IS31BL3230 integrated silicon solution, inc. ? www.issi.com 1 rev.a, 01/05/2011 8 channels constant current led driver with pwm brightness control february 2012 general description the IS31BL3230 provides eight regulated current sources, each delivers up to 40ma of load current with careful selection of external sense resistors, all outputs at the IS31BL3230 may be connected in parallel to enable the current through the led to be as high as 320ma. the IS31BL3230 does not include a charge pump and therefore has no noise and significantly improved the efficiency. the external resistor, r set1 , determines the constant current output of ports led1 thru led4, while resistor r set2 determines the constant current output of ports led5 thru led8. brightness can be controlled with pwm techniques. the constant current source is set with two external sense resistors. alternatively, a pwm signal applied to the pwm pin can vary the perceived brightness of the led. the device is in shut down mode when the pwm input is logic low. features ? ultra low headroom voltage ? cost effective led driver ? current adjustable via external resistors ? best noise and efficiency performance ? highly integrated design, minimal component ? 1.6 a (typ.) shutdown current ? small package qfn-16 3mm3mm applications ? flash led driver ? backlight led driver typical application circuit cin 1uf v in pwm gnd led1 led2 led3 led4 i set1 r set2 led5 led6 led7 led8 i set2 r set1 figure 1 typical application circuit
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 2 rev.a, 01/05/2011 pin configuration package pin configurations (top view) qfn-16 1 led6 led2 led3 led5 i set2 pwm gnd 2 3 4 16 9 10 11 12 15 14 13 5 6 7 8 led4 led1 v in v in i set1 gnd led8 led7 pwm pin description no. name description 1, 2, 11~16 led1-led8 current source outputs 1~8. 3, 7 v in input voltage. 4, 10 gnd ground. 5, 8 pwm pwm brightness control. 6 i set1 current set1 input. 9 i set2 current set2 input. copyright ? ? ? 2011 ? integrated ? silicon ? solution, ? inc. ? all ? rights ? reserved. ? issi ? reserves ? the ? right ? to ? make ? changes ? to ? this ? specification ? and ? its ? products ? at ? any ? time ? without ? notice. ? issi ? assumes ? no ? liability ? arising ? out ? of ? the ? application ? or ? use ? of ? any ? information, ? products ? or ? services ? described ? herein. ? customers ? are ? advised ? to ? obtain ? the ? latest ? version ? of ? this ? device ? specification ? before ? relying ? on ? any ? published ? information ? and ? before ? placing ? orders ? for ? products. ? integrated ? silicon ? solution, ? inc. ? does ? not ? recommend ? the ? use ? of ? any ? of ? its ? products ? in ? life ? support ? applications ? where ? the ? failure ? or ? malfunction ? of ? the ? product ? can ? reasonably ? be ? expected ? to ? cause ? failure ? of ? the ? life ? support ? system ? or ? to ? significantly ? affect ? its ? safety ? or ? effectiveness. ? products ? are ? not ? authorized ? for ? use ? in ? such ? applications ? unless ? integrated ? silicon ? solution, ? inc. ? receives ? written ? assurance ? to ? its ? satisfaction, ? that: ? a.) ? the ? risk ? of ? injury ? or ? damage ? has ? been ? minimized; ? b.) ? the ? user ? assume ? all ? such ? risks; ? and ? c.) ? potential ? liability ? of ? integrated ? silicon ? solution, ? inc ? is ? adequately ? protected ? under ? the ? circumstances
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 3 rev.a, 01/05/2011 ordering information industrial range: -40c to +85c order part no. package qty/reel IS31BL3230-qfls2-tr qfn-16, lead-free 2500
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 4 rev.a, 01/05/2011 absolute maximum ratings supply voltage, v in - 0.3v ~ +6.0v pwm - 0.3v to (v in +0.3v) / 6.0v maximum junction temperature, t jmax 150c storage temperature range, t stg - 65c ~ +150c operating temperature range, t a ? 40c ~ +85c note: stresses beyond those listed under ?absolute maximum ratings? may cause permanent damage to the device. these are stress rating s only and functional operation of the device at these or any other condition beyond those indicated in the operational sections of th e specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. electrical characteristics unless otherwise specified or noted, v in = 3.6v, r set =7.5k ? , v ledx =0.5v. limits apply for t a =25c. ( note ) symbol parameter condition min typ. max units v in supply voltage 2.7 5.5 v i ledx output current regulation 0.4v v ledx 2.0v, r set = 7.5k ? 16.0 ma v hr minimum headroom voltage(ledx) r set =7.5k ? , i ledx =20.0ma 44.0 mv v set i set pin voltage 1.2 v i ledx /i set output current to current set ratio 100.0 ma/ma i q quiescent supply current i ledx =0ma, i set =float 244.0 a i pwm shutdown supply current pwm=0 1.6 a v pwm-ih pwm input logic high 3.0v v in 5.5v 1.4 v v pwm-il pwm input logic low 3.0v v in 5.5v 0.4 v i pwm pwm pin current v(pwm) = 1.5v 5.6 a note: production testing of the device is performed at 25c. functional operation of the device and parameters specified over other temperature range, are guaranteed by design, characterization and process control.
