1 rev.1.0 parameter symbol limit unit vin power supply voltage vin -0.3 to +6.0 v apply voltage to sw vsw gnd-0.3 to vout+0.3 v apply voltage to fb vfb gnd-0.3 to vout+0.3 v apply voltage to en ven gnd-0.3 to vout+0.3 v apply voltage to vout vout -0.3 to +6.0 v power dissipation pd 250 mw operating temperature range top -30 to +85 c storage temperature range tstg -65 to 125 c general description features maximum absolute ratings ? cellular phone ? digital camera ? mp3 player ? portable machine ? wireless handset application 10 - ? current mode control ? output voltage drop protection ? thermal shutdown protection and short circuit protection ? input voltage : 0.6v to 5.0v ? output voltage : 2.5v to 6.0v ? low current consumption : typ.300 a ? shutdown current : < 1a ? low start-up voltage : typ.0.9v ? low switch on (internal switch) resistance : 0.35 ? constant frequency : typ.1.4mhz ? high ef?ciency : 96% ? package : sot-26 ELM620BA is synchronous pwm step-up dc/dc converter with high ef?ciency and 1.4mhz ?xed frequency; by adopting synchronous switch, ELM620BA is able to provide high ef?ciency without external schottky diode. ELM620BA is able to activate within the range from 0.6v to 5v of input voltage and 2.5v to 6v of output one. for 3v or 3.3v output, ELM620BA can provide current up to 260ma by a single aa cell, or to 600ma by 2 serial-connected aa cells. with 1.4mhz switching frequency, small coils and capacitors can be adopted; therefore, ELM620BA is possible to be assembled within small areas on the board . caution:permanent damage to the device may occur when ratings above maximum absolute ones are used. * taping direction is one way. ELM620BA-s symbol a package b: sot-26 b product version a c taping direction s: refer to pkg file ELM620BA - s a b c selection guide elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
2 rev.1.0 pin assignment 1) sw (pin 1) : switch pin. connect inductor between sw and vin. keep these pcb trace lengths as short and wide as possible to reduce emi and voltage overshoot. 2) gnd (pin 2) : signal and power ground. provide a short direct pcb path between gnd and the (?) side of output capacitor(s). 3) fb (pin 3) : feedback input to gm error ampli?er. connect resistor divider tap to this pin. the output voltage can be adjusted from 2.5v to 6v by : vout = 1.203v (1 + r1 ) r2 4) en (pin 4) : logic controlled shutdown input. en = high: normal free running operation, 1.4mhz typical operating frequency. en = low: shutdown, quies - cent current < 1a. output capacitor can be completely discharged through the load or feedback resistors. 5) vout (pin 5) : output voltage sense input and drain of internal synchronous recti?er mosfet. bias is derived from vout. pcb trace length from vout to output ?lter capacitor(s) should be as short and wide as possible. 6) vin (pin 6) : battery input voltage. the device gets its start-up bias from vin. once vout exceeds vin, bias comes from vout. thus, once operation is started, it is completely independent from vin and only limited by output power level and batterys internal series resistance. sot-26(top view) 1 2 3 6 5 4 pin configuration pin no. pin name pin description 1 sw switch 2 gnd ground 3 fb feedback 4 en on/off control (high enable) 5 vout output 6 vin input 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
3 rev.1.0 block diagram ? + ? + ? ? ? + optional en sw vin fb vout gnd optional schottky l 2.2h cin 22f 1v to 5v input vout 1.203v ref r1 1.02m 1% r2 604k 1% cff cout 22f 0.45 0.35 current sense g m error amp pwm comp pwm control slope comp sync drive control ramp gen 1.4mhz shutdown control shutdown elm620 b a start-up osc a/b mux a b 2.3v rc 80k cp 2 2.5pf cc 150pf vout good standard circuit + fb vout gnd vin ELM620BA vin optional schottky vout sw en on/off l=2.2h cin= 22f cout 22f r1= 1.02m 1% r2 604k 1% r1 vout=(1+ )1.203 r2 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
4 rev.1.0 parameter symbol condition min. typ. max. unit output voltage range (adj.) vout 2.5 6.0 v minimum start-up voltage vst iload=1ma 0.9 1.1 v minimum operating voltage vin en=vin 0.60 0.75 v switching frequency fsw 1.1 1.4 1.7 mhz maximum duty cycle dmax vfb=1.15v 80 87 % current limit delay to output tllimdly 40 ns feedback voltage vfb 1.165 1.203 1.241 v feedback input current ifb vfb=1.22v 1 na nmos switch leakage ileakn vsw=5v 0.1 5.0 a pmos switch leakage ileakp vsw=0v 0.1 5.0 a nmos switch on resistance rswn vout=3.3v 0.35 pmos switch on resistance rswp vout=3.3v 0.45 nmos current limit ilimn 700 950 ma quiescent current (active) iq measured on vout, non-switching 300 500 a shutdown current is ven=0v, including switch leakage 0.1 1.0 a en input high venh 1 v en input low venl 0.35 v en input current ien ven=5.5v 0.01 1.00 a electrical characteristics vin=1.2v, vout=3.3v, top=25 c , unless otherwise noted 10 - test circuits v i n s w f b l = 2 . 2 h e n g n d e l m 6 2 0 b a v o u t s b d r 2 r 1 r l v o u t c i n = 2 2 f v i n c o u t = 2 2 f elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
5 rev.1.0 application notes figure 1: recommended component placement for single layer board with optional schottky diode. traces car - rying high current are direct. trace area at fb pin is small. lead length to battery is short. 2) inductor selection ELM620BA can utilize small surface mount and chip inductors due to its fast 1.4mhz switching frequency. typically, a 2.2h inductor is recommended for most applications; larger values of inductance will allow great - er output current capability by reducing the inductor ripple current. increasing the inductance above 10h will i ncrease size while providing little improvement in output current capability . iout(max) = (ip ? vind ) (1 ? d) 2fl where: = estimated ef?ciency ip = peak current limit value (0.7a) vin = input (battery) voltage d = steady-state duty ratio = (vout ? vin) / vout f = switching frequency (1.4mhz typical) l = inductance value the inductor current ripple is typically set for 20% to 40% of the maximum inductor current (ip). high fre - quency ferrite core inductor materials reduce frequency dependent power losses compared to cheaper powdered iron types. the inductor should have low esr (series resistance of the windings) to reduce the i 2 r power losses, and must be able to handle the peak inductor current without saturating. molded chokes and some chip induc - tors usually do not have enough core to support the peak inductor currents of 950ma seen on ELM620BA. to minimize radiated noise, elm recommends using a toroid, pot core or shielded bobbin inductor. see table for some suggested components and suppliers. fig-1 1) pcb layout guidelines the high speed operation of ELM620BA demands careful attention to board layout, and in order to get adver - tised performance, a well-planned layout is required. figure-1 is an example which shows the recommended component placement with optional schottky diode. a large ground pin copper area will help to lower the chip temperature. a multilayer board with a separate ground plane is ideal, but not absolutely necessary. part l max. dcr max. dc current size: w l h vendor (h) (m) (a) (mm3) cdrh3d16 2.2 75 1.2 3.8 3.81.8 sumida cdh3b16 2.2 70 1.2 4.0 4.01.8 ceaiya table : recommended inductors. 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter 3 en vout vin 1 2 6 5 4 sw vin gnd fb en vout
6 rev.1.0 marking a b c d ? e sot-26 a to e : assembly lot no. a to z (i, o, x excepted) and 0 to 9 3) output and input capacitor selection low esr (equivalent series resistance) capacitors should be used to minimize the output voltage ripple. mul - tilayer ceramic capacitors are an excellent choice, as they have extremely low esr and are available in small footprints. a 4.7f to 22f output capacitor is suf?cient for most applications; larger values up to 22f may be used to obtain extremely low output voltage ripple and improve transient response. an additional phase lead ca - pacitor may be required with output capacitors larger than 10f to maintain acceptable phase margin. x5r and x7r dielectric materials are preferred for their ability to maintain capacitance over wide voltage and tempera - ture ranges. low esr input capacitors reduce input switching noise and reduce the peak current drawn from the battery. it follows that ceramic capacitors are also a good choice for input decoupling and should be located as closely as possible to the device. a 10f input capacitor is suf?cient for virtually any application. larger values may be used without limitations. 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
7 rev.1.0 typical characteristics ? vout=3.3v : cin=22f, cout=22f, l=2.2h, r1=46.6k , r2=26.7k , top=25c ? v=3.3v 1 10 100 1000 1 2 3 4 vin=2.4v vin=1.8v vin=1.5v iout (ma) vout (v) vout-iout vin=3v 0 10 20 30 40 50 0.1 0.2 0.3 0.4 0.5 0.6 0.7 iout (ma) vhold (v) vhold-iout 0 0.5 1 1.5 2 2.5 3 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 iout=1ma 10ma 100ma vin (v) vout (v) vout-vin 0.1 1 10 100 1000 0 20 40 60 80 100 vin=1.5v vin=1.8v vin=2.4v iout (ma) efficiency (%) efficiency-iout vin=3v 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
8 rev.1.0 0 0.4 0.8 1.2 1.6 2 2.4 2.8 3.2 3.6 4 0 1 2 3 0 1 2 time (ms) start response vout (v) ven (v) vin=ven=1.8v, no load 3.5 0 2 4 6 8 10 12 14 16 18 20 3.2 3.4 0 0.1 time (ms) load transient response vout (v) iout (a) vin=1.8v, iout=0.1ma ? 0.1a 3.3 3.5 0 10 20 30 40 50 0.8 0.9 1.0 1.1 1.2 iout (ma) vst (v) vst-iout -40 -20 0 20 40 60 80 3.26 3.28 3.30 3.32 3.34 top ( ? ) vout (v) vout-top vin=1.5v, iout=0.1a 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
9 rev.1.0 ? vout=5.0v : cin=22f, cout=22f, l=2.2h, r1=68.5k , r2=21.7k , top=25c ? v=5.0v 1 10 100 1 2 3 4 5 6 vin=1.8v vin=3v iout (ma) vout (v) vout-iout 0 10 20 30 40 50 0.3 0.4 0.5 0.6 0.7 0.8 0.9 iout (ma) vhold (v) vhold-iout 0 0.5 1 1.5 2 2.5 3 3.5 4 1.0 2.0 3.0 4.0 5.0 6.0 iout=1ma 10ma 100ma vin (v) vout (v) vout-vin 0.1 1 10 100 0 20 40 60 80 100 vin=1.8v vin=3v iout (ma) efficiency (%) efficiency-iout 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
10 rev.1.0 0 0.2 0.4 0.6 0.8 1 0 1 2 3 4 5 6 0 1 2 3 time (ms) start response vout (v) ven (v) vin=vec=3v, no load 0 2 4 6 8 10 12 14 16 18 20 5 5.25 0 0.1 time (ms) load transient response vout (v) iout (a) vin=3v, iout=0.1ma ? 0.1a 5.125 4.875 0 10 20 30 40 50 0.8 0.9 1.0 1.1 1.2 iout (ma) vst (v) vst-iout -40 -20 0 20 40 60 80 4.90 4.95 5.00 5.05 5.10 top ( ? ) vout (v) vout-top vin=3v, iout=0.1a 10 - elm620b a 1.4mhz high ef?ciency synchronous pwm step up dc/dc converter
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