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al5801 document number: ds35555 rev. 3 - 2 1 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 100v, adjustable current sink linear led driver description the al5801 combines a 100v n-channel mosfet with a pre- biased npn transistor to make a si mple, small footprint led driver. the led current is set by an external resistor connected from r ext pin (4) to gnd pin (6). the inte rnal pre-biased transistor develops approximately 0.56v across the external resistor. the al5801 open-drain output can operate from 1.1v to 100v enabling it to operate 5v to 100v power supplies without additional components. pwm dimming of the led current can be achieved by driving the bias pin (1) with an external, open-collector npn transistor or open-drain n-channel mosfet. the al5801 is available in a sot 26 package and is ideal for driving led currents up to 350ma. features ? feedback pin reference voltage v rset = 0.56v at +25c ? -40c to +125c temperature range ? 1.1v to 100v open-drain output ? negative temperature v rset co-efficient automatically reduces the led current at high temperatures ? low thermal impedance sot26 package with copper lead frame ? lead-free finish; rohs compliant (notes 1 & 2) ? halogen and antimony free. ?green? device (note 3) ? qualified to aec-q101 standards for high reliability pin assignments (top view) sot26 applications ? linear led drivers ? led signs ? offline led luminaries notes: 1. eu directive 2002/95/ec (rohs) & 2011/65/eu (roh s 2) compliant. all applicable rohs exemptions applied. 2. see http://www.diodes.com for more in formation about diodes incorpor ated?s definitions of halogen- and antimony-free, "gree n" and lead-free. ? 3. halogen- and antimony-free "green? products are defined as those which contain <900ppm br omine, <900ppm chlorine (<1500ppm t otal br + cl) and <1000ppm antimony compounds. typical applications circuit
al5801 document number: ds35555 rev. 3 - 2 2 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 pin descriptions pin number pin name function 1 bias biases the open-drain output mosfet 2 fb feedback pin 3 out open-drain led driver output 4 r ext current sense pin. led curre nt sensing resistor should be connected from here to gnd 5 comp compensation pin. connect comp pin to rext pin and insert a 1nf ceramic capacitor from comp pin to fb pin for improved transient stability 6 gnd ground reference point for setting the led current functional block diagram figure 1 block diagram absolute maximum ratings (@t a = +25c, unless otherwise specified.) symbol characteristics values unit v out output voltage relative to gnd 100 v v bias bias voltage relative to gnd (note 4) 20 v v fb fb voltage relative to gnd 6 v v comp comp voltage relative to gnd 6 v v rext rext voltage relative to gnd 6 v i out output current 350 ma t j operating junction temperature -40 to +150 c t st storage temperature -55 to +150 c note: 4. with pins 5 and 6 connected together. these are stress ratings only. operation outside the abs olute maximum ratings may cause device failure. operation at the absolute maximum rating for ex tended periods may reduce device reliability.
al5801 document number: ds35555 rev. 3 - 2 3 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 package thermal data characteristic symbol value unit power dissipation (note 5) @ t a = +25c p d 0.75 w power dissipation (note 6) @ t a = +25c 0.70 power dissipation (note 7) @ t a = +25c 0.85 power dissipation (note 8) @ t a = +25c 1.05 thermal resistance, junction to ambient air (note 5) @ t a = +25c r ja 165 c/w thermal resistance, junction to ambient air (note 6) @ t a = +25c 180 thermal resistance, junction to ambient air (note 7) @ t a = +25c 145 thermal resistance, junction to ambient air (note 8) @ t a = +25c 120 notes: 5. device mounted on 15mm x 15mm 2oz copper board. 6. device mounted on 25mm x 25mm 1oz copper board. 7. device mounted on 25mm x 25mm 2oz copper board. 8. device mounted on 50mm x 50mm 2oz copper board. recommended operating conditions (@t a = +25c, unless otherwise specified.) symbol parameter min max unit v bias supply voltage range 3.5 20 v v out out voltage range 1.1 100 i led led pin current (note 9) 25 350 ma t a operating ambient temperature range -40 125 c note: 9. subject to ambient temperature, power dissipation and pcb. nmosfet electrical ch aracteristics: (q1) (@t a = +25c, unless otherwise specified.) characteristic symbol min typ max unit test condition off characteristics drain-source breakdown voltage bv dss 100 ? ? v v gs = 0v, i d = 250a zero gate voltage drain current i dss ? ? 