet absolute maximum ratings 1 symbol description value units v in input voltage and bias power to gnd 6.0 v v lx lx to gnd -0.3 to v in + 0.3 v v out fb to gnd -0.3 to v in + 0.3 v v en en 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 information symbol description value units p d maximum power dissipation (stdfn22-8) 2 w ? ja thermal resistance 2 (stdfn22-8) 50 c/w 1. stresses above those listed in absolute maximum ratings may cause permanent damage to the device. functional operation at co nditions 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.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 4 AAT2120 500ma low-noise, step-down converter data sheet electrical characteristics 1 v in = 3.6v, 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 uvlo uvlo threshold v in rising 2.3 v hysteresis 70 mv v in falling 1.4 v v out output voltage tolerance 2 i out = 0 to 500ma, v in = 2.7v to 5.5v -3.0 3.0 % v out output voltage range 0.6 v in v i q quiescent current no load 45 85 a i shdn shutdown current en = gnd 1.0 a i lim p-channel current limit 700 ma r ds(on)h high-side switch on resistance 0.59 r ds(on)l low-side switch on resistance 0.42 ? v linereg / ? v in line regulation v in = 2.7v to 5.5v 0.2 %/v v fb feedback threshold voltage accuracy v in = 3.6v 0.591 0.600 0.609 v i fb fb leakage current v out = 1.0v 0.2 a f osc oscillator frequency 1.8 mhz t s startup time from enable to output regulation 100 s t sd over-temperature shutdown threshold 105 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 input low current v in = v en = 5.5v -1.0 1.0 a 1. the AAT2120 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. output voltage tolerance is independent of feedback resistor network accuracy.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 5 AAT2120 500ma low-noise, step-down converter data sheet typical characteristics efficiency vs. load (v out = 3.0v; l = 4.7h) output current (ma) efficiency (%) 40 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 3.6v v in = 4.2v v in = 5.0v load regulation (v out = 3.0v; l = 4.7h) output current (ma) load regulation (%) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 0.1 1 10 100 1000 v in = 3.6v v in = 5.0v v in = 4.2v efficiency vs. load (v out = 1.8v; l = 3.3h) output current (ma) efficiency (%) 40 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 2.7v v in = 3.6v v in = 4.2v load regulation (v out = 1.8v; l = 3.3h) output current (ma) load regulation (%) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 0.1 1 10 100 1000 v in = 4.2v v in = 2.7v v in = 3.6v efficiency vs. load (v out = 1.2v; l = 1.5h) output current (ma) efficiency (%) 40 50 60 70 80 90 100 0.1 1 10 100 100 0 v in = 2.7v v in = 3.6v v in = 4.2v v in = 5.0v load regulation (v out = 1.2v; l = 1.5h) output current (ma) load regulation (%) -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 0.1 1 10 100 v in = 3.6v v in = 4.2v v in = 2.7v v in = 5.0v
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 6 AAT2120 500ma low-noise, step-down converter data sheet typical characteristics soft start (v in = 3.6v; v out = 1.8v; 500ma) time (100s/div) enable and output voltage (top) (v) inductor current (bottom) (a) v o -4 -3 -2 -1 0 1 2 3 4 -0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 v en i lx line regulation (v out = 1.8v) input voltage (v) accuracy (%) -0.30 -0.20 -0.10 0.00 0.10 0.20 0.30 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 i out = 10ma i out = 500ma i out = 250ma i out = 150ma i out = 50ma i out = 0ma output voltage error vs. temperature (v in = 3.6v; v out = 1.8v; i out = 500ma) temperature (c) output error (%) -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 -40 -20 0 20 40 60 80 100 frequency variation vs. input voltage input voltage (v) frequency variation (%) -4 -3 -2 -1 0 1 2 3 4 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 v out = 3.0v v out = 1.8v switching frequency variation vs. temperature (v in = 3.6v; v out = 1.8v) temperature (c) variation (%) -10 -8 -6 -4 -2 0 2 4 6 8 10 -40 -20 0 20 40 60 80 100 no load quiescent current vs. input voltage input voltage (v) supply current (a) 20 25 30 35 40 45 50 55 60 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 85c 25c -40c
