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| mp3386 50v, 6 string white led driver mp3386 rev. 1.0 www.monolithicpower.com 1 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. the future of analog ic technology description the mp3386 is a step-up converter with 6- channel current sources designed for driving the white led arrays for large size lcd panel backlighting applications. the mp3386 uses current mode, fixed frequency architecture. the switching frequency can be selected at 1.25mhz or 625khz. it generates an output voltage up to 50v from a 4.5v to 25v input supply. the mp3386 regulates the current in each led string to the user programmed value set by an external current setting resistor. the mp3386 applies 6 internal current sources in each led string terminal to get current balance. and the current matching achieves 3% regulation accuracy between strings. its low 600mv regulation voltage on led current sources reduces power loss and improves efficiency. the mp3386 features external pwm dimming or dc input 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 dimming pwm signal can be generated internally, and the dimming frequency is programmed by an external setting capacitor. features ? high efficiency and small size ? 4.5v to 25v input voltage range ? 50v maximum step-up voltage ? balanced driver for 6 strings of wled ? 3% current matching accuracy between strings ? selectable switching frequency: 1.25mhz or 625khz ? pwm or dc input burst pwm dimming ? programmable over-voltage protection threshold ? under voltage lockout ? open and short led protection ? thermal shutdown ? small qfn24 (4x4mm) a nd 28-pin soic package applications ? notebook & netbook pc ? small lcd tv ? handy terminals display ? automotive system and tablet computer all mps parts are lead-free and adhere to the rohs directive. for mps green status, please visit mps website under quality assurance. ?mps? and ?the future of analog ic technology? are registered trademarks of monolithic power systems, inc. typical application vin 4.5v~25v mp3386 vcc vin comp vfault sw2 sw1 24 23 22 21 20 19 en osc fset pwmo gnd pwmi led6 led5 led4 led3 led2 iset pgnd1 pgnd2 ovp vout nc led1 7 8 9 10 11 12 1 2 3 4 5 6 18 17 16 15 14 13 enable pwm dimming nc l1 d1 m1 c1 c3 c2 r1 r2 r set c4 c5 c6
mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 2 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. ordering information part number package top marking free air temperature (t a ) mp3386dr * qfn24 (4x4mm) 3386dr -40 c to +85 c MP3386EY ** soic28 3386ey -20 c to +85 c * for tape & reel, add suffix ?z (e.g. mp3386dr?z). for rohs compliant packaging, add suffix ?lf (e.g. mp3386dr?lf?z) * * for tape & reel, add suffix ?z (e.g. MP3386EY?z). for rohs compliant packaging, add suffix ?lf (e.g. MP3386EY?lf?z) package reference top view 1 2 3 4 5 6 18 17 16 15 14 13 en osc fset pwmo gnd pwm1 exposed pad connect to gnd pgnd1 pgnd2 ovp vout nc led1 led6 led5 led4 led3 led2 vcc vin comp sw1 sw2 vfault 789 10 iset 11 12 24 23 22 21 20 19 1 2 3 4 5 6 7 8 9 10 11 12 13 14 28 27 26 25 24 23 22 21 20 19 18 17 16 15 top view vfault pwmo vout vcc nc en led1 ovp vin comp osc agnd fset pwmi sw2 pgnd1 nc nc pgnd2 nc iset nc led2 led4 led3 led5 led6 sw1 qfn24 (4x4mm) soic28 absolute maxi mum ratings (1) v in .................................................-0.3v to +30v v vfault ...........................................v in - 6v to v in v sw , v out , v led1 to v led6 ..................-1v to +50v all other pins ..................................-0.3v to +6v continuous power dissipation (t a = +25c) (2) qfn24 (4x4mm)???????????.2.9w soic28??????????? ?.?....2.1w junction temperature ...............................150 c lead temperature ....................................260 c storage temperature............... -65 c to +150 c recommended operating conditions (3) supply voltage v in ...........................4.5v to 25v maximum junction temp. (t j ) .............. +125c thermal resistance (4) ja jc qfn24 (4x4mm) ....................42 ....... 9 .... c/w soic28 ..................................60 ...... 30 ... 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 circui try 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 pcb.. mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 3 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. electrical characteristics v in =12v, v en = 5v, t a = +25 c, unless otherwise noted. parameters symbol condition min typ max units operating input voltage v in 4.5 25 v supply current (quiescent) i q v in =12v, v en =5v, no load. 1.8 ma supply current (shutdown) i st v en =0v, v in =12v 2 a ldo output voltage v cc v en =5v, 6v mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 5 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. pin functions qfn24 pin # soic28 pin # name description 1 5 en enable control input. do not let this pin floating. 