View MP3388S_8946109.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

MP3388S 50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 1 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. the future of analog ic technology description the MP3388S is a step-up converter with 8 current-source channels designed to drive arrays of white led for lcd-panel backlighting applications. the MP3388S uses current-mode, fixed-frequency architecture, and users can select a switching frequency of either 625khz or 1.25mhz. it generates an output voltage up to 50v from a 4.3v-to-25v input supply. the MP3388S independently regulates the current in each led string set by an external current setting resistor to a user-programmed value. the MP3388S applies an internal current source to each led string terminal, and can achieve a current balance of 2.5% regulation accuracy between strings. its low 600mv regulation voltage on led current sources reduces power loss and improves efficiency. the MP3388S features external pwm dimming or dc-input pwm dimming, which allows for flexible backlight luminance control. the dimming pwm signal can be generated internally, and the dimming frequency is programmed by an external setting capacitor. features ? high efficiency ? compact size ? 4.3v-to-25v input voltage range ? 50v maximum step-up voltage ? balanced driver for 8 wled strings ? 2.5% current-matching accuracy between strings ? selectable switching frequency of 625khz or 1.25mhz ? pwm or dc input-burst pwm dimming ? programmable over-voltage protection ? under-voltage lockout ? open- and short-led protection ? thermal shutdown ? small qfn24 (4mm 4mm) package applications ? notebook pcs ? tablet computers ? small lcd tv ? handheld terminal displays ? automotive electronics equipments a ll 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 monolithi c power systems, inc. typical application vin MP3388S enable nc c5 c3 vcc vin compvfaultsw1 sw2 pgnd1 pgnd2 ovp led1 led2 led3 led4 iset led5 led6 led7 led8 pwmi gnd pwmo fpwm osc en c1 m1 l1 d1 c2 r1 r2 c4 r set v out c6 dimming 4.5v-25v pwm
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 2 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. ordering information part number package top marking MP3388Sgr * qfn24 (4x4mm) m3388s * for tape & reel, add suffix ?z (e.g. MP3388Sgr?z). package reference top view 1 2 3 4 5 6 18 17 16 15 14 13 en osc fpwm pwmo gnd pwmi exposed pad connect to gnd pgnd1 pgnd2 ovp led1 led2 led3 led8 led7 led6 led5 iset led4 vcc vin comp sw1 sw2 vfault 7 8 9 10 11 12 24 23 22 21 20 19 absolute maxi mum ratings (1) v in ................................................. -0.3v to +30v v vfault ........................................... v in ?6v to v in v sw , v led1 to v led8 ............................ -1v to +50v all other pins .................................. -0.3v to +6v continuous power dissipation ... (t a = +25c) (2) qfn24(4mm4mm) ................................... 2.9w junction temperature ............................... 150c lead temperature .................................... 260c storage temperature ............... -65c to +150c recommended operating conditions (3) supply voltage v in ........................... 4.3v to 25v operating junction temp. (t j ). -40c to +125c thermal resistance (4) ja jc qfn24 (4 x 4mm) ................. 42 ....... 9 .... 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 tj(max), the junction-to-ambient thermal resistance ja, and the ambient temperature ta. the maximum allowable continuous powe r dissipation at any ambient temperature is calculated by pd(max)=(tj(max)-ta)/ ja. exceeding the maximum allowable power dissipation will cause excessive die temperature, and the regulator will go into thermal shutdown. internal thermal shutdown circ uitry 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.
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 3 10/29/2012 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 = +25c, unless otherwise noted. parameters symbol condition min typ max units operating input voltage v in 4.3 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 MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 4 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. electrical characteristics (continued) v in =12v, v en = 5v, t a = +25c, unless otherwise noted. parameters symbol condition min typ max units led current regulation ledx average current i led r iset =60.4k ? 19.4 20 20.6 ma current matching (5) i led =20ma 2.5 % maximum led current per string i ledmax 30 ma iset regulation voltage 1.18 1.22 1.26 v ledx regulation voltage v ledx i led =20ma 500 600 700 mv protection ovp over-voltage threshold v ovp_ov rising edge 1.17 1.23 1.3 v ovp uvlo threshold v ovp_uv step-up converter fails 48 70 102 mv ledx over-voltage threshold v ledx_ov v in >5.5v 5.1 5.5 5.9 v ledx uvlo threshold v ledx_uv 150 200 250 mv thermal shutdown threshold (6) t st 130 150 ledx over-voltage fault timer vosc=high 1.3 1.6 1.9 ms vfault pull-down current i fault 40 55 70 a vfault blocking-off voltage (with respect to v in ) v fault v in =12v, v in ?v fault 6 v notes: 5) matching is defined as the difference of the maximum to minimum current divided by 2 times average currents. 6) guarantee by design.
