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_______________________________________________________________ maxim integrated products 1 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxims website at www.maxim-ic.com. MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter general description the MAX17129/max17149 are high-efficiency drivers for white leds. they are designed for small- to medium- sized lcds that employ an array of leds as the light source. an internal switch step-up controller with quick- pwm k drives the led array, which can be configured for up to 6 strings in parallel and either 11 leds (MAX17129) or 6 leds in series (max17149) per string. each string is terminated with a ballast that achieves q 2% current- regulation accuracy, ensuring even led brightness and provides an adjustable 10ma to 45ma full-scale led current. the devices have a wide input voltage range of 6v to 26v. the MAX17129 integrates an ldo to simplify applications that have a single high-voltage supply. the devices also feature a low-input-voltage mode for appli - cations that have a 3v to 5.5v supply voltage. the devices support both pwm and hybrid dimming mode. in pwm dimming mode, the external pwm signal directly controls the brightness of leds. the dimming frequency ranges from 100hz to 25khz with 400ns mini - mum on-time. in hybrid dimming mode, the led current amplitude can be adjusted to 25% of full-scale led cur - rent to improve system efficiency when brightness is low. the devices have multiple features to protect the con - troller from fault conditions. separate voltage-feedback loops limit the output voltage to safe operation. the open and short-led detection shuts down the faulty string while keeping other strings operating normally. the devices feature cycle-by-cycle current limit on the internal switch to provide consistent operation and soft- start capability. if the devices are in current-limit condi - tion, the step-up converter is latched off after an internal timer expires. a thermal-shutdown circuit provides anoth - er level of protection and prevents ics from damage. the ics step-up controller features an internal 0.25 i (typ), 48v (max) power mosfet with lossless current sense and accurate cycle-by-cycle current limit. the quick-pwm con - trol architecture provides fast load-transient response with - out requiring an external loop compensation component, simplifies the external circuitry, and saves board area. the quick-pwm control scheme has constant off-time and adjustable pseudo-fixed frequency, which enables a wide variety of applications that can trade off component size for operating frequency. low feedback voltage at each led string (275mv typ at 20ma led current) helps reduce power loss and improve efficiency. the ics are available in a 16-pin, thin qfn package with 0.5mm lead spacing. the package is 3mm x 3mm with a maximum thickness of 0.8mm for ultra-thin lcd panel design. features s 3v to 26v input supply voltage s up to six parallel strings of multiple series- connected leds s step-up regulator with quick-pwm control scheme s two-level selectable switching frequency s 0.25 i internal hv power mosfet (48v max) s low string feedback voltage: 275mv at 20ma led current s full-scale led current adjustable from 10ma to 45ma s 2% current regulation accuracy between strings s support pwm and hybrid dimming mode s 100:1 dimming ratio s 100hz to 25khz dimming frequency for pwm dimming mode s open and short led protection s output overvoltage protection s small 16-pin, 3mm x 3mm thin qfn package applications notebook, subnotebook, and tablet computer displays automotive systems handy terminals 19-5676; rev 1; 9/11 simplified operating circuit appears at end of data sheet. + denotes lead(pb)-free/rohs-compatible package. * ep = exposed pad. quick-pwm is a trademark of maxim integrated products, inc. ordering information evaluation kit available part temp range pin-package MAX17129 ete + -40 c to +85 c 16 thin qfn-ep* max17149 ete+ -40 c to +85 c 16 thin qfn-ep* www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 2 fsel, in, brt, en to gnd .................................. -0.3v to +28v fb_, lx, ovp to pgnd ......................................... -0.3v to +48v pgnd to gnd ...................................................... -0.3v to +0.3v v cc to gnd ............................................................. -0.3v to +6v iset to gnd ............................................... -0.3v to vcc + 0.3v lx switch continuous rms current ..................................... 