2 6 osc switching frequency selection input. when fl oat this pin or connect this pin to vcc, the step-up converter switching fr equency is 1.25mhz. when connect this pin to gnd, the step-up converter switching frequency is 625khz. 3 7 fset dimming pwm frequency set. connect a capacitor between fset and gnd to set the dpwm frequency by the equation: f dpwm =3.5uf/c fset . the frequency of dpwm is recommended to be set from 100hz to 2khz. 4 8 pwmo pwm filter output. to use external pwm dimming mode, connect a capacitor between pwmo and gnd to form a low-pass filter with an internal 400k ? resistor. it filters the external pwm logic signal on pwmi pin into a dc signal whose level is inversely proportional to the duty-cycle of the input pwm signal and then the dc signal is translated into a duty-cycle of the dimming pwm. to use dc input pwm dimming mode, directly apply a dc voltage from 0.2v to 1.2v on pwmo pin for dimming pwm duty cycle control. the dc input pwm dimming polarity is negative. 5 9 gnd analog ground. 6 10 pwmi pwm signal input. to use external pwm dimming mode, apply a pwm signal on this pin for brightness control. this signal is filtered and its duty cycle is converted into a dc signal to calculat e the dpwm duty cycle. and the dpwm duty cycle equals to the input pwm duty cy cle. to use dc input pwm dimming mode, float this pin. 7 11 led6 led string 6 current input. this pin is the open-drain output of an internal dimming control switch. connect the led string 6 cathode to this pin. if this string is not used, connect vout to this pin. 8 12 led5 led string 5 current input. this pin is the open-drain output of an internal dimming control switch. connect the led string 5 cathode to this pin. if this string is not used, connect vout to this pin. 9 13 led4 led string 4 current input. this pin is the open-drain output of an internal dimming control switch. connect the led string 4 cathode to this pin. if this string is not used, connect vout to this pin. 10 14 led3 led string 3 current input. this pin is the open-drain output of an internal dimming control switch. connect the led string 3 cathode to this pin. if this string is not used, connect vout to this pin. 11 16 iset led current set. tie a current setting resistor from this pin to ground to program the current in each led string. i led = 1.21v / r set 12 18 led2 led string 4 current input. this pin is the open-drain output of an internal dimming control switch. connect the led string 4 cathode to this pin. if this string is not used, connect vout to this pin. 13 19 led1 led string 3 current input. this pin is the open-drain output of an internal dimming control switch. connect the led string 3 cathode to this pin. if this string is not used, connect vout to this pin. 14 15, 17, 20, 25, 27 nc no connection. 15 21 vout voltage output. connect this pin to output. mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 6 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. pin functions (continued) qfn24 pin # soic28 pin # name description 16 22 ovp over-voltage protection input. connect a resistor divider from output to this pin to program the ovp threshold. when this pin voltage reaches 1.23v, the mp3386 triggers ov protection mode. 17 23 pgnd2 step-up converter power ground. 18 24 pgnd1 step-up converter power ground. pgnd1 and pgnd2 should be shorted externally. 19 28 sw1 step-up converter power switch output. sw1 is the drain of the internal mosfet switch. connect the power inductor and output rectifier to sw1. sw1 can swing between gnd and 50v. sw1 and sw2 should be shorted externally. 20 26 sw2 step-up converter power switch output. sw2 is the drain of the internal mosfet switch. connect the power inductor and output rectifier to sw2. sw2 can swing between gnd and 50v. sw1 and sw2 should be shorted externally. 21 1 vfault fault disconnection switch driver ou tput. when the system starts up normally, this pin turns on the external pmos. when the mp3386 is disabled, the external pmos is turned off to disconnect the input and output. 