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zxld1366q document number: ds37078 rev. 2 - 2 1 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q automotive compliant high accuracy 1a, 60v led driver description the zxld1366q is a continuous mode inductive step-down converter, designed for driving single or multiple series conne cted leds efficiently from a voltage source higher than the le d voltage. the device operates from an input supply between 6v and 6 0v and provides an externally adjustable output current of up to 1a. the zxld1366q uses a high-side output current sensing circuit which uses an external resistor to set the nominal averag e output current. the output current can be adjusted above or be low the set value by applying an external control signal to the 'adj' pin . enhanced output current dimming resolution can be achieved by applying a pwm signal to the adj pin. soft-start can be forced using an external capacitor fr om the adj pin to ground. applying a voltage of 0.2v or lower to the adj pin turns the output off and switches the device into a low current standby state. the zxld1366q is qualified to aec-q100 grade 1 and is automotive compliant supporting ppaps. pin assignments v-dfn3030-6 typical application circuit features ? typically better than 0.8% output current accuracy ? simple and with low part count ? single pin o n/ off and brightness control using dc voltage or pwm ? pwm resolution up to 1000:1 ? high efficiency (up to 97%) ? switching frequencies up to 1mhz ? wide input voltage range: 6v to 60v ? inherent o pen -circuit led protection ? available in thermally enhanced green molding packages ? v-dfn3030-6 ? ja = +44c/w ? so -8ep ? ja = +45c/w ? tsot25 ? ja = +82c/w ? totally lead-free & fully rohs compliant (notes 1 & 2) ? halogen and antimony free. green device (note 3) ? qualified to aec-q100 standards for high reliability ? ppap capable (note 4) applications ? automotive lighting: ? internal door lights ? rear fog lamps ? position lights notes: 1. no purposely added lead. fully eu directive 2002/95/ec (rohs ), 2011/65/eu (rohs 2) & 2015/863/eu (rohs 3) compliant. 2. see https://www.diodes.com/quality/lead- free/ for more information about diodes incorporateds definitions of h alogen - and antimony-free, "green" and lead-free. 3. halogen- and antimony- free "green products are defined as those which contain <900ppm bro mine, <900ppm chlorine (< 1500ppm total br + cl) and <1000ppm antimony compounds. 4. automotive products are aec-q100 qualified and ar e ppap capable. refer to https://www.diodes.com/quality/. (top view) tsot25 i sense v in 2 1 3 4 5 adj gnd lx 12 3 4 5 6 u-dfn3030-6 (top view) lx gnd adj v in i sense gnd (top view) so-8ep 4 65 1 7 2 8 3 lx gnd gnd adj v in gnd gnd i sense
zxld1366q document number: ds37078 rev. 2 - 2 2 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q block diagram figure 1. pin connection for tsot 25 package pin description name tsot25 so -8ep v-dfn3030-6 function lx 1 1 1 drain of ndmos switch gnd 2 2, 3, 6, 7 2, 5 ground (0v) adj 3 4 3 multi-function on/off and brightness control pin: ? leave floating for normal operation. (v adj = v ref = 1.25v giving nominal average output current i outnom = 0.2v/ rs ) ? drive to voltage below 0.2v to turn off output current ? drive with dc voltage (0.3v < v adj < 2.5v) to adjust output current from 25% to 200% of i outnom ? connect a capacitor from this pin to ground to set so ft-start time. soft start time increases approximately 0.2ms/nf i sense 4 5 4 connect resistor r s from this pin to v in to define nominal average output current i outnom = 0.2v /rs . (note : r smin = 0.2v with adj pin open-circuit) v in 5 8 6 input voltage (6v to 60v). decouple to ground with 4.7 f of higher x7r ceramic capacitor close to device. pad ? pad pad exposed pad (ep) - connected to device substrate. to improve thermal impedance of package the ep must be conn ected to power ground but should not be used as the 0v (gnd) current path. it can be left floating but must not be connected to any other voltage other than 0v. low voltage dete ctor voltage regulator lx mn l1 d1 i sense adj gnd v in v in 50k 20k 1.25v 1.35v 0.2v 600khz + - + - + - r4 r5 r2 r3 r1 2 3 5 4 1 d1 + - r s c1 4.7 F 5v adj gnd c1 47 f