1.6a continuous power dissipation (t a = +70 n c) 16-pin thin qfn (derate 14.7mw/ n c above +70 n c) .. 1176mw operating temperature range .......................... -40 n c to +85 n c junction temperature ..................................................... +150 n c storage temperature range ............................ -60 n c to +150 n c esd hbm ................................................................................. 2kv mm ................................................................................ 200v lead temperature (soldering, 10s) ................................ +300 n c soldering temperature (reflow) ...................................... +260 n c electrical characteristics (circuit of figure 1. v in = 12v, r iset = 100k i , t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 n c.) (note 1) absolute maximum ratings stresses beyond those listed under absolute maximum ratings may cause permanent damage to the device. these are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. parameter conditions min typ max units in input voltage range in not connected to v cc 6 26 v in connected to v cc 3.0 5.5 in standby current v en = 3v, v in = 26v, no external loads 3.2 4 ma v en = 0v, v in = 26v 0.1 5 a v cc output voltage v en = 3v, 0 < i vcc < 10ma 3.6 3.8 4.0 v v cc current limit v cc is forced to 3.5v; in not connected to v cc 15 30 45 ma v cc uvlo threshold rising edge, typical hysteresis = 100mv 2.75 2.8 2.85 v in uvlo threshold rising edge, typical hysteresis = 100mv; in not connected to v cc 5.5 5.75 5.9 v step-up converter lx on-resistance 100ma from lx to pgnd 250 500 m lx leakage current v lx = 40v, t a = +25nc 0.05 1 a off-time fsel = gnd, v in = 12v, v ovp = 22v 450 500 550 ns fsel = v cc , v in = 12v, v ovp = 22v 900 1000 1100 lx peak current limit duty cycle = 75% 2.5 3 3.5 a minimum on-time 50 ns minimum output regulation voltage MAX17129 only 15 16.5 18 v max17149 only 6.8 8.3 9.8 v maximum output regulation voltage MAX17129 only 41.5 43 44.5 v max17149 only 23.9 25.4 26.9 v input leakage/bias currents en bias current 0.3v < v en < 3.5v, t a = +25c 6 a 4.1v < v en < 26v, t a = +25c 110 brt bias current 0.3v < v brt < 3.5v, t a = +25c 15 a 4.1v < v brt < 26v , t a = +25 c 2000 en input impedance 750 1500 k ovp input current MAX17129 only; v ovp = 40v, v fb = 0.75v 15 50 a max17149 only; v ovp = 20v, v fb = 0.75v 7.5 25 a fsel bias current 0.3v < v fsel < 3.5v, t a = +25c 6 a 4.1v < v fsel < 26v , t a = +25 c 2000 www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 3 electrical characteristics (continued) (circuit of figure 1. v in = 12v, r iset = 100k i , t a = 0 c to +85 c , unless otherwise noted. typical values are at t a = +25 n c.) (note 1) parameter conditions min typ max units led current source iset resistance range 44 250 k full-scale fb_ output current r iset = 44.44k 43.3 45 47.7 ma r iset = 66.66k 29.1 30 30.9 r iset = 100k 19.4 20 20.6 r iset = 133.33k 14.55 15 15.45 r iset = 200 k 9.65 10 10.35 r iset = 100k , hybrid dimming mode 4.4 5 5.6 r iset = 250k i , hybrid dimming mode 1.4 2 2.6 iset output voltage 1.225 1.250 1.275 v current regulation between strings i fb_ = 30ma -1.5 +1.5 % i fb_ = 20ma -2.0 +2.0 i fb_ = 15ma -2.0 +2.0 i fb_ = 10ma -2.75 +2.75 i fb_ = 5ma, hybid dimming ode -6.0 +6.0 i fb_ = 2ma, hybrid dimming mode -15.0 +15.0 minimum fb_ regulation voltage r iset = 66.66k i , 100% duty cycle 375 550 mv r iset = 100k i , 100% duty cycle 275 365 r iset = 133.33k i , 100% duty cycle 200 275 r iset = 200k i , 100% duty cycle 125 200 fb_ on-resistance v fb_ = 