1 a v ds = 60v, v gs = 0v gate-source leakage i gss ? ? 100 na v gs = 20v, v ds = 0v on characteristics gate threshold voltage v gs(th) 2.0 ? 4.1 v v ds = v gs , i d = 250a static drain-source on-resistance r ds (on) ? ? ? 0.85 0.99 v gs = 10v, i d = 1.5a v gs = 6v, i d = 1a forward transconductance g fs ? 0.9 ? s v ds = 15v, i d = 1a diode forward voltage v sd ? 0.89 1.1 v v gs = 0v, i s = 1.5a dynamic characteristics input capacitance c iss ? 129 ? pf v ds = 50v, v gs = 0v f = 1.0mhz output capacitance c oss ? 14 ? pf reverse transfer capacitance c rss ? 8 ? pf
al5801 document number: ds35555 rev. 3 - 2 4 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 pre-bias transistor electrical characteristics: (q2) (@t a = +25c, unless otherwise specified.) characteristic (note 10) symbol min typ max unit test condition input voltage v i(off) 0.4 - - v v cc = 5v, i o = 100 a v i(on) - - 1.5 v v cc = 0.3v, i o = 5ma output voltage v o(on) - 0.05 0.3 v i o /i i = 5ma/0.25ma output current i o(off) - - 0.5 a v cc = 50v, v i = 0v dc current gain g 1 80 - - - v o = 5v, i o = 10ma input resistance r 1 3.2 4.7 6.2 k ? - resistance ratio r 2 /r 1 8 10 12 - - notes: 10. short duration pulse test used to minimize self-heating effect. thermal characteristics 0.2 0.4 0.6 0.8 1.2 0 25 50 75 100 125 150 temperature (c) figure 2 derating curve m a x p o we r d issi p a t i o n (w) 1.0 0 50mm x 50mm (2oz. fr4) 25mm x 25mm (2oz. fr4) 15mm x 15mm (2oz. fr4) 0.2 0.4 0.6 0.8 1.2 0 500 1,000 1,500 2,000 2,500 copper area (mm ) figure 3 area vs. max power 2 m ax p o we r d issi p a t i o n (w) t = 25c 2oz. fr4 a 1.0 0 100 120 140 160 180 0.0001 0.001 0.01 0.1 1 10 100 1,000 pulse width (s) figure 4 transient thermal impedance j u n c t i o n t o ambie n t ai r thermal resistance (c/w) t = 25c 25mm x 25mm 1oz. fr4 a 80 60 40 20 0 d = 0.05 d = 0.1 single pulse d = 0.2 d = 0.5
al5801 document number: ds35555 rev. 3 - 2 5 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 typical performance characteristics 0.05 0.15 0.25 0.35 01 23 v (v) out figure 5 output current vs. v out i (a) out 0 0.10 0.20 0.30 0.40 i = 0.1ma bias r = 1.6 ext r = 3.75 ext r = 11.6 ext r = 22.7 ext 100 150 200 250 300 350 400 11 01 0 0 r () ext figure 6 output current vs. r ext i (ma) out 50 0 i = 0.1ma bias 0.1 0.2 0.3 0.4 0.5 01 23 v (v) out figure 7 output current vs. v out i (a) out 0 i = 0.1ma r = 1.6 bias ext t = -40c a t = 25c a t = 85c a 0.05 0.15 02 4 6 810 v (v) out figure 8 output current vs. v out 0 0.10 0.20 i (a) out i = 0.1ma r = 3.75 bias ext t = -40c a t = 25c a t = 85c a 0.01 0.02 0.03 0.04 0.05 0.06 0.07 0 5 10 15 v (v) out figure 9 output current vs. v out 0 i (a) out i = 0.1ma r = 11.6 bias ext t = -40c a t = 25c a t = 85c a 0.005 0.015 0.025 0.035 0 5 10 15 20 v (v) out figure 10 output current vs. v out 0 0.010 0.020 0.030 i (a) out i = 0.1ma r = 22.7 bias ext t = -40c a t = 25c a t = 85c a
al5801 document number: ds35555 rev. 3 - 2 6 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 typical performance characteristics (cont.) 100 200 300 400 500 600 700 800 -50 0 50 100 150 junction temperature ( c) figure 11 v vs. junction temperature rext v (mv) rext i = 0.1ma v bias bias = 5v 0 0 50 100 150 200 250 300 350 400 11 01 0 0 v (v) out figure 12 output current vs. v out i (ma) out i = 0.1ma t = 85c bias a 50mm x 50mm (2oz. fr4) 25mm x 25mm (2oz. fr4) 15mm x 15mm (2oz. fr4)
