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technical data 1 2011, february ver. 03 small outline package sop 8 high - power led driver features ? 4 constant - current output channels ? constant output current invariant to load voltage change ? maximum output constant current per channel: 240ma ? excellent output current accuracy: between channels: <3% (max.), and between ics: <6% (max.) ? output current adjusted through an external resistor ? schmitt trigger input ? 5v supply voltage ? package type: pb - free sop8 with thermal pad ordering information device operating temper a ture range package shipping ik280 4 dt = - 40 ... + 85 ? sop - 8 tape& reel current accuracy conditions between channels between ics <3% <6% i out = 40 ~ 240 ma product description ik2804 is an instant on/off led driver for high power led applications and exploits to enhance its output characteristics. at ik2804 output stage, four regulated current ports are designed to provide uniform and constant current sinks for driving leds within a large range of vf variations. ik2804 provides users 4 - channel constant current ports. users may adjust the output current from 40 ma up to 240ma through an external resistor, rext, which gives users flexibility in controlling the light intensity of leds. in addition, users can precisely adjust led brightness from 0% to 100% via o utput enable with pulse width modulation. additionally, to ensure the system reliability, ik2804 is built with tp (thermal protection) function and thermal pad. the tp function protects ic from over temperature (165c). also, the thermal pad enhance s the power dissipation. as a result, a large amount of current can be handled safely in one package. applications ? high - flux led lighting ? automotive interior lighting ? lcd backlight ? photocopier ? scanner ik2804
ik2804 2 2011, february ver. 03 typical application circuit figure 1 functional diagram
ik2804 3 2011, february ver. 03 pin configuration pin description pin no. pin name function 1 gnd ground terminal for control logic and current sink 3,4,5,6 out0~out3 constant current output terminals 7 oe output enable terminal when oe is a ctive (low), the output pins are enabled; when oe is inactive (high), all output pins are turned off (blanked). 2 r - ext terminal used to connected an external resistor (r ext ) for setting up output current for all output channels 8 vdd 5v supply voltage t erminal - thermal pad power dissipation terminals connected to gnd* *to eliminate the noise influence, the thermal pad is suggested to be connected to gnd on pcb. in addition, desired thermal conductivity will be improved, if a heat - conducting copper fo il on pcb is soldered with thermal pad.
ik2804 4 2011, february ver. 03 maximum ratings characteristic symbol rating unit supply voltage v dd 0~7.0 v input voltage v in - 0.4~v dd + 0.4 v output current i out 320* ma sustaining voltage v ds 27 .0 v gnd terminal current i gnd 1000 ma p ower dissipation* (on pcb, ta=25 oc) sop8 p d 0.8 w thermal resistance** (by simulation) r th(j - a) 33.39 oc/w empirical thermal resistance* (on pcb, ta=25 oc) 125 operating j unction temperature t j,max 125 oc operating temperature t opr - 40~+85 oc storage temperature t stg - 55~+150 oc *users must notice that the power dissipation (almost equaling to i out x v ds ) should be within the safe operation area shown in figure 7. ** provided by factory. ** * stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only and functional operation of the device at these or any other conditions beyond those indic ated under recommended operating conditions is not implied. exposure to absolute - maximum - rated conditions for extended periods may affect device reliability.
ik2804 5 2011, february ver. 03 electrical characteristics characteristics symbol condition min. typ. max. unit supply voltage v dd 4.5 5.0 5.5 v sustaining voltage at out pin v ds out0~out15 27 .0 v output current i out dc test circuit 40 240* ma input voltage h level v ih ta= - 40~85 oc 1.6 v dd v l level v il ta= - 40~85 oc gnd 0.6 v output leakage current i oh v oh = 2 7 v 0.5 ua output current 1 i out1 v ds =0.6v r ex t =2.4kohm 120 ma current skew 1 di out/iout i ol = 120 ma v ds =0.6 v r ex t =2.4kohm 1 3 % output current 2 i out2 v ds =0.8v r ex t =1.3kohm 220 ma current skew 2 di out/iout i ol = 220 ma v ds =0.8v r e x t =1.3kohm 1 3 % regulation of output current vs. sustaining voltage %/dv ds v ds within 1.0v and 3.0v 0.1 %/v regulation of output current vs. supply voltage %/dv dd v dd within 4.5v and 5.5v 1 %/v pull - up resistor r n(up) oe 300 700 800 kohm thermal shutdown temperature t xi shutdown t emp . increasing 165 oc t xd reset temp . decreasing 15 0 oc supply current off i dd (off) 1 r ext =open, out0~out15=off 5 9 ma i dd (off) 2 r ext = 2 . 4 kohm, out0~out15 =off 7 10 i dd (off) 3 r ext = 1.3 kohm, out0~out15=off 8 12 on i dd (on) 1 r ext = 2.4 kohm, out0~out15=on 4 10 i dd (on) 2 r ext = 1.3 kohm, out0~out15=on 5 10 * eac h output current, i out , can be driven up to 24 0ma, but the total output current should be smaller than 1a. test circuit for electrical characteristics
