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general description the aat1265 is a member of analogic tech's total power management ic? (tpmic?) product family and is designed for single-cell or dual-cell alkaline, nimh, or nicd battery-powered applications. it is a high efficiency, synchronous, fixed frequency, step- up converter with true output disconnect during shutdown (<1.0a), start-up inrush current limit, and short-circuit protection. the high 2mhz switching frequency and completely integrated control circuitry minimize the total solution footprint area while maintaining excellent regulation, ripple, and transient response throughout the full load range. light load switching frequency modulation and low quiescent current maintain high efficiency perform- ance for light load and sleep mode conditions. with a 1a peak switch current limit, the aat1265 is capable of delivering 100ma to a 3.3v load with a single aa cell or up to 250ma from a dual aa cell. the device has a 1.0v start-up voltage with opera- tion down to 0.8v. the aat1265 is available in a pb-free, space-sav- ing 2.0x2.1mm 8-pin sc70jw package and is rated over the -40c to +85c temperature range. features ? 100ma output from a single aa cell input ? 250ma output from a dual aa cell input ?v in operation range: 0.8v to v out ? up to 93% efficiency ? low start-up voltage: 1.0v typical ? internal synchronous rectifier ? current mode control with internal feedback and compensation ? 2mhz fixed switching frequency ? 1a current limit ? maintains high efficiency over the output current range for improved battery life ? low 40a no load bias current ? true load disconnect ? short-circuit and over-current protection ? inrush current limit and soft start ? low shutdown current: <1.0a ? -40c to +85c temperature range ? 2.0x2.1mm sc70jw-8 package applications ? bluetooth? headsets ? digital cameras ? medical instruments ? mobile handsets ? mp3 and portable music players aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package typical application 1265.2006.05.1.1 1 switchreg ? dual-cell to 3.3v efficiency vs. output current output current (ma) efficiency (%) 50 60 70 80 90 100 0.1 1.0 10.0 100.0 1000.0 v in = 3.0v v in = 2.4v v in = 2.0v 2.2h 4.7f 4.7 f v in v out vcc en vin lx out gnd aat1265
pin descriptions pin configuration sc70jw-8 (top view) pin # symbol function 1 vcc bias supply voltage after start-up and feedback to the output voltage error amplifier. 2 en enable pin. logic high enables the ic. logic low disables the ic and disconnects the load from the input. shutdown current is <1a. 3 vin battery input voltage. supplies the ic at start-up. 4 lx inductor connection. ties to the drains of the p-channel synchronous rectifier and the n-channel mosfet switch. 5 out boost converter output voltage; connects to the p-channel synchronous mosfet source. bypass with ceramic capacitor to gnd. 6, 7, 8 gnd signal and power ground. connect output capacitor return. aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 2 1265.2006.05.1.1 en vin lx gnd gnd gnd out vcc 1 2 3 45 6 7 8
absolute maximum ratings thermal characteristics 1 symbol description value units ja maximum thermal resistance 160 c/w p d maximum power dissipation 625 mw symbol description value units v n vin, out, vcc, en, lx 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 aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 1265.2006.05.1.1 3 1. mounted on an fr4 board.
electrical characteristics 1 v in = 1.2v, v out = 3.3v, t a = -40c to +85c, unless otherwise noted. typical values are t a = 25c. symbol description conditions min typ max units v in minimum start-up voltage i load = 1ma 1.0 v operating input voltage range 0.8 v out v out output voltage accuracy v in = 0.8v to 2.5v, 3.2 3.3 3.4 v pwm mode i q quiescent supply current no load 40 70 a (pfm operation) 2 i shdn shutdown current en = 0v, v in = 5.5v 1.0 a r ds(on)h pmos on-resistance t a = 25c 750 m r ds(on)l nmos on-resistance t a = 25c 400 m i limit nmos current limit 1.0 a i pfm pfm light load current threshold 20 ma efficiency i out = 50ma, l = 2.2h 82 % v out /v out load regulation i load = 0 to 100ma 1.5 % v out (v out * v in ) line regulation v in = 0.8v to 2.5v 0.2 %/v f osc switching frequency t a = 25c 1.8 2.0 2.2 mhz d tymax maximum duty cycle 90 % v th(l-in) logic input low threshold for en 0.4 v v th(h-in) logic input high threshold for en 1.0 v aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 4 1265.2006.05.1.1 1. the aat1265 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. 2. i q = i q_vout = i q_vcc .