al5801 document number: ds35555 rev. 3 - 2 7 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 application information figure 13 typical application circuit for linear mode current sink led driver the al5801 is designed for driving high brightne ss leds with typical led current up to 350ma. it provides a more cost effective way for driving low current leds when compared against more complex switching regu lator solutions. furthermore, it reduces the pcb board area o f the solution because there is no need for external component s like inductors, capacitors and/or switching diodes. figure 13 shows a typical application circuit diagram for driving an led or a string of leds. the npn transistor q2 measures th e led current by sensing the voltage across an external resistor r ext . q2 uses its v be as reference to set the voltage across r ext and controls the gate voltage of mosfet q1. q1 operates in linear mode to regulate the led current. the led current is: i led = v rset / r ext where v rset is the v be of q2. v be is 0.56v typical at a +25c device temper ature. see figure 11 for the variation of v be with q2?s junction temperature at i bias = 0.1ma. v be has a negative temperature coefficient which reduces t he led current as the device warms up, protecting the led(s). r bias should be chosen to drive 0.1ma current into the bias pin r bias = ( v cc ? 3.75v ) / 0.1ma from the above equation, for any required led current the necessary external resistor r ext can be calculated from r ext = v rset / i led the expected linear mode power dissipation must be factored into the design consideration. th e power dissipation across the dev ice can be calculated by taking the maximum supply voltage less the minimum voltage across the led string. v ds(q1) = v cc(max) ? v led(min) ? v rset p d = v ds(q1) * i led as the output led current of al5801 increases so will its powe r dissipation. the power dissipation will cause the device temper ature to rise above ambient, t a , by an amount determined by the package thermal resistance, r ja . therefore, the power dissipation supported by the device is dependent upon the pcb board material, the copper area and the ambi ent temperature. the maximum dissipati on the device can handle is given by: p d = ( t j(max) - t a ) / r ja t j(max) = + 150c is the maximum device junction temperature. refer to the thermal characteristic graphs in figure 2 to 4 for selecting the appropriate pcb copper area. figure 12 shows the current capabilities of the al5801 at + 25c with different pcb copper area heat sinks.
al5801 document number: ds35555 rev. 3 - 2 8 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 constant led current temperture compensation variation in the junction temperature of q2 will caus e variations in the value of controlled led current i led . the base-emitter v be voltage of q2 decreases with increasing temperature at a rate of approximately 2mv/ c . figure 14 shows a simple temper ature compensation network, which comprises of an ntc thermistor and resistor r base , for stabilizing the led current. figure 14 constant led current temperature compensation for al5801 the voltage drop v rset in the sense resistor r ext should be set to be 40 to 100mv higher than the v be(q2) at 25oc . figure 11 shows the typical v be(q2) is 0.56v at room temperature with 0.1ma i bias , so v rset is selected to be 0.62v. with the v rset chosen, the sense resistor value for 350ma i led is determined by r ext = v rset / i led = 0.62v / 350ma = 1.77 ? so a standard resistor value of 1.78? with 1% tolerance is used. the r th resistance of the ntc thermistor at room temperature is recommended as 10k ? . the value of base resistor r base is set to be 470 ? . q2?s base current is obtained as i b(q2) = ( v rset - v be(q2) ) / r base - v be(q2) / r th = ( 0.62v - 0.56 ) / 470 ? - 0.56v / 10k ? = 72a when v be(q2) is changed to v be t as the temperature increases to t oc , the thermistor resistance at t c required to compensate this variation is given by r th t = v be t / (( v rset - v be t ) / r base - i b(q2) ) at - 2mv/ c, v be(q2) reduces to 0.44v from 0.56v as the tem perature increases from +25c to +85c. from the above equation, the thermistor?s resistance at +85c to keep the same output current is given by r th 85 = 0.44v / (( 0.62v ? 0.44v ) / 470 ? - 72a ) = 1.4k ? the ntc thermistor is chosen for compensation whose resistance is 10k ? at + 25c and 1.38k ? at + 85c with a value of 3530 . figure 15 shows the i led variation with temperature with and without temperature compensation. figure 15 led current variation with and without temperature compensation