50mv 20 fb_ leakage current v fb_ = 28v, t a = +25c, en = 0v, v ovp = 28v 0.05 1 a v fb_ = 40v, t a = +25c, en = 0v, v ovp = 40v 2.5 5 fb_ on-time 300 ns brt input high level 2.1 v brt input low level 0.8 v brt dimming frequency 0.1 25 khz en input high level MAX17129/max17149 enabled, pwm dimming mode 2.1 v MAX17129/max17149 enabled, hybrid dimming mode 1.4 1.8 en input low level 0.8 v fault protection ovp overvoltage rising edge, hysteresis = 1.8v 44.1 45.1 46.1 v fb_ check led source current 0.60 0.665 0.73 ma fb_ check led time sequence for 6 channels 1 ms fb_ open led threshold 500 700 mv fb_ overvoltage threshold 6.7 8.0 9.6 v thermal-shutdown threshold (note 2) +160 c thermal-shutdown hysteresis (note 2) 15 c boost frequency selection fsel fsel input high level select f sw = 500khz 2.1 v fsel input low level select f sw = 1000khz 0.8 v www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 4 electrical characteristics (circuit of figure 1. v in = 12v, r iset = 100k i , t a = -40 n c to +85 n c , unless otherwise noted.) (note 1) parameter conditions min typ max units in input voltage range in not connected to v cc 6 26 v in = v cc 3 5.5 in quiescent current v en = 3v, v in = 26v, no external loads 4 ma v en = 0v, v in = 26v 5 a v cc output voltage v en = 3v, 0 < i vcc < 10ma 3.6 4.0 v v cc current limit v cc is forced to 3.5v; in not connected to v cc 15 45 ma v cc uvlo threshold rising edge, typical hysteresis = 100mv 2.75 2.85 v in uvlo threshold rising edge, typical hysteresis = 100mv; in not connected to v cc 5.5 5.9 v step-up converter lx on-resistance 100ma from lx to pgnd 500 m lx leakage current v lx = 40v, t a = +25 n c 1 f a off-time fsel = gnd v in = 12v, v ovp = 22v 450 550 ns fsel = v cc , v in = 12v, v ovp = 22v 900 1100 lx peak current limit duty cycle = 75% 2.5 3.65 a minimum output regulation voltage MAX17129 only 15 18 v max17149 only 6.8 9.8 v maximum output regulation voltage MAX17129 only 41.5 44.5 v max17149 only 23.9 26.9 v input leakage/bias currents en bias current 0.3v < v en < 3.5v, t a = +25c 6 a 4.1v < v en < 26v, t a = +25c 110 brt bias current 0.3v < v brt < 3.5v, t a = +25c 15 a 4.1 v < v brt < 26v , t a = +25 c 2000 en input impedance 750 k ovp input current MAX17129 only; v ovp = 40v, t a = +25 c, v fb = 0.75v 50 a max17149 only; v ovp = 20v, t a = +25 c, v fb = 0.75v 25 fsel bias current 0.3v < v fsel < 3.5v 6 a 4.1 v < v fsel < 26v 2000 led current source iset resistance range 44 250 k full-scale fb_ output current r iset = 44.44k 43.3 47.7 ma r iset = 66.66k 29.1 30.9 r iset = 100k 19.4 20.6 r iset = 133.33k 14.55 15.45 r iset = 200k 9.65 10.35 r iset = 100k , hybrid dimming mode 4.4 5.6 r iset = 250k , hybrid dimming mode 1.4 2.6 iset output voltage 1.225 1.275 v www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 5 electrical characteristics (continued) (circuit of figure 1. v in = 12v, r iset = 100k i , t a = -40 n c to +85 n c , unless otherwise noted.) (note 1) note 1: all devices are 100% production tested at t a = +25 n c. limits over temperature are guaranteed by design. note 2: specifications are guaranteed by design, not production tested. parameter conditions min typ max units current regulation between strings i fb_ = 30ma -1.5 +1.5 % i fb_ = 20ma -2.0 +2.0 i fb_ = 15ma -2.0 +2.0 i fb_ = 10ma -2.75 +2.75 i fb_ = 5ma, hybrid dimming mode -6.0 +6.0 i fb_ = 2ma, hybrid dimming mode -15.0 +15.0 minimum fb_ regulation voltage r iset = 66.66k , 100% duty cycle 550 mv r iset = 100k , 100% duty cycle 365 r iset = 133.33k , 100% duty cycle 275 r iset = 200k , 100% duty cycle 200 fb_ on-resistance v fb_ = 50mv 20 fb_ leakage current v fb_ = 28v, t a = +25 c, en = gnd, v ovp = 28v 1 a v fb_ = 40v, t a = +25 c, en = gnd, v ovp = 40v 5 fb_ on-time 300 ns brt input high level 2.1 v brt input low level 0.8 v brt dimming frequency 0.1 25 khz en input high level MAX17129/max17149 enabled, pwm dimming mode 2.1 v MAX17129/max17149 enabled, hybrid dimming mode 1.4 1.8 en input low level 0.8 v fault protection ovp overvoltage rising edge, hysteresis = 1.8v 44.1 46.1 v fb_ check led source current 0.60 0.73 ma fb_ open led threshold 700 mv fb_ overvoltage threshold 6.7 9.7 v boost frequency selection fsel fsel input high level select f sw = 500khz 2.1 v fsel input low level select f sw = 1000khz 0.8 v www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 6 typical operating characteristics (circuit of figure 1. v in = 12v, t a = +25 c, unless otherwise noted.) led current (i led = 20ma at 100% brightness) vs. input voltage MAX17129 toc04 input voltage (v) led current (ma) 23 20 17 14 11 8 20.05 20.10 20.15 20.20 20.00 5 26 led current (i led = 20ma at 10% brightness) vs. input voltage MAX17129 toc05 input voltage (v) led current (ma) 23 20 17 14 11 8 2.00 2.02 2.04 2.06 1.98 5 26 in quiescent current vs. in voltage MAX17129 toc06 in voltage (v) in quiescent current (ma) 23 20 17 14 11 8 1 2 3 4 5 6 0 5 26 100% brightness 200h z / 1% brightness startup waveforms (brightness = 100%) MAX17129 toc07 v en 5v/div v lx 50v/div 0v 0v 0v 0a v out 20v/div inductor current 500ma/div 4ms/div 12v boost converter efficiency vs. input voltage (v out = 31.8v /i out = 120ma, brightness = 100%) MAX17129 toc01 input voltage (v) efficiency (%) 23 20 8 11 14 17 80 82 84 86 88 90 92 94 78 5 26 boost converter efficiency vs. brightness (v in = 12v, v out = 31.8v/i out = 120ma at 100%) MAX17129 toc02 brightness (%) efficiency (%) 80 60 40 20 60 70 80 90 50 0 100 led current vs. brightness setting MAX17129 toc03 pwm duty cycle (%) led current (ma) 80 60 40 20 5 10 15 20 0 100 f brt = 200hz www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 7 typical operating characteristics (continued) (circuit of figure 1. v in = 12v, t a = +25 c, unless otherwise noted.) startup waveforms (brightness = 20%) MAX17129 toc08 v en 5v/div v lx 50v/div 0v 0v 0v 0a v out 20v/div inductor current 500ma/div 4ms/div 12v switching waveforms (v in = 12v, brightness = 100%) MAX17129 toc09 v lx 20v/div inductor current 500ma/div 0v 0ma 1s/div led open fault protection (brightness = 100%, led open on fb1) MAX17129 toc10 v fb1 1v/div v fb2 10v/div v out 10v/div i fb2 10ma/div 0v 0v 0ma 2ms/div 31.8v 20ma led short fault protection (brightness = 100%, 3 leds short on fb1) MAX17129 toc11 v fb1 10v/div i fb1 20v/div i fb2 20ma/div 0ma 0v 0ma 2ms/div 20ma 20ma www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 8 typical operating characteristics (continued) (circuit of figure 1. v in = 12v, t a = +25 c, unless otherwise noted.) line transient response (v in = 9v ? 21v, brightness = 100%) MAX17129 toc12 v in 10v/div inductor current 500ma/div i fb1 20ma/div 0a 0v v out (ac-coupled) 500mv/div 0ma 100s/div 20ma 21v 9v line transient response (v in = 21v ? 9v, brightness = 100%) MAX17129 toc13 v in 10v/div inductor current 500ma/div i fb1 20ma/div 0a 0v v out (ac-coupled) 200mv/div 0ma 200s/div 20ma 21v 9v maximum unbalance rate between strings vs. brightness (v in = 12v, f brt = 200hz, i led = 20ma) MAX17129 toc14 brightness (%) maximum unbalance rate (%) 90 80 70 60 50 40 30 20 0.2 0.4 0.6 0.8 1.0 0 10 100 ma x. unbalance rate ( %) = i fb _ -i fb (a vg ) ma x i fb (a vg ) maximum unbalance rate between strings (i led = 20ma at 100% brightness) vs. input voltage MAX17129 toc15 input voltage (v) maximum unbalance rate (%) 24 21 18 15 12 9 0.3 0.4 0.5 0.6 0.7 0.8 0.2 6 ma x. unbalance rate ( %) = i fb _ -i fb (a vg ) ma x i fb (a vg ) www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 9 pin configuration pin description 15 16 14 13 5 6 7 in fsel 8 brt fb3 fb2 fb5 1 3 gnd 4 12 10 9 iset en ep fb1 ovp pgnd lx MAX17129 max17149 v cc fb4 2 11 fb6 thin qfn 3mm 3mm top view + pin name function 1 brt pwm signal input. this pwm signal controls the led brightness by turning the led current sources on or off. 2 v cc internal ldo output. v cc provides bias supply to the devices. v cc is generated by internal ldo. connect a minimum 1 f f capacitor from v cc to gnd. all power outputs are disabled until v cc exceeds its uvlo threshold. see the input supply voltage configuration and uvlo section for supply configurations for the ics. 3 in supply input. connect in to the system input supply voltage and bypass in to gnd with a minimum 0.1 f f ceramic capacitor. the ics are disabled if v in falls below its uvlo threshold. the devices can extend the operating range down to 3.0v if in and v cc are tied together. see the input supply voltage configuration and uvlo section. 