________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 1 / 8 u m1661 high efficiency low noise pfm step - up dc/dc converter u m 166 1 sot23 - 6 general description the um1661 pfm step - up dc/dc converter drives white leds with a constant current to provide backlight in cell phones, pdas, and other h and - held devices. it features allowing series conne ction of the white leds so that the led currents are identical for uniform brightness. an enable input can be pulsed repeatedly to adjust leds brightness. the fast 500 k hz to 2mhz operation frequen cy allows for smaller capacit or and inductor. fault condition protection uses cycle - by - cycle current limiting to sense maximum inductor current and over - voltage protection. the 0.2v low reference voltage minimiz e s the power loss across the current sense r esistor. the converter can operate from 2v to 6v, and capable of delivering maximum 200ma output current at 4 - leds application with 3v input voltage. quiescent current drawn from power source is as low as 120ua. all of these features make um1661 be suitabl e for the portable devices, which are supplied by a single battery. applications features ? compact back light module ? power source for led ? constant current source ? up to 24v output voltage ? wide operation range: 2v to 6v ? maximum 2mhz operating frequency ? pwm dimming control ? shutdown current <1 a ? current limit cycle - by - cycle ? low current sense threshold: 200mv ? 24v over output voltage protection ? compact sot23 - 6 package pin configurations top view o rdering inf ormation part number packaging type marking code s hipping qty um 166 1 sot23 - 6 le9 3000 pcs/ 7 i nch tape & reel ww: week code um 1661 sot23 - 6
________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 2 / 8 u m1661 pin description pin number symbol function 1 lx switching pin 2 gnd ground pin 3 fb pin for feedback voltage 4 ce chip enable pin (active w ith h ) 5 ovp over voltage protection 6 vin power supply pin absolute maximum ratings s ymbol p arameter v alue u nit v in supply voltage on vin - 0.3 to + 8 .0 v v ce voltages on pin ce - 0.3 to v in +0.3 v i lx lx pin output current 1.6 a v lx lx pin volta ge 24 v p d continuous power dissipation 250 mw t a operating ambient temperature - 40 to +85 c t j operating junction temperature + 125 c t stg storage temperature range - 40 to + 150 c t l maximum lead temperature for soldering 10 s econds + 260 c elect rical characteristics ( v in = 3.0 v, v ce = 3.0v , t a = 25c , unless otherwise noted) symbol parameter test c onditions m in t yp m ax u nit v in input voltage range 2.0 6.0 v v fb feedback voltage 0.190 0.200 0.210 v i fb fb pin bias current 10 45 100 na i q quiescent current v fb = 0 .3v 93 120 a ce = 0v 0.4 1.0 f osc _ max maximum switching frequency v fb =0v 2 mhz i limit switching current limit 1.6 a v cesat switching v cesat i lx =300ma 260 mv i lx switching p in leak current v lx =5v 0.11 a ceh ce voltage high ce=0v to 3v 1.5 v v cel ce voltage low ce=3v to 0v 0.4 v i ce ce pin bias current 18 a ovp over voltage protection 24 v
________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 3 / 8 u m1661 function block diagram typical application circuit g n d - + p f m c o n t r o l l o g i c + - o s c s t a r t - u p l o g i c o v p v i n f b c e l x c h i p e n a b l e 2 0 0 m v e r r o r a m p c u r r e n t l i m i t d r i v e r l1 led19 vin um1661 d1 r5 r1 vin led18 led1 ovp off 4.7f ss14 led17 led1 led1 led20 4.7f gnd cout led1 lx + ce on + fb 10h cin
________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 4 / 8 u m1661 typical operating characteristics (v in = 3.0 v, v ce = 3.0v , t a = 25c , unless otherwise noted) 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 90 100 efficiency vs. output current efficiency(%) output current(ma) vin=2.5v 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 90 100 efficiency vs. output current efficiency(%) output current(ma) vin=3.0v 0 20 40 60 80 100 120 0 10 20 30 40 50 60 70 80 90 100 efficiency vs. output current efficiency(%) output current(ma) vin=6.0v 0 1 2 3 4 5 6 0 10 20 30 40 50 60 70 80 ce pin bias current vs. ce voltage ce pin bias current(ua) ce pin voltage(v) vin=vce 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 45 50 vce=3.0v vce=6.0v vin=vce ce pin current vs. temperature ce pin current(ua) temperature( o c) vce=2.5v 0 1 2 3 4 5 6 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0 quiescent current vs. supply voltage quiescent current(ua) supply voltage(v) vce=0v
________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 5 / 8 u m1661 typical operating characteristics (continued) (v in = 3.0 v, v ce = 3.0v , t a = 25c , unless otherwise noted) 0 1 2 3 4 5 6 0 10 20 30 40 50 60 70 80 90 100 quiescent current vs. supply voltage quiescent current(ua) supply voltage(v) vce=vin,vfb=0.3v 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0.12 0.14 0.16 0.18 0.20 0.22 fb pin voltage vs. supply voltage fb pin voltage(v) supply voltage(v) 20 30 40 50 60 70 80 90 100 0.12 0.14 0.16 0.18 0.20 0.22 vin=vce=3.0v fb pin voltage vs. temperature fb pin