al5801 document number: ds35555 rev. 3 - 2 9 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 pwm dimming (a) (b) figure 16 application circuits for led driver with pwm dimming functionality (a) mosfet driving and (b) transistor driving pwm dimming can be achieved by dr iving the bias pin (1). an external open-colle ctor npn transistor or open-drain n-channel mosf et can be used to drive the bias pin as shown in figure 16. dimming is achieved by turning the leds on and off for a portion of a single cycle. the pwm signal can be provided by a micro- controller or by analog circuitry. figure 17 shows the led current against the pwm signal duty ratio when the al5801 is used to driv e three series connected leds from a 12v supply. the pwm dimming frequency is set to 200hz. the pwm signal is supplied to the open-drain small signal mosfet?s gate as shown in figure 16a. the bias pin signal is an inversion of the pwm drive to the mosfet?s gate. therefore, a pwm signal duty cycle of 0% provides the maximum led current. sufficiently large pcb copper area is used for heat sinking of the al5801 in order to minimize the device self-heating at +25 c ambient. figure 17 led current against pwm dimming signal duty ratio at 200hz pwm frequency
al5801 document number: ds35555 rev. 3 - 2 10 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 ordering information part number qualification package code packaging (note 11) 7? tape and reel quantity part number suffix al5801w6-7 commercial w6 sot26 3,000/tape & reel -7 al5801w6q-7 automotive w6 sot26 3,000/tape & reel -7 notes: 11. for packaging details, go to our website at http://www.diodes.com marking information date code key year 2012 2013 2014 2015 2016 2017 2018 code z a b c d e f month jan feb mar apr may jun jul aug sep oct nov dec code 1 2 3 4 5 6 7 8 9 o n d package outline dimensions (all dimensions in mm.) suggested pad layout sot26 dim min max typ a 0.35 0.50 0.38 b 1.50 1.70 1.60 c 2.70 3.00 2.80 d ? ? 0.95 h 2.90 3.10 3.00 j 0.013 0.10 0.05 k 1.00 1.30 1.10 l 0.35 0.55 0.40 m 0.10 0.20 0.15 0 8 ? all dimensions in mm dimensions value (in mm) z 3.20 g 1.60 x 0.55 y 0.80 c1 2.40 c2 0.95 ? green ? green l100 = product type marking code ym = date code marking y = year (ex: y = 2012) m = month (ex: 9 = september) a m j l d b c h k x z y c1 c2 c2 g
al5801 document number: ds35555 rev. 3 - 2 11 of 11 www.diodes.com july 2012 ? diodes incorporated a l5801 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 rese rve the right to make modifications, enhanc ements, improvements, corrections or ot her changes without further notice to this document and any product descri bed herein. diodes incorporated does not assume any liability arising out of the application or use of this document or an y product described herein; neither does di odes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or us er of this document or products described herein in such applica tions shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthoriz ed sales channel. should customers purchase or use diodes inco rporated products for any unintended or una uthorized application, customers shall i ndemnify and hold diodes incorporated and its representativ es harmless against all claims, damages, expenses, and attorney fees arising out of, directly or indirectly, any claim of personal injury or death a ssociated with such unintended or unauthorized application. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. life support diodes incorporated products are specifically not authorized for use as critical component s in life support devices or systems without the express written approval of the chief executive offi cer of diodes incorporated. as used herein: a. life support devices or syst ems 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 proper ly used in accordance with instructions for use provided in 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 devic e or system whose failure to perform can be reasonably expect ed to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifi cations of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-rel ated requirements concerning the ir products and any use of diodes incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or s ystems-related information or support that may be provided by diodes incorporated. further, customers must fully indemnify diodes incorporate d and its representatives against any damages arisi ng out of the use of diodes incorporated pr oducts in such safety-critical, life suppor t devices or systems. copyright ? 2012, diodes incorporated www.diodes.com

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