4 fsel step-up converter switching frequency selection input. connect to v cc with a 10k resistor to set 500khz, or connect to gnd to set 1mhz. 5 lx step-up regulator switching node. connect inductor and output diode here and minimize trace area for lowest emi. 6 pgnd power ground 7 ovp boost output voltage-sensing input. this voltage is used for overvoltage protection. 8 fb1 current-balancer output. led string cathode connection. fb1 is the open-drain output of an internal regulator, which controls current through fb1. fb1 can sink up to 45ma. if unused, connect fb1 to gnd or leave high impedance. 9 fb2 current-balancer output. led string cathode connection. fb2 is the open-drain output of an internal regulator, which controls current through fb2. fb2 can sink up to 45ma. if unused, connect fb2 to gnd or leave high impedance. www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 10 pin description (contineud) pin name function 10 fb3 current-balancer output. led string cathode connection. fb3 is the open-drain output of an internal regulator, which controls current through fb3. fb3 can sink up to 45ma. if unused, connect fb3 to gnd or leave high impedance. 11 fb4 current-balancer output. led string cathode connection. fb4 is the open-drain output of an internal regulator, which controls current through fb4. fb4 can sink up to 45ma. if unused, connect fb4 to gnd or leave high impedance. 12 fb5 current-balancer output. led string cathode connection. fb5 is the open-drain output of an internal regulator, which controls current through fb5. fb5 can sink up to 45ma. if unused, connect fb5 to gnd or leave high impedance. 13 fb6 current-balancer output. led string cathode connection. fb6 is the open-drain output of an internal regulator, which controls current through fb6. fb6 can sink up to 45ma. if unused, connect fb6 to gnd or leave high impedance. 14 gnd analog ground. connect to iset resistor ground as close as possible. 15 iset full-scale led current adjustment pin. the resistance from iset to gnd controls the full-scale current in each led string: i led_fs = 20ma o 100k i /r iset the acceptable resistance range is 44.44k i < r iset < 200k i , which corresponds to full-scale led current of 45ma > i led_fs > 10ma. 16 en enable and dimming mode selection input. pull en higher than 2.1v to enable the device, and lower than 0.8v to disable the device. when v en is higher than 2.1v, direct pwm mode is selected; when v en is between 1.4v and 1.8v, hybrid dimming mode is selected. while selecting hybrid dimming mode, the device first needs to be enabled. ep exposed backside pad. solder to the circuit board ground plane with sufficient copper connection to ensure low thermal resistance. see the pcb layout guidelines section. www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 11 typical operating circuit the MAX17129 typical operating circuit is shown in figure 1. table 1 lists some recommended components, and table 2 lists the contact information for component suppliers. figure 1. MAX17129 typical operating circuit table 1. component list table 2. component suppliers lx c1 2.2f 1f r iset 100ki c in 4.7f v in 6v to 26v d1 l1 10h c2 2.2f pgnd ovp fb1 fb2 fb3 fb4 fb5 fb6 in v cc iset en brt gnd 100hz to 25khz fsel 0.1f ep MAX17129 designation description c in 4.7 f f q 10%, 25v x5r ceramic capacitor (1206) murata grm319r61e475ka12d c1, c2 2.2 f f q 20%,50v x7r ceramic capacitors (1206) murata grm31cr71h225k d1 2a, 40v schottky diode (m-flat) toshiba cms11 l1 10 f h, 1.5a, h = 1.2mm vlp6812t-100m1r5 white led 3.2v (typ), 3.5v (max) at 20ma nichia nssw008c supplier phone website murata electronics north america, inc. 770-436-1300 www.murata.com nichia corp. 248-352-6575 www.nichia.com sumida