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http://www.belling.com.cn - 1- 2/20/2013 total 13 pages white led pfm step - up dc - dc converter BL8532B selection guide BL8532B - xx x xx outline: the BL8532B is a pfm step-up dc/dc driver ic with invariant current, design for led applications. thought the external resistance, output current reach 0ma~500ma. a low ripple, high efficiency step-up dc/dc converter can be constructed of BL8532Bxx with only three external components. also available is a ce (chip enable) function that reduce power consumption features: low start voltage 0.8v ( at iout=1ma) output current range 0~ 500ma output current accuracy 10% high efficiency 82%(type) package sot-89-5. applications power source for white led supply constant current power source for a single or dual-cell battery-powered equipments pin configuration feedback voltage: 10 100mv 20 200mv 25 250mv 30 300mv 35 350mv 40 400mv package : sn sot-89-5 BL8532B- psn pin no. symbol description 1 ifb current feedback pin 2 vout output pin, power supply for internal circuits 3 ce chip enable pin (active high) 4 lx switching pin(nch open drain) 5 gnd ground pin temperature range: c standard p standard pb free
http://www.belling.com.cn - 2- 2/20/2013 total 13 pages BL8532B functional block diagram absolute maximum ratings: parameter symbal ratings units vin input voltage vin 0.3~9 v lx pin voltage vlx 0.3~vout+0.3 v ce pin voltage vce 0.3~vout+0.3 v ifb output voltage vifb 0.3~vout+0.3 v lx pin current ilx 1.5 ma sot-23-5 pd 300 mw continuous total power dissipation sot-89-5 pd 500 mw maximum operating ambient temperature tmax 150 operating ambient temperature topr -20~+85 storage temperature tstg -40~+125 soldering temperature and time tsolder 260 , 10s recommended operating conditions: min nom max unit input voltage range 0.8 vout v inductor 10 15 100 h input capacitor 0 22 f output capacitor * 47 100 220 f operating junction temperature -20 85
http://www.belling.com.cn - 3- 2/20/2013 total 13 pages BL8532B electrical characteristics: (vin 2.5v v ce =vout 3.3v r 33 t a =25 c, unless otherwise noted.) symbol item test conditions min typ. max unit 90 100 110 vout feedback voltage iout=100ma 180 200 220 mv vstart starup voltage iout=1ma, vin 0 2v 0.8 0.9 v vhold holding voltage iout=1ma, vin 2 0v 0.6 0.9 v idd2 supply current lx empty, vce=vifb=vout=3.3 v 36 a ilx lx switching current vlx=0.4v, vifb=0 700 ma ilxleak lx leakage current vout=vlx=vifb=6v 1 a ileak ce is l, leakage current of the chip vout=3.3v, vce=0, lx, ifb empty <0.1 0.5 a fosc oscillation frequency vifb=0 300 khz maxdty duty ratio on(vlx l )side 77 79 82 % efficiency iout=250ma 82 % vceh ce is h,input voltage vce 0 2v (up to work slowly with the chip) 0.6 0.9 v vcel ce is l,input voltage vce 0 2v (down to work off slowly with the chip) 0.3 0.6 v iom maximum output diver power vifb =0, vout =3.3v 500 ma note: 1 diode schottky diode forward voltage drop 0.3v 0.3a such as in5817 or 1n5819 2 inductor 15 h r<0.5 ? 3 capacitor 100 f tantalum type 4 vifb (set) is feedback voltage of the chip set up , is the first parameter of the table ,such as 100mv 200mv and so on
http://www.belling.com.cn - 4- 2/20/2013 total 13 pages BL8532B typical applications: constant output current application ( a) drive only one white led (b) drive two white-led in series and several in pa rallel connection suggestions: 1. you can increase the output capacitor properly f or improve to the characteristic of the output invariant current ( for example 150uf or 200uf). 2. to avoid the feedback voltage excursion, please wear the ring with static electricity and the electric iron connect to ground when the so ldering
