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AL8860 document number: ds 39014 rev. 1 - 2 1 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 40v 1.5a buck led driver description the AL8860 is a hysteresis mode dc/dc step - down converter, designed for driving single or multiple series connected leds efficiently from a voltage source higher than the led voltage. the device can operate from an input supply between 4.5 v and 40v and provide an external ly adjustable output current up to 1 a for tsot25 package and 1.5a for msop - 8 ep package . depending upon supply voltage and external components, this converter can provide up to 4 0 watts output power. the AL8860 in tegrate s the power switch and a high - side output current sensing circuit, which uses an external resistor to set the nominal average output current. dimming can be realiz ed by applying an external control signal to the ctrl pin. the ctrl pin will accept either a dc voltage signal or a pwm signal . the soft - start time can be adjusted by an external capacitor from the ctrl pin to ground. applying a voltage of 0.2v or lower to the ctrl pin can turn off the output and make the device enter into standby state with low current consumption . features ? low bom counts ? wide input voltage range: 4.5 v t o 40v ? output current up to 1 .5 a ? internal 40v ndmos switch ? typical 5% output current accuracy ? single pin for on/ off and brightness control by dc voltage or pwm signal ? r ecommended analog dimming range: 5% ~100% ? soft - start ? high efficiency ( up to 97%) ? led short protection ? inherent open - circuit led protection ? over temperature protection (otp) ? up to 1mhz switching frequency ? pb - free t sot2 5 and msop - 8ep packages ? totally lead - free & fully rohs compliant (notes 1 & 2) ? halogen and antimony free. green device (note 3) pin assignments ( top view ) tsot25 ( top view ) msop - 8 ep applications ? led retrofit for low voltage halogen ? low voltage industrial lighting ? illuminated signs ? external driver with multiple channels note s: 1 . no purposely added lead. fully eu directive 2002/95/ec (rohs) & 2011/65/eu (rohs 2) compliant. 2. see http://www.diodes.com/quality/lead_free.html for more information about diodes incorporated?s definitions of hal ogen - and antimony - free, "green" and lead - f ree . 3. halogen - and antim ony - free "green products are defined as those which contain <900ppm bromine, <900ppm chlorine (<1500ppm total br + cl) and <1000ppm antimony compounds.
AL8860 document number: ds 39014 rev. 1 - 2 2 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 typical applications circuit pin description s pin number pin name function tsot25 msop - 8ep 1 5,6 sw drain of ndmos switch. 2 2,3 gnd ground (0v) 3 4 ctrl ? multi - function on/off and brightness control pin: ? leave floating for normal operation. ? drive to voltage below 0.2v to turn off output current ? drive with dc voltage (0.3v < ctrl< 2.5v) to adjust output current from 0 to 100% of i out _ nom ? drive with pwm signal from open - collector or open - drain transistor, to adjust output current. linear a djustment range from 1 % to 100% of i out _ nom for f < 500hz ? connect a capacitor from this pin to ground to increase soft - start time. (default soft - start time = 0.1ms. additional soft - start time is approx.1.5ms/1nf) 4 1 set connect resistor r s from this pin to vin to define nominal average output current : i out _ nom = 0.1/rs 5 8 vin input voltag e ( 4.5v to 40v). decouple to ground with 10f or higher x7r ceramic capacitor close to device. functional block diagram a v d d g e n e r a t o r b g & r e f e r e n c e p w m / d c d i m m i n g c u r r e n t m o n i t o r h y s t e r e s i s c o n t r o l o t p l o g i c & d r i v e r v i n c t r l s e t s w g n d p w m 4 . 5 v 4 . 5 v _ d r v p w m o t p r e f c o m p a l 8 8 6 0 5 ( 8 ) 3 ( 4 ) 2 ( 2 , 3 ) 1 ( 5 , 6 ) 4 ( 1 )
