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aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 1 chargepump ? general description the aat3183 is a high efficiency step-down charge pump converter providing up to 300ma of output current. the 1/2x (gain) charge pump converter topology provides enhanced efficiency over conven- tional ldo regulators and requires only three low cost ceramic capacitors. no inductor is required; saving space and cost when compared to inductive switching regulators. the aat3183 typically consumes 35a of no load (zero output current) quiescent current, making it ideal for portable battery powered systems. shutdown current is less than 1a. the aat3183 soft-start prevents excessive inrush current while providing monotonic turn-on charac- teristics. the device includes integrated short-cir- cuit and over-temperature (thermal) protection to safeguard system components. the aat3183 is available in a pb-free 2.0x2.1mm sc70jw-8 package. operating temperature range is -40oc to +85oc. features ?v in range: 2.7v to 5.5v ?v out : 1.5v ? 300ma maximum output current ? ultra-small solution for portable applications small footprint only three external ceramic capacitors required no inductor ? high efficiency over the output current range ? excellent transient performance ? 35a typical quiescent current ? <1.0a shutdown current ? up to 2mhz switching frequency ? integrated soft-start ? short-circuit and thermal protection ? 2.0x2.1mm sc70jw-8 package ? -40oc to 85oc temperature range applications ? camcorders ? digital still cameras ? dsp core supplies ? pdas, handheld devices, notebook pcs ? smart phones typical application aat3183 c1- c1+ en in out gnd c out 4.7f c in 1f c fly 1f v in v enable v ou t
aat3183 300ma inductorless step-down converter 2 3183.2007.07.1.2 pin descriptions pin configuration sc70jw-8 (top view) pin # symbol function 1 out charge pump converter output. requires a ceramic capacitor to ground. 2 c1+ flying capacitor positive terminal. connect flying capacitor between c1+ and c1-. 3 c1- flying capacitor negative terminal. connect flying capacitor between c1+ and c1-. 4 in charge pump converter input. requires a ceramic capacitor to ground. 5 en enable pin. active high. 6, 7, 8 gnd ground. c1+ c1- in gnd gnd gnd en out 1 2 3 45 6 7 8
aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 3 absolute maximum ratings 1 thermal information symbol description value units v in input voltage to ground -0.3 to 6.0 v v en enable voltage to ground -0.3 to 6.0 v t j operating junction temperature range 2 -40 to 150 c t s storage temperature range -65 to 150 c t lead maximum soldering temperature (at leads, 10 sec) 300 c symbol description value units ja thermal resistance 3 160 c/w p d maximum power dissipation at t a = 25c 625 mw 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 tim e. 2. t j is calculated from the ambient temperature t a and power dissipation p d according to the following formula: t j = t a + p d x ja . 3. mounted on an fr4 board.
aat3183 300ma inductorless step-down converter 4 3183.2007.07.1.2 electrical characteristics 1 v in = 3.6v, c in = c fly = 1.0f, c out = 4.7f, t a = -40c to +85c, unless otherwise noted. typical values are at t a = 25c. symbol description conditions min typ max units v in input voltage 2.7 5.5 v v out output voltage accuracy no load, t a = 25c 1.485 1.500 1.515 v no load 1.470 1.500 1.530 v in rising 1.5 2 v uvlo under-voltage lockout (uvlo) hysteresis 0.15 v v in falling 1.3 i out output current 300 ma i q quiescent current v en = v in , no load 35 60 a shutdown current v en = gnd 1 i out = 300ma 12 i out = 150ma 16 v pp output voltage ripple i out = 100ma 17 mv i out = 10ma 17 v out / line regulation mv/v v in 3.2v v in 5.5v, i out = 50ma 2.9 v out / load regulation 0ma i out 150ma 0.053 mv/ma i out t ss soft-start time 100 s f clk clock frequency i out = 300ma 2 mhz v en(l) enable threshold low 0.4 v v en(h) enable threshold high 1.4 v i en en input leakage 1a r out output impedance 1 t sd over-temperature shutdown threshold 150 c t hys over-temperature shutdown hysteresis 15 c 1. the aat3183 is guaranteed to meet performance specifications over the -40c to +85c operating temperature range and is assu red by design, characterization, and correlation with statistical process controls.
aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 5 typical characteristics no load quiescent current vs. input voltage (v out = 1.5v; no load) input voltage (v) supply current (a) 0 10 20 30 40 50 60 70 80 90 100 3.2 3.7 4.2 4.7 5.2 85 c -40 c 25 c output error vs. input voltage (v out = 1.5v) input voltage (v) output error (%) -10 -8 -6 -4 -2 0 2 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 150ma 50ma 10ma .001ma efficiency vs. input voltage (v out = 1.5v) input voltage (v) efficiency (%) 0 10 20 30 40 50 60 70 80 90 100 2.7 3.1 3.5 3.9 4.3 4.7 5.1 5.5 300ma 50ma output voltage error vs. temperature (v in = 3.6v; v out = 1.5v; i out = 150ma) temperature (c) output voltage error (mv) -8.0 -6.0 -4.0 -2.0 0.0 2.0 4.0 6.0 8.0 -40 -25 -10 5 20 35 50 65 80 9 5 output error vs. output current (v out = 1.5v) output current (ma) output error (%) -3 -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 0.1 1 10 100 100 0 v in = 4.2v v in = 3.6v v in = 5.0v v in = 5.5v efficiency vs. output current (v out = 1.5v) output current (ma) efficiency (%) 0 10 20 30 40 50 60 70 80 90 0.1 1 10 100 100 0 v in = 5.5v v in = 5.0v v in = 4.2v v in = 3.6v
aat3183 300ma inductorless step-down converter 6 3183.2007.07.1.2 typical characteristics output ripple (v out = 1.5v; i out = 300ma) time (500ns/div) output ripple (v) 1.46 1.47 1.48 1.49 1.5 1.51 1.52 1.53 1.54 output ripple (v out = 1.5v; i out = 150ma) time (500ns/div) output ripple (v) 1.46 1.47 1.48 1.49 1.5 1.51 1.52 1.53 1.54 line transient (v in = 3.6v to 4.2v) time (500s/div) output voltage (top) (v) input voltage (bottom) (v) 1.47 1.475 1.48 1.485 1.49 1.495 1.5 1.505 1.51 2.9 3.4 3.9 4.4 4.9 5.4 5.9 6.4 6.9 load transient response (v in = 3.6v; v out = 1.5v; i out = 5ma to 150ma) time (50s/div) output voltage (top) (v) output current (bottom) (a) 1.38 1.4 1.42 1.44 1.46 1.48 1.5 1.52 1.54 -0.1 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 output impedance vs. input voltage input voltage (v) output impedance ( ) 0.6 0.9 1.2 1.5 1.8 2.7 2.9 3.1 3.3 3.5 3.7 3.9 4.1 85 c 25 c -40 c output voltage ripple vs. input voltage (c in /c fly = 1f; c out = 4.7f; i out = 300ma) input voltage (v) output voltage ripple (mvpp) 0 10 20 30 40 50 60 70 80 90 100 3 3.6 4.2 4.8 5.4 6 no post filter 100pf post filter
typical characteristics aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 7 short circuit (v in = 3.6v; v out = 1.5v) time (100s/div) output voltage (top) (v) load current (bottom) (a) -2.00 -1.50 -1.00 -0.50 0.00 0.50 1.00 1.50 2.00 -0.50 0.00 0.50 1.00 1.50 2.00 2.50 3.00 3.50 soft start (v in = 3.6v; i out = 150ma) time (50s/div) enable voltage (top) (v) output voltage (bottom) (v) -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 -0.5 0 0.5 1 1.5 2 2.5 3 3.5
aat3183 300ma inductorless step-down converter 8 3183.2007.07.1.2 functional block diagram functional description the aat3183 is a 1/2x (gain) charge pump con- verter providing an output voltage which is less than the input voltage. the step-down (buck) charge pump converter provides a regulated out- put voltage for input voltages greater than 2x the output voltage plus the required input voltage headroom (see the applications information sec- tion for more details). the output current range is 0ma (no load) to 300ma. the aat3183 provides an ultra-small dc-dc solu- tion achieving improved efficiency over ldo step- down regulators. the high switching frequency allows the use of small external capacitors. only three ceramic capacitors are required to achieve a complete step-down converter solution. output regulation is maintained with a pulse fre- quency modulation (pfm) control scheme. pfm compensates for input voltage and output current variations by modulating the frequency of charge pump switching intervals. switching frequency increases with high output currents (heavy loads) and decreases with low output currents (light loads); with a maximum switching frequency of 2mhz. pfm control provides decreased switching losses and increased efficiency with light loads. this extends battery life under lightly loaded oper- ating conditions. the aat3183 responds quickly to changes in line voltage and/or output current, providing stable operation with excellent line and load transient behavior. no load (zero output current) quiescent current is 35a (typical). when disabled, the device con- sumes less than 1a of current (shutdown). integrated soft-start limits inrush current, maintains monotonic turn-on characteristics and eliminates output voltage overshoot. the device includes short-circuit protection and a self-recovering over- temperature (thermal) protection. v ref ou t c1- c1+ in gnd charge transfer en oscillator, soft start thermal protection, current limit
aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 9 charge pump operation the aat3183 step-down charge pump is imple- mented using a fixed 1/2x (gain) converter topolo- gy. this configuration allows efficient energy trans- fer with a single ceramic flying capacitor. the arrangement of the internal switches requires that the voltage on the flying capacitor is greater than the output voltage plus the input voltage headroom to account for a parasitic voltage drop. energy is transferred to the flying capacitor and out- put during alternate charge and discharge inter- vals. the amount of energy transferred from the input voltage source to flying capacitor is proportion- al to the differential voltage across the flying capaci- tor (v diff = v in - v out ) which occurs during the charge interval multiplied by the switching frequen- cy. the step-down charge pump transfers energy to the output during both the charge and discharge intervals. figure 1 illustrates the energy transfer mechanism during charge and discharge intervals. pfm control compensates for changes in the input voltage and output current by modulating the fre- quency of switching intervals to maintain the desired output voltage. the output voltage is sensed through an internal resistor divider and compared against a reference voltage by an error amplifier. as the output voltage decreases, the voltage at the input to the error amplifier decreas- es. the error signal increases the effective switch- ing frequency; providing increased current to the output current thus maintaining the desired output voltage. at light loads, the effective switching fre- quency is greatly reduced which maintains output regulation while minimizing switching losses. operating efficiency () is defined as the output power divided by the input power. with a constant output current and 1/2x (gain) operation, the input current is constant regardless of input voltage. the input current is equal to 50% [1/2x (gain)] of the output current. figure 1a: step-down charge figure 1b: step-down charge pump charge interval. pump discharge interval. = (v out i out ) (v in i in ) = p in p out = (v out i out ) (v in ?i out ) = 2 v out v in i in = ?i out
aat3183 300ma inductorless step-down converter 10 3183.2007.07.1.2 a conventional ldo regulator maintains input cur- rent which is equal to the output current. operation efficiency () of an ldo regulator is as follows: therefore, the aat3183 provides a 100% efficien- cy improvement over conventional ldo regulators; as illustrated in figure 2. figure 2: aat3183 efficiency comparison vs. ldo. under-voltage lockout under-voltage lockout (uvlo) circuitry monitors the input voltage (v in ) and ensures that the device will remain in standby (v out = 0v) until a valid v in is present. when v in is less than 1.5v (typical), the input current is less than 1a and the output voltage (v out ) remains at 0v, regardless of the status of the enable pin (en). typically, the uvlo turn-on thresh- old is 150mv greater than the uvlo turn-off thresh- old. uvlo hysteresis minimizes spurious under- voltage detection and eliminates output glitches. shutdown and soft-start the aat3183 offers an enable pin (en). when v en is below 0.4v (maximum), the device is in standby (shutdown) mode and draws less than 1a of input current. the output will remain at 0v when en volt- age is low (v en 0.4v). when en is connected to a voltage greater than 1.4v (minimum), the aat3183 will initiate soft-start and resume normal operation. the product features built-in soft-start circuitry to reduce inrush current and eliminate output voltage overshoot. the soft-start circuitry is enabled when input uvlo conditions are satisfied and the en volt- age is high (v en 1.4v). if en is tied to in, the soft start is initiated when uvlo conditions are satisfied. the soft-start circuitry ramps up the output voltage in a controlled manner and minimizes output over- shoot. start-up time from en positive transitioning (v en : 0.4v to 1.4v) to output (v out ) in regulation is 100s (typical). thermal and short-circuit