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 5 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. pin functions pin # name description 1 en enable control input. do not let this pin floating. 2 osc switching-frequency selection. when left fl oating or connected to vcc, the step-up converter switching frequency is 1.25mhz. w hen connected to gnd, the step-up converter switching frequency is 625khz. 3 fpwm dimming pwm frequency setting. connect a capacitor, c fpwm , between fpwm and gnd to set the dpwm frequency using the equation: f dpwm =3.5 f/c fpwm . 4 pwmo pwm filter output. for external pwm dimming, connect a capacitor between pwmo and gnd. for dc-input pwm dimming, directly appl y a dc voltage between 0.2v and 1.2v. the dc-input pwm dimming polarity is negative. 5 gnd analog ground. 6 pwmi pwm signal input. for external pwm dimming mode, apply a pwm signal. for dc-input pwm dimming mode, leave floating. 7 led8 led string 8 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 8 cathode to this pin. 8 led7 led string 7 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 7 cathode to this pin. 9 led6 led string 6 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 6 cathode to this pin. 10 led5 led string 5 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 8 cathode to this pin. 11 iset led current setting. tie a current setting resistor from this pin to ground to program the current in each led string. i led = 1000 x 1.21v / r set 12 led4 led string 4 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 4 cathode to this pin. 13 led3 led string 3 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 3 cathode to this pin. 14 led2 led string 2 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 2 cathode to this pin. 15 led1 led string 1 current input. this pin is the ope n-drain output of an internal dimming-control switch. connect the led string 1 cathode to this pin.
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 6 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. pin functions (continued) pin # name description 16 ovp over-voltage protection input. connect to the tap of a resistor divider from the output to agnd to program the ovp threshold. when this pin voltage reaches 1.23v, the MP3388S triggers ovp mode. 17 pgnd2 step-up converter power ground. pg nd1 and pgnd2 should be shorted externally. 18 pgnd1 step-up converter power ground. pg nd1 and pgnd2 should be shorted externally. 19 sw2 step-up converter power switch output. sw2 is the drain of the internal mosfet switch. connect the power inductor and output rectif ier to sw2. sw2 can swing between gnd and 50v. sw1 and sw2 should be shorted externally. 20 sw1 step-up converter power switch output. sw1 is the drain of the internal mosfet switch. connect the power inductor and output rectif ier to sw1. sw1 can swing between gnd and 50v. sw1 and sw2 should be shorted externally. 21 vfault fault-disconnection?switch driver output. w hen the system starts up normally, this pin turns on the external pmos. when the MP3388S is disabled, the external pmos turns off to disconnect the input and output. 22 comp step-up converter compensation. this pin compensates the regulation control loop. connect a capacitor or a series rc network from comp to gnd. 23 vin supply input. vin supplies the power to the MP3388S chip. drive vin with a 4.3v-to-25v power source. must be locally bypassed. 24 vcc the internal 5v linear regulator output. vcc provides power for the internal mosfet gate driver and the internal control circuitry. bypass vcc to gnd with a ceramic capacitor. if vin is less than 5.5v, apply an exte rnal 5v supply directly on vcc.
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 7 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. typical performanc e characteristics v in =15v, 10 leds in series, 8 strings in parallel, 20ma/string, unless otherwise noted. 70 75 80 85 90 95 100 4 9 14 19 24 29 input voltage (v) efficiency(%) efficiency vs. input voltage steady state v sw 20v/div v sw 20v/div v in 10v/div v led8 500mv/div v out/ac 500mv/div v out 20v/div i led 100ma/div v sw 20v/div v led8 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 5v/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 400ns/div 2ms/div 2ms/div 1ms/div 200us/div 200us/div 400ms/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
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 8 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. block diagram control logic + - current sense amplifier + - pwm comparator oscillator + - 1.23v ov comparator + - + - led1 + - dpwm oscillator dpwm comparator 400 1.2v 0.2v current control + - 1.21v max min feedback control 5.5v ea led ov comparator short string protection regulator led 8 ovp pgnd gnd vin vcc sw pwmo pwmi fpwm iset comp osc vfault en enable control 600mv figure 1: functional block diagram
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 9 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. operation the MP3388S employs a constant-frequency, peak-current?mode step-up converter and 8 channels of regulated current sources to regulate up to 8 strings of white leds. internal 5v regulator the MP3388S includes an internal linear regulator (vcc). when vin exceeds 5.5v, this regulator provides a 5v power supply for the internal mosfet switch gate driver and the internal control circuitry. vcc drops to 0v when the chip shuts down. in applications where vin is less than 5.5v, tie vcc and vin together. the MP3388S features under-voltage lockout (uvlo). the chip is disabled until vcc exceeds the uvlo threshold. the uvlo hysteresis is approximately 200mv. system startup when the MP3388S is enabled, the chip checks the topology connection first. the vfault pin slowly turns on the external fault disconnection pmos. and after a 400s delay, the chip monitors the ovp pin to check for the schottky diode or if the boost output is shorted to gnd. if the ovp voltage is below 70mv, the chip is disabled and the external pmos is turned off together. the MP3388S also checks other safety limits, including uvlo and otp if the ovp test passes. if the circuit passes all tests, then the MP3388S uses an internal soft-start to boosting the step-up converter. for best results, use the following start-up sequence: either v in or the pwm dimming signal first, and then the enable signal (see figure 2). the MP3388S does not require a power-off sequence (see figure 4) (a) (b) figure 2: recommended start-up sequence if using any other start-up sequence, as shown in figure 3(a), and the unused ledx pins are not connected to v out , then decrease the input-voltage rise-time ( ). for a 6-string led application, select less than 20ms as shown in figure 3(b) (a) v in 0v 4.5v (b) figure 3: input voltage rise-time indicator for a 6-string led application note: use any power sequence if the v in rise-time from 0v to 4.5v is less than 20ms .