AL8860 document number: ds 39014 rev. 1 - 2 3 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 absolute maximum ratings (@ t a = +25 c, unless otherwise specified) (note 4 ) symbol parameter rating unit esd hbm human body model esd protection 2.5 kv esd m m machine model esd protection 200 v v in input voltage - 0.3 to +42 v v sw , v se t sw, set pin voltage - 0.3 to +42 v v ctrl ctrl pin voltage - 0.3 to +6 v t j operating junction temperature +150 c t stg storage temperature range - 65 to + 1 7 0 c t lead lead temperature (soldering, 10 sec) +260 c ja thermal resistance (junction to ambient) tsot25 (note 5 ) 147. 4 c /w msop - 8ep (note 6 ) 55.7 j c thermal resistance (junction to case ) tsot25 (note 5 ) 27.2 c /w msop - 8ep (note 6 ) 15. 3 note : 4. stresses greater than those listed under absolute maximum ratings may cause permanent damage to the device. these are stres s ratings only, and functional operation of the device at these or any other conditions beyond those indicated under recommended operating condi tions is not implied. exposure to absolute maximum ratings for extended periods may affect device reli ability. 5 . device mounted on 1"x1" fr - 4 mrp substrate pc board, 2oz cooper, with minimum recommended pad layout . 6 . device mounted on 2"*2" fr - 4 substrate pc board, 2oz copper , with minimum recommended pad layout. recommended operating conditions (@ t a = +25c, unless otherwise specified.) symbol parameter min max unit v in input voltage 4.5 40 v f sw switching frequency - 1 mhz i out continuous output current tsot25 - 1 a msop - 8ep - 1.5 - recommended analog dimming range 5 100 % t a operating ambient temperature (note 7) - 40 + 105 c note: 7 . the device may operate normally at + 125 c ambient temperature under the condition not trigger temperature protection .
AL8860 document number: ds 39014 rev. 1 - 2 4 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 electrical characteristics (@ t a = +25c, unless otherwise specified.) symbol parameter condition min typ max unit v in input voltage - 4.5 - 40 v i q quiescent current ctrl pin floating, v in =16v - 0.55 - ma i shdn shutdown supply current ctrl pin grounded - 50 8 0 a v sense mean current sense threshold voltage measured on set pin with respect to v in 9 6 100 10 4 mv v sense_hys sense threshold hysteresis - - 20 - % i set set pin input current v se t = v in - 0.1 - 8 - a v en ctrl range on ctrl pin for analog dimming 0. 3 - 2.5 v v en(on) dc voltage on ctrl pin to enable v en rising - 0.25 - v v en(off) dc voltage on ctrl pin to disable v en falling - 0.2 - v r sw sw switch on resistance @i sw = 100ma - 0.2 - sw(leak) sw switch leakage current - - - 5 a ss soft start time v in = 16v, c en = 1nf - 1.5 - ms f sw operating frequency v i n = 16v, v o = 9.6v (3 leds) l = 47f, i = 0.25a (i led = 1a) - 2 50 - khz t on _rec recommended minimum switch on time for 4% accuracy - 500 - ns f sw(max) recommended maximum switch frequency - - - 1.0 mhz d sw (max) max duty circle - - 98 - % d sw recommended duty cycle range - 25 - 75 % t pd internal comparator propagation delay ( note 8 ) - - 45 - ns t otp over temperature protection - - + 150 - c t otp_hys temp erature protection hysteresis - - + 30 - c note : 8 . guaranteed by design .
