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| IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 1 dual channel, linear led driver with fade in/fade out preliminary information august 2014 general description the IS32LT3120 is a linear programmable current regulator consisting of 2 output channels capable of up to 200ma each. each channel features an on/off input pin to toggle the channel between the off condition and the source condition. a single external resistor programs the current level for both of the channels, while a separate, single resistor programs the fade in and fade out rate for both channels. the device integrates a 63 steps fade in and fade out algorithm (gamma correction) which causes the output led current to gradually ramp up to the full source value after the channel?s control pin is pulsed. the same controller causes the led current to gradually ramp down to zero if the channel?s input control pin is pulsed while the output channel is on. the led current output can be controlled by a momentary contact switch or logic level signal. the IS32LT3120 is targeted at the automotive market with end applications to include map and dome lighting as well as exterior accent lighting. for 12v automotive applications the low dropout driver can support 1 to 3 leds per channel. it is offered in a small thermally enhanced sop-8-ep packages. features ? dual output channels can source up to 200ma each ? independent on/off control for each channel -inputs are debounced ? programmable current via a single external resistor ? programmable fade in, fade out via external resistor - pull down resistor value sets fade speed - gamma corrected fade in/out algorithm ? fault protection: - led string shorted to gnd - over temperature ? sop-8-ep packages ? automotive grade - aec-q100 (pending) ? operating temperature range from -40c ~ +125c applications ? automotive interior: - map light - dome lighting - puddle lamp in doors - glove box - vanity mirror typical application circuit figure 1 typical application circuit
IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 2 pin configuration package pin configuration (top view) sop-8-ep pin description no. pin description 1 tset timing control for the fade in and fade out feature. connect a resistor between this pin and gnd to set the fade in and fade out time. connect this pin directly to ground to disable the fade function for instant on/off. 2 iset output current setting for both channel 1 and channel 2. connect a resistor between this pin and gnd to set the maximum output current. 3 gnd ground pin for the device. 4 out1 output current source channel 1. 5 out2 output current source channel 2. 6 vcc power supply input pin. 7 en2 internally debounced input pin for control of channel 2. momentary contact will toggle the state of the corresponding out2 led. pin condition is ignored until completion of fade in or fade out function. 8 en1 internally debounced input pin for control of channel 1. momentary contact will toggle the state of the corresponding out1 led. pin condition is ignored until completion of fade in or fade out function. thermal pad connect to gnd. IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 3 ordering information automotive range: -40c to +125c order part no. package qty/reel IS32LT3120-grla3-tr sop-8-ep, lead-free 2500 copyright ? ? ? 2014 ? 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 ? IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 4 absolute maximum ratings vcc, out1, out2 -0.3v ~ +50v en1, en2, iset, tset -0.3v ~ +7.0v ambient operating temperature, t a -40c ~ +125c maximum continuous junction temperature, t j ( max ) 150c storage temperature range, t stg -55c ~ +150c maximum power dissipation, p dmax 2.86w esd (hbm) esd (cdm) 2kv 750v note: stresses beyond those listed under ?absolute maximum ratings? ma y cause permanent damage to the device. these are stress rating s only and functional operation of the device at t hese or any other condition beyond those i ndicated in the operational sections of th e specifications is not implied. exposure to absolute maximum rating condi tions for extended periods may affect device reliability. thermal characteristics characteristic test conditions value package thermal resistance (junction to