22 2 comp step-up converter compensation pin. this pin is used to compensate the regulation control loop. connect a capac itor or a series rc network from comp to gnd. 23 3 vin supply input. vin supplies the power to the chip, as well as the step-up converter switch. drive vin with a 4.5v to 25v power source. must be locally bypassed. 24 4 vcc the internal 5v linear regulator output. vcc provides power supply for the internal mosfet switch gate driver an d the internal control circuitry. bypass vcc to gnd with a ceramic capacitor. if vin is less than 5.5v, apply an external 5v supply directly on vcc. mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 7 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performanc e characteristics v in =12v, 10 leds in series, 6 strings parallel, 20ma/string, unless otherwise noted. input voltage (v) efficiency(%) efficiency vs. input voltage steady state v sw 20v/div v sw 20v/div v in 5v/div v out 20v/div v out 20v/div i led 100ma/div v sw 20v/div v led6 20v/div v out 20v/div i led 100ma/div i led 100ma/div v sw 20v/div v en 5v/div v out 20v/div i led 100ma/div v sw 20v/div v pwmi 2v/div v out 20v/div i led 100ma/div v sw 20v/div v fault 5v/div v out 20v/div i led 100ma/div v sw 20v/div v fault 10v/div v out 20v/div i led 100ma/div 1us/div 1ms/div 1ms/div 2ms/div 200us/div 10ms/div 20ms/div vin startup ven startup pwm dimming f pwm =2khz, d pwm =50% open led protection open all led strings at working short led protecton short vout to ledx at working short led protection short vout to gnd at working 70 75 80 85 90 95 410162228 mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 8 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. function diagram control logic + - current sense amplifier + - pwm comparator oscillator + - 1.23v ov comparator + - + - led1 + - dpwm oscillator dpwm comparator 400k? 1.2v 0.2v current control + - 1.21v max min feedback control 5.5v ea led ov comparator short string protection regulator led6 ovp pgnd gnd vin vcc sw pwmo pwmi fset iset comp osc vfault en enable control 600mv vout figure 1?mp3386 function diagram mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 9 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. operation the mp3386 employs a constant frequency, peak current mode step-up converter and 6- channels regulated current sources architecture to regulate the array of 6 strings white leds. the operation of the mp3386 can be understood by referring to the block diagram of figure 1. internal 5v regulator the mp3386 includes an internal linear regulator (vcc). when vin is greater than 5.5v, this regulator offers a 5v power supply for the internal mosfet switch gate driver and the internal control circuitry. the vcc voltage drops to 0v when the chip shuts down. in the application of vin smaller than 5.5v, tie vcc and vin together and connect them to an external 5v power supply. the mp3386 features under voltage lockout. the chip is disabled until vcc exceeds the uvlo threshold. and the hysteresis of uvlo is approximately 200mv. system startup when the mp3386 is enabled, the chip checks the topology connection first. the vfault pin drives the external fault disconnection pmos to turn on slowly. and after 400us delay, the chip monitors the ovp pin to see if the schottky diode is not connected or the boost output is short to gnd. if the ovp voltage is lower than 70mv, the chip will be disabled and the external pmos is turned off together. the mp3386 will also check other safety limit, including uvlo and otp after the ovp test is passed. if they are all in function, it then starts boosting the step-up converter with an internal soft-start. it is recommended on the start up sequence that the enable signal comes after input voltage and pwm dimming signal established. step-up converter the converter operation frequency is selectable (1.25mhz or 625khz), which is helpful for optimizing the external components sizes and improving the efficiency. at the beginning of each oscillator cycle, the power fet is turned on. 