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mp3304 36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 1 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. the future of analog ic technology description the mp3304 is a monolithic step-up converter designed for driving arrays of wleds from 5v input or a single cell lithium ion battery. the mp3304 uses current mode, fixed frequency architecture to regulate the led current, which is measured through an external current sense resistor. its low 200mv feedback voltage reduces power loss and improves efficiency. the mp3304 features up to 50khz true pwm dimming, which allows the flexible control of the backlighting luminance under wide range of the ambient brightness, and also avoids the possibility of pwm dimming audible noise. the mp3304 is turned off if an over-voltage condition is present due to an open circuit condition. mp3304 also includes under-voltage lockout, current limiting and thermal overload protection preventing damage in the event of an output overload. the mp3304 is available in small 8-pin qfn 2x3mm package. features ? internal power mosfet ? drives up to 10 series white leds ? up to 88% efficiency ? pwm dimming frequency from 250hz to 50khz ? 2.2mhz fixed switching frequency ? open load shutdown ? low 200mv feedback voltage ? uvlo, thermal shutdown ? internal 1.3a current limit ? available in 2x3mm qfn8 package applications ? lcd panels ? digital picture frames ? handheld computers and pdas ? digital still cameras ? small lcd displays ?monolithic power systems?, ?mps?, and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application mp3304 v in 5v enable/ dimming control led1 led2 led3 led28 led29 led30 in en gnd led iset sw string 1 string 10 ... c1 c2 r set l d v in vs. efficiency 50 60 70 80 90 100 3 3.5 4 4.5 5 5.5 6 6.5 v in (v) efficiency (%)
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 2 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. ordering information part number* over voltage protection package top marking free air temperature (t a ) mp3304add** 38v qfn8(2x 3mm) 5q ?40 c to +85 c mp3304bdd** 26v qfn8(2x 3mm) 6r ?40 c to +85 c MP3304CDD 20v qfn8(2x 3mm) 2g ?40 c to +85 c *for tape & reel, add suffix ?z (eg. mp3304 x dd-z). for rohs compliant packaging, ad d suffix ?lf (eg. mp3304 xdd?lf?z) **contact factory for availability package reference top view sw pgnd in n/c 1 2 3 4 gnd iset led en 8 7 6 5 exposed pad connected to gnd absolute maxi mum ratings (1) sw pin, led pin..........................?0.5v to +42v all other pins ..............................?0.3v to +6.5v storage temperature.............. ?55 c to +150 c continuous power dissipation (t a = +25c) (2) ???????????????????1.9w recommended operating conditions (3) in supply voltage .................................3v to 6v sw pin mp3304add ................................... v in to +36v mp3304bdd .................................... v in to +24v MP3304CDD.................................... v in to +18v operating junct. temp (t j )..... ?40 c to +125 c thermal resistance (4) ja jc qfn8 2x3mm..........................65 ...... 13 ... 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 pd (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 operating conditions. 4) measured on jesd51-7, 4-layer pcb.
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 3 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. electrical characteristics v in = v en = 5v, t a = +25 c, unless otherwise noted. parameters symbol condition min typ max units operating input voltage v in 2.5 6 v supply current (shutdown) i in_sd v en = 0v 1 2 a supply current (quiescent) i in_qs v iset =0.3v 690 850 a switching frequency f sw 1.7 2.2 2.7 mhz maximum duty cycle d max v iset = 0v 90 % under voltage lockout in under voltage lockout v uvlo v in rising 2.25 2.45 v under voltage lockout hysteresis 92 mv v ov rising, mp3304add 38 v v ov rising, mp3304bdd 26 v open lamp shutdown threshold v ovp v ov rising, MP3304CDD 20 v enable en off threshold v en_low v en falling 0.4 v en on threshold v en_high v en rising 1.8 v disable timer 5 ms feedback iset voltage v iset v en > 2v 185 200 215 mv iset input bias current v iset = 0.2v -600 -300 na output switch sw on-resistance r on 0.4 ? sw current limit duty cycle = 60% 1.33 a thermal shutdown 150 c led switch(m2, refer block diagram) on resistance 0.8 ?
