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-1 to vin+1 (6v max.) v gnd-1 to vin-3 (20ns max.) apply voltage to vout vout -0.3 to +6.0 v apply voltage to en ven gnd-0.3 to vin+0.3 v power dissipation pd 200 mw operating temperature range top -40 to +85 c storage temperature range tstg -65 to +150 c elm601b a 1.5a 2.5mhz high ef?ciency synchronous pwm step-down dc/dc converter general description features maximum absolute ratings ? bluetooth product ? dsc and pmp ? gps device ? pol regulator ? portable hdd ? wireless lan application 7 - ? low output noise across load range ? excellent transient response ? start up into pre-bias output ? internal soft start ? input under-voltage lockout ? over voltage protection ? short circuit protection ? thermal shutdown protection ? input voltage : 2.9v to 5.5v ? output voltage range (adj.) : 1v to 5v ? output current : max.1.5a ? shutdown current : typ.1a ? high ef?ciency : 93% ? constant frequency : typ.2.5mhz ? duty-cycle low dropout operation : 0 to 100% ? package : sot-25 ELM601BA is high efficiency synchronous step down dc/dc converter operated with current mode and 2.5mhz constant frequency; internal switch and synchronous rectifier are integrated for high efficiency. in application, ELM601BA does not require any external schottky diode. internal current consumption under operation of ELM601BA is as low as 300a and shutdown current is typ.1a. with supply voltage from 2.9 v to 5.5v, ELM601BA can supply load current of 1.5a. the output voltage range of ELM601BA is 1v to 5v, and can be adjusted by fb pin. with 2.5mhz switching frequency, ELM601BA makes it possible to adopt small surface amount inductors and capacitors. switch duty cycle would be on continuously and 100% at maximum when input voltage is set to be lower than output voltage. caution:permanent damage to the device may occur when ratings above maximum absolute ones are used.
2 rev.1.0 sot-25(top view) 1 2 3 5 4 pin configuration 7 - pin no. pin name pin description 1 vin input power supply 2 gnd ground 3 en enable control input 4 fb feedback input 5 sw switching node. pins description vin : input power supply. powers the internal circuitry and is connected to the source of high side p channel mosfet. gnd : ground. en : enable pin. when connected to logic high or tied to vin pin, ELM601BA is on. when connected to logic low, the device enters shutdown and current consumption typ.1ua. the enable pin has a 1m internal pull-down resistor. this resistor is switched in circuit whenever the en pin is below the enable input high threshold, or when the part is in under-voltage lockout. fb : input to control output voltage. sw : switching node. the inductor should be connected between this pin and output capacitor. * taping direction is one way. ELM601BA-s symbol a package b: sot-25 b product version a c taping direction s: refer to pkg file ELM601BA - s a b c selection guide elm601b a 1.5a 2.5mhz high ef?ciency synchronous pwm step-down dc/dc converter
3 rev.1.0 block diagram 7 - standard circuit en sw gnd vin vin fb ELM601BA cin= enable vout r1 r2 cout= l=1.2h 10f 10f + _ + _ reference en 1.0v fb oscillator error ampli?er slope comp pwm comparator clock pwm logic vin m1 m2 sw gnd current sense ampli?er shut down control ? vout = 1.0 (1 + r1/r2) elm601b a 1.5a 2.5mhz high ef?ciency synchronous pwm step-down dc/dc converter
4 rev.1.0 parameter symbol test condition min. typ. max. unit supply voltage vin 2.9 5.5 v output voltage vout adjustable 1 5 v output current iout 1.5 a output voltage tolerance * vout vin=3.6v to 5.0v, no load -2.5 +2.5 % feedback voltage vfb top=+25c 0.98 1.00 1.02 v current limit ilimit peak inductor current 2.0 a under-voltage lockout uvlo rising vin 2.60 2.70 2.80 v hysteresis 250 mv quiescent current iq en=vin, no switching 300 a vin shutdown current ishdn en=gnd 1 10 a high side switch resistance rdsonp ilx=100ma 150 m low side switch resistance rdsonn ilx=-100ma 125 m sw leakage current ilk(sw) vin=5.5v, sw=0v, en=gnd 1 10 a vin=5.5v, sw=5.0v, en=gnd -10 -1 line regulation vline-reg vin=3.6v to 5.0v, iout=0a -1.0 % load regulation vload-reg vin=5.0v, iout=10ma to 1.5a -1.0 % oscillator frequency fosc 2.0 2.5 3.0 mhz soft-start time tss 100 s en input high current ien_hi en=vin -2.0 2.0 a en input low current ien_lo en=gnd -2.0 2.0 a en input high threshold ven_hi 1.2 v en input low threshold ven_lo 0.4 v fb over voltage protection vovp 115 % thermal shutdown temperature tsd junction temperature +160 c thermal shutdown hysteresis tsd_hys junction temperature 10 c electrical characteristics vin=5.0v, cin=10f, cout=10f, l=1.2h, top=25c, unless otherwise noted * : the output voltage tolerance includes output voltage accuracy, voltage drift over temperature and line regulation. 7 - test circuits v i n s w f b v i n l = 1 . 2 h c o u t = 1 0 f e l m 6 0 1 b a r 1 r 2 r l v o u t e n g n d c i n = 1 0 f elm601b a 1.5a 2.5mhz high ef?ciency synchronous pwm step-down dc/dc converter