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 pwm comparator. when this voltage equals to the output voltage of the error amplifier (v comp ) the power fet is turned off. the voltage at the output of the internal error amplifier is an amplified signal of the difference between the 600mv reference voltage and the feedback voltage. the converter automatically chooses the lowest active ledx pin voltage for providing enough bus voltage to power all the led arrays. if the feedback voltage drops to smaller than the 600mv reference, 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. in this way it forms a close loop to make the output voltage in regulation. at light-load or vout near to vin operation, the converter runs into the pulse-skipping mode, the fet is turned on for a minimum on-time of approximately 100ns, and then the converter discharges the power to the output in the remnant period. the fet will keep off until the output voltage needs to be boosted again. dimming control the mp3386 provides several pwm dimming methods: external pwm signal from pwmi pin or dc input pwm dimming mode (see figure 2). these methods results in pwm chopping of the current in the leds for all 6 channels to provide an average led current. + - dpwm oscillator dpwm comparator 400 k? 1.2v 0.2v pwmo pwmi fset ex-pwm input c pwmo c fset dpwm output 1.2v 0.2v dc input figure 2?pwm dimming method mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 10 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. when applying a pwm signal to the pwmi pin, the mp3386 generates a dc voltage on pwmo pin which is proportional to the duty cycle of the pwmi pin signal. by comparing the pwmo pin signal with the fset pin triangle waveform, the converter gets a low frequency chopping signal that the duty cycle is same as the input signal. this low frequency chopping signal will modulate the led current. a dc analog signal can be directly applied at the pwmo pin to modulate the led current. and the dc signal is translated into the duty-cycle of the low frequency chopping signal. the polarity is negative. the brightness of the led array is proportional to the duty cycle of the dpwm signal. the dpwm signal frequency is set by the cap at the fset pin. open string protection the open string protection is achieved through the over voltage protection. if one or more strings are open, the respective ledx pins are pulled to ground and the ic keeps charging the output voltage until it reach ovp threshold. then the part will mark off the open strings whose ledx pin voltage is less than 175mv. once the mark- off operation completes, the remaining led strings will force the output voltage back into tight regulation. the string with the highest voltage drop is the ruling string during output regulation. the mp3386 always tries to light at least one string and if all strings in use are open, the mp3386 shuts down the step-up converter. the part will maintain mark-off information until the part shuts down. short string protection the mp3386 monitors the ledx pin voltage to judge if the short string occurs. if one or more strings are short, the respective ledx pins will be pulled up to the boost output and tolerate high voltage stress. if the ledx pin voltage is higher than 5.5v when the internal dimming control logic is on, the short string condition is detected on the respective string. when the short string fault (ledx over-voltage fault) continues for greater than 1.6ms, the string is marked off and disabled. once a string is marked off, its current regulation is forced to disconnect from the output voltage loop regulation. the marked-off led strings are shut off totally until the part restarts. if all strings in use are short, the mp3386 shuts down the step-up converter. mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 11 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. application information selecting the switching frequency the switching frequency of the step-up converter is alternative from 1.25mhz and 625khz. a bi- level switching frequency selection (osc) input sets the internal oscillator frequency for the step- up converter. tie osc pin to gnd corresponds to the frequency 625khz and tie osc pin to vcc or floating corresponds to 1.25mhz. setting the led current the led string currents are identical and set through the current setting resistor on the iset pin. i led = 1000 x1.21v / r set for r set =60.4k ? , the led current is set to 20ma. the iset pin can not be open. setting the over voltage protection the open string protection is achieved through the over voltage protection (ovp). in some cases, an led string failure results in the feedback voltage always zero. the part then keeps boosting the output voltage higher and higher. if the output voltage ever exceeds the programmed ovp threshold, the protection will be triggered. to make sure the chip functions properly, the ovp setting resistor divider must be set with proper value. the recommended ovp point is about 1.3 times higher than the output voltage for normal operation. v ovp =1.23v x (r 1 +r 2 )/r 2 selecting dimming control mode the