2007. 8. 22 1/6 revision no : 1 semiconductor technical data KAC3305DN analog cmos integrated circuits 700ma white led regulating charge pump for camera flashes and movie lights the KAC3305DN is charge pumps drive white leds, including camera strobes, with regulated current up to 700ma. the very low open-loop output resistance allows high flash brightness, even from a low battery input voltage. the adaptive 1 /2 regulating charge pump operation provides high efficiency while in movie mode or backlighting. fast switching allows the use of tiny external components. the KAC3305DN use an external resistor to set the full-scale led current. features up to 700ma output drive capability current regulation for flash 2.7v to 5.5v supply voltage range pwm dimming control soft-start limits inrush current over voltage protection on output low shutdown current thermal shutdown protection 8 top view bottom view side view tdfn-8 millimeters c c e e f f j i i j g g h h d d a b a a b dim 1.950 ref 0.3 0.05 + _ 0.4 0.05 + _ 1.6 0.05 + _ 0.65 3.0 0.1 + _ 2.3 0.05 + _ 0.203 0.008 + _ 0.0 ~ 0.05 0.75 0.05 + _ 1 5 4 en1 en2 gnd cp fb cn v in v out 8 1 4 5 tdfn-8 top view gnd fb en cp rs cn 4.7 f 10 f 2.7v to 5.5v KAC3305DN v out 1 f v in off on typical operating circuit pin configuration applications white led flashes strobes, and movie lights lcd backlighting camera phones, cell phones, and smart phones, pdas, digital cameras, and camcorders generic lighting flash, and strobo applications
2007. 8. 22 2/6 revision no : 1 KAC3305DN cp cn v out en1 en2 gnd fb v in charge pump ( 1, 2) soft start osc (1mhz) tsd ovp + reference control 3 2 6 7 8 1 4 5 block diagram pin descriptions pin name function 1 en1 current and shutdown control input 2 cp positive terminal of switched capacitor 3 cn negative terminal of switched capacitor 4 en2 current and shutdown control input 5 gnd ground. 6 v in power supply voltage input 7 fb feedback input for the current control 8 v out output of the charge pump
2007. 8. 22 3/6 revision no : 1 KAC3305DN electrical characteristics (v in = 3.6v, c in =10 f, c=1 f, c out =4.7 f, ta= 25 , unless otherwise noted.) parameter symbol conditions min typ max units input supply voltage v in 2.7 - 5.5 v supply current i in no load - 1 2 ma shutdown supply current i shut en1=en2=gnd - - 1 a soft start time t soft - 0.3 - ms out overvoltage protection v ovp - 5.3 - v fb regulation voltage (v out -v fb ) v reg(fb) en1=en2=v in 270 300 330 mv maximum out current i out v led =3.8v 500 700 - ma open loop out resistance r out 1 mode - 1 - 2 mode - 4.5 - out internal pulldown in shutdown en1=en2=gnd - 5 - k switching frequency f osc - 1 - mhz en logic high voltage v en_ih v in =2.7v to 5.5v 1.4 - - v en logic low voltage v en_il v in =2.7v to 5.5v - - 0.4 v logic input current i en v en =0v to 5.5v - - 1 a thermal shutdown threshold t sd - 150 - characteristics symbol rating units input supply voltage v in -0.3 to +6.0 v input pin en1, en2 -0.3 to (v in +0.2) v maximum power dissipation, ( ta=25 ) p d 1.6 w thermal resistance ja 62.43 /w operating ambient ta -40 to +85 junction temperature range t j 150 storage temperature range t stg -65 to +150 lead temperature t lead 300 absolute maximum ratings
2007. 8. 22 4/6 revision no : 1 KAC3305DN application information output current the KAC3305DN is designed to deliver 200ma of continuos current and up to 700ma of pulsed current(about 500ms). the charge pump switching frequency is approximately 1mhz, enabilng the use of small external flying capacitor. mode switching the KAC3305DN has two modes of operation to control the output current : the 1 mode and 2 mode. when v in is greater than v out , the KAC3305DN regulate the current through rs. as v in decreases and detects a dropout condition, the 2 charge pump starts boosting the output to maintain the regulation current. shutdown (en1=en2=low) when voltage of the enable pin goes under 0.4v, the KAC3305DN enter the shutdown mode. in shutdown mode, input current of ic go to zero and there are no current between output capacitors