voltage(v) temperature( o c) 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4led*100ma switch frequency vs. supply voltage switch frequency(mhz) supply voltage(v) 20 30 40 50 60 70 80 90 100 0.00 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 4led*100ma switch frequency vs. temperature switch frequency(mhz) temperature( o c) 0 5 10 15 20 25 30 0 100 200 300 400 500 600 vin=6v vin=3v vin=2.5v maximum output current vs. output voltage maximum output current (ma) output voltage (v)
________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 6 / 8 u m1661 application information led current control the um1661 regulates the led current by setting the current sense resistor (r1) connecting to feedback and ground. t he um1661 feedback voltage (v fb ) is 0.20 v. the led c urrent (i led ) can be set by a resistor r1. i led = 0.2 0 /r1 . in order to have an accurate led current, a precision resistor is preferred (1% is recommended). pwm dimming control when adding the pwm signal to ce pin, the um1661 is turned on or off by the pwm signal, so the leds operate at either zero or full current. the average led current increase proportionally with the duty cycle of the pwm signal. the magnitude of the pwm signal should be higher than the maximum enable voltage of en pin, in order to let the dimming control perform correctly . the r ecommended frequency range of the pwm signal is from 100 hz to 100 khz . inductor selection the recommended value of inductor is 2.2 h to 10 h. small size and better efficiency are the major concerns for portable device, such as um1661 used for mobile phone. the inductor should have low core loss at 2mhz and low dcr for better efficiency. to avoid inductor saturation current rating should be considered. capacitor selection input and output ceramic capacitors of 4. 7 f are recommended for um1661 applications. for better voltage filtering, ceramic capacitors with low esr are recommended. x5r and x7r types are suitable because of their wider voltage and temperature ranges. diode selection schottky diode is a good choic e for um1661 because of its low forward voltage drop and fast reverses recovery. using schottky diode can get better efficiency. the high speed rectification is also a good characteristic of schottky diode for high switching frequency. current rating of th e diode must meet the root mean square of the peak current and output average current multiplication as following : i d(rms) (i out i peak ) 1/2 the diodes reverse breakdown voltage should be larger than the output voltage. ss0520 is recommended schottky diode for rectifier. layout guide ? a full gnd plane without gap break. ? minimized lx node copper area to reduce emi. ? minimized fb node copper area and keep far away from noise sources.
________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 7 / 8 u m1661 package information u m 1661 : sot23 - 6 outline drawing dimensions symbol millimeters inches min typ max min typ max a 1.0 13 1.15 1. 40 0.04 0 0.045 0.0 55 a1 0.0 0 0.05 0.10 0.000 0.002 0.00 4 a2 1.0 0 1.10 1. 30 0.0 39 0.043 0.0 51 b 0. 30 - 0.50 0.01 2 - 0.020 c 0. 10 0.15 0.20 0.004 0.006 0.008 d 2. 82 - 3. 10 0.11 1 - 0.1 22 e 1.50 1.60 1.70 0.059 0.063 0.067 e1 2.60 2.80 3.00 0.102 0.110 0.11 8 e 0.95ref 0.037ref e1 1.90ref 0.075ref l 0. 30 - 0. 60 0.01 2 - 0.02 4 0 - 8 0 - 8 land pattern notes: 1. compound dimension: 2.92 1 .60 2. unit: mm; 3. general tolerance 0.0 5 mm unless otherwise specified; 4. the layout is just for reference. tape and reel orientation e 1 e 1 b d e e a 2 a 1 a t o p v i e w s i d e v i e w 4 1 3 c l e n d v i e w 2 6 5 0 . 5 6 0 . 9 5 0 . 9 5 2 . 3 5 1 . 2 0 w w l e 9
________________________________________________________________________ http://www.union - ic.com rev.0 5 m a y .20 1 6 8 / 8 u m1661 green compliance union semiconductor is committed to environmental excellence in all aspects of its operations including meeting or exceeding regulatory r equirements with respect to the use of hazardous substances. numerous successful programs have been implemented to reduce the use of hazardous substances and/or emissions. all union components are compliant with the rohs directive, which helps to support c ustomers in their compliance with environmental directives. for more green compliance information , please visit: http://www.union - ic.com/index.aspx?cat_code=rohsdeclaration important notice the information in this document has been carefully reviewed and is believed to be accurate. nonetheless, this document is subject to change without notice. union assumes no responsibility for any inaccuracies that ma y be contained in this document, and makes no commitment to update or to keep current the contained information, or to notify a person or organization of any update. union reserves the right to make changes, at any time, in order to improve reliability, fu nction or design and to attempt to supply the best product possible. union semiconductor, inc add : unit 606, no.570 shengxia r oa d, shanghai 2012 10 tel: 021 - 51093966 fax: 021 - 51026018 website: www.union - ic.com
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