mp3386 provides 4 different dimming methods 1, pwm dimming mode with internal triangle waveform generator apply a 100hz to 50khz square waveform to the pwmi pin. the internal 400k ? and external capacitor on pwmo pin filters the dimming signal to a dc voltage(0.2v~1.2v).then dc voltage is modulated to a internal pwm dimming signal whose frequency is set via the capacitor on fset pin according to the equation: f dpwm = 3.5uf / c fset the minimum recommended amplitude of the pwm signal is 2.1v (see figure 3) c1 fset pwmi pwmo mp3388 pwm dimming 100hz~50khz c2 vcc c3 figure 3?pwm dimming with internal triangle waveform generator 2, direct pwm dimming with positive logic an external pwm dimming signal is directly employed to achieve pwm dimming control. connect a 100k ? resistor from fset pin to gnd and apply the 100hz to 2khz pwm dimming signal to pwmi pin. the minimum recommended amplitude of the pwm signal is 1.5v (see figure 4). vcc c1 fset pwmi pwmo mp3388 pwm dimming 100hz~2khz r1 100 k figure 4?direct pwm dimming with positive logic 3, direct pwm dimming with negative logic it is similar to method 2. apply a 100hz to 2 khz external square waveform to the pwmo pin for negative logic pwm dimming. the minimum recommended amplitude of the pwm signal is 1.5v (see figure 5) mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 12 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. vcc c1 fset pwmi pwmo mp3386 pwm dimming 100hz~2khz r1 100 k figure 5? direct pwm dimming with negative logic 4, dc input pwm dimming to apply dc input pwm dimming, apply an analog signal (range from 0.2v to 1.2v) at the pwmo pin to modulate the led current directly. if the pwmo is applied with a dc voltage<0.2v, the pwm duty cycle will be 100%. if the pwmo pin is applied with a dc voltage>1.2v, the output will be 0% (see figure 6). the capacitor on fset pin set the frequency of internal triangle waveform. c1 fset pwmi pwmo mp3386 analog dimming 0.2v~1.2v figure 6?dc input pwm dimming selecting the inductor a 10 h (for 1.25mhz switching frequency) /22uh (for 625khz switching frequency) inductor with a dc current rating of at least 40% higher than the maximum input current is recommended for most applications. for highest efficiency, the inductor?s dc resistance should be as small as possible. selecting the input capacitor the input capacitor reduces the surge current drawn from the input supply and the switching noise from the device. the input capacitor impedance at the switching frequency should be less than the input source impedance to prevent high frequency switching current from passing through the input. ceramic capacitors with x5r or x7r dielectrics are highly recommended because of their low esr and small temperature coefficients. for most applications, a 4.7 f capacitor is sufficient. selecting the output capacitor the output capacitor keeps the output voltage ripple small and ensures feedback loop stability. the output capacitor impedance should be low at the switching frequency. ceramic capacitors with x7r dielectrics are recommended for their low esr characteristics. for most applications, a 2.2 f ceramic capacitor will be sufficient. 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 mp3386 sw to pgnd pin (u1), output diode (d1), and output capacitor (c2) is flowing with high frequency pulse current. it must be as short as possible (see figure 7). figure 7?layout consideration the ic exposed pad is internally connected to gnd pin, and all logic signals are refer to the gnd. the pgnd should be externally connected to gnd and is recommended to keep away from the logic signals. mp3386- 50v, 6 strings white led drivers mp3386 rev. 1.0 www.monolithicpower.com 13 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. package information qfn24 (4mm x 4mm) side view top view 1 24 19 18 13 12 7 6 bottom view 3.90 4.10 2.50 2.80 3.90 4.10 2.50 2.80 0.50 bsc 0.18 0.30 0.80 1.00 0.00 0.05 0.20 ref pin 1 id marking 2.70 0.25 recommended land pattern 3.90 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 confirms to jedec mo-220, variation vggd. 5) drawing is not to scale. pin 1 id see detail a pin 1 id option a 0.30x45 o typ. pin 1 id option b r0.25 typ. detail a pin 1 id index area 0.70 0.35 0.45 0.50 mp3386- 50v, 6 strings white led drivers 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. mp3386 rev. 1.0 www.monolithicpower.com 14 1/19/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. package information (continued) soic28 |
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