IS31PW3500 integrated silicon solution, inc. ? www.issi.com 1 rev.a, 12/30/2011 1.1mhz boost converter with 30v internal fet switch february 2012 general description the IS31PW3500 is a constant current step-up converter. the step-up converter topology allows series connection of the white leds so the led currents are identical for uniform brightness as well as constant output voltage to drive other devices. the IS31PW3500 switches at 1.1mhz, allowing the use of tiny external components. the input and output capacitor can be as small as 1 f, saving space and cost versus alternative solutions. a low 0.25v feedback voltage minimizes power loss in the current setting resistor for better efficiency. the IS31PW3500 is available in small dfn-8, 2mm 2mm package. features ? 2.4v to 5.5v input range ? 26v output with over voltage protection ? high efficiency :85 % typical ? pwm dimming control ? internal high power 30v mosfet switch ? fast 1.1mhz switching frequency ? small, low-profile inductors and capacitors ? dfn-8, 2mm 2mm package ? rohs compliant and 100% lead (pb)-free applications ? mobile phone ? digital still camera ? pdas, handheld computers ? mp3 players ? gps receivers typical application circuit figure 1 typical application circiut
IS31PW3500 integrated silicon solution, inc. ? www.issi.com 2 rev.a, 12/30/2011 pin configuration package pin configuration (top view) dfn-8 pin description no. pin description 1 pgnd signal ground, connect to ground. 2 vin input supply voltage. 3 en chip enable pin. connect to 1.4v or higher to enable device, 0.4v or less to disable device. 4 ain audio input. (note1) 5 aout audio output. (note1) 6 fb feedback pin. reference voltage is 0.25v. connect cathode of lowest led and resistor here. calculate resistor value according to the formula: r fb = 0.25/i led , calculate output voltage according to the formula: v out = (r2+r1)0.25v/r2. 7 gnd common ground 8 lx switch pin. connect inductor/diode here. minimize trace area at this pin to reduce emi. thermal pad connect to gnd. note 1: see section constant output voltage for class-g audio amplifier in application information. 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
IS31PW3500 integrated silicon solution, inc. ? www.issi.com 3 rev.a, 12/30/2011 ordering information industrial range: -40c to +85c order part no. package qty/reel IS31PW3500-dls2-tr dfn-8, lead-free 3000
IS31PW3500 integrated silicon solution, inc. ? www.issi.com 4 rev.a, 12/30/2011 absolute maximum ratings supply voltage, v in - 0.3v ~ +6.0v voltage at any input pin - 0.3v ~ +6.0v l x - 0.3v ~ +30v 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 v in =3.6v, t a = 25c, unless otherwise specified. symbol parameter condition min. typ. max. unit system supply input v in supply voltage 2.4 6.0 v uvlo under voltage lock out 2.2 2.45 2.6 v maximum output voltage 29 v i cc1 supply current v in = 6v, continuously switching 1 ma i cc2 quiescent current v in = 6v, v fb = 1.3v, no switching 70 120 170 a i cc3 shutdown current v in = 6v, v en <0.4v 0.1 1 a oscillator f osc operation frequency 0.8 1.0 1.2 mhz d max maximum duty cycle 85 90 % reference voltage v fb feedback voltage 0.237 0.25 0.263 v mosfet rds(on) on resistance of mosfet 0.6 0.7 1.0 ? i x current limit 400 800 1450 ma control and protection v enl shutdown voltage 0.4 v v enh enable voltage 1.4 v i en en pin pull low current 0.1 a
IS31PW3500 integrated silicon solution, inc. ? www.issi.com 5 rev.a, 12/30/2011 application information constant output voltage figure 3 is an application of IS31PW3500 for backlight of main panel and flashlight. setting the divider-resistors (r1 & r2) is to get a constant output voltage that depends on the forward voltage and the numbers of series-leds. there are three kinds of mode controll ed by the switches - backlight mode /flashlight mode /backlight + flashlight mode. it can turn on backlight or flashlight at one time or both at the same time. applying different duty cycle of pwm signal above 22khz to backlight's switch can also control the brightness. the following formula (2), (3) can determine r3. v out = (r2+r10.25v/r2 (1) r3 = v out - 3v fb - v ds /i b (2) v ds = i b r ds(on) (3) en pgnd vin gnd fb lx sn3500 lx 10 h dimming control c2 1 f c1 10 f d1 c1 10 f r1 239k r2 5.1k gpio1 r3 v out =12v vf f ib figure 2 constant output voltage for backlight and flashlight constant output voltage for class-g audio amplifier figure 4 is another application for driving class g audio amplifier, is31ap4915. setting the divider-resistors (r1 & r2) is to get a higher constant output voltage that can drive audio amplifier intends to get larger audio power. the following formula (4) can determine the output voltage. other applications for audio amplifier, please contact us for more information. v out = (r2+r1)0.25v/r2 (4) figure 3 constant output voltage for class-g audio amplifier IS31PW3500 is31ap4915 is31p w 3500
IS31PW3500 integrated silicon solution, inc. ? www.issi.com 6 rev.a, 12/30/2011 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 4 classification profile
IS31PW3500 integrated silicon solution, inc. ? www.issi.com 7 rev.a, 12/30/2011 tape and reel information note: all dimensions in millimeters unless otherwise stated.
IS31PW3500 integrated silicon solution, inc. ? www.issi.com 8 rev.a, 12/30/2011 package information dfn-8 note: all dimensions in millimeters unless otherwise stated.
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