ik2804 6 2011, february ver. 03 figure 2 switching characteristics characteristics symbol condition m in. t yp. max. unit propagati on delay time( l to h ) oe - outn t plh v dd =5.0v v ds =1.0v v ih =v dd v il =gnd r ext =1226ohm (i outn =240ma) v l =4.0v r l =12.5ohm c l =10pf 0.3 0.5 1 u s propagation delay time( h to l ) oe - outn t phl 0.3 0.5 1 u s pulse width oe t w(oe ) 1 - - u s output rise time of out (turn off) t or 0.3 0.5 1 u s output rise time of out (turn on) t of 0.3 0.5 1 u s test circuit for switching characteristics figure 3
ik2804 7 2011, february ver. 03 application circuits (a) ik2804 application circuit, where v led and v dd share a single voltage source. (b) ik2804 application circuit with dimming control by pwm signal, where v led and v dd use voltage sources separately. figure 4
ik2804 8 2011, february ver. 03 constant current in led lighting applications, ik2804 provides nearly no var iation in current from channel to channel and from ic to ic. this can be achieved by: 1) the maximum current variation between channels is less than 3%, and that between ics is less than 6 %. 2) in addition, the current characteristic of output st age is flat and users can refer to the figure as shown below. the output current can be kept constant regardless of the variations of led forward voltages (v f ). this guarantees led to be performed on the same brightness as users specification. figure 5 iout versus vds 0 40 80 120 160 200 240 280 0 0,5 1 1,5 2 2,5 3 vds (v) iout (ma) 7,73k 3,72k 2,44k 1,82k 1,44k 1,19k
ik2804 9 2011, february ver. 03 setting output current the output current of each channel (iout) is set by an external resistor, rext. the relationship between iout and rext is shown in the following figure and table. figure 6 iout ma rext kohm 240 1,19 200 1,44 160 1,82 120 2,44 80 3,72 40 7,73 the output current can be calculated from the equation: v r - ext = 1.24v; rext = (v r - ext / iout) 236 = (1.24v / iout) 236, iout = (v r - exr / rext) 236 = (1.24v / rext) 236 within 6% chip skew where rext is the resistance of the external resistor connected to r - ext terminal and v r - ext is the voltage of r - ext terminal. the magnitude of current (as a function of rext) is aroun d 225ma at 1.3k? and 122ma at 2.4k? . iout versus rext 0 40 80 120 160 200 240 280 0 1 2 3 4 5 6 7 8 rext (kohm) iout (ma)
ik2804 10 2011, february ver. 03 package power dissipation (pd) the maximum power dissipation, p d (max) = (t j,max C t a ) / r th(j - a) , decreases as the ambient temperature increases. figure 7 the maximum allowable package power dissipat ion is determined as p d (max) = (t j,max C t a ) / r th(j - a) . when 4 output channels are turned on simultaneously, the actual package power dissipation is : p d (act) = (i dd x v dd ) + (i out x duty x v ds x 4). therefore, to keep p d (act) p d (max), the allowable max imum output current as a function of duty cycle is: i out = { [(t j C t a ) / r th(j - a) ] C (i dd x v dd ) } / v ds / duty / 4, where t j = 125c; duty= t on / t; t on : the time of leds turning on; t: signal period *note: the empirical thermal resistor r th(j - a) =125 c/w is based on the following structure.
ik2804 11 2011, february ver. 03 tp function (thermal protection) therma l protection turns off the output current when the junction temper ature rises to approximately 165 c, allowing the device to cool. when the junction tem per ature cool s to approximately 15 0 c, the output c urrent is turned on again. depending on power dissi pation, thermal resistance, and ambient tempe rature, the thermal protection circuit may cycle on and off. this limits the dissipation of the driver , protecting it from damage due to overheating. load supply voltage (vled) ik2804 is designed to operate with adequate v ds to achieve constant current. v ds together with i out should not exceed the package power dissipation limit, p d(max) . as in figure 8, v ds = v led C v f , and v led is the load supply voltage. p d(act) will be greater than p d(max) , if v ds drops too much voltage on the driver. in this case, it is recommended to use the lowest possible supply voltage or to set an external voltage reducer, v drop . a voltage reducer lets v ds = (v led C v f ) C v drop . resistors can be used in the applications as shown in figure 8. figure 8
ik2804 12 2011, february ver. 03 package dimensions sop 8 note: the unit for the outline drawing is mm.

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