AL8860 document number: ds 39014 rev. 1 - 2 5 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 typical performance characteristics (@t a = +25c, v in = 16v, unless otherwise specified.) quiescent current vs. input voltage quiescent current vs. temperature shutdown current vs. input voltage shutdown current vs. temperature set threshold voltage vs. input voltage pwm dimming (vin=16v, 3leds, 47 h, rs=0.3 ) output current vs. duty cycle 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 360 380 400 420 440 460 480 500 520 540 560 quiescent current ( ? a) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 40 42 44 46 48 50 52 54 56 58 60 shutdown current ( ? a) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 60 65 70 75 80 85 90 95 100 105 110 115 120 set threshold voltage(mv) input voltage(v) v th_h v th_mean v th_l -50 -25 0 25 50 75 100 125 400 420 440 460 480 500 520 540 560 580 600 quiescent current ( ? a) temperature('c) v in =16v -50 -25 0 25 50 75 100 125 0 10 20 30 40 50 60 70 80 90 100 shutdown current ( ? a) temperature('c) v in =16v 0 10 20 30 40 50 60 70 80 90 100 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 output current (ma) duty cycle(%) l=47 ? h,freq=680khz f pwm =100hz f pwm =200hz f pwm =500hz f pwm =1khz
AL8860 document number: ds 39014 rev. 1 - 2 6 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 typical performance characteristics (cont.) (@t a = +25c, v in = 16v, unless otherwise specified.) analog dimming (v in =16v, 3leds, 47h, rs=0.3) efficiency vs. input voltage led current vs. ctrl pin voltage (tsot25, rs=0.3 , l=100 h) efficiency vs. input voltage efficiency vs. input voltage (tsot25, rs=0.15 , l=47 h) (tsot25, rs=0.1 , l=33 h) efficiency vs. input voltage efficiency vs. input voltage ( msop - 8ep , rs=0. 1 , l= 68 h) ( msop - 8ep , rs=0. 067 , l= 47 h) 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 0 20 40 60 80 100 120 140 160 180 200 220 240 260 280 300 320 340 led current (ma) ctrl pin voltage (v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 efficiency(%) input voltage(v) l=100 ? h, rs=0.3 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 efficiency (%) input voltage(v) l=47 ? h, rs=0.15 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 efficiency(%) input voltage(v) l=33 ? h, rs=0.1 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 efficiency(%) input voltage(v) l=47uh, rs=0.067 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 60 62 64 66 68 70 72 74 76 78 80 82 84 86 88 90 92 94 96 98 100 efficiency(%) input voltage(v) l=68 ? h, rs=0.1 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v
AL8860 document number: ds 39014 rev. 1 - 2 7 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 typical performance characteristics (cont.) (@t a = +25c, v in = 16v, unless otherwise specified.) led current vs. input voltage led current vs. input voltage (tsot25, rs=0. 3 , l= 100 h) (tsot25, rs=0.1 5 , l= 47 h) led current vs. input voltage led current vs. input voltage (tsot25, rs=0.1 , l=33 h) ( msop - 8ep , rs=0. 1 , l= 68 h) led current vs. input voltage operating frequency vs. input voltage ( msop - 8ep , rs=0.067 , l=47 h) (tsot25, rs=0. 3 , l= 100 h) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 l=100 ? h, rs=0.3 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v frequency(khz) input voltage(v) 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 l=47 ? h, rs=0.067 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v led current(a) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 970 975 980 985 990 995 1000 1005 1010 1015 1020 1025 1030 l=33 ? h, rs=0.1 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v led current(ma) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 640 645 650 655 660 665 670 675 680 685 690 695 700 l=47 ? h, rs=0.15 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v led current(ma) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 320 322 324 326 328 330 332 334 336 338 340 342 344 346 348 350 l=100 ? h, rs=0.3 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v led current(ma) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 970 975 980 985 990 995 1000 1005 1010 1015 1020 1025 1030 l=68 ? h, rs=0.1 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v led current(ma) input voltage(v)
