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mp24893 step down white led driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 1 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. the future of analog ic technology description the mp24893 is a high efficiency step-down converter designed in continuous current mode for driving the high brightness leds from wide input voltage of 6v to 36v. the mp24893 employs hysteretic control architecture to regulate a highly accurate led current, which is measured through an external high-side current-sense resistor. moreover, this control scheme provides optimal circuit stabilization and a very quick response time without loop compensation. its low 200mv average feedback voltage reduces power loss and improves the converter efficiency. the mp24893 implements pwm and analog dimming together through the dim pin. the mp24893 includes under-voltage lockout, thermal overload protection to prevent damage in the event of an output overload. the mp24893 is available in tsot23-5 and qfn6 packages. features ? internal 36v mosfet ? wide 6v-to-36v input range ? 1a output current ? high efficiency ? hysteretic control ? pwm and analog dimming ? 1000:1 pwm dimming resolution ? uvlo, thermal shutdown ? available in tsot23-5 and qfn6 packages applications ? low-voltage halogen replacement ? low-voltage general illumination ? automotive/decorative led lighting ? signs/emergency lighting ? led backlighting all mps parts are lead-free and adhere to the rohs directive. for mps green status, please visit mps websit e under products, quality assurance page. ?mps? and ?the future of analog ic technology? are registered trademarks o f monolithic power systems, inc. typical application v in 6 v -36v r sense d 1 l 1 in c in rs sw en / dim gnd mp24893
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 2 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. ordering information part number package top marking mp24893dj * tsot23-5 abd MP24893DQ ** qfn6 (3x3mm) abd * for tape & reel, add suffix ?z (e.g. mp24893dj?z); for rohs compliant packaging, add suffix ?lf (e.g. mp24893dj?lf?z) * * for tape & reel, add suffix ?z (e.g. MP24893DQ?z); for rohs compliant packaging, add suffix ?lf (e.g. MP24893DQ?lf?z) package reference tsot23-5 qfn6 (3x3mm) absolute maxi mum ratings (1) v in , v sw .........................................-0.3v to +40v v rs ..................................................v in -5v to v in all other pins ...............................-0.3v to +6.3v continuous power dissipation (t a = +25c) (2) tsot23-5 .................................................. 1.1w qfn6 (3x3mm) .......................................... 2.5w junction temperature ...............................150c lead temperature ....................................260c storage temperature............... -65c to +150c recommended operating conditions (3) supply voltage v in ..............................6v to 36v operating junction temp. (t j ). -40c to +125c thermal resistance (4) ja jc tsot23-5 .............................110 ..... 55 ... c/w qfn6 (3x3mm) ......................50 ...... 14 ... c/w notes: 1) exceeding these ratings may damage the device. 2) the maximum allowable power dissipation is a function of the maximum junction temperature t j (max), the junction-to- ambient thermal resistance ja , and the ambient temperature t a . the maximum allowable continuous power dissipation at any ambient temperature is calculated by p d (max)=(t j (max)- t a )/ ja . exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circuitry protects the device from permanent damage. 3) the device is not guaranteed to function outside of its operation conditions. 4) measured on jesd51-7 4-layer board.
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 3 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. electrical characteristics v in = 24v, t a = +25c, unless otherwise noted. parameter symbol condition min typ max units input voltage v in 6 36 v in under-voltage lockout v in_uvlo v in rising 5.3 5.9 v under-voltage lockout hysteresis 700 mv shutdown supply current i sd 100 120 a quiescent supply current i q no switching 0.7 1 ma feedback reference voltage peak (with respect to v in ) v in -v rs v en/dim = 5v 220 230 240 mv feedback reference voltage valley (with respect to v in ) v in -v rs v en/dim = 5v 160 170 180 mv en/dim max. dimming voltage (5) v dim_max 2.56 v en/dim min. dimming voltage (5) v dim_min 0.3 v en/dim enable high voltage v en_high v en rising 0.2 0.25 0.3 v en/dim enable hysterisis v en_hys 20 50 80 mv en/dim pull-up resistor r en 45 k ? internal reference voltage v ref 1.275 v switch on resistance r ds_on3 0.2 ? minimum on time (5) t on_min 100 ns minimum off time (5) t off_min 100 ns recommended duty cycle range d 30 70 % notes: 5) guaranteed by design
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 4 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. pin functions tsot23-5 pin# qfn6 (3x3mm) pin# name description 1 1 sw drain of internal mosfet. connect the inductor common terminal and schottky anode to this pin. 2 2 gnd ground. 3 5 en/dim enable/dimming command input. for pwm dimming, apply a square wave signal to this pin. for analog dimmi ng, apply a 0.3v-to-2.5v dc voltage to linearly control the led current range fr om 25% to 200%. turn off the output current when pulling this pin below 0.2v. leave it open for normal operation (v en/dim =1.28v). 4 4 rs led current sense input. connect a curr ent-sense resistor to program the led average current to in pin. 5 3 in input supply pin. connect an appropriate decoupling capacitor from the in pin to gnd. 6 n/c not connected.
