innovative power tm - 1 - www.active-semi.com copyright ? 2011 active-semi, inc. act6360 high-efficiency, 40v step -up wled bias supplies rev 1, 14-feb-11 simplified application circuit features ? high-efficiency dc/dc wled bias supply ? internal 40v, 0.55 ? power mosfet ? up to 10 wleds per string ? 1000ma peak current ? supports analog and pwm led dimming ? integrated over-voltage protection (ovp) ? thermal shutdown ? cycle-by-cycle over current protection ? tiny sot23-6 package applications ? tft lcd displays ? smart phones ? portable media players ? gps/personal navigation devices general description the act6360 step-up dc/dc converter drives white leds with an externally programmable con- stant current. this device features an integrated, 40v power mosfet that is capable of driving up to ten white leds in series, providing inherent current matching for uniform brightness. wled brightness adjustment is easily achieved via simple external circuitry, which accepts either a pwm or an analog dimming control signal. the act6360 features a variety of protection cir- cuits, including integrated over voltage protection (ovp), cycle-by-cycle curr ent limiting, and thermal shutdown protection circuitry. the act6360 has a 1000ma current limit, and is available in a small 6-pin sot23-6 package. act6360 in sw ov fb g v out v in en up to 10 wleds on off l1 c in r ov1 r ov2 r fb c out d1
act6360 rev 1, 14-feb-11 innovative power tm - 2 - www.active-semi.com copyright ? 2011 active-semi, inc. part number current limit temperature range package pins packaging act6360us-t 1a -40c to 85c sot23-6 6 tape & reel top mark wjfs pin name description 1 sw switch output. connect this pin to the inductor and the schottky diode. 2 g ground 3 ov over voltage protection input. the ic is automat ically disabled when the voltage at this pin exceeds 1.21v. connect ov to the center point of a resistive voltage divider connected across the led string. 4 fb feedback input. connect this pin to the cath ode of the bottom led, and a current feedback resistor between this pin and g to set the led bias current. 5 en enable control. drive to a logic high to enable the device. connect to a logic low to disable the device. en should not be left floating; connect en to in when unused. 6 in supply input pin configuration pin descriptions ordering information sw gen fb ov in 6 4 1 3 5 2 act6360 sot23-6
act6360 rev 1, 14-feb-11 innovative power tm - 3 - www.active-semi.com copyright ? 2011 active-semi, inc. absolute maximum ratings c parameter value unit sw to g -0.3 to 42 v in, en to g -0.3 to 6 v fb, ov to g -0.3 to v in + 0.3 v continuous sw current internally limited junction to ambient thermal resistance ( ja ) 200 c/w 0.727 w operating junction temperature -40 to 150 c storage temperature -55 to 150 c lead temperature (soldering, 10 sec) 300 c maximum power dissipation c : do not exceed these limits to prevent damage to the device. exposure to absolute maximum rati ng conditions for long periods m ay affect device reliability.
act6360 rev 1, 14-feb-11 innovative power tm - 4 - www.active-semi.com copyright ? 2011 active-semi, inc. (v in = v en = 3.3v, t a = 25c, unless otherwise specified.) electrical characteristics parameter test conditions min typ max unit power switch voltage rating 40 v input voltage 2.6 5.5 v under voltage lockout threshold v in rising 2.1 2.25 2.45 v under voltage lockout hysteresis 80 mv supply current not switching 0.1 0.25 ma switching 0.25 0.5 supply current in shutdown en = g 0.1 10 a maximum on time v in = 3.3v 2.6 4.0 5.8 s maximum on time constant (k) k = t maxon v in 13.2 s v minimum off time 220 320 450 ns fb feedback voltage v en 1.8v 275 290 305 mv fb input current v fb = 1v 0 200 na switch current limit 510 1000 1400 ma switch on resistance 0.55 0.9 ? switch leakage current v sw = 38v, en = g 0 10 a over voltage protection threshold v ov rising 1.11 1.21 1.31 v ov input current v ov = 1.5v 0 200 na en logic high threshold 1.4 v en logic low threshold 0.4 v en input current v en = 0v, 3.3v 18 36 a thermal shutdown temperature 160 c thermal shutdown hysteresis 20 c
act6360 rev 1, 14-feb-11 innovative power tm - 5 - www.active-semi.com copyright ? 2011 active-semi, inc. functional block diagram control scheme the act6360 uses a minimum off-time, current- mode control scheme to achieve excellent perform- ance under high duty-cycle operating conditions. this control scheme initiates a switching cycle only when needed to maintain output voltage regulation, resulting in very high efficiency operation. during each switching cycle, the n-channel power mosfet turns on, increasing the inductor current. the switching cycle terminates when either the in- ductor current reaches the current limit (1000ma) or when the cycle lasts longer than the maximum on- time of 4s. once the mosfet turns off, it remains off for at least the minimum off-time of 320ns, then another switching begins when the error compara- tor detects that the output is falling out of regulation again. over voltage protection the act6360 includes internal over-voltage protec- tion circuitry that monitors the ov pin voltage. over- voltage protection is critical when one of the leds in the led string fails as an open circuit. when this happens the feedback voltage drops to zero, and the control switches at maximum on time causing the output voltage to keep rising until it exceeds the maximum voltage rating of the power mosfet. the over-voltage protection circuit detects this con- dition and switching ceases if the voltage at the ov pin reaches 1.21v. to set the maximum output voltage, connect a re- sistor divider from the output node to g, with center tap at