ambient), r ja on 4-layer pcb based on jedec standard 35c/w on 2-layer generic test pcb with 0.8 in 2 copper 62c/w package thermal resistance (junction to pad), r jp 2c/w electrical characteristics t j = -40c ~ +125c, v cc =12v, the detail refer to each condition description. typical values are at t j = 25c. symbol parameter condition min. typ. max. unit v cc supply voltage range 6 45 v v do minimum dropout voltage v cc ? v outx , i outx = -200ma tbd mv v cc ? v outx , i outx = -100ma 700 mv i cc quiescent supply current out1 and out2 is shutdown 0.1 1 ma i set =20k ? , enable. outx connected to vcc 3.6 ma t on startup time v cc > 6v to i outx <-5ma (note 3) 400 s i out_rng output current range 20 200 ma i out_lim output limit current outx sourcing current, v iset = 0v 260 310 ma i out output current (note1,2,4) i set = 20k ? , t j = 25c 97 100 103 ma i set = 20k ? , -40c < t j < +105c 95 100 105 i set = 20k ? , t j = 125c 86 e iout absolute current accuracy (note1,2) -50ma i outx <-20ma, -40c IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 6 typical performance characteristics supply current (ma) supply voltage (v) 5 1015202530354045 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 r tset = 100k ? r iset = 20k ? no load shutdown mode operating mode figure 2 supply current vs. supply voltage output current (ma) r iset (k ? ) 0 25 50 75 100 125 150 175 200 225 250 0 20406080100120140160180200 v cc = 12v r tset = 100k ? v hd = 1v t j = 25 c figure 4 output current vs. r iset fade time (ms) supply voltage (v) 5 1015202530354045 0 500 1000 1500 2000 2500 3000 3500 r iset = 20k ? r tset = 100k ? r tset = 510k ? r tset = 1m ? figure 6 fade time vs. supply voltage output current (ma) supply voltage (v) 0 50 100 150 200 250 5 1015202530354045 r tset = 100k ? v hd = 1v r iset = 10k ? r iset = 20k ? r iset = 40k ? r iset = 200k ? figure 3 output current vs. supply voltage output current (ma) headroom voltage (mv) 0 25 50 75 100 125 150 175 200 225 250 0 1000 2000 3000 4000 5000 6000 7000 8000 9000 10000 r tset = 100k ? t j = 25 c r iset = 200k ? r iset = 40k ? r iset = 20k ? r iset = 10k ? figure 5 output current vs. headroom voltage temperature ( c ) fade time (ms) -40 -25 -10 5 20 35 50 65 80 95 110 125 0 500 1000 1500 2000 2500 3000 3500 v cc = 12v r iset = 20k ? r tset = 100k ? r tset = 510k ? r tset = 1m ? figure 7 fade time vs. temperature IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 7 temperature ( c ) supply current (ma) -40 -25 -10 5 20 35 50 65 80 95 110 125 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 v cc = 12v r tset = 100k ? r iset = 20k ? no load shutdown mode operating mode figure 8 supply current vs. temperature i out 20ma/div v en 2v/div time (1s/div) fade in r tset = 1m ? figure 10 v en vs. i out i out 20ma/div v en 2v/div time (400ms/div) fade in r tset = 510k ? figure 12 v en vs. i out temperature ( c ) output current (ma) -40 -25 -10 5 20 35 50 65 80 95 110 125 0 25 50 75 100 125 150 175 200 225 250 v cc = 12v r tset = 0 ? v hd = 1v r iset = 10k ? r iset = 20k ? r iset = 40k ? r iset = 200k ? figure 9 output current vs. temperature i out 20ma/div v en 2v/div time (1s/div) fade out r tset = 1m ? figure 11 v en vs. i out i out 20ma/div v en 2v/div time (400ms/div) fade out r tset = 510k ? figure 13 v en vs. i out IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 8 i out 20ma/div v en 2v/div time (100ms/div) fade in r tset = 100k ? figure 14 v en vs. i out i out 20ma/div time (40s/div) r tset = 0 ? figure 16 instant on i out 20ma/div v en 2v/div time (100ms/div) fade out r tset = 100k ? figure 15 v en vs. i out i out 20ma/div time (40s/div) r tset = 0 ? figure 17 instant off IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 9 functional block diagram en1 switch debounce & detection logic en2 tset iset outx gnd fade in/ fade out control output driver - constant current control - open circuit detect output current reference - dc current setting thermal current rollback vcc IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 10 application information the IS32LT3120 is a 2-channel linear current driver optimized to drive an automotive interior map light, or other interior lamp which is frequently toggled between the on and off condition. the device integrates a separate input control