unisonic technologies co., ltd uc3551 preliminary cmos ic www.unisonic.com.tw 1 of 6 copyright ? 2011 unisonic technologies co., ltd qw-r502-555.a advanced pwm step-up dc-dc converter ? description the utc uc3551 is a step-up dc/dc converter with high efficiency and low start-up voltage. it is operaded in stable waveforms without external compensate. this device incorporates an adaptive current mode pwm c ontrol loop in which an error amplifier, ramp generator, com parator, switch pass element and driver are included. besides, this circuit provides a stable and high efficient operation over a wi de range of load currents. the utc uc3551 features high switching rate which is up to 450 khz, making the external component counts less required. moreover, it features 17 a low quiescent current, which makes the battery life longer. the low start-up input voltage below 1v makes utc uc3551 suitable for 1 to 4 battery cells applications of providing up to 300ma output current. two external resistors determine t he value of the output voltage. the external power devices (nmos or npn) are derived by both internal 2a switch and driver. the utc uc3551 is intended to be used in pda, dsc, lcd panel, rf-tags, mp3, portable in strument and wireless equipment. ? features * low start-up input voltage is as low as 1.0v * efficiency up to 90% * high supply capability to deliver 3.3v 100ma with 1 alkaline cell * quiescent (switch-off) supply current: 17a * zero shutdown mode supply current * fixed switching frequency: 450khz * both internal and external power switches for maximum flexibility ? ordering information ordering number lead free halogen free package packing uc3551l-ag6-r UC3551G-AG6-R sot-26 tape reel uc3551l-ag6-r (1)packing type (2)package type (1) r: tape reel (2) ag6: sot-26 (3) g: halogen free, l: lead free (3)lead free
uc3551 preliminary cmos ic unisonic technologies co., ltd 2 of 6 www.unisonic.com.tw qw-r502-555.a ? marking information package voltage code marking sot-26 ad:adj ? pin configuration ? pin description pin no. pin name description 1 ce chip enable uc3551 gets into shutdown mode when ce pin set to low. 2 ext output pin for driving external nmos 3 gnd ground 4 lx pin for switching 5 v dd input positive power pin of uc3551 6 fb feedback input pin internal reference voltage for the error amplifier is 1.25v.
uc3551 preliminary cmos ic unisonic technologies co., ltd 3 of 6 www.unisonic.com.tw qw-r502-555.a ? block diagram lx gnd ext en - + fb vdd over temp detector vlx limiter buffer vref chip enable control circuit
uc3551 preliminary cmos ic unisonic technologies co., ltd 4 of 6 www.unisonic.com.tw qw-r502-555.a ? absolute maximum rating parameter symbol ratings unit supply voltage v in ? 0.3 ~ 7 v lx pin switch voltage v lx ? 0.3 ~ (v dd + 0.8) v other i/o pin voltages ? 0.3 ~ (v dd + 0.3) v lx pin switch current i lx 2.5 a ext pin driver current i ext 200 ma operating junction temperature t opr 125 c storage temperature t stg -65~+150 c notes: absolute maximum ratings are those values beyond which the device could be permanently damaged. absolute maximum ratings are stress ratings only and functional device oper ation is not implied. ? thermal data parameter symbol ratings unit junction to case jc 145 c/w ? electrical characteristics (t a = 25c,v in = 1.5v, v dd = 3.3v, load current = 0, unless otherwise specified) parameter symbol conditions min typ max unit start-up voltage v st i l = 1ma 0.98 1.05 v operating vdd range v dd v dd pin voltage 2 6.5 (note ) v no load current i (v in ) i no load v in = 1.5v, v out = 3.3v 75 a switch-off current i (v dd ) i switch off v in = 6v 17 a shutdown current i (v in ) i off ce pin = 0v, v in = 4.5v 0.01 1 a feedback reference voltage v ref close loop, v dd = 3.3v 1.225 1.25 1.275 v switching frequency f s v dd = 3.3v 450 khz maximum duty d max v dd = 3.3v 95 % lx on resistance v dd = 3.3v 0.3 ? current limit setting i limit v dd = 3.3v 2 a ext on resistance to v dd v dd = 3.3v 5 ? ext on resistance to gnd v dd = 3.3v 5 ? line regulation ? v line v in = 1.5 ~ 2.5v, i l = 1ma 10 mv/v load regulation ? v load v in = 2.5v, i l = 1 ~ 100ma 0.25 mv/ma ce pin trip level v dd = 3.3v 0.4 0.8 1.2 v temperature stability for vout t s 50 ppm/c thermal shutdown t sd 165 c thermal shutdown hysterises ? t sd 10 c note: the ce pin shall be tied to v dd pin and inhibit to act the on/off state whenever the v dd pin voltage may reach to 5.5v or above.
uc3551 preliminary cmos ic unisonic technologies co., ltd 5 of 6 www.unisonic.com.tw qw-r502-555.a ? test circuit l 1 en vdd lx gnd utc uc3551 r2 1m 3.3~10h fb ext ext c in 100f d1 d1n5819 c2 1f c1 102 r1 3m c out 100f v out v in ? typical application circuit l1 en v dd lx gnd utc uc3551 r2 1m 3.3~10h fb ext ext c in 100f d1 d1n5819 c2 1f c1 102 r1 3m c out 100f v out v in l1 en v dd lx gnd utc uc3551 r2 1m 3.3~10h fb ext c in 100f d1 d1n5819 c2 1f c1 102 r1 3m c out 100f v out v in m1 nmos
uc3551 preliminary cmos ic unisonic technologies co., ltd 6 of 6 www.unisonic.com.tw qw-r502-555.a utc assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all utc products described or contained herein. utc products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. the information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
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