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 5 rev.a, 01/05/2011 typical performance characteristics led current(ma) output voltage(v ledx )( mv) 0 5 10 15 20 25 30 35 40 45 0 50 100 150 200 v in = 3.3v r set = 3.0k ? r set = 4.0k ? r set = 6.0k ? r set = 7.5k ? r set = 12.0k ? figure 2 output voltage vs. led current quiescent current(a) power supply(v) r set = 7.5k ? 220 230 240 250 260 270 280 290 33.5 44.5 5 figure 4 power supply vs. quiescent current power supply(v) led cur r ent (ma) r set =6.0k r set =7.5k r set =12.0k v in =3.3v v ledx =0.2v figure 3 power supply vs. led current led current(ma) rset( k ? ) 0 5 10 15 20 25 30 35 40 45 3 8 13 18 23 28 30 v in = 3.3v figure 5 r set vs. led current
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 6 rev.a, 01/05/2011 application information circuit description the IS31BL3230 is a white-led driver with eight matched current outputs. the matched current regulators each has a 100:1 current ratio between the led x outputs and the i set currents. the mirror controls the current through the leds without the use of external ballast resistors. with a total of 320ma of total output current available, the IS31BL3230 is capable of providing 40ma to each of the eight outputs through the proper selection of the r set1 & r set2 resistor. led brightness control can be achieved on the IS31BL3230 with pwm signal. shutdown when the voltage on the active-high-logic pwm pin is low, the IS31BL3230 will be in shutdown mode. while disabled, the IS31BL3230 typically draws 1.6 a form the power supply. there is no internal pull-up or pull-down on the pwm pin of the IS31BL3230. output current capability the IS31BL3230 can provide up to 40ma of current to each of the eight outputs given an input voltage of 2.7v to 5.5v. an external resistor can be used to set the output current, as approximated with the following the equation: r set1, 2 =100 (v iset1, 2 / i ledx ) r set1 determines the constant current output of ports led1 thru led4, r set2 determines the constant current output of ports led5 thru led8, v iset is the voltage of r set resistance, it is 1.20v typically. in order for the output currents to be regulated properly, sufficient headroom voltage (v hr ) is required. the headroom voltage refers to the minimum amount of voltage that must be present across the current source in order to ensure the desired current is realizable. to ensure the desired current is obtained, using the following equations to find the minimum input voltage required: v in - v ledx v hr v ledx is the diode forward voltage; v hr is typically as shown in table1. table1 . i led , r set and v hr-min , v cc =3.3v i led r set v headroom 10.0ma 12.0k ? 27 mv(typ.) 16.0ma 7.5k ? 44 mv(typ.) 20.0ma 6.0k ? 53 mv(typ.) 30.0ma 4.0k ? 66 mv(typ.) 40.0ma 3.0k ? 75 mv(typ.) pwm brightness control brightness control can be implemented by pulsing a signal at the pwm pin. the r set value should be selected using the r set equation. the led brightness is proportional to the duty cycle (d) of the pwm signal. the pwm frequency (f) should be limited to accommodate the turn-on time (t on =50 s) of the device. d (1/f) > t on f max = d min / t on if the pwm frequency is much less than 100hz, flicker may be seen in the leds. for the IS31BL3230, zero duty cycle will turn off the leds and a 50% duty cycle will result in an average i led being half of the programmed led current. for example, if r set is set to program 16ma, a 50% duty cycle will result in an average i led of 8ma, i led being half the programmed led current. r set should be chosen not to exceed the maximum current delivery capability of the device. led selection the IS31BL3230 has ultra low headroom voltage and it is designed to drive white-leds with a typical forward voltage up to 3.5v. as the voltage drop below the recommend v hr , the drive current will automatically scale down to reduce the led current consumption. power dissipation the maximum allowable power dissipation that this package can handle is determined by the following: p dmax = (t jmax - t a ) / ja where t jmax is the maximum junction temperature, t a is the ambient temperature and ja is the junction-to-ambient thermal resistance of the specified package. the IS31BL3230 come in the qfn-16 3mm3mm package, and it has a junction-to-ambient thermal resistance ja equal to 34.5c/w. this value of ja is highly dependant upon the layout of the pc board. the actual power dissipated by the IS31BL3230 follows the equation: p diss = (v in i cc ) - n(v ledx i ledx ) where n equals the number of active outputs, v ledx is the led forward voltage, and i ledx is the current supplied to the led. input capacitor selection the IS31BL3230 is designed to run off of a fixed input voltage. depending on the stability and condition of this voltage rail, it may be necessary to add some small input capacitors to help filter out any noise that may be present on the line. in the event that filtering is needed, surface-mount multi-layer ceramic capacitors are recommended. these capacitors are small and inexpensive. two capacitances, a 0.1 f and a 1 f are typically sufficient.
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 7 rev.a, 01/05/2011 classification reflow profiles profile feature pb-free assembly preheat & soak temperature min (tsmin) temperature max (tsmax) time (tsmin to tsmax) (ts) 150c 200c 60-120 seconds average ramp-up rate (tsmax to tp) 3c/second max. liquidous temperature (tl) time at liquidous (tl) 217c 60-150 seconds peak package body temperature (tp)* max 260c time (tp)** within 5c of the specified classification temperature (tc) max 30 seconds average ramp-down rate (tp to tsmax) 6c/second max. time 25c to peak temperature 8 minutes max. figure 6 classification profile
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 8 rev.a, 01/05/2011 tape and reel information
IS31BL3230 integrated silicon solution, inc. ? www.issi.com 9 rev.a, 01/05/2011 package information qfn-16 note: all dimensions in millimeters unless otherwise stated.
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