zxld1366q document number: ds37078 rev. 2 - 2 3 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q absolute maximum ratings (note 5) (@ t a = +25c, unless otherwise specified.) symbol parameter rating unit v in input voltage -0.3 to +65 v v sense i sense voltage (note 6) +0.3 to -5 v v lx lx output voltage -0.3 to +65 v v adj adjust pin input voltage -0.3 to +6 v i lx switch output current 1.25 a p tot power dissipation (refer to package thermal de-rating curve on page 25) tsot25 1 w so -8ep 2.2 v-dfn3030-6 1.8 t op operating temperature -40 to + 125 c t st storage temperature -55 to + 150 c t j max junction temperature + 150 c esd susceptibility tsot25 so -8ep v-dfn3030-6 hbm human body model <250 (note 7) <250 500 v c dm charged device model 1000 1000 1000 v notes: 5. all voltages unless otherwise stated are measured with respect to gnd. 6. v sense is measured with respect to v in . 7. although value is reduced, no physical change to device. caution: stresses greater than the 'absolute maximum ratings' sp ecified above may cause permanent damage to the device. these are stress ratings only; functional operation of the device at conditions between maximum re commended operating conditions and absolute maximum ratings is not implied . device reliability may be affected by exposure to absolute maximum rating conditions for extended periods of time. semiconductor devices are esd sensitive and may be damaged by exposu re to esd events. suitable esd precautions should be take n when handling and transporting these devices. the human body model is a 100pf capacitor discharge through a 1.5k? resistor pin. thermal resistance symbol parameter rating unit tsot25 so -8ep v-dfn3030-6 ? ja junction to ambient 82 45 44 c/w ? jb junction to board 33 ? jc junction to case 7 14 recommended operating conditions symbol parameter min max unit v in input voltage (note 8) 6 60 v i lx maximum recommended continuous/rms switch c urrent 1 a v adj external control voltage range on adj pin for dc brightne ss control (note 9) 0.3 2.5 v v adjoff dc voltage on adj pin to ensure devices is o ff 0.25 v t offmin minimum switch o ff -time 800 ns t onmin minimum switch on-time 800 ns f lx max recommended maximum operating frequency (note 10 ) 625 khz d lx duty cycle r ange 0.01 0.99 d lx(limit) recommended duty cycle range of output switch at f lxmax 0.3 0.7 t op operating temperature r ange (junction and ambient) - 40 +125 c notes: 8. v in > 16v to fully enhance output transistor. otherwise out current must be derated - see graphs. operation at low supply may cause excessive h eating due to increased on-resistance. 9. 100% brightness corresponds to v adj = v adj(nom) = v ref . driving the adj pin above v ref will increase the v sense threshold and output current proportionally. 10 . zxld1366q will operate at higher frequencies but accuracy will be affected due to propagation delays.
zxld1366q document number: ds37078 rev. 2 - 2 4 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q electrical characteristics (test conditions: (@ v in = 24v, t a = +25c, unless otherwise specified.)) symb ol parameter condition min typ max unit v su internal regulator start- up threshold 4.85 5.20 v v sd internal regulator shutdown threshold 4.40 4.75 v i inqoff quiescent supply current with output off adj pin grounded 65 108 a i inqon quiescent supply current with output switching (note 12) adj pin floating, l = 68h, 3 leds, f = 260khz 1.6 ma v sense mean current sense threshold voltage (defines led current setting accuracy) measured on i sense pin with respect to v in v adj = 1.25v; v in = 18v 195 200 205 mv v sensehys sense threshold hysteresis 15 % i sense i sense pin input c urrent v sense = v in -0.2v 4 10 a v ref internal reference voltage measured on adj pin with pin floating 1.25 v ? v ref / ? t temperature coefficient of v ref 50 ppm/c v adj external control voltage r ange on adj pin for dc brightness control (note 11) 0.3 2.5 v v adjoff dc voltage on adj pin to switch device from active (o n) state to quiescent (off) state v adj falling 0.15 0.20 0.27 v v adjon dc voltage on adj pin to switch device from quiescent (off) state to active (o n) state v adj rising 0.20 0.25 0.30 v r adj resistance between adj pin and v ref 0 < v adj < v ref v adj > v ref +100mv 30 10.4 50 14.2 65 18 .0 k? i lxmean continuous lx switch c urrent 1 a r lx lx s witch on resistance @ i lx = 1a 0.50 0.75 ? i lx(leak) lx switch leakage c urrent 5 a d pwm(lf) duty cycle range of pwm signal applied to adj pin during low frequency pwm dimming m ode pw m frequency < 300hz pwm amplitude = v ref measured on adj pin 0.001 1.000 v brightness control r ange 1000:1 dc adj dc brightness control r ange (note 13) 5:1 t ss soft-start ttime time taken for output current to reach 90% of final value after voltage on adj pin has risen above 0.3v. requires external capacitor 22nf. see graphs for more details 2 ms f lx operating frequency (see graphs for m ore details) adj pin floating l = 68h (0.2v) i out = 1a @ v led = 3.6v driving 3 leds 260 khz t onmin minimum s witch on time lx switch on 130 ns t offmin minimum s witch off time lx switch off 70 ns notes: 11. 100% brightness corresponds to v adj = v adj(nom) = v ref . driving the adj pin above v ref will increase the v sense threshold and output current proportionally. 12. static current of device is approximately 700a, see graph, p age 15. 13. ratio of maximum brightness to minimum brightness before shutdown v ref = 1.25/0.3. v ref externally driven to 2.5v, ratio 10:1.