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 5 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performanc e characteristics v in =24v, 3 led s in series, i out =1a, unless otherwise noted. v sw 10v/div. v en 1v/div. v in 10v/div. i l 500ma/div. v sw 10v/div. v en 1v/div. v in 10v/div. i out 1a/div. v sw 10v/div. v en 1v/div. v pwm 5v/div. i out 500ma/div. v sw 10v/div. v led+ 10v/div. i out 500ma/div. v sw 10v/div. v led- 10v/div. i out 500ma/div. v sw 20v/div. v en 1v/div. v in 20v/div. i out 1a/div. steady state v in startup v en startup pwm dimming f pwm = 200hz, d pwm = 50% open led protection open leds at working short led protection short leds at working 90 91 92 93 94 95 15 20 25 30 35 40 input voltage (v) analog dimming curve 0 200 400 600 800 1000 1200 0 0.2 0.4 0.6 0.8 1 1.2 1.4 analog dimming level(v) led current(ma) efficiency vs. input voltage efficiency (%)
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 6 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. function diagram gnd en /dim v in in rs rsense sw l d c in 1.275v reference filter + 0.2v hv regulator 5v enable high side current sense + pwm driver r1 r2 dim figure 1: mp24893 functional block diagram
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 7 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. operation steady state the mp24893 is a hysteretic-controlled, step- down led driver that is easily configured for various applications with an input range from 6v to 36v. the converter employs a high-side current-sense resistor to detect and regulate the led current. the voltage across the current- sense resistor is measured and regulated to within 202mv30mv. the internal 1.275v reference voltage provides a 0.2v reference to enable the part and a 1.275v pull-up voltage as current reference. when v en >0.2v, the output of the comparator goes high and the other blocks are enabled. a high-side resistor, r sense , senses the output current. when the switch is on, r2 is shorted and r1 sets the output current upper-threshold. when the switch is off, r1 and r2 set the output current lower-threshold, and the ratio of r1 and r2 determines the current hysteresis. enable control once input voltage is applied, the internal 1.275v reference is connected to en/dim pin through pull up resistor. if the en/dim pin is left open, the ic will automatically start up to the maximum brightness. adding a capacitor to this pin can hereby program a soft-start time. applying an external voltage range from 0.2v to 1.25v to the en/dim pin linearly controls the current-sense voltage reference from 0mv to 202mv for analog dimming. applying an external pwm voltage with an amplitude of 1.25v to the en/dim pin achieves pwm dimming. for additional information on the flexible external pwm dimming method, please refer to the ?selecting dimming control mode? section. system soft start the voltage on the en/dim pin is the inductor current reference. an external capacitor from the en/dim pin to ground provides a soft-start delay. when v in starts, internal voltage source charges the capacitor from 0v to 1.25v for soft-start. dimming control mp24893 provides two dimming methods: pwm dimming and dc analog dimming. to use pwm dimming, apply a square wave to the en/dim pin. to use analog dimming, apply a 0.3v-to-2.5v dc voltage to this pin.