protection high device temperature may result at elevated ambient temperatures or in cases where high output current causes self heating of the device. the device will disable all switching of the charge pump when the internal junction temperature exceeds 150c (typi- cal). the device will restart and enable the soft-start sequence when the temperature is reduced 15c. this hysteresis ensures that the absolute device temperature is maintained below the over-tempera- ture threshold and protects the device from damage. in the event of a short circuit, an internal current limit is activated and limits the output current to 1a (typical). this current is maintained until the output fault condition is removed or device over-tempera- ture is reached. under sustained short-circuit con- ditions, the device will typically reach over-temper- ature and latch off. the device will cool down after a short period and continue to oscillate between active and over-temperature protection states until the fault is removed. under these worst case con- ditions, the device average junction temperature will be less than 150c. efficiency vs. output current (v in = 3.6v; v out = 1.5v) output current (ma) efficiency (%) 10 20 30 40 50 60 70 80 90 0 50 100 150 200 250 300 ldo aat3183 = (v out i out ) (v in i in ) = p in p out = (v out i out ) (v in i out ) = v out v in i in = i out
aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 11 applications information input voltage headroom the input voltage headroom is the required mini- mum input voltage in excess of 2x the output volt- age. the following equation can be used to calcu- late the required input voltage headroom: v hr : input voltage headroom i out : output current r out : output impedance (see output impedance vs. input voltage performance graph in the typical characteristics section of this datasheet) m: charge pump gain [aat3183: ?] design example: aat3183 application conditions: i out = 200ma (max) v out = 1.5v what is the required minimum input voltage? analysis: minimum input voltage: input voltage headroom: output voltage: v out = 1.5v minimum input voltage: v in(min) = 0.4v + 2 1.5v = 3.4v solution: the required minimum input voltage is 3.4v. capacitor selection the aat3183 requires three external capacitors; c in , c fly and c out . the capacitor size and type can have a significant impact on charge pump per- formance, including input and output ripple, stabili- ty and operating efficiency. surface-mount x5r multi-layer ceramic (mlc) capacitors are a suitable choice due to their small size and 15% capacitance tolerance over the operating temperature range -55oc to +85oc. x7r mlc capacitors provide similar performance over the extended temperature range -55oc to +125oc. initial tolerance of 10% is recommended. mlc capacitors offer superior size (high energy density), low equivalent series resistance (esr), and low equivalent series inductance (esl) when com- pared to tantalum and aluminum electrolytic capac- itor varieties. in addition, mlc capacitors are not polarized which simplifies placement on the printed circuit board. negligible circuit losses and fast charge/discharge rates are possible with mlc capacitors due to their low esr, which is typically less than 10m. switching noise is minimized due to their low esl which produces voltage spikes due to the fast switching current events in charge pump converters. esl is typically less than 1nh in mlc capacitors. mlc capacitance is reduced with an increasing dc bias voltage. capacitance derating varies with case size, voltage rating and vendor. it is recom- mended that circuit performance, including output current capability and input/output voltage ripple, be verified under worst-case operating conditions. the capacitor combinations listed in table 1 are suit- able for output currents up to 220ma and 300ma. smaller capacitors may be considered for applica- tions requiring less than 300ma output current. smaller solution size can be achieved at the cost of increased input and output voltage ripple and decreased output current capability. c in , c fly and c out should be located close to the aat3183 device in order to minimize stray para- sitics; specifically esr and esl due to pcb layout traces. see the pcb layout guidelines section of this datasheet for details. v hr = (i out r out ) m v in(min) = v hr + 2 v out v hr = (i out r out ) m = = 0.4v (0.2a 1) ?