zxld1366q document number: ds37078 rev. 2 - 2 5 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q device description the device, in conjunction with the coil (l1) and current sens e resistor (r s ), forms a self-oscillating continuous-mode buck convert er. device operation (refer to figure 1 block diagram and figure 2 operating wavefor ms) figure 2. theoretical operating waveforms operation can be understood by assuming that the adj pin of the device is unconnected and the voltage on this pin (v adj ) appears directly at the (+) input of the comparator. when input voltage v in is first applied, the initial current in l1 and r s is zero and there is no output from the current sense circuit. under this condition, the (-) input to the comparator is at ground a nd its output is high. this turns mn on and switches the lx pin low, causing current to flow from v in to ground, via r s , l1 and the led(s). the current rises at a rate dete rmined by v in and l1 to produce a voltage ramp (v sense ) across r s . the supply referred voltage v sense is forced across internal resistor r1 by the current sense circuit and produces a proportional current in inter nal resistors r2 and r3. this produces a ground referred ris ing voltage at the (-) input of the comparator. when this reaches the threshold voltage (v adj ), the comparator output switches low, and mn turns of f. the comparator output also drives another nmos switch, which bypasses internal resistor r3 to provide a controlled amount of hysteresi s. the hysteresis is set by r3 to be nominally 15% of v adj . when mn is off, the current in l1 continues to flow via d1 a nd the led(s) back to v in . the current decays at a rate determined by the led(s) and diode forward voltages to produce a falling voltage at th e input of the comparator. when this voltage returns to v adj , the comparator output switches high again. this cycle of events repeats, with the comparator input ramping between limits of v adj 15%. switching thresholds with v adj = v ref , the ratios of r1, r2 and r3 define an average v sense switching threshold of 200mv (measured on the i sense pin with respect to v in ). the average output current i outnom is then defined by this voltage and r s according to: i outnom = 200mv/r s nominal ripple current is 30mv/r s . 0v v in 200mv 230mv 0v sense voltage v sense+ v sense- toff ton 170mv 0v 5v v in 0.15v adj 0.15v adj i outnom i outnom +15% i outnom -15% v adj lx voltage coil current comparator input voltage comparator output t off t on
zxld1366q document number: ds37078 rev. 2 - 2 6 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q device description (cont.) actual operating waveforms v in = 15v, r s = 0.2 , l = 68h normal operation. output current (ch. 3) and lx voltage (ch. 2) v in = 30v, r s = 0.2 , l = 68h normal operation. output current (ch. 3) and lx voltage (ch. 2) v in = 60v, r s = 0.2 , l = 68h normal operation. output current (ch. 3) and lx voltage ( ch . 2) adjusting output current the device contains a low pass filter between the adj pin and the threshold comparator and an internal current limiting r esis tor (50k nom) between adj and the internal reference voltage. this allo ws the adj pin to be overdriven with either dc or pulse signals to change the v sense switching threshold and adjust the output current. details of the different modes of adjusting output curre nt are given in the applications section. output shutdown the output of the low pass filter drives the shutdown circu it. when the input voltage to this circuit falls below the t hreshold (0.2v nom.), the internal regulator and the output switch are turned off. the voltage reference remains powered during shutdown to p rovide the bias current for the shutdown circuit. quiescent supply c urrent during shutdown is nominally 60a and switch leakage is below 5a.