5 rev.1.0 application notes ELM601BA is constant frequency current mode pwm step down converter which is suitable for applications that require high ef?ciency and small assembly area and use low voltage, wuch as li-ion battery . by external resistor divider, output voltage of ELM601BA can be set within the range from 1v to 5v. to provide operation with high ef?ciency, ELM601BA consists of main switch and synchronous recti?er while external schottky diode is not necessary. duty cycle of ELM601BA can reach upto 100%. duty cycle of step down converter is de?ned as follows: d = ton fosc 100% (vout/vin) 100% ton=main switch on time; fosc=oscillator frequency (2.5mhz); vout=output voltage; vin=input voltage 1) current mode pwm control slope compensated current mode pwm control provides superior load and line response, and protection of in - ternal main switch and synchronous recti?er to current limit by stable switching and switch cycle. ELM601BA switches at a constant frequency (2.5mhz) and regulates output voltage. during each cycle, the pwm compara - tor modulates the power transferred to the load by changing inductor peak current which is based on the feed - back error voltage. under normal operation, the main switch is turned on for a certain time to ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor current is above the error voltage. when the main switch is off, the synchronous recti?er will be turned on immediately and stay on until either the next cycle starts or the inductor current drops to zero. 2) dropout operation ELM601BA allows the main switch to remain on for more than one switching cycle and increases duty cycle while the input voltage is dropping under the output voltage. when duty cycle reaches 100%, the main switch transistor would be on continuously to supply current to output until current limit generates. output voltage then is input voltage minus voltage drop across main switch the inductor . 3) short circuit protection ELM601BA consists of short circuit protection; when output is short to ground, the oscillator frequency is re - duced to prevent the inductor current from increasing beyond the p mosfet current limit. the frequency will return to normal values once the short circuit condition is recovered and the feedback voltage goes back to 0.6v . 4) maximum load current ELM601BA can operatewhen input voltage is down to 2.5v; however, the maximum load current would de - scend because of the increase ir drop which results from the on resistor of main switch and synchronous recti - ?er. along with the drop of input voltage. the slope compensation signal would reduce the peak inductor current to avoid sub-harmonic oscillations when duty cycle is larger than 50%; on the contrary, it would increase the peak inductor current when duty cycle is decreased, as which is shown in the graph. 7 - a b c d e sot-25 a to e : assembly lot no. a to z (i, o, x excepted) and 0 to 9 marking elm601b a 1.5a 2.5mhz high ef?ciency synchronous pwm step-down dc/dc converter
6 rev.1.0 7 - typical characteristics 0 1.5 3 4.5 0.4 0.8 1.2 1.6 2.0 2.4 iout=1ma 100ma vin (v) vout (v) vout-vin 5.5 ? v=1.8v 0.1 1 10 100 1000 0 20 40 60 80 100 vin=5v iout (ma) efficiency (%) efficiency-iout 0 0.5 1 1.5 2 0 1 2 0 1 2 3 4 5 time (ms) start response vout (v) ven (v) ven=vin=5v, no load 1 10 100 1000 1.7 1.8 1.9 vin=5v iout (ma) vout (v) vout-iout 0 0.2 0.4 0.6 0.8 1 1.5 2 2.5 0 1 2 time (ms) load transient response vout (v) iout (a) vin=5v, iout=10ma ? 1.3a 1.3 0 0.2 0.4 0.6 0.8 1 1.5 2 2.5 0 1 2 time (ms) load transient response vout (v) iout (a) vin=5v, iout=200ma ? 1.3a 1.3 ? vout=1.8v : cin=10f, cout=10f, l=1.2h, r1=44k , r2=55k , top=25c elm601b a 1.5a 2.5mhz high ef?ciency synchronous pwm step-down dc/dc converter
7 rev.1.0 ? v=3.3v 0 1.5 3 4.5 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 iout=1ma 100ma vin (v) vout (v) vout-vin 5.5 0.1 1 10 100 1000 0 20 40 60 80 100 vin=5v iout (ma) efficiency (%) efficiency-iout 0 0.5 1 1.5 2 0 1 2 3 0 1 2 3 4 5 time (ms) start response vout (v) ven (v) ven=vin=5v, no load 3.5 1 10 100 1000 3.1 3.2 3.3 3.4 3.5 vin=5v iout (ma) vout (v) vout-iout 0 0.5 1 1.5 2 2.5 3 3.5 4 3 3.5 4 0 1 2 time (ms) load transient response vout (v) iout (a) vin=5v, iout=10ma ? 1.3a 1.3 0 0.5 1 1.5 2 2.5 3 3.5 4 3 3.5 4 0 1 2 time (ms) load transient response vout (v) iout (a) vin=5v, iout=200ma ? 1.3a 1.3 7 - ? vout=3.3v : cin=10f, cout=10f, l=1.2h, r1=69k , r2=30k , top=25c elm601b a 1.5a 2.5mhz high ef?ciency synchronous pwm step-down dc/dc converter
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