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 4 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. pin functions pin # name pin function 1 sw power switch output. sw is the drain of the internal mosfet switch. connect the power inductor and output rectifier to sw. sw can swing between gnd and 36v (mp3304a), 24v (mp3304b) or 18v (mp3304c). 2 pgnd power ground. 3 in input supply pin. must be locally bypassed. 4 n/c no connect. 5 en on/off control and dimming command input. holding en pin low for more than 5ms will turn the part off. to use pwm dimming, add a 250hz to 50khz square wave signal to this pin. 6 led led current input. this pin is the open-dra in output of an internal dimming control switch. connect the led cathode to this pin. 7 iset led current set. this pin is the source out put of an internal dimming control switch. the mp3304 regulates the voltage across t he current setting resistor. tie a current setting resistor from this pin to ground. the regulation voltage is 200mv. 8 gnd, exposed pad ground. connect exposed pad to gnd plane for optimal thermal performance.
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 5 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical performanc e characteristics v in = 5v, i led = 200ma, 3wleds 10strings, unless otherwise noted. open load protection pwm dimming f pwm =50khz, dpwm=50% steady state operation enable startup enable shutdown i inductor 500ma/div fb 50mv/div v out (ac) 200mv/div sw 5v/div i led 100ma/div en 2v/div v out 2v/div sw 10v/div i led 100ma/div v out 5v/div sw 10v/div i led 100ma/div en 2v/div v out 2v/div sw 10v/div i led 100ma/div pwm 2v/div v out 10v/div sw 10v/div 400ns/div v in vs. efficiency 50 60 70 80 90 100 3 3.5 4 4.5 5 5.5 6 6.5 v in (v) efficiency (%) pwm dimming duty vs. wled current 0 20 40 60 80 100 120 140 160 180 200 020406080100 pwm dimming duty (%) wled current (ma) 50khz 20khz 250hz 1khz
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 6 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. operation the mp3304 uses a constant frequency, peak current mode boost regulator architecture to regulate the series string of white leds. the operation of the mp3304 can be understood by referring to the block diagram of figure 1. at the start of each oscillator cycle the fet is turned on through the control circuitry. to prevent sub-harmonic oscillations at duty cycles greater than 50 percent, a stabilizing ramp is added to the output of the current sense amplifier and the result is fed into the positive input of the pwm comparator. when this voltage equals the output voltage of the error amplifier the power fet is turned off. the voltage at the output of the error amplifier is an amplified version of the difference between the 200mv reference voltage and the feedback voltage. in this way the peak current level keeps the output in regulation. if the feedback voltage starts to drop, the output of the error amplifier increases. this results in more current flowing through the power fet, thus increasing the power delivered to the output. pwm comparator amplifier enable control logic current sense amplifier sw m1 gnd - + led iset iset en 2.2mhz osc enable & dimming control - + + - + 200mv m2 figure 1?functional block diagram
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 7 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. application information enable/ dimming control mp3304 v in 5v mbr0520 in en gnd led iset sw ld1 figure 2?circuit for driving 10 strings of 3 wleds a typical application circuit can be seen in figure 2. the 10 strings of 3 white leds can be driven from a 5v voltage at an output current of 200ma. a 2.2f output capacitor is sufficient for most applications. a 2.2h inductor with low dcr (inductor dc resistance) is recommended to improve efficiency. a 10f ceramic capacitor is recommended for the input capacitance in the real system. schottky diodes have fast recovery and a low forward voltage are recommended. schottky diodes rated with 500ma are sufficient for the mp3304. the mp3304 has internal soft- start to limit the amount of current through vin at startup and to also limit the amount of overshoot on the output. the ramped voltage that is added to the current sense amplifier reduces the current output as the duty cycle increases. as more leds are added, the output voltage rises but the current that can be delivered to the load is reduced as well. setting the led current the led current is controlled by the current setting resistor, r1. the current through the leds is given by: i led = 200mv/r1. table 1 shows the selection of resistors for a given led current. table 1?i led vs. r1 r set i led (ma) r1 ( ? ) 1 200 5 40 10 20 20 10 60 3.33 180 1.11 200 1 pwm dimming apply a 250hz to 50khz square waveform to the en pin to implement pwm dimming of the leds. the minimum recommended amplitude of the pwm signal is 2v. open load protection open load protection will shut off the mp3304 if the output voltage goes too high. in some cases an led may fail, this will result in the feedback voltage always being zero. the part will run at maximum duty cycle boosting the output voltage higher and higher. if the output voltage ever exceeds the open load protection threshold voltage, the mp3304 will shut down. the part will not switch again until the power is recycled. for mp3304a, mp3304b, and mp3304c, the open load protection threshold voltages are 38v, 26v, and 20v respectively.