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 7 AAT2120 500ma low-noise, step-down converter data sheet typical characteristics p-channel r ds(on) vs. input voltage input voltage (v) r ds(on) (m ) 300 400 500 600 700 800 900 1000 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 100c 85c 120c 25c 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 100c 85c 120c 25c load transient response (1ma to 500ma; v in = 3.6v; v out = 1.8v; c out = 4.7f; c ff = 100pf) time (20s/div) output voltage (top) (v) load and inductor current (bottom) (400ma/div) 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 v o i o i lx load transient response (350ma to 500ma; v in = 3.6v; v out = 1.8v; c out = 4.7f; c ff = 100pf) time (25s/div) output voltage (top) (v) load and inductor current (bottom) (100ma/div) i o 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 1.9 2.0 v o i lx line response (v out = 1.8v @ 500ma) time (25s/div) output voltage (top) (v) input voltage (bottom) (v) 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 v o v in
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 8 AAT2120 500ma low-noise, step-down converter data sheet typical characteristics output ripple (v in = 3.6v; v out = 1.8v; i out = 1ma) time (2s/div) output voltage (ac coupled) (top) (mv) inductor current (bottom) (a) -120 -100 -80 -60 -40 -20 0 20 40 -0.02 0.00 0.02 0.04 0.06 0.08 0.10 0.12 0.14 v o i lx output ripple (v in = 3.6v; v out = 1.8v; i out = 500ma) time (200ns/div) output voltage (ac coupled) (top) (mv) inductor current (bottom) (a) -120 -100 -80 -60 -40 -20 0 20 40 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 v o i lx
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 9 AAT2120 500ma low-noise, step-down converter data sheet functional description the AAT2120 is a high performance 500ma, 1.8mhz monolithic step-down converter designed to operate with an input voltage range of 2.7v to 5.5v. the converter operates at 1.8mhz, which minimizes the size of external components. typical values are 3.3 h for the output inductor and 4.7 f for the ceramic output capacitor. the device is designed to operate with an output voltage as low as 0.6v. power devices are sized for 500ma cur- rent capability while maintaining over 90% efficiency at full load. low current efficiency is maintained at greater than 80% down to 1ma of load current. at dropout, the converter duty cycle increases to 100% and the output voltage tracks the input voltage minus the r ds(on) drop of the p-channel highside mosfet. a high-dc gain error amplifier with internal compensa- tion controls the output. it provides excellent transient response and load/line regulation. soft start eliminates any output voltage overshoot when the enable or the input voltage is applied. control loop the AAT2120 is a 500ma current mode step-down con- verter. the current through the p-channel mosfet (high side) is sensed for current loop control, as well as short- functional block diagram en lx err amp logic dh dl pgnd vp fb gnd voltage reference input vin
