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________________________________________________________________ _ maxim integrated products _ _ 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. MAX8969 step-up converter for handheld applications 19-6038; rev 0; 9/11 typical operating circuit general description the MAX8969 is a simple 1a step-up converter in a small package that can be used in any single-cell li-ion appli - cation. this ic provides protection features such as input undervoltage lockout, short circuit, and overtemperature shutdown. the ic transitions to skip mode seamlessly under light- load conditions to improve efficiency. under these conditions, switching occurs only as needed, reducing switching frequency and supply current to maintain high efficiency. when the input voltage is sufficient to drive the load, the ic can be operated in track mode or automatic track mode (atm). in track mode, the p-channel mosfet acts as a current-limited load switch and quiescent current is as low as 30a under a no-load condition. in atm mode, the p-channel mosfet acts as a current-limited load switch and quiescent current is as low as 60a under a no-load condition. in atm mode, the internal boost cir - cuitry is enabled, allowing for fast transitions into boost mode. the ic is available in a small, 1.25mm x 1.25mm, 9-bump wlp (0.4mm pitch) package. applications cell phones smartphones mobile internet devices gps, pnd ebooks features s compact_ layout small,_ 1.25mm_ x_ 1.25mm_ wlp_ package 3mhz_ pwm_ switching_ frequency small_ external_ components s safe_ and_ efficient_ step-up_ mode up_ to_ 1a_ output_ current 2.5v_ to_ 5.5v_ input_ voltage_ range 3.3v_ to_ 5v_ ouput_ voltage_ range over_ 90%_ efficiency_ with_ internal_ synchronous _ __ rectifier low_ 45a_ no-load_ quiescent_ current soft-start_ controls_ inrush_ current true_ shutdown? low_ 1a_ shutdown_ current s track_ mode 1a_ current_ limited 130m i _ on-resistance low_ 30a_ no_ load_ quiescent_ current s automatic_ track_ mode 130m i _ on-resistance low_ 60a_ no-load_ quiescent_ current boost_ circuitry_ enabled_ for_ fast_ transition_ into _ __ boost true shutdown is a trademark of maxim integrated products, inc. note: the output voltage range is from 3.3v to 5v. contact the factory for output options and availability. + denotes a lead(pb)-free/rohs-compliant package. ordering information evaluation_kit available in out_ lx_ gnd_ c in 4.7 f l1 1 h c out 22f inpu t 2.5v to 5.5v output 3.7v, 1a en MAX8969 tren part v out (v) temp_range pin- package MAX8969ewl33+ 3.3 -40 n c to +85 n c 9 wlp MAX8969ewl35+ 3.5 -40 n c to +85 n c 9 wlp MAX8969ewl37+ 3.7 -40 n c to +85 n c 9 wlp MAX8969ewl42+ 4.25 -40 n c to +85 n c 9 wlp MAX8969ewl50+ 5.0 -40 n c to +85 n c 9 wlp
2 _ _ _______________________________________________________________________________________ MAX8969 step-up converter for handheld applications stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. in, out_ to gnd_ ................................................ -0.3v to +6.0v en, tren to gnd_ ............ -0.3v to lower of (v in + 0.3v) or 6v total lx_ current ........................................................... 3.2a rms out_ short circuit to gnd_ ..................................... continuous continuous power dissipation (t a = +70 n c) wlp (derate 12mw/ n c above +70 n c) ......................... 960mw operating temperature range .......................... -40 n c to +85 n c junction temperature ..................................................... +150 n c storage temperature range ............................ -65 n c to +150 n c soldering temperature (reflow) (note 1) ........................ +260 n c electrical_ characteristics (v in = 2.6v, t a = -40 n c to +85 n c, unless otherwise noted. typical values are t a = +25 n c.) (note 3) absolute_ maximum_ ratings note_ 1: this device is constructed using a unique set of packaging techniques that impose a limit on the thermal profile that the device can be exposed to during board level solder attach and rework. this limit permits only the use of the solder pro - files recommended in the industry-standard specification jedec 020a, paragraph 7.6, table 3 for ir/vpr and convection reflow. preheating is required. hand or wave soldering is not allowed. wlp junction-to-ambient thermal resistance ( b ja ) .......... 83 n c/w junction-to-case thermal resistance ( b jc ) ............... 50 n c/w package_ thermal_ characteristics_ (note_ 2) note_ 2: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . parameter conditions min typ max units operating input voltage range 2.5 5.5 v minimum startup voltage 2.3 v undervoltage lockout threshold (uvlo) v in falling, 75mv hysteresis 2.1 2.2 2.3 v shutdown supply current v en = v tren = v out = 0v, v in = 4.8v t a = +25 n c 0.8 5 f a t a = +85 n c 1 thermal shutdown t a rising, 20 n c hysteresis +165 n c boost_mode continuous output current v in > 2.5v (note 4) 1 a peak output current v in > 2.5v, pulse load v out = 3.3v 0.9 a v out = 3.5v 0.8 v out = 3.7v 0.7 v out = 4.25v 0.7 v out = 4.7v 0.7 v out = 5.0v 0.7 switching frequency (note 4) 3 mhz output voltage accuracy no load, v out _ target = 3.3v 3.175 3.30 3.40 v no load, v out _ target = 3.5v 3.40 3.50 3.60 no load, v out _ target = 3.7v 3.64 3.75 3.85 no load, v out _ target = 4.25v 4.10 4.25 4.35 no load, v out _ target = 5v 4.85 5.00 5.10
_______________________________________________________________________________________ _ _ 3 MAX8969 step-up converter for handheld applications electrical_ characteristics_ (continued) (v in = 2.6v, t a = -40 n c to +85 n c, unless otherwise noted. typical values are t a = +25 n c.) (note 3) parameter conditions min typ max units steady-state output voltage (notes 5, 6) 2.5v < v in < v atmrt , conditions emulating 0 < i out < 1a, c out = 22 f f, l = 1 f h, v out _ target = 3.3v 3.00 3.45 v 2.5v < v in < v atmrt , conditions emulating 0 < i out < 1a, c out = 22 f f, l = 1 f h, v out _ target = 3.5v 3.15 3.65 2.5v < v in < v atmrt , conditions emulating 0 < i out < 1a, c out = 22 f f, l = 1 f h, v out _ target = 3.7v 3.35 3.85 2.5v < v in < v atmrt , conditions emulating 0 < i out < 600ma, c out = 22 f f, l = 1 f h, v out _ target = 4.25v 3.95 4.35 2.5v < v in < v atmrt , conditions emulating 0 < i out < 500ma, c out = 22 f f, l = 1 f h, v out _ target = 5v 4.50 5.10 lx_ leakage current v lx = 0v, 4.8v t a = +25 n c 0.1 5 f a t a = +85 n c 0.2 skip-mode supply current en = high, i out = 0a, 1 f h inductor (tren is low, not switching) 45 f a pmos turn-off current (zero-cross current) 10 ma lx_ nmos current limit 2.6 3.2 a maximum duty cycle 83 % minimum duty cycle 0 % pmos on-resistance v out = 3.3v 120 m i v out = 3.5v 115 v out = 3.7v 110 v out = 4.25v 100 v out = 5v 91 nmos on-resistance v out = 3.3v 65 m i v out = 3.5v 63 v out = 3.7v 60 v out = 4.25v 55 v out = 5v 51 minimum output capacitance for stable operation (actual) 8 f f maximum output capacitance (actual) 0 < i out < 0.3a during startup v out = 3.3v 70 f f v out = 3.5v 55 v out = 3.7v 45 v out = 4.25v 30 v out = 5v 20
4 _ _ _______________________________________________________________________________________ MAX8969 step-up converter for handheld applications electrical_ characteristics_ (continued) (v in = 2.6v, t a = -40 n c to +85 n c, unless otherwise noted. typical values are t a = +25 n c.) (note 3) note_ 3: specifications are 100% production tested at t a = +25 c. limits over the operating temperature range are guaranteed by design and characterization. note _ 4: continuous operation with 1a at elevated ambient temperature and low voltage is not guaranteed. under worst-case con - ditions, die thermal protection cannot be activated after 100ms of 1a load application. see the continuous output current parameter for a conservative estimate of current that can be maintained at t a = +85 c. note_ 5: switching frequency decreases if input voltage is > 83% of the output voltage selected. this allows duty factor to drop to values necessary to boost output voltage less than 25% without the use of pulse widths less than 60ns. note_ 6: contact factory for other options. note_ 7: the output voltage regulation is a direct function of the peak current in the nmos power switch. the inductor current (i lx ) described in the conditions of the steady-state output voltage specification corresponds to the peak inductor current. note _ 8: once atm threshold is reached boost switching stops in 1s (typ), but the transition to atm does not occur until v out has fallen equal to v in . parameter conditions min typ max units output voltage ripple i out = 150ma, circuit of figure 1 20 mv p-p soft-start interval i out = 10ma, see the output capacitor selection section f s track_mode pmosfet on-resistance i out = 500ma, v in = 2.7v 130 m i i out = 500ma, v in = 3.2v 110 track current limit v out = 3.6v 1 2 a track mode quiescent current en = low, tren = high 30 f a automatic_track_mode_(atm) atm supply current v in = 5.4v 65 f a atm v in rising threshold (v atmrt) v out _ target = 3.3v 3.15 v v out _ target = 3.5v 3.35 v out _ target = 3.7v 3.55 v out _ target = 4.25v 4.04 v out _ target = 5v 4.74 atm v in falling threshold (v atmft) v out _ target = 3.3v 3.10 v v out _ target = 3.5v 3.29 v out _ target = 3.7v 3.5 v out _ target = 4.25v 3.99 v out _ target = 5v 4.69 boost to atm transition time (note 7) 1 f s atm to boost transition time 1 f s logic_control en, tren logic input high voltage 2.3v < v in < 5.5v 1.05 v en, tren logic input low voltage 2.3v < v in < 5.5v 0.4 v en, tren leakage current v en = v tren = 0v t a = +25 n c -1 0.01 +1 f a t a = +85 n c 0.1
_______________________________________________________________________________________ _ _ 5 MAX8969 step-up converter for handheld applications typical operating characteristics (v in = 3.6v, c out = 22f, x5r, 6.3v local and 10f, x5r, 6.3v, 1h inductor, circuit of f igure 1, t a = +25 n c, unless otherwise noted.) MAX8969 toc01 load current (ma) efficiency (%) 100 10 1 1000 efficiency vs. output current (v out = 5v) 65 70 75 80 85 90 95 100 v in = 4.3v v in = 3.6v l = toko dfe252012 1h v in = 2.5v v in = 3.1v 60 maximum output current vs. input voltage MAX8969 toc04 input voltage (v) maximum output current (ma) 5.0 4.5 4.0 3.5 3.0 1000 1500 2000 2500 3000 500 2.5 5.5 v out , 3.7v 3.35v v out , 5v 4.5v efficiency vs. output current (v out = 3.7v) MAX8969 toc02 load current (ma) efficiency (%) 100 10 82 84 86 88 90 92 94 96 98 100 80 1 1000 v in = 2.5v v in = 3.1v l = toko dfe252012 1h output voltage (v out = 5v) vs. output current MAX8969 toc05 output current (ma) output voltage (v) 800 600 400 200 4.60 4.65 4.70 4.75 4.80 4.85 4.90 4.95 5.00 5.05 4.55 0 1000 v in = 2.5v v in = 3.2v v in = 3.6v v in = 4.3v no-load supply current vs. input voltage MAX8969 toc03 input voltage (v) no-load supply current (ua) 5.0 4.5 3.0 3.5 4.0 v out = 3.7v v out = 5v 10 20 30 40 50 60 70 80 0 2.5 5.5 output current (ma) output voltage (v) 800 600 400 200 3.4 3.6 3.8 4.0 4.2 4.4 3.2 0 1000 output voltage (v out = 3.7v) vs. output current MAX8969 toc06 v in = 3.2v v in = 4.3v v in = 2.5v v in = 3.6v output voltage (v out = 5v) vs. input voltage MAX8969 toc07 input voltage (v) output voltage (v) 5.0 4.5 4.0 3.5 3.0 3.5 4.0 4.5 i out = 1000ma i out = 10ma i out = 100ma i out = 600ma automatic frequency adjustment automatic track mode transition 5.0 5.5 3.0 2.5 5.5 output voltage (v out = 3.7v) vs. input voltage MAX8969 toc08 input voltage (v) output voltage (v) 4.0 3.5 3.0 3.0 3.5 4.0 4.5 5.0 2.5 2.5 4.5 i out = 600ma i out = 100ma i out = 10ma i out = 1000ma automatic frequency adjustment automatic track mode transition
6 _ _ _______________________________________________________________________________________ MAX8969 step-up converter for handheld applications typical operating characteristics (continued) (v in = 3.6v, c out = 22f, x5r, 6.3v local and 10f, x5r, 6.3v, 1h inductor, circuit of f igure 1, t a = +25 n c, unless otherwise noted.) 3.7v line transient MAX8969 toc09 2.6v ac-coupled 100mv/div 3v v out v in 100s /div tren = v in , i out = 200ma 3.7v load transient (0ma-50ma-0ma) MAX8969 toc11 ac-coupled 50mv/div 5v/div 50ma 0 0 i out v out v lx 200s /div v in = 2.6v 3.7v load transient (50ma-500ma-50ma) MAX8969 toc13 ac-coupled 200mv/div 5v/div 500ma 50ma 0 i out v out v lx 20s /div v in = 2.8v 5v line transient MAX8969 toc10 3.3v ac-coupled 100mv/div 3.7v v out v in 100s /div tren = v in , i out = 200ma 5v load transient (0ma-50ma-0ma) MAX8969 toc12 ac-coupled 50mv/div 5v/div 50ma 0 0 i out v out v lx 200s /div v in = 3.8v 5v load transient (50ma-500ma-50ma) MAX8969 toc14 ac-coupled 100mv/div 5v/div 500ma 50ma 0 i out v out v lx 20s /div v in = 3.8v
_______________________________________________________________________________________ _ _ 7 MAX8969 step-up converter for handheld applications typical operating characteristics (v in = 3.6v, c out = 22f, x5r, 6.3v local and 10f, x5r, 6.3v, 1h inductor, circuit of f igure 1, t a = +25 n c, unless otherwise noted.) light-load ripple MAX8969 toc15 ac-coupled 20mv/div 2v/div 0 v out v lx 40s /div i out = 1ma, v in = 3.6v startup (v out = 5v) MAX8969 toc17 2v/div 2v/div 0 0 2v/div 0 v en v out v lx 200s /div c out , typ = 32f, tren = gnd, i out = 10ma, v in = 3.2v hard-short (v out = 5v) MAX8969 toc19 2v/div 2a /div 0 0 0 2v/div 2a /div 0 v out v lx i out v in = 3.2v, 0.1i load i lx 20s /div startup (v out = 3.7v) MAX8969 toc16 2v/div 2v/div 0 0 2v/div 0 v en v out v lx 200s /div c out , typ = 32f, tren = gnd, i out = 10ma, v in = 2.6v hard-short (v out = 3.7v) MAX8969 toc18 2v/div 2a /div 0 0 0 2v/div 2a /div 0 v out v lx i out v in = 3.2v, 0.1i load i lx 40s /div shutdown MAX8969 toc20 2v/div 0 0 0 2v/div 2v/div v out v en v lx 10i load, tren = gnd 2s /div
8 _ _ _______________________________________________________________________________________ MAX8969 step-up converter for handheld applications pin configuration pin description top view (bump side down) wlp (1 .25mm 1 .25mm) out1 out2 in lx1 lx2 en gnd1 gnd2 tren a b c 1 2 3 MAX8969 + pin name function a1 out1 power output. bypass out_ to ground with a 22 f f rated ceramic capacitor. for optimal performance place the ceramic capacitor as close as possible to out_. out1 and out2 should be shorted together directly under the ic. in true shutdown, the output voltage can fall to 0v, but out_ has a diode with its cathode connected to in. see figure 3. a2 out2 a3 in input supply voltage. bypass in to gnd_ with a 4.7 f f ceramic capacitor. a larger capacitance may be required to reduce noise. b1 lx1 converter switching node. connect a 1 f h inductor from lx_ to in. lx_ is high impedance in shutdown. lx1 and lx2 should be shorted together directly under the ic. b2 lx2 b3 en enable input. drive en logic-high to enable boost mode, regardless of the logic level of tren. connect en to ground or drive logic-low to allow tren to select either true shutdown or track mode. see table 1. c1 gnd1 ground. connect gnd_ to a large ground plane. gnd1 and gnd2 should be shorted together directly under the ic. c2 gnd2 c3 tren track enable input. drive tren logic-high to enable track mode. connect tren to ground or drive logic-low to place the ic in true shutdown. see table 1.
_______________________________________________________________________________________ _ _ 9 MAX8969 step-up converter for handheld applications figure 1. functional diagram detailed description the MAX8969 is a step-up dc-dc switching converter that utilizes a fixed-frequency pwm architecture with true shutdown. with an advanced voltage-positioning control scheme and high 3mhz switching frequency, the ic is inexpensive to implement and compact, using only a few small easily obtained external components. under light-load conditions, the ic switches only when needed, consuming only 45 f a (typ) of quiescent current. the ic is highly efficient with an internal switch and synchronous rectifier. shutdown typically reduces the quiescent current to 1 f a (typ). low quiescent current and high efficiency make this device ideal for powering portable equipment. internal soft-start limits inrush current to less than 720ma (typ), while output voltage is less than input voltage. once output voltage approaches input voltage approaches input voltage after a brief delay, output voltage is boosted to its final value at a rate of approximately 25mv/s. during this period, as well as being limited by the volt - age, ramp rate current is limited by the normal 2.6a boost mode current limit. in boost mode, the step-up converter boosts to v out_target from battery input voltages ranging from 2.5v to v out_target . when the input voltage ranges from 0.95 x v out_target to 5.5v, the ic enters atm and the output voltage approximately follows the input volt - age. during boost mode, the input current limit is set to 2.6a to guarantee delivery of the rated out current (e.g., 1a output current when boosting from a 2.5v input supply to a 3.7v output). control scheme the step-up converter uses a load/line control scheme. the load/line control scheme allows the output voltage to sag under load, but prevents overshoot when the load is suddenly removed. the load/line control scheme reduces the total range of voltages reached during transients at the expense of dc output impedance. reference current limit control logic l1 1h gnd_ tren 0.95 x v out_target en in out_ c in 4.7f c out 22f lx_ atm p1 n1 atm comparator track enable in pwm logic ramp generator true shutdown in MAX8969
10 _ _ ______________________________________________________________________________________ MAX8969 step-up converter for handheld applications figure 2. state diagram true shutdown n1 = of f p1 = off i q = 1a (typ) track mode* n1 = off p1 = current- limited switch i q = 30a (typ) automatic track mode (atm)* n1 = off p1 = current- limited switch i q = 65a (typ) boost circuitry enabled v in comparator boost soft-start n1 = switching p1 = of f boost exit mode n1 = off p1 = off ic waits until v out = v in boost mode n1 = switching p1 = switching v out = v out_targe t i q = 45a (skip mode ) uvlo, excessive temperature, or short circui t from any state en = 1, or tren = 1 en = 0, tren = 0 en = 0, tren = 0 1 0 en = 1, v ou t > (v in - 300mv) v in comparator = 0 v in comparator = 1 soft-star t voltage ramp complete output below targe t [v ou t < (0.72 x v out_target )] v ou t < v in , tren = 0 v ou t < v in , tren = 1 en = 0 en = 0 *en takes priority over tren. see table 1.
______________________________________________________________________________________ _ _ 11 MAX8969 step-up converter for handheld applications figure 3. modes of operation p1 body diode out_ p1 = off n1 = off lx_ in true shutdown: p1 body diode out_ p1 = current- limited switch n1 = off lx_ in track/atm mode: p1 body diode out_ p1 = off n1 = off lx_ in boost exit mode: p1 body diode out_ p1 = off n1 = switching lx_ in boost soft-start: p1 body diode out_ p1 = switching n1 = switching lx_ in boost mode:
12 _ _ ______________________________________________________________________________________ MAX8969 step-up converter for handheld applications the ic is designed to operate with the input voltage range straddling its output voltage set point. two tech - niques are used to accomplish this. the first technique is to activate atm if the input voltage exceeds 95% of the output set point; see the automatic track mode (atm) section. the second technique is automatic frequency adjustment. automatic track mode (atm) atm is entered when an internal comparator signals that the input voltage has exceeded the atm threshold. the atm threshold is 95% of the output voltage target. at this point, the ic enters atm, with the pmos switch turned on, regardless of the status of tren. note that en must be high to enable atm mode. this behavior is summa - rized in table 1. automatic frequency adjustment automatic frequency adjustment is used to maintain stability if the input voltage is above 80% and below 95% of the output set point. frequency adjustment is required because the n-channel has a minimum on-time of approximately 60ns. at 3mhz, this would lead to the p-channel having a maximum duty factor of 82%. with an input voltage more than 82% of the output set point, the p-channels duty factor must be increased by reduc - ing operating frequency either through cycle skipping or adjusting the clocks frequency. the ic adjusts its clock frequency rather than simply skipping cycles. this adjustment is done in two steps. the first step occurs if the input voltage exceeds approximately 83% of the out - put voltage and reduces clock speed to approximately 1.6mhz. the second step occurs if the input voltage is greater than output voltage less 460mv. if this condition is met, clock frequency is reduced to approximately 1mhz. frequency adjustment allows the converter to operate at a known frequency under all conditions. fault protection in track, atm, and boost modes, the ic has protection against overload and overheating. ? in track and atm, current is limited to prevent excessive inrush current during soft-start and to protect against overload conditions. if the die tem - perature exceeds +165c in track/atm, the switch turns off until the die temperature has cooled to +145 n c. ? in boost mode, during each 3mhz switching cycle, if the inductor current exceeds 2.6a, the n-channel mosfet is shut off and the p-channel mosfet is switched on. the end result is that lx_ current is regulated to 2.6a or less. a 2.6a inductor current is a large enough current to guarantee a 1a output load current under all intended operating conditions. the ic can operate indefinitely while regulating the inductor current to 2.6a or less. however, if a short circuit or extremely heavy load is applied to the output, the output voltage decreases since the inductor current is limited to 2.6a. if the output voltage decreases to less than 72% of the regulation voltage target (i.e., 2.8v with v out_target of 3.7v), a short circuit is assumed, and the ic returns to the shutdown state. the ic then attempts to start up if the output short is removed. even if the output short persists indefinitely, the ic thermal protection ensures that the die is not damaged. true shutdown during ope ration in boost mode, the p-channel mosfet prevents current from flowing from out_ to lx_. in all other modes of operation, it is desirable to block current flowing from lx_ to out_. true shutdown prevents current from flowing from lx_ to out_ while the ic is shut down by reversing the internal body diode of the p-channel mosfet. this feature is also active during track/atm to allow current limit to function as anticipated. upon leaving boost mode, the p-channel mosfet continues to prevent current from flowing from out_ to lx_ until out_ and in are approximately the same volt - age. after this condition has been met, track/atm and shutdo wn operate normally. table_ 1._ modes_ of_ operation x = don't care. _v in _comparator en tren mode_of_operation x 0 0 true shutdown x 0 1 track 0 1 x boost 1 1 x atm
______________________________________________________________________________________ _ _ 13 MAX8969 step-up converter for handheld applications thermal considerations in most app lications, the ic does not dissipate much heat due to its high efficiency. but in applications where the ic runs at high ambient temperature with heavy loads, the heat dissipated may cause the temperature to exceed the maximum junction temperature of the part. if the junction temperature reaches approximately +165 n c, the thermal overload protection is activated. the maximum power dissipation depends on the thermal resistance of the ic package and circuit board. the power dissipated (p d ) in the device is: p d = p out x (1/ e - 1) where e is the efficiency of the converter and p out is the output power of the step-up converter. the maximum allowed power dissipation is: p max = (t jmax - t a )/ b ja where (t jmax - t a ) is the temperature difference between the ics maximum rated junction temperature and the surrounding air, and b ja is the thermal resistance of the junction through the pcb, copper traces, and other materials to the sur rounding air. applications information step-up inductor selection due t o the small size of the recommended capacitor, the inductors value is limited to approximately 1 f h. inductors of approximately 1 f h guarantee stable operation of the converter with capacitance as small as 8 f f (actual) pres - ent on the converters output. if the inductors value is reduced significantly below 1 f h, ripple can become exce ssive. output capacitor selection an output ca pacitor (c out ) is required to keep the output-voltage ripple small and to ensure regulation loop stability. the output capacitor must have low imped - ance at the switching frequency. ceramic capacitors are highly recommended due to their small size and low esr. ceramic capacitors with x5r or x7r temperature characteristics generally perform well. one 22 f f (with a minimum actual capacitance of 6 f f under operating conditions) is recommended. this capacitor along with an additional 10 f f of bypass capacitance, associated with the load, guarantee proper performance of the ic. the minimum combined capacitance is required to be 8 f f or larger. these capacitors can be found with case size 0603 or l arger. input capacitor selection the input capacitor (c in ) reduces the current peaks drawn from the battery or input power source. the impedance of c in at the switching frequency should be kept very low. ceramic capacitors with x5r or x7r temperature characteristics are highly recommended due to their small size, low esr, and small temperature coefficients. note that some ceramic dielectrics exhibit large capacitance and esr variation with temperature and dc bias. ceramic capacitors with z5u or y5v temperature characteristics should be avoided. a 4.7 f f input capacitor is recommended for most applications. this assumes that the input power source has at least 22 f f of additional capacitance near the ic. for optimum noise immunity and low input-voltage ripple, the input capacitor value can be increased. recommended pcb layout and routing poor layout can affect the ic performance, causing electromagnetic interference (emi) and electromagnetic compatibility (emc) performance, ground bounce, and voltage losses. poor layout can also affect regulation and stability. a good layout is implemented using the following rules: ? place the inductor, input capacitor, and output capacitor close to the ic using short traces. these components carry high switching frequencies and large traces act like antennas. the output capacitor placement is the most important in the pcb layout and should be placed directly next to the ic. the inductor and input capacitor placement are second - ary to the output capacitors placement but should remain close to the ic. ? route the output voltage path away from the induc - tor and lx_ switching node to minimize noise and magnetic interference. ? maximize the size of the ground metal on the com - ponent side to help with thermal dissipation. use a ground plane with several vias connecting to the component-side ground to further reduce noise interference on sensitive circuit nodes. refer to the MAX8969 evaluation kit for more details. chip information process: bicmos
14 _ _ ______________________________________________________________________________________ MAX8969 step-up converter for handheld applications package information for the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package_type package_code outline_no. land_pattern_no. 9 wlp w91b1+7 21-0459 refer to _ application_note_1891
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 15 ? 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. MAX8969 step-up converter for handheld applications revision history revision number revision date description pages changed 0 9/11 initial release

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