ov, and select the two resistors with the fol- lowing equation: where v ov is the over voltage detection threshold, r ov1 is the resistor between ov and g, and r ov2 is the resistor from the output to the ov pin. as a first estimate, the ov threshold can often be set to 4v times the number of leds in the string. setting the led current the led current is programmed by appropriate se- lection of the feedback resistor r fb connected be- tween fb and g. to set the led current, choose the resistor according to the equation: where v fb is the fb feedback voltage (typically 290mv at v en = 3.3v) and i led is the desired maxi- mum led current. driver enable circuit uvlo control logic thermal shutdown bandgap reference maximum on time minimum off time 1.21v ov comparator + - error comparator + - en g fb in ov sw act6360 0.29v ? ? ? ? ? ? ? ? ? ? ? ? ? = 1 v 21 . 1 v r r ov 1 ov 2 ov led fb fb i v r =
act6360 rev 1, 14-feb-11 innovative power tm - 6 - www.active-semi.com copyright ? 2011 active-semi, inc. capacitor selection the act6360 requires only a tiny 0.47f output capacitor for most applications. for circuits driving 6 or fewer leds, a 4.7f input capacitor is generally suitable. for circuits driving more than 6 leds, a 10f input capacitor may be required. when choosing a larger inductor which results in ccm operation, stability and ripple can be improved by adding a small feed forward capacitor from out to fb. about 3000pf is a good starting point for most applications, although a larger value can be used to achieve best results in applications with 6 or fewer leds. ceramic capacitors are recommended for most ap- plications. for best performance, use x5r and x7r type ceramic capacitors, which possess less degra- dation in capacitance over voltage and temperature. diode selection the act6360 requires a schottky diode as the rec- tifier. select a low forward voltage drop schottky diode with forward current (i f ) rating that exceeds the peak current limit 1a and a peak repetitive re- verse voltage (v rrm ) rating that exceeds the maxi- mum output voltage, typically set by the ov thresh- old. shutdown the act6360 features a low-current shutdown mode. in shutdown mode, the control circuitry is disabled and the quiescent supply current drops to less than 1a. to disable the ic, simply drive en to a logic low. to enable the ics, drive en to a logic high or connect it to the input supply. low input voltage applications in applications that have low input voltage range, such as those powered from 2-3 aa cells, the act6360 may still be used if there is a suitable sys- tem supply (such as 3.3v) available to power the controller. in such an application, the inductor may be connected directly to the battery, while the ic power is supplied by the system supply.
act6360 rev 1, 14-feb-11 innovative power tm - 7 - www.active-semi.com copyright ? 2011 active-semi, inc. typical performanc e characteristics (v vin = 3.6v, t a = 25c, unless otherwise specified.) efficiency vs. load current efficiency (%) load current (ma) 50 act6360-001 5 0 efficiency vs. load current efficiency (%) act6360-002 60 70 80 90 100 10 15 20 25 50 60 70 80 90 100 4 leds 4 leds efficiency vs. load current efficiency (%) act6360-003 50 60 70 80 90 100 6 leds 30 load current (ma) 5 0 10 15 20 25 30 load current (ma) 5 0 10 15 20 25 30 v in = 3.6v l = 33h l = 22h l = 33h v in = 3.2v v in = 5v v in = 3.6v v in = 3.6v l = 33h l = 22h efficiency vs. load current efficiency (%) load current (ma) 50 act6360-004 5 0 60 efficiency vs. load current efficiency (%) act6360-005 70 80 90 100 10 15 20 25 50 60 70 80 90 100 6 leds 8 leds efficiency vs. load current efficiency (%) act6360-006 50 60 70 80 90 100 8 leds 30 load current (ma) 5 0 10 15 20 25 30 load current (ma) 5 0 10 15 20 25 30 v in = 5v l = 33h v in = 3.6v l = 33h v in = 3.2v v in = 3.6v l = 33h l = 22h v in = 5v v in = 3.2v v in = 3.6v
act6360 rev 1, 14-feb-11 innovative power tm - 8 - www.active-semi.com copyright ? 2011 active-semi, inc. typical performanc e characteristics (v vin = 3.6v, t a = 25c, unless otherwise specified.) act6360 efficiency vs. load current efficiency (%) act6360-007 50 60 70 80 90 100 10 leds act6360 efficiency vs. load current efficiency (%) act6360-008 50 60 70 80 90 100 10 leds load current (ma) 5 0 10 15 20 25 30 load current (ma) 5 0 10 15 20 25 30 v in = 5v l = 33h v in = 3.6v l = 33h l = 22h v in = 3.2v v in = 3.6v
act6360 rev 1, 14-feb-11 innovative power tm - 9 - www.active-semi.com copyright ? 2011 active-semi, inc. package outline sot23-6 package outline and dimensions d b e1 e e e1 a1 a2 a c ll1 0.2 symbol dimension in millimeters dimension in inches min max min max a - 1.450 - 0.057 a1 0.000 0.150 0.000 0.006 a2 0.900 1.300 0.035 0.051 b 0.300 0.500 0.012 0.020 c 0.080 0.220 0.003 0.009 d 2.900 bsc 0.114 bsc e 1.600 bsc 0.063 bsc e1 2.800 bsc 0.110 bsc e 0.950 bsc 0.037 bsc e1 1.900 bsc 0.075 bsc l 0.300 0.600 0.012 0.024 0 8 0 8 active-semi, inc. reserves the right to modify the circuitry or specifications without notice. user s should evaluate each product to make sure that it is suitable for their applicat ions. active-semi products are not intended or authorized for use as critical components in life-support dev ices or systems. active-semi, inc. does not assume any liability arising out of the use of any product or circuit described in this datasheet, nor does it convey any patent license. active-semi and its logo are trademarks of active-semi, inc. for more information on this and other products, contact sales@active-semi.com or visit http://www.active-semi.com . ? is a registered trademark of active-semi.
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