r1240x/r1244n series 1.2a ? 30v input pwm step-down dc/dc converter no.ek-190-121001 step-down dc/dc converter the r1240x/r1244n series are 30v input, cmos-based pwm step-down dc/dc converters featuring 1.2a ? output current. r1240x/r1244n include a soft start circuit and a latch or a fold-back protection circuit. (r1244n includes a fold-back protection circuit onl y.) by simply using an inductor, resistors, a diode, and capacitors as external components, a high-efficiency step-down dc/dc converter can be easi ly configured. due to current mode pwm control, the r1240x/r1244n provide a fast response and high efficiency. ceramic output capa citors can be used. two different pin layout of sot-23-6w package as r1240n and r1244n are available. features ? supply current (i dd ) typ. 500 a (no switching) ? standby current (i standby ) max. 5 a (ce="l") ? input voltage range (v in ) 4.5v to 30.0v ? output voltage range (v out ) 0.8v to 15.0v (externally adjustable) (feedback voltage : 0.8v) ? feedback voltage accuracy 12mv ? output current (i out ) 1.2a ? ? oscillator frequency (f osc ) 1.25mhz ? oscillator maximum duty cycle (maxduty) r1240x : min. 75%, typ. 85% r1244n : typ. 85% ? minimum on time (t min ) typ.100ns ? uvlo detect voltage (v uvlo ) typ. 3.8v ? soft start time (t start ) typ. 0.4ms ? high side switch limit current typ. 2a ? thermal shutdown circuit stops at 160 c. ? latch protection circuit de lay time for protection typ. 2ms (a version) ? fold-back protection circuit fold-back frequency typ. 310khz (b version ) ? packages dfn(plp)2527-10, sot-23-6w ? ) this is an approximate value, because output current depending on conditions and external parts. block diagram typical application r1240x/r1244n (v out =3.3v) v in v fb gnd ce l x bst c out 10 f "h"active c bst 100nf v out =3.3v v in c in 10 f r1 3.75k h r bst 51 5.1k (optional) r1240x/r1244n v fb thermal shutdown l x bst ce v in gnd uvlo regulator soft start current slope peak current limit vref limit latch (ver.a only) d s r regulator osc (1250khz/ 310khz) 0.8v maxduty setpulse shutdown c spd : speed-up capacitor c in , c out : ceramic capacitors can be used. c bst : bootstrap capacitor r1, r2 : resistors for setting output voltage r bst : lx slew-rate adjustable resistor selection guides halogen free package q'ty per reel part no. dfn(plp)2527-10 5,000 pcs r1240k003 . ? -tr r1240n001 . ? -tr-fe sot-23-6w 3,000 pcs R1244N001B-TR-FE . ? : select the protection circuit from ( . a . ) latch type or ( . b . ) fold-back type. packages typica l characteristic dfn(plp)2527-10 sot-23-6w 1 3 6 4 2 5 bottom view top view 6 10 7 8 9 5 1 4 3 2 10 6 9 8 7 1 5 2 3 4 ? r1240n r1244n 1 lx 2 v in ??? 3 v in ??? 4 ce 5 test ?? 6 gnd 7 nc 8 v fb 9 nc 10 bst ? ) the tab is substrate level (gnd). 1 ce 2 v in 3 l x 4 bst 5 gnd 6 v fb 1 bst 2gnd 3v fb 4ce 5v in 6l x r1240x/r1244n efficiency vs. output current ?? ) test pin should be open. ??? ) the v in pin must be wired together when it is mounted on board. applications ? power source for digital home appliances such as digital tvs and dvd players ? power source for office automation equipment such as printers and fax machines ? power source for hand-held communication equipment, cameras, and vcrs ? power source for battery-powered equipment output current i out (ma) efficiency (%) 1 10 100 1000 10000 0 100 60 80 90 40 20 50 70 30 10 v out =3.3v, v in =12v free datasheet http://
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