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 8 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. layout considerations careful attention must be paid to the pcb board layout and components placement. proper layout of the high frequency switching path is critical to prevent noise and electromagnetic interference problems. the loop of mp3304 sw to gnd pin, output diode, and output capacitor is flowing with high frequency ripple current, it must be as short as possible. the in pin of the ic must be locally bypassed. a rc filter is highly recommended for eliminating the noise on in pin. it could be implemented as shown in figure 3. mp3304 sw gnd in input figure 3?input bias filtering
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 9 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical application circuits mp3304c v in 5v enable/ dimming control led1 led2 led3 led28 led29 led30 in en gnd led iset sw string 1 string 10 ... c1 10uf c2 2.2uf l1 2uh d1 b0530 figure 4 ? driving 30 wleds (3 wleds in series and 10 strings paralleled) with 5v input voltage mp3304a sw in iset led pgnd gnd en vin bias en gnd c2 4.7uf 16v c1 4.7uf 16v l1 4.7uh 5v d1 b0540 c5 0.47uf 50v led+ led- c3 0.1uf c4 ns r4 ns r3 3.32 1% r2 0 r1 100 u1 jp1 5 8 7 6 2 1 3 figure 5 ? driving 27 wleds (9 wleds in series and 3 strings paralleled) with 5v input voltage
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 10 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical application circuits (continued) mp3304a sw in iset led pgnd gnd en led+ led- c2 330nf 50v d2 5.6v 7.5 zener d1 b0540 l1 10uh optional bias circuit gnd en vin 3.3v -18v c1 10uf 25v c3 0.1uf 50v 2 31 6 7 5 8 figure 6 ? driving 27 wleds (9 wleds in series and 3 strings paralleled) with 3.3v-18v input voltage in order to improve the mosfet on-resistance at low input voltage and make the chip compatible for high input voltage, the additional bias circuit should be used. mp3304a sw led in iset pgnd gnd en gnd en led+ led- vin 4.5v-18v c1 10uf 25v c4 330nf 50v c3 0.1uf 25v q2 2n3904 d2 5.6v zener required bias circuit for high input voltage l1 d1 10uh b0540 7 8 2 31 6 5 figure 7 ? wide input voltage step-up converter for 27 wleds ( 9 wleds in series and 3 strings paralleled )
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming mp3304 rev. 0.91 www.monolithicpower.com 11 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. typical application circuits (continued) mp3304a sw in led gnd iset pgnd en c3 330nf r1 r2 d1 b0540 l1 led1 led2 led3 led4 led5 led6 led7 led8 led9 led10 gnd en vin 5v c1 16v c2 16v 1 27 5 8 6 3 1% figure 8 ? driving 10 wleds in series with 5v input voltage
mp3304 ?36v, 1.3a, step-up white led driver with high frequency true pwm dimming notice: the information in this document is subject to change wi thout notice. users should warra nt and guarantee that third party intellectual property rights are not infringed upon w hen integrating mps products into any application. mps will not assume any legal responsibility for any said applications. mp3304 rev. 0.91 www.monolithicpower.com 12 4/19/2010 mps proprietary information. unaut horized photocopy and duplication prohibited. ? 2010 mps. all rights reserved. package information qfn8 (2mm x 3mm) side view top view bottom view 2.90 3.10 1.90 2.10 0.00 0.05 pin 1 id marking 1.70 0.50 0.25 recommended land pattern 2.90 note: 1) all dimensions are in millimeters. 2) exposed paddle size does not include mold flash. 3) lead coplanarity shall be 0.10 millimeter max. 4) drawing conforms to jedec mo-229, variation vced-2. 5) drawing is not to scale. 1.60 0.70 pin 1 id option b r0.20 typ. detail a pin 1 id index area 1 8 5 4 1.65 1.85 1.50 1.70 0.50 bsc 0.18 0.30 pin 1 id see detail a 0.30 0.50 0.80 1.00 0.20 ref pin 1 id option a 0.30x45? typ.

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