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 10 AAT2120 500ma low-noise, step-down converter data sheet circuit and overload protection. a fixed slope compensa- tion signal is added to the sensed current to maintain stability for duty cycles greater than 50%. the peak cur- rent mode loop appears as a voltage-programmed cur- rent source in parallel with the output capacitor. the output of the voltage error amplifier programs the current mode loop for the necessary peak switch current to force a constant output voltage for all load and line conditions. internal loop compensation terminates the transconductance voltage error amplifier output. the error amplifier reference is fixed at 0.6v. soft start / enable soft start increases the inductor current limit point in discrete steps when the input voltage or enable input is applied. it limits the current surge seen at the input and eliminates output voltage overshoot. when pulled low, the enable input forces the AAT2120 into a low-power, non-switching state. the total input current during shut- down is less than 1 a. current limit and over-temperature protection for overload conditions, the peak input current is limit- ed. as load impedance decreases and the output voltage falls closer to zero, more power is dissipated internally, raising the device temperature. thermal protection com- pletely disables switching when internal dissipation becomes excessive, protecting the device from damage. the junction over-temperature threshold is 105c with 15c of hysteresis. under-voltage lockout internal bias of all circuits is controlled via the v in power. under-voltage lockout (uvlo) guarantees sufficient v in bias and proper operation of all internal circuits prior to activation. applications information inductor selection the step-down converter uses peak current mode control 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 AAT2120 is 0.45a/ s. this equates to a slope compensation that is 75% of the inductor cur- rent down slope for a 1.8v output and 3.0 h inductor. 0.75 ? v o m = = = 0.45 l 0.75 ? 1.8v 3.0h a s this is the internal slope compensation for the AAT2120. when externally programming to 3.0v, the calculated inductance is 5.0 h. 0.75 ? v o l = = 1.67 ? v o = 1.67 ? 3.0v = 5.0h m 0.75 ? v o 0.45a s a s a a s in this case, a standard 4.7 h value is selected. for most designs, the AAT2120 operates with an inductor value of 1 h to 4.7 h. table 1 displays inductor values for the AAT2120 with different output voltage options. manufacturer?s specifications list both the inductor dc cur- rent rating, which is a thermal limitation, and the peak current rating, which is determined by the saturation char- acteristics. 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.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 11 AAT2120 500ma low-noise, step-down converter data sheet output voltage (v) l1 ( h) 1.0 1.5 1.2 2.2 1.5 2.7 1.8 3.0 2.5 3.9 3.0 4.7 3.3 5.6 table 1: inductor values. the 3.0 h cdrh2d09 series inductor selected from sumida has a 150m dcr and a 470ma dc current rating. at full load, the inductor dc loss is 9.375mw which gives a 2.08% loss in efficiency for a 250ma, 1.8v 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 in . 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 ?? 1 - = for v in = 2 v o ?? v o v in v o v in 1 4 c in(min) = 1 ?? - esr 4 f s ?? v pp i o always examine the ceramic capacitor dc voltage coeffi- cient 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 maximum input capacitor rms current is: ?? i rms = i o 1 - ?? v o v in v o 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. ?? 1 - = d (1 - d) = 0.5 2 = ?? v o v in v o v in 1 2 for v in = 2 v o i o rms(max) i 2 = the term ?? 1 - ?? v o v in v o v in appears in both the input voltage ripple and input capacitor rms current equations and 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 AAT2120. 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 layout in figure 2. a laboratory test set-up typically consists of two long wires running from the bench power supply to the eval- uation 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 induc- tance cannot be reduced to a level that does not affect the converter performance, a high esr tantalum or alu- minum electrolytic should be placed in parallel with the low esr, esl bypass ceramic. 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. for enhanced