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 10 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. v pwm v in v en v pwm v in v en v pwm v in v en (a) (b) (c) figure 4: recommended power-off sequence step-up converter the converter operation frequency is selectable (625khz or 1.25mhz), which can optimize for external component sizes and improve efficiency. at the beginning of each cycle, the internal clock turns on the power mosfet. to prevent sub-harmonic oscillations at d>50%, add a stabilizing ramp to the output of the current-sense amplifier; the output goes to the positive input of the pwm comparator. when the pwm comparator?s positive input voltage equals the output voltage of the error amplifier (v comp ) the power mosfet turns off. the internal error amplifier amplifies the difference between the 600mv reference voltage and the feedback voltage. the converter automatically chooses the lowest active ledx pin voltage to provide the bus voltage to power all the led arrays. if the feedback voltage drops below the 600mv reference, the output of the error amplifier increases to increase the current flowing through the power mosfet, thus increasing the power delivered to the output. this forms a closed loop to regulate the output voltage. at light-load operation?or v out vin?the converter enters pulse-skipping mode where the mosfet turns on for a minimum on-time of approximately 100ns before the converter discharges the power to the output. the mosfet repeats this cycle until the output voltage requires a boost. dimming control the MP3388S provides two pwm dimming methods: external pwm signal from the pwmi pin or dc-input pwm dimming mode (see figure 5). figure 5: pwm dimming when applying a pwm signal to the pwmi pin, the MP3388S generates a dc voltage on the pwmo pin that is proportional to the duty cycle of the pwmi signal. by comparing the pwmo pin signal to the fpwm pin triangle waveform, the converter gets a choppy low-frequency signal with a duty cycle the same as the input?s. this choppy low-frequency signal modulates the led current. directly applying a dc analog signal to the pwmo pin also modulates the led current: the dc signal is converted to a dpwm signal set at the oscillation frequency. the polarity is negative. the brightness of the led array is proportional to the duty cycle of the dpwm signal. the capacitor at the fpwm pin sets the dpwm signal frequency.
MP3388S?50v, 8-string, white led drivers MP3388S rev.1.01 www.monolithicpower.com 11 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. open-string protection the open string protection is achieved through over-voltage protection (ovp). if one or more strings are open, the device pulls the respective ledx pins to ground and the output voltage continues rising until it reaches the ovp threshold. then the device records and disable the open ledx strings with pin voltages less than 175mv. once recording completes, the remaining led strings force the output voltage back into tight regulation. the string with the highest voltage drop determines the output regulation level. the MP3388S will always try to light at least one string. if all strings in use are open, the MP3388S shuts down the step-up converter. the part retains low-voltage ledx string information until the part shuts down. short-string protection the MP3388S monitors each ledx pin voltage to determine if there is a short string. if one or more strings are shorted, the respective ledx pins will be pulled up to the boosted output and tolerate high voltage stress. if the ledx pin voltage exceeds 5.5v, the device treats this condition as a short string fault (ledx over-voltage fault). if the voltage remains above 5.5v more than than 1.6ms (v osc =high), the device records the string and disables it. once a string is recorded as a short, its current regulation is forced to disconnect from the output voltage loop regulation. the recorded led strings remain off until the part restarts. if all strings in use are shorted, the MP3388S shuts down the step-up converter.