for each channel allowing for independent on/off operation of either channel. in addition, a programmable fade in and fade out feature is integrated into each channel?s control block to allow the end customer maximum flexibility in setting up their light timing requirements. the device led current outputs can be connected in parallel or left unused as required. the regulated led current (up to 200ma) from each channel output is set by a single reference resistor (r iset ). current is matched in each string eliminating the need for ballast resistors. (note: when connecting the outputs in parallel, both enx inputs should also be connected together so that both outx channels are controlled by the same signal.) output current setting a single programming resistor (r iset ) controls the maximum output current for both output channels simultaneously. the programming resistor may be computed using the following equation (1): set iset i r 2000 ? (1) (10k ? r iset 100k ? ) the device is protected fr om an output overcurrent condition caused by an accidental short circuit of the iset pin, by internally limiting the maximum current in the event of an iset short circuit to 260ma. en pin operation the en inputs to the device include internal pull-up sources so that no external components are required to provide the input high level to the pin. both output channels power up in the ?off? condition. toggling the en pin from high to low on a given channel for a period of time that exceeds the debounce time will cause that channel?s output to toggle from the off condition to the source condition. when this happens, the output current of the channel gradually ramps up from zero to the programmed value (set by r iset ) over the time set by the resistor (r tset ) attached to the iset pin. conversely, if a channel is already in the source condition, and that channel?s en pin is toggled low, then the output current shall begin to ramp down towards zero in the time period as programmed by the resistor (r tset ) attached to the tset pin. figure 18 enx debounced debounce - output control is provided by a debounced switch input, providing an on/off toggle action for various switch or button characteristics. an internal debounce circuit will condition the input signal so a single press of the me chanical switch doesn't appear like multiple presses. the enx inputs are debounced by typically 37ms. note: the debounce time applies to both falling and rising edges of the enx signal. fade in and fade out when an enx channel is turned on (pulled low), the output current of the channel shall gradually ramp up from zero to the final value as programmed by the resistor (r iset ) connected to the iset pin. the time period over which the ramping happens is determined by the resistor (r tset ) connected to the tset pin. the output current shall ramp up (or down) in 63 steps, with integrated gamma correction for an extremely linear ramping of the luminous output of the led bulb. setting the fade time the fade time, either in or out, for both channels is the same, and is set by a single external programming resistor (r tset ). the fade time is programmable by equation (2): s r t tset ? 5 . 2 ? ? (2) for example, r tset =100k ? , fade time is about 0.25s. note: in order to get the optimized effect, the recommended fading time is between 1.5s (r tset =600k ? ) and 0.25s (r tset =100k ? ). if the tset pin is tied directly to gnd, the fade in/out function is canceled and the ramp time is about 73s, or ?instant on?. however, the debounce feature of the enx pin is not disabled. IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 11 fade time (ms) r tset ( k ? ) 0 500 1000 1500 2000 2500 0 100 200 300 400 500 600 700 800 900 1000 v cc = 12v r iset = 20k ? t j = 25 c figure 19 fade time vs. r tset gamma correction in order to perform a better visual led breathing effect we recommend using a gamma corrected value to set the led intensity. this results in a reduced number of steps for the led intensit y setting, but causes the change in intensity to appear more linear to the human eye. gamma correction, also known as gamma compression or encoding, is used to encode linear luminance to match the non-linear characteristics of display. gamma correction will vary the step size of the