zxld1366q document number: ds37078 rev. 2 - 2 7 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions 0 10 20 30 40 50 60 supply voltage (v) output current, l = 68 H 1.100 1.080 1.060 1.040 1.020 1.000 0.980 output current (a) 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) output current deviation, l = 68 H 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 10 86 4 2 0 -2 output current deviation (%) -4-6 -8 -10 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) efficiency, l = 68 H 100 9590 85 80 75 70 efficiency (%) 6560 55 50 output current, l = 68 h output current deviation, l = 68 h efficiency, l = 68 h
zxld1366q document number: ds37078 rev. 2 - 2 8 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (c ont .) 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) switching frequency, l = 68 H 500 450 400 150 100 50 0 switching frequency (khz) 350 300 250 200 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) duty cycle, l = 68 H 100 9080 30 20 10 0 duty cycle (%) 7060 50 40 h switching frequency, l = 68 h duty cycle, l = 68 h
zxld1366q document number: ds37078 rev. 2 - 2 9 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) output current, l = 100 H 1.100 1.080 1.060 1.040 1.020 1.000 0.980 output current (a) 0.960 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) output current deviation, l = 100 H 10 86 4 2 0 -2 output current deviation (%) -4-6 -8 -10 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) efficiency, l = 100 H output current, l = 100 h efficiency, l = 100 h output current deviation, l = 100 h
zxld1366q document number: ds37078 rev. 2 - 2 10 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) 1 led 3 leds 5 leds 7 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) switching frequency, l = 100 H 500 450 400 150 100 50 0 switching frequency (khz) 350 300 250 200 1 led 3 leds 5 leds 7 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) duty cycle, l = 100 H 100 9080 30 20 10 0 duty cycle (%) 7060 50 40 switching frequency, l = 100 h duty cycle, l = 100 h
zxld1366q document number: ds37078 rev. 2 - 2 11 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) 0 10 20 30 40 50 60 supply voltage (v) output current, l = 150 H 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 1.100 1.080 1.060 1.040 1.020 1.000 0.980 output current (a) 0 10 20 30 40 50 60 supply voltage (v) output current deviation, l = 150 H 10 86 4 2 0 -2 output current deviation (%) -4-6 -8 -10 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) efficiency, l = 150 H 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds output current, l = 150 h output current deviation, l = 150 h efficiency, l = 150 h
zxld1366q document number: ds37078 rev. 2 - 2 12 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) 1 led 3 leds 5 leds 7 leds 11 leds 13 leds 15 leds 500 450 400 150 100 50 0 switching frequency (khz) 350 300 250 200 0 10 20 30 40 50 60 supply voltage (v) switching frequency, l = 150 H 100 9080 30 20 10 0 duty cycle (%) 7060 50 40 0 10 20 30 40 50 60 supply voltage (v) duty cycle, l = 150 H 1 led 3 leds 5 leds 7 leds 11 leds 13 leds 15 leds h duty cycle, l = 150 h switching frequency, l = 150 h
zxld1366q document number: ds37078 rev. 2 - 2 13 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) 0 10 20 30 40 50 60 supply voltage (v) output current, l = 220 H 1.100 1.080 1.060 1.040 1.020 1.000 0.980 output current (a) 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) output current deviation, l = 220 H 10 86 4 2 0 -2 output current deviation (%) -4-6 -8 -10 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) efficiency, l = 220 H 1 led 3 leds 5 leds 7 leds 9 leds 11 leds 13 leds 15 leds efficiency (%) output current, l = 220 h output current deviation, l = 220 h efficiency, l = 220 h
zxld1366q document number: ds37078 rev. 2 - 2 14 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) 0 10 20 30 40 50 60 supply voltage (v) switching frequency, l = 220 H 500 450 400 150 100 50 0 switching frequency (khz) 350 300 250 200 1 led 3 leds 5 leds 7 leds 11 leds 13 leds 15 leds 0 10 20 30 40 50 60 supply voltage (v) duty cycle, l = 220 H 100 9080 30 20 10 0 duty cycle (%) 7060 50 40 1 led 3 leds 5 leds 7 leds 11 leds 13 leds 15 leds duty cycle, l = 220 h switching frequency, l = 220 h
zxld1366q document number: ds37078 rev. 2 - 2 15 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) adj pin voltage (v) led current vs. adj 0 3 2 1 1200 1000 800 600 400 200 0 led current (ma) r = 200m ? r = 300m ? r = 680m ? supply voltage (v) 0 70 50 10 20 30 40 60 800 500 400 300 200 100 0 supply current (ma) 600 700 supply voltage (v) 0 70 50 10 20 30 40 60 1.2430 1.2415 1.2410 1.2405 1.2400 1.2395 1.2380 adj pin voltage (v) 1.2420 1.2425 1.2385 1.2390 supply voltage (v) 0 70 50 10 20 30 40 60 9060 50 40 30 0 shutdown current (ma) 70 8010 20 supply current (a)
zxld1366q document number: ds37078 rev. 2 - 2 16 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q typical operating conditions (cont.) 0 5 30 35 10 15 20 25 supply voltage (v) lx on-resistance vs. supply voltage -40 C 20 C 150 C 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 on-resistance ( ) ? 7v 9v12v 20v 30v -50 0 200 50 100 150 temperature ( C ) v vs. temperature adj 1.262 1.260 1.258 1.256 1.254 1.250 1.248 1.246 1.244 v (v) adj 1.252 7v 9v12v 30v 20v -50 0 200 50 100 150 die temperature ( C ) lx on-resisitance vs. die temperature 1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0 on-resistance ( ) ? ( c ) ( c ) - 40 c 20 c 150 c
