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1 parameter symbol limit unit vin voltage vin gnd-0.3 to 6 v vo voltage vo gnd-0.3 to 6 v en1,en2 voltage ven gnd-0.3 to vin+0.3 v vo current, led current io, iled 1500 * ma operating temperature top -40 to +85 c storage temperature tstg -40 to +125 c ELM901Fxa 1a 2x charge pump led driver ELM901Fxa-s symbol a package f: qfn b package type a: qfn16-4x4 b: qfn16-3x3(under development) c product version a d taping direction s: refer to pkg file elm901 f x a - s a b c d general description features maximum absolute ratings selection guide ? camera light supply ? high luminosity led ?ashlight application 11 - ? low voltage operation : 2.6v-4.4v ? low power operation : 300 a (1x), 9ma(2x) ? low standby current : max.1 a ? large output current : max.1a ? led protection : high current lightening timer ? internal led constant current circuit : external resistance program ? soft-start : led current start and switch of 1x & 2x mode ? package : qfn16-4x4, qfn16-3x3(under development) ? thermal shutdown function included ELM901Fxa is a high current led driver with internal automatic mode switch pump circuit of pass-through mode (1x mode) and boost charge mode (2x mode) and constant current drive circuit; maximum output current of elm901 series can reach 1a. elm901 series is ideally suited for high luminosity white led electrical applications which are powered by 1-cell lithium-ion/polymer battery. the required external parts of elm901 series can be limited to the minimum of 3 capacitors and 3 programming resistors. with 4mm x 4mm & 3mm x 3mm qfn package, elm901 series is possible to be assembled within limited space. the sink current, which can be switched to 3 different kinds by enable signal during operation,of led pin is set by external programming resistors. for led protection, it is possible to set high current lighting timer with external resistor; the light will be turned off forcibly by timer (3 options among 0.2 sec. to 1 sec.). built-in soft-start circuitry makes elm901 series be able to limit excessive power during start-up and switch of 1x & 2x mode. * based on long-term current denslty limitations. assumes an operating duty cycle of 10% under absolute maximum conditions for durations less than 10 seconds. max current for continuous operation is 600ma.
2 pin configuration ELM901Fxa 1a 2x charge pump led driver qfn16-4x4(top view) 4 3 2 1 1 6 1 5 1 4 1 3 1 2 1 1 1 0 9 8 7 6 5 qfn16-4x4(bottom view) 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 pin no. pin name 1 iset2 2 iset1 3 en2 4 en1 5 agnd 6 fs 7 vin 8 pgnd1 9 cm 10 pvin 11 cp 12 nc 13 vo 14 nc 15 pgnd2 16 led qfn16-3x3(top view) qfn16-3x3(bottom view) 4 3 2 1 1 6 1 5 1 4 1 3 1 2 1 1 1 0 9 8 7 6 5 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 1 3 1 4 1 5 1 6 11 - pin description iset2 : led current setting 2 the pin that is for the connection of led current setting resistor(rset2) between iset2-gnd. the output becomes 1.22v constantly when en2 is high. the constant current of led pin will be 3250x of the one ?ows to iset2. (e.g.) when rset2=6.8k, iled=1.22/6.8k3250=583ma. iset1 : led current setting 1 the pin that is for the connection of led current setting resistor(rset1) between iset1-gnd. the output becomes 1.22v constantly when en1 is high. the constant current of led pin will be 3250x of the one ?ows to iset1. (e.g.) when rset1=20k, iled=1.22/20k3250=198.3ma. en2 : on/off control 2 led output current on/off control pin of set current of iset2. this pin is pulled down to ground inside the ic and the control logic is high active. the set current of iset2 sinks from led pin when this pin is connected to vin.