current such that the fading of the light appears linear to the human eye. even though there may be 250 linear steps for the fading algorithm, when gamma corrected, the actual number of steps could be as low as 63. table 1 63 gamma steps with 250 linear steps c(0) c(1) c(2) c(3) c(4) c(5) c(6) c(7) 0 1 2 3 4 5 6 7 c(8) c(9) c(10) c(11) c(12) c(13) c(14) c(15) 8 10 12 14 16 18 20 22 c(16) c(17) c(18) c(19) c(20) c(21) c(22) c(23) 24 26 29 32 35 38 41 44 c(24) c(25) c(26) c(27) c(28) c(29) c(30) c(31) 47 50 53 57 61 65 69 73 c(32) c(33) c(34) c(35) c(36) c(37) c(38) c(39) 77 81 85 89 94 99 104 109 c(40) c(41) c(42) c(43) c(44) c(45) c(46) c(47) 114 119 124 129 134 140 146 152 c(48) c(49) c(50) c(51) c(52) c(53) c(54) c(55) 158 164 170 176 182 188 195 202 c(56) c(57) c(58) c(59) c(60) c(61) c(62) 209 216 223 230 237 244 250 intensity data gamma steps 0 50 100 150 200 250 0 5 10 15 20 25 30 35 40 45 50 55 60 62 figure 20 gamma correction(63 steps) fault detection an output shorted to gnd faul t is detected if the output voltage on a channel drops below the low voltage threshold v scd and remains below the threshold for t fd . the channel (outx) with the short condition will reduce its output current to 20% of i set . when short condition is removed, output current will recover to original value. when output current is larger than limit value, about 260ma, the output current will be clamped. when the open fault condition is recovered, there will be a large current pulse about 10s. overtemperature protection the device features an integrated thermal rollback feature which will reduce the output current of both channels in a linear fashion if the silicon temperature exceeds 125c ( typical) . in the event that the die temperature continues to increase, the device will enter thermal shutdown if the temperature exceeds 155c. thermal rolloff the output current of both channels will be equal to the set value so long as the die temperature of the ic remains below 125c (typical). if the die temperature exceeds this threshold, the output current of the device will begin to reduce at a rate of 3%/c. the roll off slope is related to iset value. when i set =20ma, the roll off slope is about 3.7%. when i set =200ma, the roll off slope is about 2.2%. thermal shutdown in the event that the die temperature exceeds 155c, both output channels will go to the ?off? state. at this point, the ic presumably begins to cool off. any attempt to toggle one or both of the channels back to the source condition before the ic cooled to < 135c will be blocked and the ic will not be allowed to restart. IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 12 thermal considerations the package thermal resistance, r ja , determines the amount of heat that can pass from the silicon die to the surrounding ambient environment. the r ja is a measure of the temperatur e rise created by power dissipation and is usually measured in degree celsius per watt (c/w). the junction temperature, t j , can be calculated by the rise of the silicon temperature, ? t, the power dissipation, p d , and the package thermal resistance, r ja , as in equation (3): ? ? ? ? ? ? ? 2 1 ) ( x i v v i v p outx ledx cc cc cc d (3) and, ja d a a j r p t t t t ? ? ? ? ? ? ? (4) where v cc is the supply voltage, v ledx is the voltage across v cc to outx and t a is the ambient temperature. when operating the chip at high ambient temperatures, or when driving maximum load current, care must be taken to avoid exceeding the package power dissipation limits. the maximum power dissipation can be calculated using the following equation (5): ja max d r c c p ? ? ? ? ? 25 125 ) ( (5) so, w w c c c p max d 86 . 2 / 35 25 125 ) ( ? ? ? ? ? ? figure 21, shows the po wer derating of the IS32LT3120 on a jedec boards (in accordance with jesd 51-5 and jesd 51-7) standing in still air. temperature ( c ) power dissipation (w) -40 -25 -10 5 20 35 50 65 80 95 110 125 0 0.5 1 1.5 2 2.5 3 3.5 sop-8-ep figure 21 dissipation curve IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 13 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 22 classification profile IS32LT3120 integrated silicon solution, inc. ? www.issi.com rev.0a, 08/15/2014 14 package information sop-8-ep |
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