zxld1366q document number: ds37078 rev. 2 - 2 17 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information setting nominal average output current with external resistor r s the nominal average output current in the led(s) is det ermined by the value of the external current sense resi stor (r s ) connected between v in and i sense and is given by: i outnom = 0.2/r s for r s 0.2 the table below gives values of nominal average output current for several preferred values of current se nse resistor (r s ) in the typical application circuit shown on page 1: r s ( ) nominal av erage output current (ma) 0.20 1, 000 0.27 740 0.56 357 the above values assume that the adj pin is floating and at a nominal voltage of v ref (= 1.25v). note that r s = 0.2 is the minimum allowed value of sense resistor under these conditions to maintain s witch current below the specified maximum value. it is possible to use different values of r s if the adj pin is driven from an external voltage (s ee next section). output current adjustment by external dc control voltage the adj pin can be driven by an external dc voltage (v adj ), as shown, to adjust the output current to a value ab ove or below the nominal average value defined by r s . the nominal average output current in this case is given b y: i outdc = (v adj /1.25) x (0.2/r s ) for 0.3 < v adj < 2.5v note that the 100% brightness setting corresponds to v adj = v ref . when driving the adj pin above 1.25v, r s must be increased in proportion to prevent i outdc exceeding 1a maximum. the input impedance of the adj pin is 50k 25% for volta ges below v ref and 14.2k 25% for voltages above v ref +100mv. output current adjustment by pwm control directly driving adj i nput a pulse width modulated (pwm) signal with duty cycle dpwm can be applied to the adj pin, as shown below, to adjust the output current to a value above or below the nominal average value set by resist or r s :
zxld1366q document number: ds37078 rev. 2 - 2 18 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (c ont .) driving the adj input via open collector transistor the recommended method of driving the adj pin and controlling th e amplitude of the pwm waveform is to use a small npn s witching transistor as shown below: this scheme uses the 50k resistor between the adj pin an d the internal voltage reference as a pull-up resistor fo r the external transistor. driving the adj input from a microcontroller another possibility is to drive the device from the open-d rain output of a microcontroller. the diagram below shows one method of doing this: if the nmos transistor within the microcontroller has high ga te / drain capacitance, this arrangement can inject a neg ative spike into the adj input of the zxld1366q and cause erratic operation, but t he addition of a schottky clamp diode (eg diodes incorpora ted sd103cws) to ground and inclusion of a series resistor (3.3k) will prevent this. see the section on pwm dimming for more details of the var ious modes of control using high frequency and low frequency pwm signals. shutdown mode taking the adj pin to a voltage bel ow 0.2v for more than approximately 100s will turn off the output and supply current to a low standby level of 65a nominal. note that the adj pin is not a logic input. taking the adj pin to a voltage above v ref will increase output current above the 100% nominal average value. (see page 15 graphs for details).
zxld1366q document number: ds37078 rev. 2 - 2 19 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) soft-start an external capacitor from the adj pin to ground will p rovide a soft-start delay by increasing the time taken for t he voltage on this pin to rise to the turn-on threshold and by slowing down the rate of rise o f the control voltage at the input of the comparator. add ing capacitance increases this delay by approximately 0.2ms/nf. the graph below shows the v ariation of soft-start time for different values of capa citor. actual operating waveform [v in = 60v, r s = 0.2 ? , l = 68h, 22nf on adj] soft-start operation, lx voltage (ch2) and output curre nt (ch3) using a 22nf external capacitor on the adj pin. 60 80 100 120 0 20 40 capacitance (nf) soft-start time vs. capacitance form adj to ground 1614 12 10 42 0 -2 86 soft-start time (ms)
zxld1366q document number: ds37078 rev. 2 - 2 20 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) v in capacitor selection a low esr capacitor should be used for input decoupling, a s the esr of this capacitor appears in series with the su pply source impedance and lowers overall efficiency. this capacitor has to supply the relatively high peak current to the coil and smooth the cu rrent ripple on the input supply. to avoid transients into the ic, the size of the input capacito r will depend on the v in voltage: v in = 6 to 40v, c in = 2.2f v in = 40 to 50v, c in = 4.7f v in = 50 to 60v, c in = 10f when the input voltage is close to the output voltage, the input current increases which puts more demand on the input capacitor. the minimum value of 2.2f may need to be increased to 4.7f; higher values will improve performance at lower input voltages, esp ecially when the source impedance is high. the input capacitor should be placed as c lose as possible to the ic. for maximum stability over temperature and voltage, capac itors with x7r, x5r, or better dielectric is recommended. capacitors with y5v dielectric are not suitable for decoupling in this application and sho uld not be used. when higher voltages are used with the c in = 10f, an electrolytic capacitor can be used provided t hat a suitable 1f ceramic capacitor is also used and positioned as close to the v in pin as possible. a suitable capacitor would be nacew100m1006.3x8tr13f (nic components). the following web sites are useful when finding alternatives: www.murata.com www.niccomp.com www.kemet.com inductor selection recommended inductor values for the zxld1366q are in the range 68h to 220h. higher values of inductance are recommended at higher supply voltages in order to minimize errors due to switching delays, which result in increased ripple and lower efficiency. higher values of inductance also result in a smaller change in output current over t he supply voltage range (see graphs pages 7-14). the inductor should be mounted as close to the device as possible with low resistance conn ections to the lx and vin pins. the chosen coil should have a saturation current higher tha n the peak output current and a continuous current r ating above the required mean output current. suitable coils for use with the zxld1366q may be selected from the mss range manufactured by coilcraft, or the np is range manufactured by nic components. the following websites may be useful in finding suit able components. www.coilcraft.com www.niccomp.com www.wuerth-elektronik.de the inductor value should be chosen to maintain operating duty cycle and switch 'on'/'off' time within the specified li mits over the supply voltage and load current range. figures 3, 4 and 5 (below ), can be used to select a recommended inductor based on maintaining the zxld1366q case temperature below +60c. for detailed performance characteristics for the inductor v alues 68, 100, 150 and 220h see graphs on pages 7-14.