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 12 AAT2120 500ma low-noise, step-down converter data sheet transient response and low temperature operation appli- cation, a 10 f (x5r, x7r) ceramic capacitor is recom- mended to stabilize extreme pulsed load conditions. the output voltage droop due to a load transient is domi- nated 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. within two or three switching cycles, the loop responds and the inductor current increases to match the load current demand. the relationship of the output volt- age droop during the three switching cycles to the output capacitance 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 s 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 resistors r1 and r2 of figure 1 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 suggested value for r2 is 59k . decreased resistor values are nec- essary to maintain noise immunity on the fb pin, result- ing in increased quiescent current. table 2 summarizes the resistor values for various output voltages. ?? ?? r1 = -1 r2 = - 1 59k = 267k v out v ref ?? ?? 3.3v 0.6v with enhanced transient response for extreme pulsed load application, an external feed-forward capacitor, (c3 in figure 1), can be added. v out (v) r2 = 59k r1 (k ) r2 = 221k r1 (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 3.3 267 1000 table 2: adjustable resistor values for step-down converter. thermal calculations there are three types of losses associated with the AAT2120 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 switch- ing devices. at full load, assuming continuous conduction 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 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 dson(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.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 13 AAT2120 500ma low-noise, step-down converter data sheet given the total losses, the maximum junction tempera- ture can be derived from the ja for the stdfn22-8 package which is 50c/w. t j(max) = p total ja + t amb layout the suggested pcb layout for the AAT2120 in an stdfn22-8 package is shown in figures 2, 3, and 4. the following guidelines should be used to help ensure a proper layout. 1. the input capacitor (c1) should connect as closely as possible to vp (pin 1), pgnd (pin 8), and gnd (pin 3) 2. c2 and l1 should be connected as closely as possi- ble. the connection of l1 to the lx pin (pin 7) should be as short as possible. do not make the node small by using narrow trace. the trace should be kept wide, direct and short. 3. the feedback pin (pin 4) 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. feedback resistors should be placed as closely as possible to the fb pin (pin 4) to minimize the length of the high impedance feedback trace. if possible, they should also be placed away from the lx (switching node) and inductor to improve noise immunity. 4. the resistance of the trace from the load return to pgnd (pin 8) and gnd (pin 3) 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. 5. a high density, small footprint layout can be achieved using an inexpensive, miniature, non-shielded, high dcr inductor. r1 adj. r2 59k l1 4.7f c2 4.7f c1 vp 1 gnd 3 n/c 5 en 6 lx 7 pgnd 8 vin 2 fb 4 AAT2120 u1 vin gnd +vout gnd c3 (optional) 100pf lx figure 1: AAT2120 schematic.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 14 AAT2120 500ma low-noise, step-down converter data sheet figure 2: AAT2120 evaluation board figure 3: exploded view of AAT2120 top side layout. evaluation board top side layout. figure 4: AAT2120 evaluation board bottom side layout.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 15 AAT2120 500ma low-noise, step-down converter data sheet step-down converter design example specifications v o = 1.8v @ 250ma, pulsed load ? i load = 200ma v in = 2.7v to 4.2v (3.6v nominal) f s = 1.8mhz t amb = 85c 1.8v output inductor l1 = 1.67 ? v o2 = 1.67 ? 