http://www.belling.com.cn - 5- 2/20/2013 total 13 pages BL8532B detailed description: the BL8532B is a dc/dc step-up converter with volt age type , pfm control mode , output invariablenes current. it has only three per ipheral components that is a inductor a output capacitor a schottky diode and a resistor with set-up output current, that can afford to a invariant output current between 0 and 500ma . rc set-up method if the output current is iout that rc= iout v ifb for example, want to the current value of 100ma , s elect the chip of vifb=200mv, that rc=200mv/100ma=2 selection of the external components: thus it can be seen, the inductor and shottk y diode affect the conversion efficiency greatly. the inductor and the capacitor also have great infl uence on the output voltage ripple of the converter. so it is necessary to choose a suitable inductor, a capacitor and a right shottky diode, to obtain high efficiency, low ripple and low noise . before discussion we define: vout vin vout d - o . 1 inductor selection make sure dc-dc can natural work firstly in the mod el of the minimum continuous current that is lmin lmin R f r d d l 2 ) 1( 2 - . this formula deduce that ignoring the autoecious resistor and a diode with the forward voltage drop, but the actual value is still big. if the ind uctance less than lmin, inductor will reach magnetic saturation, efficiency will greatly drop, and hardly output steady voltage. secondly , considering the current ripple of the inductor, ignoring the autoecious parameter in the mode of continuous current. i= lf vin d imax= l r d vin 2 ) 1( - + lf dvin 2 . when l is too small, will lead to high curren t ripple of the inductor , and the maximum current of the inductor , schottky diode , power tu be of the chip are excessive . thirdly, generally speaking, not considering e fficiency , small inductor can drive load more then large inductor .but in the same load condition s , large inductor with the current ripple and the maximum current value are small. so the large i nductor should be able to start up circuit in the low input voltage. use inductor with an inductance of 10 h or more ,its ensure to normal work . if output p ort has load with output large current (for example: ou tput current is more than 50ma), for improving to efficiency, suggest to use large induc tor. at the same time, in the large load, the resistor is in series with the inductor that will a ffect the switching efficiency. supposed , the resistor is rl rload that the power consumption as follow 2 1 d r r load l -
http://www.belling.com.cn - 6- 2/20/2013 total 13 pages BL8532B for example, input 1.5v, output 3.0v, load 20 (150ma),rl=0.5 ,efficiency loss 10% . considering, suggest to use an inductance of 15 uh , <0.5 . 2 capacitor selection no considering the inductor with equivalent series resistor(esr), output voltage ripple is r= vout vout d = cf r d load considering the inductors esr, the output rip ple will be increase vout r ax r r esr + = im suggest to use tantalum type with the low esr o r more parallel-resistor. 3 diode selection it is recommended that the diode have great effect to dc-dc efficiency, we suggest to use schottky diode with the lower positive turn-on volt age and the lower corresponsive time. for example, 1n5817 1n5819 . 4 input capacitor power supply is stably, even if no input capacitor, dc-dc can output voltage with the lower ripple and the lower noise. but we suggest to conne ct with the capacitor of 10uf or more when the power supply was far away dc-dc, for minish the output noise. 5 resistor r1 r2 for output voltage detect application to invariant current , the formula of r 1 r2 1 2 1 + = r r v vout ifb
http://www.belling.com.cn - 7- 2/20/2013 total 13 pages BL8532B test circuits: (1) feedback voltage test circuit (2) start-up voltage test circuit i load =1ma (3) hold-on voltage test circuit i load =1ma
http://www.belling.com.cn - 8- 2/20/2013 total 13 pages BL8532B (4) quiescent current test circuit (5) oscillator frequency and duty cycle test circu it (6) lx switching current test circuit (7) lx leakage current test circuit
http://www.belling.com.cn - 9- 2/20/2013 total 13 pages BL8532B (8) ce h voltage test circuit (9) ce l voltage test circuit
http://www.belling.com.cn - 10- 2/20/2013 total 13 pages BL8532B package description: package sot-89-5 number of each volume 1000 unit mm brede size mode (1) is the standard package; mode (2) is customized for client.
http://www.belling.com.cn - 11- 2/20/2013 total 13 pages BL8532B

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