corp. 847-545-6700 www.sumida.com toshiba america electronic components, inc. 949-623-2900 www.toshiba.com/taec vishay 402-563-6866 www.vishay.com www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 12 figure 2. functional diagram startup 3.8v ldo logic-circuit supply in v cc fsel iset en error amp en t on /t off calculation iset current sense off-time one-shot test and otp smbus control and driver logic current source pgnd gnd fb2 fb1 lx lx ovp 40.8v 8v brt overvoltage output overvoltage vsat fault control thermal shutdown n n g m hvc lvc fb6 fb5 fb4 fb3 fb2 current source current source current source current source fb3 fb4 fb5 fb6 en from fault control dpwm control 45v MAX17129 max17149 www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 13 detailed description the MAX17129/max17149 are high-efficiency drivers for arrays of white leds. they contain a quick-pwm step-up controller, a 3.8v linear regulator, pwm dimming control circuit, internal power mosfet, and six regulated current sources. figure 2 shows the devices' functional diagram. when enabled, the step-up controller boosts the output voltage to provide sufficient headroom for the current sources to regulate their respective string currents. the devices feature adjustable pseudo-fixed frequency, which allows trade-offs between external component size and operating efficiency. both devices have a wide input voltage range, from 6v to 26v; when in and v cc are tied together, the range is extended to the 3v to 5.5v range. both devices can implement two different brightness- control methods: pwm dimming and hybid dimming. when in direct pwm mode, the led brightness is con - trolled by the frequency and duty cycle of the square- wave signal applied on the brt pin. when in hybrid dimming mode, the amplitude of led current is adjusted to 25% of the full-scale value, which is set by the resistor from the iset pin to gnd. the devices have multiple features to protect the control - ler from faulty conditions. a separate feedback loop lim - its the output voltage in all circumstances. the devices monitor each fb_ voltage during the operation. if one or more strings are open, the corresponding fb_ voltages are pulled below 700mv (max) and the ovp output is forced to increase over the overvoltage threshold; once the open fault is detected, the respective current sources are so disabled. when one or more leds are shorted and the related fb_ voltage exceeds 8v, short fault is detected and the respective current source is disabled. when in led open or short conditions, only the faulty string is disabled while other strings can still operate normally. the devices also feature other kinds of fault protec - tions, which are overcurrent, output overvoltage, and thermal shutdown. the cycle-by-cycle current limit is to provide consistent operation and soft-start protection; when in overcurrent condition, the devices latch off after a 0.8ms typical (at full brighteness) overcurrent fault timer expires. an output overvoltage protection prevents the devices from switching when the output exceeds a threshold voltage; a thermal-shutdown circuit prevents the devices from excessive power dissipation. quick-pwm step-up controller the step-up converter is a quick-pwm type for good performance. the quick-pwm control architecture is a pseudo-fixed-frequency, constant-off-time, current- mode regulator. the control algorithm is simple: the internal switch off-time is determined solely by a one- shot whose period is inversely proportional to output volt - age, and directly proportional to input voltage. figure 4 shows the functional diagram with quick-pwm control architecture. the off-time one-shot triggers when the error comparator goes low, the inductor current is below the current-limit threshold, and the minimum on-time one-shot times out. once the step-up starts up, the output voltage is regu - lated by selecting the minimum fb voltage between the detected active current-balancer outputs and compar - ing it to the ovp divider. the soft-start mechanism is inserted to provide a