3 ELM901Fxa 1a 2x charge pump led driver 11 - en1 : on/off control 1 led output current on/off control pin of set current of iset1. this pin is pulled down to ground inside the ic and the control logic is high active. the set current of iset1 sinks from led pin when this pin is connected to vin. agnd : internal analog circuit ground this pin should be connected to gnd of internal analog circuit and is connected in short circuit with internal circuit on back pad. the connection to pgnd1 & pgnd2 is required and should be designed according to the external wiring. fs : fail safe setting when en1=en2=1 continues for a period of time, fail safe function will turn down led current forcibly. this function aims for thermal protection of led, and it is possible to be turned off. there are 3 timer options according to the resistor connected between fs and gnd since en1=en2=1 until led current is off: (1)1s when the resistor is short, (2)0.2s when the resistor is 20k, and (3)0.5s when the resistor is 51k. this fail safe function becomes ineffective when it is short between fs and vin or fs is open. vin : internal circuit power this pin should be connected to the power pin of internal circuit. the connection to pvin is required and should be designed according to the external wiring; gnd-connected ceramic capacitor( above 2.2f) is also necessary. pgnd1 : charge pump circuit ground this pin should be connected to gnd of charge pump circuit. the connection to agnd & pgnd2 is required and should be designed according to the external wiring. cm : step-up capacitor connection( low potential) this pin should be connected to the low potential of step-up capacitor. the wiring of step-up capacitor should be connected between cm and cp as closely as possible; elm recommends using 2.2f capacitor. pvin : charge pump power this pin is power supply of charge pump circuit. this pin should be connected to vin according to the external wiring. cp : step-up capacitor connection( high potential) this pin should be connected to the high potential of step-up capacitor. the wiring of step-up capacitor should be connected between cm and cp as close as possible; elm recommends using 2.2f capacitor. vo : step-up output the output voltage is almost the same as vin under 1x mode, while it becomes 5.5v under step-up mode. this pin should be connected to led anode. pgnd2 : led current drive circuit ground this pin should be connected to the gnd of led current drive circuit. the connection to agnd & pgnd1 is required and should be designed according to the external wiring. led : constant current sink to sink the output current which is set by iset1 & iset2. this pin should be connected to led cathode.
4 standard circuit ELM901Fxa 1a 2x charge pump led driver 11 - charge pump 900khz osc timer cc control nc 12 11 10 9 cp pvin cm 13 14 15 16 1 2 3 4 5 6 6 7 8 pgnd1 vin fs agnd c3 rfs en1 en2 iset1 iset2 rset2 rset1 led pgnd2 nc vo c1 c2 led block diagram x1/x2 charge pump pvin cp cm vin fs en1 en2 iset1 iset2 agnd pgnd2 pgnd1 led vo x1/x2 switch drop out detection vref vref(soft) short protection thermal protection step-up circuit 900khz oscillator current sense control control logic fail safe circuit
5 ELM901Fxa 1a 2x charge pump led driver operation 11 - elm901 is designed to drive high luminosity led which is powered by 1 lithium-ion/polymer battery with constant current. when the battery voltage is much higher than led forward voltage, led is lit by connecting directly to the battery; output voltage is stepped up to 5.5v by internal charge pump circuit to light led when voltage drops. led current is driven by the constant current circuit which is set by external programming resis - tors. with 2 types of led current programming resistors, 3 current-driving options can be designed by different combinations of enable circuit. elm901a is capable of supplying output current up to 1a and thus able to pro - vide high luminosity. to avoid led burnout caused by longtime lighting by large current, the internal lighting timer of elm901a can shut down current forcibly. the timer only operates when maximum setting current is on and can be set to 3 options-0.2s, 0.5s, 1s by external resistors connected to fs. this timer can be turned off when it is short between fs and vin or fs is open. operation right after power is supplied elm901 becomes standby operation when en1=en2=0 or open(standby); unde this operation, high resistance pmos switch between vin and vo becomes on. pmos switch (=switch 4) between cp and vo and nmos switch (=switch 1) between cm and pgnd1 also become on. hence, output capacitor co and ?ying capacitor c1 are gradually charged through high resistance pmos switch; it takes 5ms to full- charge after the power is on. rush current may happen when operation starts within 5ms after power is on. standby mode in this mode, output capacitor co and ?ying capacitor become fully charged, and through individual high resistance pmos switch, vin is turned to be output mode. with maintenance of fully-charged mode during standby situation, it is possible to avoid rush current when operation begins and lighten led rapidly . start-up mode during start-up, elm901 detects vo short ?rst; the low resistance switch between vin-vo becomes on and operates in 1x mode if short is not detected. when short is detected, vo maintains the same condi - tion as in standby mode, the output of led also remains off while other internal circuits are operated nor - mally. 1x mode is operated right after short is solved. it takes 30ms(typ.) from start-up to 1x mode output. vo=vin under normal operation, and inrush current does not occur due to the charge of capacitor. when abnormality (vo>0.7v) such as short between vo and gnd which is resulted from resistance of 10~1k, inrush current occurs due to the charge of capacitor. led current becomes on after 130s(typ.) after starp- up; it takes less than 100us since led current becomes on until the set current ? ows. 1x mode when dropout of led pin is detected under 1x mode, the operation switches to 2x mode automatically. when led current works under low current mode, the operation remains 1x mode for around 150ms even if the dropout of led pin is detected; if dropout is dissolved during this period of time, timer is reset and 1x mode continues. when the operation is by high or low+high current, it becomes 2x mode after 2ms; if dropout is dissolved during this period of time, timer is reset and 1x mode continues. dropout de - tection voltage is in proportion to iled when it is above 240ma(typ.) and the voltage is regulated to 100mv when iled is small.