AL8860 document number: ds 39014 rev. 1 - 2 8 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 typical performance characteristics (cont.) (@t a = +25c, v in =16v, unless otherwise specified.) operating frequency vs. input voltage operating frequency vs. input voltage (tsot25, rs=0.15 , l=47 h) (tsot25, rs=0.1 , l=33 h) operating frequency vs. input voltage operating frequency vs. input voltage ( msop - 8ep , rs=0. 1 , l= 68 h) ( msop - 8ep , rs=0.067 , l=47 h) led current vs. output voltage led current vs. output voltage (tsot25, rs=0.3 , l=100 h) (tsot25, rs=0.15 , l=47 h) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 0 50 100 150 200 250 300 350 400 l=68 ? h, rs=0.1 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v frequency(khz) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 0 50 100 150 200 250 300 350 400 450 500 l=47 ? h, rs=0.067 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v frequency(khz) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 l=47 ? h, rs=0.15 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v frequency(khz) input voltage(v) 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 0 50 100 150 200 250 300 350 400 450 500 550 600 650 700 750 800 850 900 l=33 ? h, rs=0.1 vo=3.3v vo=6.6v vo=9.9v vo=13.2v vo=16.5v vo=19.8v vo=23.1v vo=26.4v vo=29.7v vo=33v frequency(khz) input voltage(v) 3 6 9 12 15 18 21 24 27 30 33 640 645 650 655 660 665 670 675 680 685 690 695 700 l=47 ? h, rs=0.15 vin=10v vin=12v vin=16v vin=20v vin=24v vin=28v vin=32v vin=36v vin=40v led current(ma) output voltage(v) 3 6 9 12 15 18 21 24 27 30 33 320 322 324 326 328 330 332 334 336 338 340 342 344 346 348 350 l=100 ? h, rs=0.3 vin=10v vin=12v vin=16v vin=20v vin=24v vin=28v vin=32v vin=36v vin=40v led current(ma) output voltage(v)
AL8860 document number: ds 39014 rev. 1 - 2 9 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 typical performance characteristics (cont.) (@t a = +25c, v in = 16v, unless otherwise specified.) led current vs. out put voltage led current vs. out put voltage (tsot25, rs=0.1 , l=33 h) (msop - 8ep, rs=0.1 , l=68 h) led current vs. out put voltage (msop - 8ep, rs=0.067 , l=47 h) 3 6 9 12 15 18 21 24 27 30 33 1.48 1.49 1.50 1.51 1.52 1.53 1.54 1.55 1.56 l=47uh, rs=0.067 vin=10v vin=12v vin=16v vin=20v vin=24v vin=28v vin=32v vin=36v vin=40v led current(a) output voltage(v) 3 6 9 12 15 18 21 24 27 30 33 970 975 980 985 990 995 1000 1005 1010 1015 1020 1025 1030 l=33h, rs=0.1 vin=10v vin=12v vin=16v vin=20v vin=24v vin=28v vin=32v vin=36v vin=40v led current(ma) output voltage(v) 3 6 9 12 15 18 21 24 27 30 33 970 975 980 985 990 995 1000 1005 1010 1015 1020 1025 1030 l=68h, rs=0.1 vin=10v vin=12v vin=16v vin=20v vin=24v vin=28v vin=32v vin=36v vin=40v led current(ma) output voltage(v)
AL8860 document number: ds 39014 rev. 1 - 2 10 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 performance characteristics (@ v in =16v, 3leds, r s =0.3 , l=47 h, t a = +25c, unless otherwise specified.) steady state start up pwm dimming (100hz, duty=50%) pulse skip mode led open protection i l 10 0ma/div v sw 5 v/div time 1 ? s/div time 20 ? s/div time 5m s/div time 20 ? s/div v sw 10 v/div v in 10 v/div i l 20 0ma/div v sw 1 0v/div v ctrl 2 v/div i l 2 00ma/div v sw 5 v/div i l 1 00ma/div time 1m s/div v sw 1 0v/div i l 2 00ma/div v led - 5 v/div v ctrl 2 v/div