zxld1366q document number: ds37078 rev. 2 - 2 21 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) figure 3. zxld1366q minimum recommended inductor (tsot25) figure 4. zxld1366q minimum recommended inductor (so-8ep) minimum recommended inductor 2% accuracy, <60c case temperature 0 10 20 30 40 50 60 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 number of leds supply voltage (v) legend 68uh 100uh 150uh 220uh 0 10 20 30 40 50 60 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 legend 47 H 68 H 100 H 150 H 47 H 68 H 100 H 150 H t < 70 C , i = 1a c led number of leds supply voltage (v) t c < 70 c , i led = 1a 47 h 68 h 100 h 150 h 47 h 68 h 100 h 150 h
zxld1366q document number: ds37078 rev. 2 - 2 22 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) figure 5. zxld1366q minimum recommended inductor (v-dfn3030- 6) m in im u m r e c o m m e n d e d in d u c to r 2% accuracy, <60c c ase t em perature 0.00 10.00 20.00 30.00 40.00 50.00 60.00 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 n um ber of led s s u p p ly v o lta g e (v ) legend 68h 100h 150h 220h
zxld1366q document number: ds37078 rev. 2 - 2 23 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) diode selection for maximum efficiency and performance, the rectifier (d1) should be a fast, low capacitance schottky diode* with low reverse leakage at the maximum operating voltage and temperature. they also provide better efficiency than silicon diodes, due to a combination of lower forward voltage and reduced recove ry time. it is important to select parts with a peak current rat ing above the peak coil current and a continuous current rating higher than the maximum output load current. it is very important to consider the rever se leakage of the diode when operating above +85c. exces s leakage will increase the power dissipation in the device and if close to the load may create a t hermal runaway condition. the higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak volta ge on the lx output. if a silicon diode is used, care should be taken to ensure that the t otal voltage appearing on the lx pin including supply ripple, does not exceed the specified maximum value. *a suitable schottky diode would be pds 3100 q (diodes incorporated)
zxld1366q document number: ds37078 rev. 2 - 2 24 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) reducing output ripple peak- to -peak ripple current in the led(s) can be reduced if req uired, by shunting a capacitor cled across the led(s) as s hown below: figure 6. reduced output ripple a value of 1f will reduce the supply ripple current by a factor of three (approximately). proportionally, lower ripple can be ac hieved with higher capacitor values. note that the capacitor will not affec t operating frequency or efficiency, but will increase sta rt-up delay by reducing the rate of rise of led voltage. by adding this capacitor, the current waveform through the led(s) changes from a triangular ramp to a more sinusoida l version without altering the mean current value. operation at low supply voltage below the undervoltage lockout threshold (v sd ), the drive to the output transistor is turned off to prevent device operation with excessive on- resistance of the output transistor. the output transis tor is not fully enhanced until the supply voltage exce eds approximately 17v. at supply voltages between v sd and 17v, care must be taken to avoid excessive power dissipation due to the on-resistance. note that when driving loads of two or more leds, the fo rward drop will normally be sufficient to prevent the dev ice from switching below approximately 6v. this will minimize the risk of damage to the device.