aat3183 300ma inductorless step-down converter 12 3183.2007.07.1.2 the input capacitor (c in ) is required to maintain low input voltage ripple as well as minimize noise cou- pling to nearby circuitry. the size of the required input capacitor can vary, and depends on the source impedance of the input voltage source. a small 1f to 2.2f mlc input capacitor is suitable in most applications. mlc capacitors sized as small as 0402 are available which meet these requirements. the flying capacitor (c fly ) transfers energy to the output during both charge and discharge inter- vals. c fly is sized to maintain the maximum output load and maintain acceptable output voltage ripple at the minimum input voltage. the ratio c out to c fly is determined by the input to output voltage ratio and should be maintained near 5:1 for best performance across the operating range. table 1: aat3183 capacitor size selection chart (see table 2 for corresponding manufacturer part numbers). table 2: ceramic capacitors for the 300ma aat3183 step-down charge pump converter. input capacitor output capacitor input [1f(min)] and flying capacitors maximum output current i out (ma) size c in (f/v) size c out (f/v) size c fly (f/v) 0402 2.2/6.3 0603 2.2/6.3 0402 0.47/10 220 0603 4.7/6.3 0603 4.7/6.3 0402 1/10 300 input and output capacitors input [1f(min)] and flying capacitors c in / c out value voltage (size) mfg part number c fly value voltage (size) mfg part number 2.2f 16v (0603) tdk c1608x5r1c225k 0.47f 10v (0402) tdk c1005x5r1a474k 4.7f 10v (0603) tdk c1608x5r1a475k 1f 10v (0402) tdk c1005x5r1a105k 2.2f 16v (0603) murata grm188r61c225k 0.47f 10v (0402) murata grm155r61a474k 4.7f 6.3v (0603) murata grm188r60j475k 1f 10v (0402) murata grm155r61a105k 2.2f 16v (0603) taiyo-yuden emk107bj225ka 0.47f 10v (0402) taiyo-yuden lmk105bj474kv 4.7f 10v (0603) taiyo-yuden lmk107bj475ka 1f 16v (0603) taiyo-yuden emk107bj105ka
aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 13 input and output voltage ripple: charge pump operation the aat3183 minimizes switching noise with pfm control. pfm switches only when required to main- tain the output load, reducing the total switching noise. pfm control generates a small amount of v in and v out regulation ripple (v pfm ) due to the charge and discharge of the input and output capacitors. additional voltage ripple is due to the parasitic resistance and inductance distributed on circuit traces and within the input, fly, and output capacitors themselves; see figure 3 for the graph- ic illustration of the ac parasitic components of a aat3183 typical application circuit. during the charge pump switching events, an ac current path (i ac ) is established from the voltage source (v in ) and input capacitor (c in ) through the flying capacitor (c fly ) to the output capacitor (c out ) and returning through the ground plane (gnd). the ac voltage ripple signal is measured across c in and c out and is highest at full load and high v in . these ac currents charge and discharge the flying capacitor and flow through the esr and esl, which are parasitic elements within the capacitors. circuit board traces can add to esr and esl and will con- tribute to the ac voltage ripple. proper component selection and good layout practice are critical in pro- viding low ripple, low emi performance. these para- sitic elements should be minimized to optimize loop transient response and achieve stable operation. the i ac current from the flying capacitor flows through parasitic esr and esl. voltage ripple across the input and output capacitors due to esr and esl are approximated: the total ac voltage ripple (v ripple ) is the sum of the individual ac voltage ripple signals. due to fast switching, a large amount of ac switch- ing noise due to the parasitic esl within the c in and c out ceramic capacitors is seen on the output ripple. this noise may be attenuated with a small amount of input and output filtering. figure 3: ac parasitic components of an aat3183 typical application circuit. v ripple = v esr + v esl + v pfm v esl = v esr = esr tot i ac (esl tot i ac ) t rise-fall v in c out c fly v out r load aat3183 c in esr esr esl esl l trace l trace i ac gnd esr esl