controlled current profile during step-up startup phases. off-time one-shot the quick-pwm core contains a fast, low-jitter, adjust - able one-shot that sets the internal mosfets off-time. the one-shot varies the off-time in response to the input and feedback voltages. the internal switch off-time is inversely proportional to the output voltage (v ovp ), and proportional to the input voltage (v in ): in off ovp v t v k = where the switching period (k) is set by the fsel pin. this algorithm results in a nearly constant switching frequency and balanced inductor currents despite the lack of a fixed-frequency clock generator. the benefits of a near-constant switching frequency are two-fold: first, the frequency can be selected to avoid noise-sensitive regions; second, the inductor ripple-current operating point remains relatively constant, resulting in easy design methodology and predictable output-voltage ripple. the off-time one-shots have good accuracy at the operating points specified in the electrical characteristics table. off-times translate only roughly to switching frequencies. the off-times guaranteed in the electrical characteristics table are influenced by internal switching delays. resistive losses, including the inductor, internal mosfet, the for - ward voltage of the output diode, output capacitor esr, and pcb copper losses in the output and ground tend to raise the switching frequency at higher output currents. www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 14 the actual switching frequency can be approximated by: in in dson s off ovp d in dson v i r 1 f t v v i r ? = + ? where: v d is the forward voltage of the output diode. r dson is the on-resistance of the internal mosfet. the switching frequency is adjustable by changing the off-time at each supply turn-on cycle. as mentioned above, it is implemented by changing the voltage level of the fsel pin. high-frequency operation optimizes the regulator for the smallest component size at the expense of efficiency due to increased switching losses. low-frequency oper - ation offers the best overall efficiency but requires larger components and pcb area. input supply voltage configuration and uvlo the devices include an internal low-dropout linear regulator (v cc ) and are disabled until v cc exceeds the uvlo threshold. the hysteresis on uvlo is approxi - mately 100mv. when v in is higher than 6v with en high, this linear regulator generates a 3.8v supply to power the internal pwm controller, control logic, and mosfet driver. the v cc voltage drops to 0v with en low. when the v cc and in pins are connected together, the devices can operate in a low input-voltage range from 3v to 5.5v. figure 4. MAX17129/max17149 quick-pwm control functional diagram lx ovp v in in en ovp fb fsel MAX17129 max17149 on- /off-time calculation one-shot current sense ref ref int error comparator ss soft-start integrator www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 15 figure 5 shows possible supply connection configura - tions for the devices. the v cc pin should be bypassed to gnd with a minimum 1 f f ceramic capacitor. startup at startup, the devices perform an led check by pull - ing up each fb_ pin with a current source to determine whether a string of leds are connected. if an fb_ pin is not connected with leds, it is disabled. the process takes approximately 1ms. then the current sources are turned on. shutdown the devices can be placed into shutdown by pulling the en pin low; when in shutdown mode, the current con - sumption is 5 f a max. in the devices, the v cc voltage drops to 0v with en low. overvoltage protection to protect the step-up regulator when the load is open, or the output voltage becomes excessive for any rea - son, the devices feature a dedicated overvoltage feed - back input by monitoring output (ovp). there are two thresholds for ovp and they provide careful protections. when the ovp voltage exceeds the 43v (typ) for the MAX17129 or 25.4v for the max17149, an overvoltage flag is set to enable the open-string detection. when the ovp voltage