zxld1366q document number: ds37078 rev. 2 - 2 25 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) thermal considerations when operating the device at high ambient temperatures, o r when driving maximum load current, care must be taken to avoid exceeding the package power dissipation limits. the graph below gives details for power derating. this assumes the device to be mounted on a 25mm 2 pcb with 1oz copper standing in still air. note that the device power dissipation will most often be a maximum at minimum supply voltage. it will also increase if the efficiency of the circuit is low. this may result from the use of unsuitable coils, or excessive parasitic output capacitance on the switch o utput. in order to maximize the thermal capabilities of the so- 8ep package, thermal vias should be incorporated into the p cb. see figure 7 for examples used in the zxld1366q evaluation boards. figure 7. suggested layout for so-8ep package vias ensure an effective path to the ground plane for th e heat flow therefore reducing the thermal impedance be tween junction and ambient temperature. diodes incorporated came to the conclusion t hat the compromise is reached by using more than 10 vias with 1mm of diameter and a 0.5 hole size. the use of vias for the tsot25 package should also be impleme nted to guarantee an effective thermal path. maximum power dissipation
zxld1366q document number: ds37078 rev. 2 - 2 26 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) thermal compensation of output current high luminance leds often need to be supplied with a tempe rature compensated current in order to maintain stable and reliable operation at all drive levels. the leds are usually mounted remotely from th e device so, for this reason, the temperature coefficien ts of the internal circuits for the zxld1366q is optimized to minimize the change in output current when no compensation is employed. if output current compensation is required, it is possible to use an external temperature sensing netw ork normally, using negative temperature coefficient (ntc) ther mistors and/or diodes, mounted very close to the led(s). the output of the sen sing network can be used to drive the adj pin in order to reduce output current with increasing temperature. layout considerations lx p in the lx pin of the device is a fast switching node, so pcb t racks should be kept as short as possible. to minimize grou nd 'bounce', the ground pin of the device should be soldered directly to the ground plane . coil and decoupling capacitors and current sense resistor it is particularly important to mount the coil and the input decoupling capacitor as close to the device pi ns as possible to minimize parasitic resistance and inductance, which will degrade efficiency. i t is also important to minimize any track resistance in series with current sense resistor r s . it is best to connect v in directly to one end of r s and i sense di rectly to the opposite end of r s with no other currents flowing in these tracks. it is important that the cathode current of the schottky diode does not flow in a track between r s and v in as this may give an apparent higher measure of current than is actually present, because of track resistance. adj p in the adj pin is a high-impedance input for voltages up to 1.3 5v, so when left floating, pcb tracks to this pin should be as short as possible to reduce noise pickup. a 100nf capacitor from the adj pin to ground will reduce frequency modulation of the output under these conditions. an additional series 3.3k resistor can also be used when driving the adj pin from a n external circuit. this resistor will provide filtering for low - frequency noise and provide protection against high-voltage transients. high-voltage tracks avoid running any high-voltage tracks close to the adj pin to reduce the risk of leakage currents due to board con tamination. the adj pin is soft- clamped for voltages above 1.35v to desensitize it to lea kage that might raise the adj pin voltage and cause exc essive output current. however, a ground ring placed around the adj pin is recommended to min imize changes in output current under these conditions. evaluation pcb zxld1366q evaluation boards are available up on request. terminals allow users to interface the boards to their preferred led products.
zxld1366q document number: ds37078 rev. 2 - 2 27 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) dimming o utput current using pwm low frequency pwm m ode when the adj pin is driven with a low frequency pwm signal ( eg 100hz), with a high-level voltage v adj and a low level of zero, the output of the internal low-pass filter will swing between 0v and v adj , causing the input to the shutdown circuit to fall below its turn-off threshold (200mv nom), when the adj pin is low. this will cause the output current to be switched on and off at the pwm frequency, res ulting in an average output current i outavg proportional to the pwm duty cycle. (see figure 8 - low frequency pwm operating waveforms). the average value of output current in this mode is given by : i outavg 0.2d pwm /r s [for d pwm >0.001] this mode is preferable if optimum led 'whiteness' is required. it will also provide the widest possible dimming range (approx. 1000:1) and higher efficiency at the expense of greater output ripple. figure 8. low frequency pwm operating waveforms v adj pwm voltage ton ioutavg 0v 0 toff 0.2/rs ioutnom output current t on t off
zxld1366q document number: ds37078 rev. 2 - 2 28 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q application information (cont.) fault condition operation the zxld1366q has by default, open led protection. if th e leds should become open circuit, the zxld1366q will stop oscillating; the i sense pin will rise to v in and the lx pin will then fall to gnd. no excessive voltages will be see n by the zxld1366q. if the leds should become shorted together, the zxld1 366q will continue to switch, however, the duty cycle at w hich it will operate will change dramatically and the switching frequency will most likely decr ease. the on-time of the internal power mosfet switch will be significantly reduced because almost all of the input voltage is now developed across the inductor. the off- ti me will be significantly increased because the reverse voltage across the inductor is now just the schot tky diode voltage (see figure 9) causing a much slower decay in inductor current. during this condition, the inductor current will remain within its controlled levels and so no excessive heat will be genera ted within the zxld1366q. figure 9. switching characteristics (normal open to short led c hain)