6 ELM901Fxa 1a 2x charge pump led driver 11 - soft step-up the operation becomes soft step-up by charge pump operation right after 2x mode starts. rush current is decreased by soft step-up which increases vo straight. the current is controlled when iled becomes 1/2 of the setting during soft step-up. iled is limited under 350ma(typ.) forcibly to avoid abrupt change of iled within 10us after step-up operation starts. iled control current returns to the setting after step-up is ? nished. 2x mode after switching to normal 2x mode, operation remains this mode until standby mode(en1=en2=gnd) starts. to work under 1x mode again, it is necessary to restart after switching to standby mode. protection function thermal protection when junction temperature becomes over 150c, vo output is turned to be off (only high resistance pmos switch is on)thermal shutdown circuit and led output is shut down by thermal shutdown circuit. to shut down thermal protection, it is necessary to restart operation after returning to standby mode. iset1/iset2 short protection when en1=01 during start-up, if rset which is connected to iset1 is under 3.9k(setting current of iled is above 1a),led current which is the same with[low] current is shut down. if iset2 is under normal operation under this situation, led current which is the same with[high] current is ?owed. when it is short between iset1 and gnd under the operation that en1=1, led current limit is detected by 1.5a and shut down without ?owing to en logic. when en2=01 during start-up, if rset which is connected to iset2 is under 3.9k( setting current of iled is above 1a), led current which is the same with[high] current is shut down. if iset1 is under nor - mal operation under this situation, led current which is the same with[low] current is ?owed. when it is short between iset2 and gnd under the operation that en2=1, led current limit is detected by 1.5a and shut down without ?owing to en logic. led current becomes 0 when [low]+[high]current reaches 1.5a under en1=en2=1 under the above-men - tioned 2 situations. vo short protection when vo lowers to around 0.7v during operation, device shuts down the outputs of both vo and led; vin and vo become connected by high resistance pmos switch(standby output) under this situation. after vo short is dissolved and vo rises above 0.7v, outputs of vo and led restart. when vo short is detected un - der 2x mode, the operation switches to standby mode. fail safe function fail safe function refers to the function that the output of led is turned to be off automatically when low+high current(en1=en2=1) continues for certain period of time. to dissolve the function that led output is turned to be off forcibly, it is necessary to switch en1=en2=1 to other modes. 3 options are available for fs time; fs time is set by external resistors (rfs). this function can be turned off by setting short between fs and vin pins or fs to be open.
7 ELM901Fxa 1a 2x charge pump led driver parameter symbol condition min. typ. max. unit input voltage range vin 2.6 4.4 v current consumption under still condition 1 iqs1 1x mode, iled=0ma 300 550 a current consumption under still condition 2 iqs2 2x mode, iled=0ma 9 16 ma standby current isd en1=en2=0v 0.1 1.0 a led current led current ratio1 (iled/iset1/2) iled1 vin=3.8v, iled=200ma, vf=3.3v typ. 0.96 3250 typ. 1.04 ma/ma led current ratio2 (iled/iset1/2) iled2 vin=3.3 to 4.4v, iled=200 to 800ma typ. 0.90 3250 typ. 1.10 ma/ma iled dropout voltage1 vled1 (min.) mode switch threshold voltage, iled=300ma 125 225 mv iled dropout voltage2 vled2 (min.) mode switch threshold voltage, iled=150ma 80 100 120 mv mode switch delay time1 td1 en1=high, en2=low 100 150 200 ms mode switch delay time2 td2 en1=low or high, en2=high 1 2 3 ms led current on time led(on) since en is on until led current starts 50 130 250 s current capability iled (max.) vin=3.3v, en1=en2=high, set iled=1a, vf=4.6v 900 ma led current stablize time1 tiled1 iled=0ma200ma 40 s led current stablize time2 tiled2 iled=200ma700ma 60 s led current during soft step-up iled (soft) set iled=700ma 250 350 450 ma charge pump soft step-up tsoft iled=700ma, vo=3.7v5.2v 75 150 300 s 1x mode output voltage vo(x1) iled=0ma vin v 2x mode output voltage vo(x2) iled=0ma typ. 0.95 5.5 typ. 1.05 v 1x mode output impedance ro(x1) vin=3.4v 0.25 0.37 2x mode output impedance ro(x2) (2vin-vo)/io, vin=3.2v, vo=5.1v 1.70 2.55 oscillation frequency fosc 0.72 0.90 1.08 mhz en1, en2 output on control voltage vc(on) vin=2.9 to 4.4v, each pin 0.95 v output off control voltage vc(off) vin=2.9 to 4.4v, each pin 0.45 v en bias current ic(on) ven=3.6v, each pin 20 50 a iset1, iset2 reference voltage vref iset=50a, each pin 1.202 1.220 1.238 v iset set current iset each pin 310 a electrical characteristics when conditions are not mentioned speci?cally, vin=3.6v, cin=c1=2.2 f, co=4.7 f, ta=25c 11 -