aat3183 300ma inductorless step-down converter 14 3183.2007.07.1.2 thermal performance power de-rating of the aat3183 is not necessary in most cases due to the low thermal resistance of the sc70jw-8 package, and the limited device losses. under operating conditions v out = 1.5v and i out = 300ma, the estimated worst-case operating effi- ciency () is 68% (v in = 4.2v). device power dissipation (p d ) can be estimated: the typical junction-to-ambient thermal resistance (r ja ) of a sc70jw-8 package mounted on an fr4 board is 160oc/w. the maximum junction temper- ature (t j(max) ) of the device at 85oc ambient is esti- mated: this is below the maximum recommended device junction temperature of 125oc. pcb layout guidelines proper circuit board layout will maximize efficiency while minimizing switching noise and emi. the fol- lowing guidelines should be observed when designing the printed circuit board layout for the aat3183 step-down converter: 1. place the three external capacitors as close to the aat3183 device as possible. maintain the circuit board traces as short and wide as pos- sible. this will minimize noise resulting from parasitic esr and esl in the ac current path. 2. maintain short and wide traces from ground plane to circuit nodes. this will minimize stray parasitics. 3. a good example of an optimal layout for the aat3183 is the aat3183 evaluation board shown in figures 4 and 5. the evaluation board schematic is shown in figure 6. t j(max) = t amb(max) + (p d r = v out i out (1 - ) = 1.5v 0.3a = 211.8mw (1 - 0.68) 0.68 = - p out p d = p in - p out p out = (v out i out ) (v in i in ) = p out p in
aat3183 300ma inductorless step-down converter 3183.2007.07.1.2 15 figure 4: aat3183 evaluation board figure 5: aat3183 evaluation board top layer. bottom layer figure 6: aat3183 evaluation board schematic. v in en out in c1+ c1- c1 [c in ] aat 3183 gnd c2 [c fly ] v ou t c3 [c out ] 1 5 6,7,8 4 32 r1 jp1
aat3183 300ma inductorless step-down converter 16 3183.2007.07.1.2 advanced analogic technologies, inc. 830 e. arques avenue, sunnyvale, ca 94085 phone (408) 737-4600 fax (408) 737-4611 ? advanced analogic technologies, inc. analogictech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an analogictech pr oduct. no circuit patent licenses, copyrights, mask work rights, or other intellectual property rights are implied. analogictech reserves the right to make changes to their products or specifications or to discontinue any product or service with- out notice. except as provided in analogictechs terms and conditions of sale, analogictech assumes no liability whatsoever, an d analogictech disclaims any express or implied war- ranty relating to the sale and/or use of analogictech products including liability or warranties relating to fitness for a part icular purpose, merchantability, or infringement of any patent, copyright or other intellectual property right. in order to minimize risks associated with the customers applications, adequa te design and operating safeguards must be provided by the customer to minimize inherent or procedural hazards. testing and other quality control techniques are utilized to the extent an alogictech deems necessary to support this warranty. specific testing of all parameters of each device is not necessarily performed. analogictech and the analogictech logo are trad emarks of advanced analogic technologies incorporated. all other brand and product names appearing in this document are registered trademarks or trademarks of their respective holder s. ordering information packaging information all dimensions in millimeters. output voltage package marking 1 part number (tape and reel) 2 1.5v sc70jw-8 ujxyy aat3183ijs-1.5-t1 1. xyy = assembly and date code. 2. sample stock is generally held on part numbers listed in bold . 0.225 all analogictech products are offered in pb-free packaging. the term ?pb-free? means semiconductor products that are in compliance with current rohs standards, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. for more information, please visit our website at http://www.analogictech.com/pbfree.

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