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 8 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. application information setting the led current the led current is set by the current-setting resistor between the in and rs pins, where: r set =202mv/i led for r set =0.36 ? , the led current is set to 550ma selecting the inductor lower values of the inductor result in higher switching frequencies, leading to larger switch loss. for most applications, select a switching frequency between 200khz and 600khz. estimate the inductor value based on the desired switching frequency, where: out out in led sw v (1- ) v v l 0.3 i f = for higher efficiency, use inductors with low dc resistance. selecting the diode the output diode supplies current to the inductor when the internal mosfet is off. to reduce losses due to the diode forward voltage and recovery time, use a schottky diode. select a diode rated with a reverse voltage greater than the input voltage. the average current rating must be exceed the maximum expected load current, and the peak current rating must exceed the peak inductor current. selecting the input capacitor the input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. select capacitor value between 10f and 22f for most applications. the voltage rating should exceed the input voltage. use a low-esr capacitor input decoupling. selecting the output capacitor for most applications, an output capacitor is not necessary. but if the peak-to-peak ripple led current must be less than 30% of the average current, add a capacitor across the leds, where a higher capacitor value leads to a proportionally lower ripple. a 2.2f capacitor will meet most requirements. selecting soft-start capacitor the delay time with the soft-start capacitor can be estimated by 0.2ms/nf. in pwm dimming, select a c<2.2nf to eliminate its effect on the average led current. selecting dimming control mode mp24893 provides two dimming methods: dc analog dimming and pwm dimming. 1. dc analog dimming mode apply a 0.3v-to-2.5v dc voltage to the en/dim pin. the voltage from 0.3v to 2.5v changes the inductor current reference directly and linearly controls the inductor current range from 25% to 200% (see figure 2). en/dim en/dim gnd mp24893 vin in tp4 r6 0 c5 1nf figure 2: analog dimming external circuit 2. pwm dimming mode apply a 100hz-to-2khz square waveform to the en/dim pin. the average led current is proportional to the pwm duty cycle. add an npn- transistor on/off circuit to separate the pwm signal from the current reference (see figure 3) because this pin is pulled up by the 1.25v internal source as the inductor current reference. the minimum pwm amplitude is 1.5v. en/dim gnd mp24893 vin in en/dim tp4 r6 nc r4 1k q1 r5 ns c5 82pf figure 3: pwm dimming external circuit
mp24893 ? step down wled driver with wide 6v-to-36v input voltage mp24893 rev.1.02 www.monolithicpower.com 9 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. circuit layout consideration pay careful attention to the pcb board layout and components placement. r sense should be placed close to the in pin and rs pin to minimize set current error. the input loop?including the input capacitor, schottky diode, and internal mosfet?should be as short as possible.
mp24893 ? step down wled driver with wide 6v~36v input voltage mp24893 rev.1.02 www.monolithicpower.com 10 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical application circuit pgnd agnd pgnd 0.4 r1 nc r4 c2 nc q1 0.4 r2 en/dim 1nf c5 0 r6 led- led+ b260 d1 c1 l1 nc c4 gnd 2 sw 1 in 5 rs 4 en/dim 3 mp24893 u1 nc c3 agnd nc r5 vin nc r3 figure 4: drive 3 leds in series, 1a current output
mp24893 ? step down wled driver with wide 6v~36v input voltage mp24893 rev.1.02 www.monolithicpower.com 11 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. package information tsot23-5 0.30 0.50 seating plane 0.95 bsc 0.84 0.90 1.00 max 0.00 0.10 top view front view side view recommended land pattern 2.80 3.00 1.50 1.70 2.60 3.00 13 4 5 0.09 0.20 note: 1) all dimensions are in millimeters . 2) package length does not include mold flash , protrusion or gate burr. 3) package width does not include interlead flash or protrusion. 4) lead coplanarity (bottom of leads after forming ) shall be 0.10 millimeters max. 5) drawing conforms to jedec mo-193, variation aa. 6) drawing is not to scale . 0.30 0.50 0 o -8 o 0.25 bsc gauge plane 2.60 typ 1.20 typ 0.95 bsc 0.60 typ see detail "a" detail A
mp24893 ? step down wled driver with wide 6v~36v input voltage notice: the information in this document is subject to change wi thout notice. users should warrant and guarantee that third party intellectual property rights are not infringed upon when integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp24893 rev.1.02 www.monolithicpower.com 12 12/7/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. qfn6 (3x3mm) side view top view 1 6 4 3 bottom view 2.90 3.10 1.40 1.60 2.90 3.10 2.20 2.40 0.95 bsc 0.35 0.45 0.80 1.00 0.00 0.05 0.20 ref pin 1 id marking 1.50 0.95 0.40 recommended land pattern 2.90 note: 1) all dimensions are in millimeters . 2) exposed paddle size does not include mold flas h . 3) lead coplanarity shall be 0.10 millimeter max. 4) jedec reference is mo-229, variation veea-2. 5) drawing is not to scale . pin 1 id see detail a 2.30 0.80 pin 1 id option a r0.20 typ. pin 1 id option b r0.20 typ. detail a 0.35 0.55 pin 1 id index area

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