MP3388S?50v, 8-string, step-up, white led driver MP3388S rev.1.01 www.monolithicpower.com 12 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. application information selecting the switching frequency the user can select either a 625khz or a 1.25mhz step-up converter switching frequency. a bi-level switching frequency selection input (the osc pin) sets the internal oscillator frequency. tie the osc pin to gnd corresponds for 625khz, and to vcc or float for 1.25mhz. setting the led current the iset pin sets the led string currents to the same level as per the equation below: set led r v . i 21 1 1000 ? ? for r set =60.4k ? , the led current is 20ma. do not leave the iset pin open. setting the over-voltage protection threshold the open string protection is achieved through ovp. in some cases, an led string failure results in a 0v feedback voltage. the MP3388S then continues boosting the output voltage. ovp triggers if the output voltage reaches the programmed ovp threshold. to ensure proper chip function, set the ovp setting resistor divider with appropriate values. select an ovp threshold about 1.3x higher than the output voltage for normal operation. 2 2 1 23 1 r r r . v ovp ? ? ? selecting the dimming-control mode the MP3388S provides four different dimming methods: pwm dimming mode with internal triangle waveform generator apply a 100hz-to-50khz square waveform to the pwmi pin. the internal 400k ? resistor and the external capacitor on the pwmo pin filters the dimming signal to a dc voltage (0.2v to 1.2v). then an internal pwm dimming signal whose frequency is set by a capacitor on the fpwm pin modulates the dc voltage, where: fpwm dpwm c f . f ? ? 5 3 the minimum recommended pwm signal amplitude is 2.1v (see figure 6). figure 6: pwm dimming with internal triangle waveform generator direct pwm dimming with positive logic to use a direct external pwm dimming signal, connect a 100k ? resistor from the fpwm pin to gnd and apply a 100hz-to-30khz (high sw frequency) pwm dimming signal to the pwmi pin. the minimum recommended amplitude of the pwm signal is 1.5v (see figure 7). figure 7: direct pwm dimming with positive logic table 1 shows the pwm dimming duty range with different pwm dimming frequencies.
MP3388S?50v, 8-string, white led drivers MP3388S rev.1.01 www.monolithicpower.com 13 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. table 1: pwm frequency range and dimming duty cycle f pwm (hz) d min d max 1001.2v, the output will be 0% (see figure 9). the capacitor on the fpwm pin sets the internal triangle waveform frequency. figure 9: dc-input pwm dimming selecting the inductor a larger inductor results in less ripple current, lowering both the peak inductor current and stress on the internal n-channel mosfet. however, a larger value inductor is larger physical size with a higher series resistance and a lower saturation current. choose an inductor that does not saturate under worst-case load conditions. select the minimum inductance value to ensure that the boost converter works in continuous conduction mode, for high efficiency and good emi performance. calculate the minimum inductance value with: 2 out load sw vd(1d) l 2i f ?? ? ? ? ? ?? in out v d1 v ?? where v in is the input voltage, v out is the output voltage, f sw is the switching frequency, i load is the led load current, and is the efficiency. use either a 10 h (at a 1.25mhz switching frequency) or a 22h (at a 625khz switching frequency) inductor with a dc current rating of at least 40% higher than the maximum input current for most applications. select an inductor with the smallest-possible dc resistance for greatest efficiency. selecting the input capacitor the input capacitor reduces both 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. for best results, use ceramic capacitors with x5r or x7r dielectrics because of their low esr and small temperature coefficients. for most applications, use a 4.7 f capacitor.
MP3388S?50v, 8-string, white led drivers MP3388S rev.1.01 www.monolithicpower.com 14 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. selecting the output capacitor the output capacitor minimizes the output voltage ripple and ensures a stable feedback loop. the output capacitor impedance should be low at the switching frequency. use ceramic capacitors with x7r dielectrics for their low esr characteristics. the output voltage ripple is estimated as: in led out ripple sw v 1 - i v v c2 f ?? ? ?? ?? ? ? where v ripple is the output ripple voltage, v in and v out are the input and output voltages respectively, i led is the led current, f sw is the switching frequency, and c2 is the output capacitor. for most applications, use a 2.2 f ceramic capacitor. layout considerations layout and component placement on the pcb requires careful attention. proper high-frequency switching-path layout can prevent noise and electromagnetic interference problems. the loop from sw (u1), to the output diode (d1), to the output capacitor (c3), to pgnd (u1) carries a high-frequency pulse current: minimize the loop length and enclosed area (see figure 10). figure 10: sample layout the ic exposed pad is internally connected to gnd pin, and all logic signals are refer to the gnd. externally connects pgnd to gnd, and avoid placing pgnd near logic signals.
MP3388S?50v, 8-string, step-up, white led driver 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. MP3388S rev. 1.01 www.monolithicpower.com 15 10/29/2012 mps proprietary information. patent protec ted. unauthorized photocopy and duplication prohibited. ? 2012 mps. all rights reserved. package information qfn24 (4mm 4mm)

▲Up To Search▲

Price & Availability of MP3388S

	To Download MP3388S Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .