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19-3997; rev 5; 8/14 max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters evaluation kit available for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maximintegrated.com. general description the max8640y/max8640z step-down converters areoptimized for applications where small size, high effi- ciency, and low output ripple are priorities. they utilize a proprietary pwm control scheme that optimizes the switching frequency for high efficiency with small exter- nal components and maintains low output ripple volt- age at all loads. the max8640z switches at up to 4mhz to allow a tiny 1? inductor and 2.2? output capacitor. the max8640y switches at up to 2mhz for higher efficiency while still allowing small 2.2? and 4.7? components. output current is guaranteed up to 500ma, while typical quiescent current is 28?. factory-preset output voltages from 0.8v to 2.5v elimi- nate external feedback components. internal synchronous rectification greatly improves effi- ciency and replaces the external schottky diode required in conventional step-down converters. internal fast soft-start eliminates inrush current so as to reduce input capacitor requirements. the max8640y/max8640z are available in the tiny 6- pin, sc70 (2.0mm x 2.1mm) and ?fn (1.5mm x 1.0mm) packages. both packages are lead-free. applications microprocessor/dsp core poweri/o power cell phones, pdas, dscs, mp3s other handhelds where space is limited features ? tiny sc70 and dfn packages ? 500ma guaranteed output current ? 4mhz or 2mhz pwm switching frequency ? tiny external components: 1 h/2.2 f or 2.2 h/4.7 f ? 28 a quiescent current ? factory preset outputs from 0.8v to 2.5v ? ?% initial accuracy ? low output ripple at all loads ? ultrasonic skip mode down to 1ma loads ? ultra-fast line- and load-transient response ? fast soft-start eliminates inrush current ordering information part* pin-package top mark max8640y ext08+t 6 sc70 acq max8640yext10+t 6 sc70 adf max8640yext11+t 6 sc70 acr max8640yext12+t 6 sc70 acs max8640yext13+t 6 sc70 acg max8640yext15+t 6 sc70 add max8640yext16+t 6 sc70 adb max8640yext18+t 6 sc70 aci max8640yext19+t 6 sc70 ach max8640yext82+t 6 sc70 adj gnd out 1 + + 6 in 5 gnd lx gnd out lx max8640y max8640z max8640y max8640z sc70 2.0mm x 2.1mm top view 23 6 54 4 12 3 shdn ingnd shdn dfn 1.5mm x 1.0mm pin configurations l1 1 h or 2.2 h c2 2.2 f or 4.7 f c1 2.2 f out lx gnd in shdn on/off max8640y max8640z input 2.7v to 5.5v output 0.8v to 2.5v up to 500ma typical operating circuit ordering information continued and selector guide appears at end of data sheet. * contact factory for availability of each version. for 2.85v output (82 version), request application note that includes limitations and typical operating characteristics. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. note: all devices are specified over the -40? to +85? operating temperature range. downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 2 maxim integrated absolute maximum ratings stresses beyond those listed under ?bsolute 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 to gnd .................................................................-0.3v to +6v out, shdn to gnd ....................................-0.3v to (v in + 0.3v) lx current (note 1) ........................................................0.8a rms output short circuit to gnd ...................................continuous continuous power dissipation (t a = +70?) 6-pin sc70 (derate 3.1mw/? above +70?) ..............245mw 6-pin ?fn (derate 2.1mw/? above +70?) ..............167.7mw operating temperature range ...........................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? electrical characteristics(v in = 3.6v, shdn = in, t a = -40? to +85?, typical values are at t a = +25?, unless otherwise noted.) (note 2) parameter symbol conditions min typ max units supply range v in 2.7 5.5 v uvlo threshold uvlo v in rising, 100mv hysteresis 2.44 2.6 2.70 v no load, no switching 28 48 t a = +25? 0.01 0.1 supply current i cc shdn = gnd t a = +85? 0.1 ? output voltage range v out factory preset 0.8 2.5 v i load = 0ma, t a = +25? -1 0 +1 output voltage accuracy(falling edge) i load = 0ma, t a = -40c to +85c -2 +2 % output load regulation(voltage positioning) equal to inductor dc resistance r l v/a v ih v in = 2.7v to 5.5v 1.4 shdn logic input level v il v in = 2.7v to 5.5v 0.4 v t a = +25? 0.001 1 shdn input bias current i ih,il v in = 5.5v, shdn = gnd or in t a = +85? 0.01 ? minimum required shdn reset time t shdn 10 ? peak current limit i limp pfet switch 590 770 1400 ma valley current limit i limn nfet rectifier 450 650 1300 ma rectifier off-current threshold i lxoff nfet rectifier 10 40 70 ma r onp pfet switch, i lx = -40ma 0.6 1.2 on-resistance r onn nfet rectifier, i lx = 40ma 0.35 0.7 t a = +25? 0.1 1 lx leakage current i lxlkg v in = 5.5v, lx = gnd to in, shdn = gnd t a = +85? 1 ? t on ( min ) 95 minimum on and off times t off ( min ) 95 ns thermal shutdown +160 ? thermal-shutdown hysteresis 20 ? note 1: lx has internal clamp diodes to in and gnd. applications that forward bias these diodes should not exceed the ic? packagepower-dissipation limit. note 2: all devices are 100% production tested at t a = +25?. limits over the operating temperature range are guaranteed by design. downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 3 maxim integrated typical operating characteristics (v in = 3.6v, v out = 1.5v, max8640z, l = murata lqh32cn series, t a = +25?, unless otherwise noted.) efficiency vs. load current 1.8v output load current (ma) efficiency (%) max8640y/z toc01 0 10 20 30 40 50 60 70 80 90 100 0.1 1 10 100 1000 max8640yext18 5 1510 2520 30 35 2.7 3.9 4.3 3.1 3.5 4.7 5.1 5.5 no-load supply current vs. supply voltage max8640y/z toc02 supply voltage (v) supply current ( a) max8640yext18 max8640zext15 switching frequency vs. load current load current (ma) switching frequency (mhz) max8640y/z toc03 0 100 200 300 400 500 0.1 1 10 max8640zext15 max8640yext18 output voltage vs. load current (voltage positioning) load current (ma) output voltage (v) max8640y/z toc04 0 100 200 300 400 500 1.30 1.35 1.40 1.45 1.50 1.55 max8640zext15 i lx v lx v out 200ma/div 2v/div 20mv/div(ac-coupled) 10 s/div light-load switching waveforms (i out = 1ma) max8640y/z toc05 i lx v lx v out 200ma/div 2v/div0v 0ma 20mv/div(ac-coupled) 200ns/div medium-load switching waveforms (i out = 40ma) max8640y/z toc06 i lx v lx v out 200ma/div 2v/div0v 0ma 20mv/div(ac-coupled) 200ns/div heavy-load switching waveforms (i out = 300ma) max8640y/z toc07 downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 4 maxim integrated typical operating characteristics (continued) (v in = 3.6v, v out = 1.5v, max8640z, l = murata lqh32cn series, t a = +25?, unless otherwise noted.) i lx i in v shdn v out 100ma/div500ma/div 1v/div0v 0ma 0ma 5v/div 20 s/div light-load startup waveform (100 load) max8640y/z toc08 i lx i in v shdn v out 100ma/div500ma/div 1v/div0v 0ma 0ma 5v/div 20 s/div heavy-load startup waveform (5 load) max8640y/z toc09 i lx v out v in 20mv/div ac-coupled 200ma/div 0ma 1v/div 4v 20 s/div line-transient response (4v to 3.5v to 4v) max8640y/z toc10 i out v out i lx 500ma/div 50m/div ac-coupled 200ma/div 0ma 40 s/div load-transient response (5ma to 250ma to 5ma) max8640y/z toc11 i out v out i lx 500ma/div 100mv/div ac-coupled 200ma/div 0v 40 s/div load-transient response (10ma to 500ma to 10ma) max8640y/z toc12 downloaded from: http:///
pin name function 1l x inductor connection to the internal drains of the p-channel and n-channel mosfets. high impedanceduring shutdown. 2, 5 gnd ground. connect these pins together directly under the ic. 3 out output sense input. bypass with a ceramic capacitor as close as possible to pin 3 (out) and pin 2 (gnd).out is internally connected to the internal feedback network. 4 shdn acti ve- low s hutd ow n inp ut. a l og i c- l ow on s hd n d i sab l es the step - d ow n d c - d c and r esets the l og i c. a l og i c- hi g h on s hd n enab l es the step - d ow n d c - d c . e nsur e that s hd n i s l ow for 10? ( t s h d n ) after v i n r i ses ab ove i ts und er vol tag e l ockout thr eshol d ( u v lo ) to r eset the l og i c. s ee the s hutd ow n m od e secti on for m or e i nfor m ati on. 6i n supply voltage input. input voltage range is 2.7v to 5.5v. bypass with a ceramic capacitor as close aspossible to pin 6 (in) and pin 5 (gnd). pin description max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 5 maxim integrated detailed description the max8640y/max8640z step-down converters deliv- er over 500ma to outputs from 0.8v to 2.5v. they utilize a proprietary hysteretic pwm control scheme that switches at up to 4mhz (max8640z) or 2mhz (max8640y), allowing some trade-off between efficien- cy and size of external components. at loads below 100ma, the max8640y/max8640z automatically switch to pulse-skipping mode to minimize the typical quies- cent current (28?). output ripple remains low at all loads, while the skip-mode switching frequency remains ultrasonic down to 1ma (typ) loads. figure 1 is the simplified functional diagram. control scheme a proprietary hysteretic pwm control scheme ensureshigh efficiency, fast switching, fast transient response, low output ripple, and physically tiny external compo- nents. this control scheme is simple: when the output voltage is below the regulation threshold, the error comparator begins a switching cycle by turning on the high-side switch. this switch remains on until the mini- mum on-time expires and the output voltage is above the regulation threshold or the inductor current is above the current-limit threshold. once off, the high-side switch remains off until the minimum off-time expires and the output voltage falls again below the regulation threshold. during the off period, the low-side synchro- nous rectifier turns on and remains on until either the high-side switch turns on again or the inductor current approaches zero. the internal synchronous rectifier eliminates the need for an external schottky diode. voltage-positioning load regulation the max8640y/max8640z utilize a unique feedbacknetwork. by taking dc feedback from the lx node, the usual phase lag due to the output capacitor is removed, making the loop exceedingly stable and allowing the use of very small ceramic output capacitors. this configuration yields load regulation equal to the inductor? series resistance multiplied by the load current. this voltage-positioning load regulation greatly reduces overshoot during load transients, effectively halving the peak-to-peak output-voltage excursions compared to tra- ditional step-down converters. see the load-transient response in the typical operating characteristics . shutdown mode a logic-low on shdn places the max8640y/max8640z in shutdown mode by disabling the step-down dc-dcand resetting its logic. in shutdown mode, the supply current (i cc ) is reduced to 0.01? typical. additionally, the power mosfets between in, lx, and gnd (figure 1) are open such that lx is high impedance. ensure that shdn is low for 10? (t shdn ) after v in rises above its undervoltage lockout threshold (uvlo)to reset the logic. in the majority of systems, this t shdn requirement is fulfilled naturally because the upstreamlogic controlling shdn is powered off of the same v in as the max8640y/max8640z. however, systems thatwant an always on regulator without the burden of enable/disable logic can use an r and c circuit on shdn as shown in figure 2. downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 6 maxim integrated soft-start the max8640y/max8640z include internal soft-startcircuitry that eliminates inrush current at startup, reduc- ing transients on the input source. soft-start is particu- larly useful for higher impedance input sources, such as li+ and alkaline cells. see the soft-start responsein the typical operating characteristics . applications information the max8640y/max8640z are optimized for use with atiny inductor and small ceramic capacitors. the correct selection of external components ensures high efficien- cy, low output ripple, and fast transient response. inductor selection a 1? inductor is recommended for use with themax8640z, and 2.2? is recommended for the max8640y. a 1? inductor is physically smaller but requires faster switching, resulting in some efficiency loss. table 1 lists several recommended inductors. it is acceptable to use a 1.5? inductor with either the max8640y or max8640z, but efficiency and ripple should be verified. similarly, it is acceptable to use a 3.3? inductor with the max8640y, but performance should be verified. for optimum voltage positioning of load transients, choose an inductor with dc series resistance in the 75m to 150m range. for higher efficiency at heavy loads (above 200ma) or minimal load regulation (butsome transient overshoot), the resistance should be kept as low as possible. for light-load applications up to 200ma, higher resistance is acceptable with very lit- tle impact on performance. capacitor selection output capacitor the output capacitor, c2, is required to keep the outputvoltage ripple small and to ensure regulation loop sta- bility. c2 must have low impedance at the switching fre- quency. ceramic capacitors are recommended due to their small size and low esr. make sure the capacitor maintains its capacitance over temperature and dc bias. capacitors with x5r or x7r temperature charac- teristics typically perform well. the output capacitance can be very low; see the selector guide for recom- mended capacitance values. for optimum load-tran-sient performance and very low output ripple, the output capacitor value in ? should be equal to or larger than the inductor value in ?. max8640 shdngnd 100k in esd diode vin 4.7nf figure 2. using an r and c circuit to create an always on regu- lator pwm logic max8640y max8640z gnd lx in shdn 0.6v out figure 1. simplified functional diagram downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 7 maxim integrated table 1. suggested inductors manufacturer series inductance (?) dc resistance ( typ) current rating (ma) dimensions l x w x h (mm) mipft2520d 2.0 0.16 900 2.5 x 2.0 x 0.5 1.5 0.07 1500 2.2 0.08 1300 fdk mipf2520d 3.3 0.10 1200 2.5 x 2.0 x 1.0 1.0 0.12 1200 1.5 0.16 1000 murata lqm31p 2.2 0.22 900 3.2 x 1.6 x 0.95 1.2 0.08 590 1.5 0.09 520 sumida cdrh2d09 2.2 0.12 440 3.0 x 3.0 x 1.0 1.0 0.11 1100 1.5 0.13 1000 taiyo yuden ckp3216t 2.2 0.14 900 3.2 x 1.6 x 0.9 1.0 0.15 460 glf201208t 2.2 0.36 300 2.0 x 1.25 x 0.9 1.0 0.07 400 glf2012t 2.2 0.10 300 2.0 x 1.25 x 1.35 1.0 0.10 800 tdk glf251812t 2.2 0.20 600 2.5 x 1.8 x 1.35 1.0 0.05 1000 mdt2520-cr 2.2 0.08 700 2.5 x 2.0 x 1.0 1.0 0.07 1100 toko d2812c 2.2 0.14 770 2.8 x 2.8 x 1.2 input capacitor the input capacitor, c1, reduces the current peaksdrawn from the battery or input power source and reduces switching noise in the ic. the impedance of c1 at the switching frequency should be kept very low. ceramic capacitors are recommended due to their small size and low esr. make sure the capacitor main- tains its capacitance over temperature and dc bias. capacitors with x5r or x7r temperature characteristics typically perform well. due to the max8640y/ max8640z soft-start, the input capacitance can be very low. for optimum noise immunity and low input ripple, choose a capacitor value in ? that is equal to or larger than the inductor? value in ?. pcb layout and routing high switching frequencies and large peak currentsmake pcb layout a very important part of design. good design minimizes excessive emi on the feedback paths and voltage gradients in the ground plane, both of which can result in instability or regulation errors. connect the inductor, input capacitor, and output capacitor as close together as possible, and keep their traces short, direct, and wide. connect the two gnd pins under the ic and directly to the grounds of the input and output capacitors. keep noisy traces, such as the lx node, as short as possible. refer to the max8640z evaluation kit for an example pcb layout and routing scheme. downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 8 maxim integrated selector guide recommended components part output voltage (v) frequency (mhz) l1 (?) c2 (?) top mark max8640y ext08 0.8 1.2 2.2 10 acq max8640yext10 1.0 1.6 2.2 4.7 adf max8640yext11 1.1 1.7 2.2 4.7 acr max8640yext12 1.2 1.8 2.2 4.7 acs max8640yext13 1.3 1.9 2.2 4.7 acg max8640yext15 1.5 2.0 2.2 4.7 add max8640yext16 1.6 2.0 2.2 4.7 adb max8640yext18 1.8 2.0 2.2 4.7 aci max8640yext19 1.9 2.0 2.2 4.7 ach max8640yext24 2.4 2.0 2.2 4.7 adm max8640yext25 2.5 1.7 2.2 4.7 acj max8640yext82 2.85 1.5 2.2 4.7 adj max8640yelt08 0.8 1.2 2.2 10 nb max8640yelt11 1.1 1.7 2.2 4.7 nc max8640yelt12 1.2 1.8 2.2 4.7 nd max8640yelt13 1.3 1.9 2.2 4.7 ne max8640yelt15 1.5 2.0 2.2 4.7 nf max8640yelt16 1.6 2.0 2.2 4.7 ng max8640yelt18 1.8 2.0 2.2 4.7 nh max8640yelt19 1.9 2.0 2.2 4.7 ni max8640yelt25 2.5 1.7 2.2 4.7 nj max8640yelt82 2.85 1.5 2.2 4.7 ow max8640z ext08 0.8 2.4 1 4.7 acl max8640zext11 1.1 3.4 1 2.2 acm max8640zext12 1.2 3.6 1 2.2 acn max8640zext13 1.3 3.7 1 2.2 aco max8640zext15 1.5 3.9 1 2.2 acp max8640zext18 1.8 4.0 1 2.2 acu max8640zelt08 0.8 2.4 1 4.7 nk max8640zelt11 1.1 3.4 1 2.2 nl downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 9 maxim integrated ordering information (continued) part* pin-package top mark max8640yext24+t 6 sc70 adm max8640yext25+t 6 sc70 acj max8640yelt08+t 6 ?fn nb max8640yelt11+t 6 ?fn nc max8640yelt12+t 6 ?fn nd max8640yelt13+t 6 ?fn ne max8640yelt15+t 6 ?fn nf max8640yelt16+t 6 ?fn ng max8640yelt18+t 6 ?fn nh max8640yelt19+t 6 ?fn ni max8640yelt25+t 6 ?fn nj max8640yelt82+t 6 ?fn ow part* pin-package top mark max8640z ext08+t 6 sc70 acl max8640zext11+t 6 sc70 acm max8640zext12+t 6 sc70 acn max8640zext13+t 6 sc70 aco max8640zext15+t 6 sc70 acp max8640zext18+t 6 sc70 acu max8640zelt08+t 6 ?fn nk max8640zelt11+t 6 ?fn nl max8640zelt12+t 6 ?fn nm max8640zelt13+t 6 ?fn nn max8640zelt15+t 6 ?fn no max8640zelt18+t 6 ?fn np chip information process: bicmos selector guide (continued) recommended components part output voltage (v) frequency (mhz) l1 (?) c2 (?) top mark max8640zelt12 1.2 3.6 1 2.2 nm max8640zelt13 1.3 3.7 1 2.2 nn max8640zelt15 1.5 3.9 1 2.2 no max8640zelt18 1.8 4.0 1 2.2 np * contact factory for availability of each version. for 2.85v output (82 version), request application note that includes limitations and typical operating characteristics. + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel. note: all devices are specified over the -40? to +85? operating temperature range. downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 10 maxim integrated scott schroeder 01/12/12 package information for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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 thepackage regardless of rohs status. package type package code document no. 6 ?fn l611-1 21-0147 6 sc70 x6s-1 21-0077 downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 11 maxim integrated scott schroeder 01/12/12 package information (continued) for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. downloaded from: http:///
max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters 12 maxim integrated package information (continued) for the latest package outline information and land patterns (footprints), go to www.maximintegrated.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. downloaded from: http:///
maxim integrated cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim integrated product. no circuit patent licenses are implied. maxim integrated reserves the right to change the circuitry and specifications without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated 160 rio robles, san jose, ca 95134 usa 1-408-601-1000 ________________________________ 13 2014 maxim integrated products, inc. maxim integrated and the maxim integrated logo are trademarks of maxim integrated products, inc. max8640y/max8640z tiny 500ma, 4mhz/2mhz synchronous step-down dc-dc converters revision history revision number revision date description pages changed 3 6/08 added max8640yext10+t voltage option 7 4 2/09 added max8640yext24+t voltage option andmax8640yelt82+max8640yext82+ (82 = 2.85v), and corrected error 1, 2, 7, 8 5 8/14 updated electrical characteristics table, pin description , and shutdown mode sections 2, 5 downloaded from: http:///

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