zxld1366q document number: ds37078 rev. 2 - 2 29 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q ordering information part number packaging (note 14) pack code reel size (inches) reel width (mm) quantity per reel part number suffix qualification (note 15) zxld1366qdac tc v-dfn3030-6 dac 13 8 3, 000 tc automotive compliant ZXLD1366QEN8TC so -8ep en8 13 12 2, 500 tc automotive compliant zxld1366qet5ta tsot25 et5 7 8 3, 000 ta automotive complia nt no te s: 14. for packaging details, go to our website at https://www.diod es.com/design/support/packaging/diodes-packaging/. 15. zxld1366q has been qualified to aec-q100 grade 1 and is classified as automotive compliant support ing ppap documentation. s ee zxld1366 datasheet for commercial qualified versions. marking information (1) tsot25 (2) v-dfn3030-6 (3) so -8ep 1366 : identification c ode zxld 1366 : part number yy : year : 17, 18, 19~ ww : week : 01 to 52; 52 represents weeks 52 and 53
zxld1366q document number: ds37078 rev. 2 - 2 30 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q package outline dimensions please see http://www.diodes.com/package-outlines.html for the latest version. 1) package type : tsot25 2) package type: v-dfn3030-6 3) package type: so-8ep tsot25 dim min max typ a - 1.00 - a1 0.01 0.10 - a2 0.84 0.90 - b 0.30 0.45 - c 0.12 0.20 - d - - 2.90 e - - 2.80 e1 - - 1.60 e 0. 95 bsc e1 1.90 bsc l 0.30 0.50 l2 0.25 bsc 0 8 4 1 4 12 - all dimensions in mm v-dfn3030-6 dim min max typ a 0.80 0.90 0.85 a1 0 0.05 - a3 - - 0.203 b 0.30 0.40 0.35 d 2.95 3.05 3.00 d2 1.95 2.05 2.00 e 2.95 3.05 3.00 e2 1.15 1.25 1.20 e - - 0.95 e1 - - 1.90 l 0.45 0.55 0.50 all dimensions in mm so -8ep dim min max typ a 1.40 1.50 1.45 a1 0.00 0.13 - b 0.30 0.50 0.40 c 0.15 0.25 0.20 d 4.85 4.95 4.90 e 3.80 3.90 3.85 e0 3.85 3.95 3.90 e1 5.90 6.10 6.00 e - - 1.27 f 2.75 3.35 3.05 h 2.11 2.71 2.41 l 0.62 0.82 0.72 n - - 0.35 q 0.60 0.70 0.65 all dimensions in mm chamfer 0.300x45 pin #1 id e1 e d seating plane e2 d2 l b e a3 a a1 1 b e e1 a a1 9 ( all side) 43 c q n 45 r 0.1 7 d e0 e l seating plane gauge plane f h exposed pad d e1 e1/2 e1 e e/2 e a a2 a1 seating plane 0 l2 l gauge plane 01( 4x) 01( 4x) c b seating plane
zxld1366q document number: ds37078 rev. 2 - 2 31 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q suggested pad layout please see http://www.diodes.com/package-outlines.html for the latest version. 1) package type : tsot25 2) package type: v-dfn3030-6 dimensions value (in mm) c 0.950 x 0.450 x1 2.100 y 0.630 y1 1.300 y2 3.160 3) package type: so -8ep dimensions value (in mm) c 0.950 x 0.700 y 1.000 y1 3.199 dimensions value (in mm) c 1.270 x 0.802 x1 3.502 x2 4.612 y 1.505 y1 2.613 y2 6.500 y1 c x y y1 x1 y x c y2 c - 0.329 c y1 x1 x y y2 x2
zxld1366q document number: ds37078 rev. 2 - 2 32 of 32 www.diodes.com april 2018 ? diodes incorporated zxld1366q important notice diodes incorporated makes no warranty of any kind, expres s or implied, with regards to this document, including, but not limited to, the implied warranties of me rchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, correction s or other changes without further notice to this document and any produ ct described herein. diodes incorporated does not assume any liability arising out of the application or use of this document or any product des cribed herein; neither does diodes incorporated convey a ny license under its patent or trademark rights, nor the rights of others. any custome r or user of this document or products described here in in such applications shall assume all risks of such use and will agree to hold diodes incorpo rated and all the companies whose products are represe nted on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any lia bility whatsoever in respect of any products purchased through unauthorized sales channel. should customers purchase or use diodes incorporated prod ucts for any unintended or unauthorized application, cus tomers shall indemnify and hold diodes incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. pro duct names and markings noted herein may also be covered by one or more unite d states, international or foreign trademarks. this document is written in english but may be translated int o multiple languages for reference. only the english version of this document is the final and determinative format released by diodes incorporat ed. life support diodes incorporated products are specifically not auth orized for use as critical components in life support dev ices or systems without the express written approval of the chief executive officer of diodes i ncorporated. as used herein: a. life support devices or systems are devices or sy stems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perfor m when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in signi ficant injury to the user. b. a critical component is any component in a life sup port device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect i ts safety or effectiveness. customers represent that they have all necessary exp ertise in the safety and regulatory ramifications of their lif e support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concern ing their products and any use of diodes incorporated products in such safety-criti cal, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by diodes incorpo rated. further, customers must fully indemnify diodes incor porated and its representatives against any damages arising out of the u se of diodes incorporated products in such safety-critic al, life support devices or systems. copyright ? 2018, diodes incorporated www.diodes.com

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