8 parameter symbol condition min. typ. max. unit short protection circuit iled limit when iset is short iled (short) iset1&2 turn iled to be off for short protection, vin=3.9v, vled=1.0v, 2x operation 1.5 a vo short protection detection voltage vo (short) iled is off when short protection is activated 0.45 0.60 0.95 v vo short current ishort vin=3.6v 30 ma thermal protection circuit thermal protection circuit ohp iled is off when thermal protection circuit is activated 150 c fail safe circuit fail safe set range tfs (range) * fail safe function is off when fs-vin is short or open. 0.2 1.0 s fail safe time1 tfs1 0.80 1.00 1.20 s fail safe time2 tfs2 0.16 0.20 0.24 s fail safe time3 tfs3 0.40 0.50 0.60 s fail safe current ifs 10 15 20 a fs threshold voltage1 vfs1 0.120 0.150 0.180 v fs threshold voltage2 vfs2 0.405 0.450 0.495 v fs threshold voltage3 vfs3 1.080 1.220 1.360 v ELM901Fxa 1a 2x charge pump led driver parameter condition en logic & led current en logic en1 en2 * en1 & en2 will be in standby mode when being pulled down to be open. standby(output off) 0 0 low current 1 0 high current 0 1 low+high current 1 1 marking 11 - ? qfn16-4x4 package : ELM901Faa ? qfn16-3x3 package : ELM901Fba e l m b c 9 0 1 f a a a e l m b c 9 0 1 f b a a mark content ELM901Faa name abc ( 000 to 999) assembly lot no. mark content ELM901Fba name abc ( 000 to 999) assembly lot no.
9 ELM901Fxa 1a 2x charge pump led driver typical characteristics 11 - 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 10 20 30 40 50 60 70 80 90 100 efficiency-vin vin (v) efficiency (%) iled= 200ma 400ma 600ma 800ma led = lumileds lxhl-lw3c 200 400 600 800 1000 0.1 0.2 0.3 0.4 0.5 0 dropout voltage-iled iled (ma) dropout voltage (v) 0 20 40 60 80 100 120 140 160 180 200 0 100 200 300 400 500 600 700 800 900 1000 iled-rset rset (k ? ) iled (ma) 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 100 200 300 400 500 600 700 800 900 1000 iled-vled vled (v) iled (ma) iled=800ma 600ma 400ma 200ma 100ma -40 -20 0 20 40 60 80 0 0.05 0.1 0.15 0.2 0.25 1x mode output resistance - top top ( ? ) 1x mode output resistance ( ? ) vin=3.3v vin=3.6v vin=3.9v -40 -20 0 20 40 60 80 0 0.5 1 1.5 2 2.5 2x mode output resistance - top top ( ? ) 2x mode output resistance ( ? ) vin=3.2v, vo=4.8v
10 ELM901Fxa 1a 2x charge pump led driver 11 - 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 0 0.02 0.04 0.06 0.08 0.1 isd-vin vin (v) isd ( ? a) top=85 ? top= ?? 40 ? top=25 ? 2.6 2.8 3 3.2 3.4 3.6 3.8 4 4.2 4.4 820 840 860 880 900 920 940 frequency - vin vin (v) frequency (khz) top=85 ? top=25 ? top= -40 ? -40 -20 0 20 40 60 80 1.2 1.21 1.22 1.23 1.24 vref-top top ( ? ) vref (v) -40 -20 0 20 40 60 80 10 15 20 25 30 en pin input current-top top ( ? ) en pin input current (ua) -40 -20 0 20 40 60 80 0.5 0.6 0.7 0.8 0.9 en threshold voltage-top top ( ? ) en thereshold voltage (v) -40 -20 0 20 40 60 80 3200 3220 3240 3260 3280 3300 iled/iset ratio-top top ( ? ) iled/iset ratio
11 ELM901Fxa 1a 2x charge pump led driver 11 - 0 200 400 600 800 3150 3200 3250 3300 3350 iled/iset ratio-iled iled (ma) iled/iset ratio top= -40 ? top=25 ? top=85 ? 0 80 160 240 320 400 0 100 200 300 iled start response time (us) v(en1) : 0v ? 3.6v iled (ma) vin=3.6v, iled=0ma ? 200ma 0 0.8 1.6 2.4 3.2 4 0 400 800 1x to 2x mode switch response time (ms) v(en2) : 0v ? 3.6v iled (ma) vin=3.6v, iled=200ma ? 800ma vo iled vo, v(en2) (2v/div) 0 2 4 6 8 10 -40 -20 0 20 40 -200 -100 0 100 200 iled, vo ripple voltage time (us) vo a/c coulpled iled (ma) vin=3.6v, iled=800ma iled a/c coulpled vo (mv)

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