typical characteristics aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 1265.2006.05.1.1 5 pfm mode output current threshold vs. input voltage input voltage (v) output current (ma) 0 20 40 60 80 100 120 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 increasing load decreasing load minimum start-up voltage vs. load current current (ma) voltage (v) 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 0 2 40 60 80 100 120 140 160 resistive load constant current load dual-cell load regulation (v o = 3.3v) output current (ma) v out error (%) -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 0.1 1 10 100 1000 v in = 2.0v v in = 2.4v v in = 3.0v single-cell load regulation (v o = 3.3v) output current (ma) v out error (%) -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 0.1 1 10 100 v in = 1.5v v in = 1.2v dual-cell to 3.3v efficiency output current (ma) efficiency (%) 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 3.0v v in = 2.4v v in = 2.0v single-cell to 3.3v efficiency output current (ma) efficiency (%) 50 60 70 80 90 100 0.1 1 10 100 1000 v in = 1.2v v in = 1.5v
typical characteristics aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 6 1265.2006.05.1.1 line transient response (i o = 50ma; l = 2.2h; c o = 4.7f) output voltage (v) input voltage (v) time (50s/div) 3.26 3.28 3.30 3.32 3.34 1.50 1.75 2.00 2.25 2.50 2.4v 1.9v output voltage vs. temperature (v in = 1.5v; i o = 10ma) temperature ( c) output voltage error (%) -0.80 -0.60 -0.40 -0.20 0.00 0.20 0.40 -40 -20 0 20 40 60 80 load transient response (v in = 1.2v; l = 2.2h; c o = 4.7f) output current (a) output voltage (v) time (50s/div) 0.00 0.05 0.10 0.15 3.20 3.25 3.30 3.35 3.40 50ma 100ma maximum load current capacity for a 4% drop in output voltage vs. input voltage (v out = 3.3v) input voltage (v) load current (ma) 0 100 200 300 400 500 600 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 switching frequency vs. temperature temperature ( c) switching frequency change (%) -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 -40 -15 10 35 60 85 no load input current vs. input voltage input voltage (v) input current (a) 0 40 80 120 160 200 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0
typical characteristics aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 1265.2006.05.1.1 7 soft-start inrush current (v in = 1.2v; i o = 40ma; v o = 3.3v) enable and output voltage (v) input current (a) time (500s/div) -4 -3 -2 -1 0 1 2 3 4 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 output voltage input current enable light load output ripple (v in = 1.2v; 10ma load) time (1s/div) v out (ac coupled) (20mv/div) v lx (2v/div) i l (200ma/div) full load output ripple (v in = 1.2v; 100ma load) time (250ns/div) v out (ac coupled) (20mv/div) v lx (2v/div) i l (100ma/div) soft-start inrush current (v in = 2.4v; i o = 100ma; v o = 3.3v) enable and output voltage (v) input current (a) time (500s/div) -4 -3 -2 -1 0 1 2 3 4 -0.25 0 0.25 0.5 0.75 1 1.25 1.5 1.75 output voltage enable input current
aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 8 1265.2006.05.1.1 functional block diagram functional description the aat1265 synchronous step-up converter is targeted for single- or dual-cell alkaline, nimh, and nicd battery applications. it has a 1v typical start- up voltage with operation after start-up to less than 0.8v. the high 2mhz switching frequency of the aat1265 facilitates output filter component size reduction for improved power density and reduced overall footprint. it also provides greater bandwidth and improved transient response over other lower frequency step-up converters. the compensation and feedback is integrated with only three external components (c in , c out , l). low r ds(on) synchronous power switches provide high efficiency for heavy load conditions. switching frequency modulation and low quiescent current maintains this high efficiency for light load and sleep mode conditions. in addition to the improved efficiency, the synchro- nous boost has the added performance advantage of true load disconnect during shutdown (<1a shutdown current), inrush current limit, and short- circuit protection. pwm / pfm control the aat1265 is a fixed frequency pwm peak cur- rent mode control step-up converter. for light load conditions (10 to 20ma and below), the converter transitions to a variable frequency (pfm) mode to reduce the dominant switching losses. in addition to pfm operation, a zero current comparator blocks reverse current in the p-channel synchro- voltage reference logic dh dl v ref out gnd en gnd lx comp. vin vcc mode control low voltage start-up start-up inrush control current sense error amp. 2mhz oscillator
nous mosfet, forcing dcm operation at light load. these controls, along with very low quiescent cur- rent, help to maintain high efficiency over the com- plete load range without the compromise of increased output voltage ripple during light load conditions. start-up and inrush current limit the start-up sequence of the aat1265 varies depending upon whether the input voltage is greater than or less than 2v. above 1v, a start-up oscillator operating at 25% duty cycle controls the synchronous power stage and charges the output to 2v. for an input voltage greater than 2v, the out- put is charged at a constant current of 300ma until the output reaches a voltage level just below the input voltage. the step-up converter then takes control and continues to charge the output to the steady-state voltage. the step-up converter n- channel switch current is limited to 1a and the typ- ical start-up time is 2.5ms. shutdown and output disconnect a typical synchronous step-up (boost) converter has a conduction path from the input to the output via the body diode of the p-channel mosfet. the aat1265 design disconnects this body diode from the output and eliminates this conduction path. this enables the aat1265 to provide true load dis- connect during shutdown and inrush current limit at turn-on. short-circuit protection the p-channel synchronous mosfet body diode disconnect feature also gives the aat1265 the ability to provide output short-circuit current limit protection. applications information inductor selection the aat1265 is designed to operate with a 2.2h inductor for all input/output voltage combinations. the inductor saturation current rating should be greater than the nmos current limit specification listed in the electrical characteristics table. if nec- essary, the peak inductor current can exceed the saturation level by a small amount with no signifi- cant effect on performance. table 1 provides a list of some suggested inductor manufacturers and their part numbers. output and input capacitor selection surface mount x5r or x7r ceramic capacitors are suggested for both the output and the input. for the output capacitor (c1 in figure 4) a 4.7f, 10v, x5r ceramic capacitor is necessary for stability, tran- sient response, and ripple performance. the same 0805 sized capacitor is used for the input (c2 of figure 4). if desired, a smaller, 0603 sized, 4.7f, 6.3v, x5r ceramic capacitor can be substituted for the input capacitor (c2). suggested ceramic capacitor suppliers are listed in table 1. pcb layout guidelines figures 1, 2, and 3 display the evaluation board layout and suggested component placement. due to the high switching speed of the aat1265, it is important that the evaluation board layout be fol- lowed. even the best switch-mode power supply design cannot overcome the problems that can be caused by a poor layout. for the aat1265, it is necessary that c1 and c2 be placed as close as possible to the ic with a good low impedance path to the gnd pins of the ic. it is also good practice to minimize the length of the trace from the out pin to the output inductor. this prevents switching noise from radiating into other high noise sensitive, high impedance circuits. aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 1265.2006.05.1.1 9
figure 1: aat1265 evaluation board figure 2: component placement. top side. figure 3: aat1265 evaluation board bottom side. figure 4: aat1265 evaluation board schematic. aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 10 1265.2006.05.1.1 2.2h l1 4.7f c1 4.7f c2 u1 aat1265 sc70jw-8 l1 sd3118-2r2 c1, c2 4.7f 10v 0805 x5r v out v in 1 2 3 enable vcc 1 en 2 vin 3 lx 4 out 5 gnd 6 gnd 7 gnd 8 aat1265 u1
table 1: suggested component selection. manufacturer value part i sat voltage case size part number sumida 2.2h inductor 1.50a 75m 3.2 x 3.2 x 1.55 cdrh2d14-2r2 www.sumida.com cooper electronics 2.2h inductor 1.62a 69m 3.1 x 3.1 x 1.85 sd3118-2r2 www.cooperet.com manufacturer value part voltage case size part number murata 4.7f output or input capacitor 10v 0805 grm21br61a475ka73l www.murata.com input capacitor 6.3v 0603 grm188r60j475ke19d tdk 4.7f output or input capacitor 10v 0805 c2012x5r1a475k www.tdk.com input capacitor 6.3v 0603 c1608x5roj475k taiyo yuden 4.7f output or input capacitor 10v 0805 lmk212bj475mg www.t-yuden.com input capacitor 6.3v 0603 jmk107bj475ma aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 1265.2006.05.1.1 11
aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 12 1265.2006.05.1.1 ordering information package information sc70jw-8 all dimensions in millimeters. voltage package marking 1 part number (tape and reel) 2 3.3v sc70jw-8 rlxyy aat1265ijs-3.3-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.
aat1265 low voltage 2mhz step-up dc/dc converter in sc70jw package 1265.2006.05.1.1 13 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 specifi cations or to discontinue any product or service without notice. customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information b eing relied on is current and complete. all products are sold sub- ject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. analogictech warrants performance of its semiconductor products to the specifications applicable at the time of sale in accordance with anal ogictech?s standard warranty. testing and other quality con- trol techniques are utilized to the extent analogictech deems necessary to support this warranty. specific testing of all param eters of each device is not necessarily performed. analogictech and the analogictech logo are trademarks of advanced analogic technologies incorporated. all other brand and produ ct names appearing in this document are regis- tered trademarks or trademarks of their respective holders.

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