AL8860 document number: ds 39014 rev. 1 - 2 11 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 application information the al88 60 is a hysteretic mode led driver with integrated power switch. it is available for two packages that provide a tradeoff between pcb area and power dissipation capability. it is recommended that for higher led currents/smaller pcbs that the msop - 8ep version should be used to maximize the allowable led current over a wider ambient temperature range. AL8860 operation in normal operation, when normal input voltage is applied at vin, the AL8860 internal switch will turn on. current starts to flow through sense resistor r s , inductor l1, and the leds. the current ramps up linearly, and the ramp rate is determined by the input voltage v in and the inductor l1. this rising current produces a voltage ramp across r s . the internal circuit of the AL8860 senses the voltage across r s and applies a proportional voltage to the input of the internal comparator. when this voltage reaches an internally set upper threshold, the internal switch is turned off. the inductor current continues to flow through r s , l1 , leds and diode d1, and back to the supply rail, but it decays, with the rate determined by the forward voltage drop of leds and the diode d1 . this decaying current produces a falling voltage on r s , which is sensed by the AL8860 . a voltage proportional to the sense voltage across r s will be applied at the input of internal comparator. when this voltage falls to the internally set lower threshold, the internal swit ch is turned on again. this switch - on - and - off cycle continues to provide the average led curren t set by the sense resistor r s . led current c onfiguration the nominal average output current in the led(s) is determined by the value of the external current sense resistor (r s ) connected between vin and set and is given by: the table below gives values of nominal average output current for several preferred values of current setting resistor (r s ) in the typical application circuit shown on page 1 . r s ( ) nominal average output current (ma) 0.066 1500 0.1 1000 0.13 760 0.15 667 0.3 333 the above values assume that the ctrl pin is floating and at a nominal reference voltage for internal comparator . it is possible to use different values of r s if the ctrl pin is driven by an external dimming signal . analog dimming apply a dc voltage from 0. 3 v to 2.5 v on ctrl pin can adjust output current from 0 to 100% of i out _ nom linearly, as shown in figure 1. if the ctrl pin is brought higher than 2.5v, the led current will be clamped to 100% of i out _ nom while if the ctrl voltage falls below the threshold of 0.3v, the output switch will turn off. pwm dimming led current can be adjusted digitall y, by applying a low frequency p ulse - w idth - m odulated (pwm) logic signal to the ctrl pin to turn the device on and off. this will produce an average output current proportional to the duty cycle of the control signal. to achieve a high resolution the pwm frequency is recommend ed to be lower than 500hz, however higher dimming frequencies can be used, at the expense of dimming dynamic range and accuracy. typically, for a pwm frequency of 500hz the accuracy is better than 1% for pwm ranging from 1% to 100%. the accuracy of the low duty cycle dimming is affected by both the pwm frequency and also the switching frequency of the AL8860 . for best accuracy/resolution the switching frequency should be increased while the pwm frequency should be reduced. the ctrl pin is designed to be driven by both 3.3v and 5v logic levels directly from a logic output with either an open drain output o r push pu ll output stage.