1.8v = 3h s a s a (use 3.0 h; see table 1) for sumida inductor cdrh2d09-3r0, 3.0 h, dcr = 150m . v o v o 1.8 v 1.8v i l1 = ? 1 - = ? 1 - = 190m a l1 ? f s v in 3.0h ? 1.8mhz 4.2v i pkl1 = i o + i l1 = 250ma + 95ma = 345ma 2 p l1 = i o 2 ? dcr = 250ma 2 ? 150m = 9.375mw ? ? ? ? ? ? ? ? 1.8v output capacitor v droop = 0.1v 1 23 1 1.8v (4.2v - 1.8v) 3.0h 1.8mhz 4.2v 23 rms i l1 f s v in(max) = 3 i load v droop f s 3 0.2a 0.1v 1.8mhz c out = = = 3.3f (use 3.3f) = 66marms (v o ) (v in(max) - v o ) = p esr = esr i rms 2 = 5m (66ma) 2 = 21.8w input capacitor input ripple v pp = 25mv c in = = = 1.16f (use 4.7f ) 1 ?? - esr 4 f s ?? v pp i o 1 ?? - 5m 4 1.8mhz ?? 25mv 0.2a i o rms i p = esr i rms 2 = 5m (0.1a) 2 = 0.05mw 2 = = 0.1arms
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 16 AAT2120 500ma low-noise, step-down converter data sheet AAT2120 losses p total + (t sw f s i o + i q ) v in i o 2 (r ds(on)h v o + r ds(on)l [v in -v o ] ) v in = = + (5ns 1.8mhz 0.2a + 45a) 4.2v = 19.71mw 0.2 2 (0.59 1.8v + 0.42 [4.2v - 1.8v]) 4.2v t j(max) = t amb + ja p loss = 85 c + (50 c/w) 26.14mw = 86 c
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 17 AAT2120 500ma low-noise, step-down converter data sheet output voltage v out (v) r2 = 59k r1 (k ) r2 = 221k 1 r1 (k ) l1 ( h) 0.62 ? ? 1.5 0.8 19.6 75 1.5 0.9 29.4 113 1.5 1.0 39.2 150 1.5 1.1 49.9 187 1.5 1.2 59.0 221 1.5 1.3 68.1 261 1.5 1.4 78.7 301 2.2 1.5 88.7 332 2.7 1.8 118 442 3.0/3.3 1.85 124 464 3.0/3.3 2.0 137 523 3.0/3.3 2.5 187 715 3.9/4.2 3.3 267 1000 5.6 table 3: evaluation board component values. manufacturer part number inductance ( h) max dc current (ma) dcr (m ) size (mm) lxwxh type sumida cdrh2d14-1r5 1.5 1800 50 3.0x3.0x1.55 shielded sumida cdrh2d14-2r2 2.2 1500 75 3.0x3.0x1.55 shielded sumida cdrh2d14-2r7 2.7 1350 85 3.0x3.0x1.55 shielded sumida cdrh2d14-3r3 3.3 1200 100 3.0x3.0x1.55 shielded sumida cdrh2d14-3r9 3.9 1100 110 3.0x3.0x1.55 shielded sumida cdrh2d14-4r7 4.7 1000 135 3.0x3.0x1.55 shielded sumida cdrh2d14-5r6 5.6 950 150 3.0x3.0x1.55 shielded sumida cdrh2d11-1r5 1.5 900 54 3.2x3.2x1.2 shielded sumida cdrh2d11-2r2 2.2 780 78 3.2x3.2x1.2 shielded sumida cdrh2d11-3r3 3.3 600 98 3.2x3.2x1.2 shielded sumida cdrh2d11-4r7 4.7 500 135 3.2x3.2x1.2 shielded taiyo yuden nr3010 1.5 1200 80 3.0x3.0x1.0 shielded taiyo yuden nr3010 2.2 1100 95 3.0x3.0x1.0 shielded taiyo yuden nr3010 3.3 870 140 3.0x3.0x1.0 shielded taiyo yuden nr3010 4.7 750 190 3.0x3.0x1.0 shielded fdk mipwt3226d-1r5 1.5 1200 90 3.2x2.6x0.8 chip shielded fdk mipwt3226d-2r2 2.2 1100 100 3.2x2.6x0.8 chip shielded fdk mipwt3226d-3r0 3 1000 120 3.2x2.6x0.8 chip shielded fdk mipwt3226d-4r2 4.2 900 140 3.2x2.6x0.8 chip shielded table 4: suggested inductors and suppliers. manufacturer part number value ( f) voltage rating temp. co. case size murata grm118r60j475ke19b 4.7 6.3 x5r 0603 murata grm188r60j106me47d 10 6.3 x5r 0603 table 5: surface mount capacitors. 1. for reduced quiescent current, r2 = 221k . 2. r2 is opened, r1 is shorted.
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 18 AAT2120 500ma low-noise, step-down converter data sheet ordering information output voltage package marking 1 part number (tape and reel) 2 0.6v stdfn22-8 ydxyy AAT2120ies-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. 1. xyy = assembly and date code. 2. sample stock is generally held on all part numbers listed in bold .
skyworks solutions, inc. ? phone [781] 376-3000 ? fax [781] 376-3100 ? sales@skyworksinc.com ? www.skyworksinc.com 202005a ? skyworks proprietary information ? products and product information are subject to change without notice. ? may 24, 2012 19 AAT2120 500ma low-noise, step-down converter data sheet copyright ? 2012 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. package information 1 stdfn22-8 2.00 all dimensions in millimeters. 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.

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