and transfer capacitor. soft-start to limit excessive inrush current at turn-on, the KAC3305DN employs built-in soft-start circuitry. when starting up with an output voltage that is not near the input voltage, the output capacitor and flying capacitor are charged directly from the input until the output voltage approaches the input voltage. soft-start is achieved a period of approximately 300 s. if detects a dropout condition, the KAC3305DN automatically switches to the 2 mode soft-start. short protection if output is shorted to ground, output current is limited until v out exceeds 2.3v. overvoltage protection the KAC3305DN has over voltage protection. if the output voltage rises above the 5.3v threshold, the over voltage protection shuts off all of the output switches to prevent the output voltage from rising further. thermal protection when the temperature of the KAC3305DN rises above 150 , the over temperature protection circuitry turns off the output switches to prevent damage to the device. if the temperature drops back down below 110 , the part automatically recovers. setting the output current the output regulation current is set by rs by the equation : rs=(v out -v fb )/i out where i out is the output current and (v out -v fb ) is the reference voltage. the resistor power obtained in the full current would be : p=(v out -v fb ) i out 300 v 700 a=210 w for this application, the over 210mw resistor is recom- mended. capacitor selection to reduce noise and ripple, it is recommended that low equivalent series resistance(esr) ceramic capacitors be used for both c in and c out . tantalum and aluminum capacitors are not recommended because of their high esr. the flying capacitors control the strength of the charge pump. in order to achieve the rated output current it is necessary to have at least 1 f of actual capacitance. ceramic capacitors with x5r or x7r temperature grade are recommended for most applications. power efficiency to calculate the power efficiency of a white led driver chip, the led power should be compared to the input power. the difference between these two numbers represents lost power whether it is in the charge pump or the current sources. the power efficiency is given by = p led /p in =(v led i led )/(v in 2 i led ) v led /2 v in layout considerations due to its high switching frequency and the transient currents produced the KAC3305DN, careful board layout is necessary. the input and output capacitors should be located as close to the v in and v out as possible to obtain best bypassing. the flying capacitor should be located as close to the cp and cn as possible. connect the exposed pad to gnd directly under the ic and allow sufficient copper area for cooling
2007. 8. 22 5/6 revision no : 1 KAC3305DN start up [i out =700mv] en i out : 200ma/div v out : 2v/div input and output ripples in 1 mode input and output ripples in 2 mode [i out =200ma] input and output ripples in 2 mode [i out =700ma] v out : 100mv/div v in : 100mv/div v out : 100mv/div 1 s/div, ac coupled 40 s/div 1 s/div, ac coupled 1 s/div, ac coupled v in : 100mv/div v out : 100mv/div v in : 100mv/div led current vs. temperature [i out =200ma] 190 210 198 196 194 192 208 206 204 202 200 -15 10 35 -40 85 60 temperature ( ) c efficiency vs. supply voltage [i out = 700ma] v in (v) 3.1 20 30 70 80 90 40 60 50 10 0 3.5 4.3 4.7 3.9 2.7 5.5 5.1 efficiency (%) led current (ma) v led = 3.5v v led = 4.3v
2007. 8. 22 6/6 revision no : 1 KAC3305DN reference voltage vs. temperature 295 301 303 305 299 297 -15 10 35 60 -40 85 led current vs. supply voltage [i out =700ma] v in (v) v in (v) 3.1 400 100 800 500 600 700 200 0 300 3.5 4.3 4.7 3.9 2.7 5.5 5.1 i out (mv) v led =3.5v v led =4.3v r s ( ? ) 0.5 400 100 800 500 600 700 200 0 300 1.0 2.0 2.5 1.5 0.0 3.0 led current (ma) v led =3.5v v led =4.3v led current vs. r s battery current vs. supply voltage [i out =700ma] 3.1 400 1600 800 1200 600 1400 200 0 1000 3.5 4.3 4.7 3.9 2.7 5.5 5.1 i in (mv) temperature ( ) c reference voltage (mv)
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