AL8860 document number: ds 39014 rev. 1 - 2 12 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 application information ( cont .) fig ure 1. a nalog d imming c urve soft start the default soft start time for the AL8860 is only 0.1ms C this provides very fast turn o n of the output , improving pwm dimming accuracy . never theless, adding an external capacitor from the ctrl pin to ground will provide a longer soft - start delay. this is achieved by increasing the time for the ctrl voltage ris ing to the turn - on threshold and by slowing down the rising rate of the control voltage at the input of hysteresis comparator. the additional soft start time is related to the capacitance between ctrl and gnd, the typical value will be 1.5ms/nf. capacitor selection a low esr capacitor should be used for input decoupling, as the esr o f this capacitor appears in series with the supply source impedance and will lower overall efficiency. this capacitor has to supply the relatively high peak current to the coil and smooth the ripple on the input current . the minimum capacitance needed is determined by input power, cable ? s length and peak current. 4.7~10 f is a common used value for most of cases. a higher value will imp rove performance at lower input voltages, especially when the source impedance is high. the input capacitor should be plac ed as close as possible to the ic. for maximum stability over temperature and voltage, capacitors with x7r, x5r, or better dielectric a re recommended. capacitors with y5v dielectric are not suitable for decoupling in this application and should not be used. diode selection for maximum efficiency and performance, the freewheeling diode (d1) shou ld be a fast low capacitance s chottky diode with low reverse leakage current . it also provide s better efficiency than silicon diodes, due to lower forward voltag e and reduced recovery time. it is important to select parts with a peak current rating above the peak coil current and a continuous current rating higher than the maximum output load current. it is very important to consider the reverse leakage current of the diode when operating above +85c. excess leakage current will increase power dissipation. the higher forward voltage and overshoot due to reverse recovery time in silicon diodes will increase the peak voltage on the sw ou tput. if a silicon diode is used, more care should be taken to ensure that the total voltage appearing on the sw pin including supply ripple, won ? t exceed the specified maximum value. 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3.0 0 200 400 600 800 1000 1200 1400 1600 output current(ma) ctrl pin voltage rs=0.067 rs=0.1 rs=0.15 rs=0.3
AL8860 document number: ds 39014 rev. 1 - 2 13 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 application information ( cont .) inductor selection recommended inductor value for the AL8860 are in the range 33h to 100h. higher induc tance are recommended at higher supply voltages in order to minimize output current tolerance due to switching delays, which will result in increased ripple and lower efficien cy. hi gher inductance also result s in a better line regulation . the inductor should be mo unted as close to the device as possibl e with lo w resistance connections to sw pins . the chosen coil should have saturation current higher than the peak output current and a continuous current rating above the required mean output current. the inductor value should be chosen to maintain operating duty cycle and switch ?on?/?off? times within the specified limits over the supply voltage and load current range. the following e quations can be used as a guide. sw switch ?on? time sw switch ?o ff ? time where: l is the coil inductance; r l is the coil resistance; r s is the current sense resistance ; i led is the required led current; i is the coil peak - peak ripple current (internally set to 0.25 x i led ); v in is the supply voltage; v led is the total led forward voltage; r sw is the switch resistance (0.3 nominal); v d i s the diode forward voltage at the required load current . thermal protection the al88 60 includes over - temperature protection (otp) circuitry that will turn off the device if its junction temperature reaches t otp . this is to protect the device from excessive heat damage. the otp circuitry includes thermal hysteresis that will cause the device to restart normal operation once its junction temperature has cooled down by approximately t otp_hys . thermal fold - back the AL8860 has thermal fold - back function: the ic has analog dimming function with a dc voltage from 0. 3 v to 2.5 v on ctrl pin to adjust output current from 0 to 100% of i out _ nom linearly . the ctrl pin allows the direct connection of an ntc to ground to sense ambient temperature. the ic has internal constant current source of 1.5 a to charge ctrl pin. when the ambient temperature increase s , the ctrl pin voltage decreases which equals to 1.5 a x r ntc . when the ctrl pin voltage drops below 2.5v, the out put current is decreased proportionally to the ctrl pin voltage. open circuit leds the AL8860 has by default open led protection. if the leds should become open circuit the AL8860 will stop oscillating; the set pin will rise to vin and the sw pin will then fall to gnd. no excessive voltages will be seen by the AL8860 . led chain shorte d together if the led chain should become shorted together (the anode of the top led becomes shorted to the cathode of the bottom led) t he al886 0 will continue to switch and the current through the AL8860 ?s internal switch will still be at the regulated current - so no excessive heat will be generated within the AL8860 . however, the duty cycle at which it operates will change dramatically and the switching frequency will most likely decrease. see figure 2 for an example of this behavior at 24v input voltage driving 3 leds. the on - time of the internal power mosfet switch is significantly reduced because almost all of the input voltage is now developed across the inductor. the off - time is significantly increased because the reverse voltage across the inductor is now just the schottky diode voltage (see f igure 2 ) causing a much slower decay in inductor current.
AL8860 document number: ds 39014 rev. 1 - 2 14 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 application information ( cont .) fig ure 2 . switching characteristics ( normal operation to led chain shorted out ) ordering information part number package code package tape and reel quantity part number suffix AL8860wt - 7 wt t so t25 30 00/tape & reel - 7 AL8860mp - 13 mp msop - 8ep 25 00/tape & reel - 13 i led 200ma/div v sw 20v/div v led - 10v/div a l 8 8 6 0 x - x p a c k a g e w t : t s o t 2 5 m p : m s o p - 8 e p 7 / 1 3 : t a p e & r e e l p r o d u c t n a m e p a c k i n g
AL8860 document number: ds 39014 rev. 1 - 2 15 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 marking information device package identification code AL8860wt - 7 t so t25 a 5 a l886 0mp - 13 msop - 8ep - package outline dimensions (all d imensions in mm . ) (1) package type : tsot25 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 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
AL8860 document number: ds 39014 rev. 1 - 2 16 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 package outline dimensions (all d imensions in mm .) ( cont .) ( 2 ) package type : msop - 8ep msop - 8ep dim min max typ a - 1.10 - a1 0.05 0.15 0.10 a2 0.75 0.95 0.86 a3 0.29 0.49 0.39 b 0.22 0.38 0.30 c 0.08 0.23 0.15 d 2.90 3.10 3.00 d1 1.60 2.00 1.80 e 4.70 5.10 4.90 e1 2.90 3.10 3.00 e2 1.30 1.70 1.50 e3 2.85 3.05 2.95 e - - 0.65 l 0.40 0.80 0.60 a 0 8 4 x - - 0.750 y - - 0.750 all dimensions in mm suggested pad layout (1) package type : tsot25 ( 2 ) package type : msop - 8ep dimensions value (in mm) c 0.950 x 0.700 y 1.000 y1 3.199 dimensions value (in mm) c 0.650 g 0.450 x 0.450 x1 2.000 y 1.350 y1 1.700 y2 5.300 1 d a a1 a2 e e y x seating plane gauge plane 0.25 l 4x10 4x10 d 8xb see detail c detail c c a e1 e3 a3 d1 e2 y1 c x y x c y y2 y1 x1 g
AL8860 document number: ds 39014 rev. 1 - 2 17 of 17 www.diodes.com september 2016 ? diodes incorporated new product AL8860 important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability 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, corrections or other c hanges without further notice to this document and any product described herein. diodes incorporated does not assume any liability arising out of the application or use of this document or any product described herein; neither does diodes incorporated convey any license unde r its patent or trademark rights, nor the rights of others. any customer or user of this document or products described herein in such applications shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diod es incorporated website, harmless against all damages. diodes incorporated do es not warrant or accept any liability whatsoever in respect of any products purchased through unauthorized sales channel. should customers purchase or use diodes incorporated products for any unintended or unauthorized application, customers shall indemni fy and hold diodes incorporated and its representatives harmless against all claims, damages, expenses, and attorney fees arising ou t of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized applicat ion. products described herein may be covered by one or more united states, internation al or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. this docu ment is written in english but may be translated into multiple languages for reference. only the english version of this doc ument is the final and determinative format released by diodes incorporated. life support diodes incorporated products are specif ically not authorized for use as critical components in life support devices or systems without the express written approval of the chief executive officer of diodes incorporated. as used herein: a. life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided i n the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support device or system whose failure to perform can be reasonably expe cted to cause the failure of the life support device or to affect its safety or effectiveness. custom ers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support devices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety - related requirements c oncerning their products and any use of diodes incorporated products in such safety - critical, life support devices or systems, notwithstanding any devices - or systems - related information or support that may be pr ovided by diodes incorporated. further, cust omers must fully indemnify diodes incorporated and its representatives against any damages arising out of the use of diodes incorporated products in such safety - critical, life support devices or systems. copyright ? 201 6 , diodes incorporated www.diodes.com

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