exceeds 45.2v (typ), the internal power mosfet stops switching. this step-up regulator switch is reenabled after the v ovp drops 1.8v (typ hysteresis) below the protection threshold. this overvoltage protec - tion feature ensures the step-up regulator fail-safe opera - tion when the led strings are disconnected from the output. considering overvoltage threshold and minimum output regulation voltage, the max17149 is suitable for 3C6 leds per string and the MAX17129 is suitable for 6C11 leds per string. overcurrent protection when in overcurrent condition, the devices latch off after a fault timer expires. if running at full brightness, the timeout is approximately 0.8ms (typ). if dimming, this timeout is dependent on the dimming frequency and duty cycle: the sum of the on-time cycles, during which the device is in overcurrent condition, must be 0.8ms (typ) for the timeout to expire. led current sources maintaining uniform led brightness and dimming capa - bility is critical for backlight applications. the ics are equipped with a bank of six matched current sources. these specialized current sources are accurate within q 3% and match with each other within 2%. the led full-scale current is set through the iset pin (10ma < i led_fs < 45ma). the minimum voltage drop across each current source is 275mv (typ) when the led current is 20ma. the low- voltage drop helps reduce dissipation while maintaining sufficient compliance to control the led current within the required tolerances. the led current sources can be disabled by connecting the respective fb_ pin to gnd before startup. when the devices are enabled, the controller scans settings for all fb_ pins. if a fb_ pin is not tied to gnd, an internal circuit pulls this pin high, and the controller enables the corresponding current source to regulate the string cur - rent. if the fb_ pin is tied to gnd, the controller disables the corresponding current regulator. the current regula - tor cannot be disabled by connecting the respective fb_ pin to gnd after the ic is enabled. all fb_ pins in use are combined to extract a lowest fb_ voltage (lvc) (see figure 2). lvc is fed into the step-up regulators error amplifier and is used to set the output voltage. figure 5. supply configurations for the MAX17129/max17149 lx in v cc v in 6v to 26v MAX17129 max17149 lx in v cc v s 3.0v to 5.5v MAX17129 max17149 www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 16 current-source fault protection an led fault open/short is detected after the startup. when one or more strings fail after the startup, the corre - sponding current source is disabled. the remaining led strings still operate normally. led short and string mismatch protection the devices can tolerate a slight mismatch between led strings. when severe mismatches or wled shorts occur, the fb_ voltages are uneven because of mismatched voltage drop across strings. when fb_ voltage is higher than 8v (typ) after led turn on, an led short is detected. the remaining led strings can still operate normally. open current-source protection the devices step-up regulator output voltage is regu - lated according to the minimum fb_ voltages on all the strings in use. if one or more strings are open, the respective fb_ pins are pulled to ground. for any fb_ lower than 700mv (max), the corresponding current source is disabled. the remaining led strings can still operate normally. if all strings in use are open, the devices shut the step-up regulator down. pwm dimming control the devices perform brightness control with the brt input signal. the current in the leds follows the duty cycle and frequency of the brt signal. the dimming frequency can be from 0.1khz to 25khz. full-scale led current the full-scale led current i led_fs is set by the resistor connected from iset to gnd and: led_fs iset 20ma 100k i r ? = the acceptable resistance range for iset is 44.44k i < r iset < 200k i , which corresponds to a full-scale led current of 45ma > i led_fs > 10ma. hybrid dimming mode the devices can implement hybrid dimming by control - ling the voltage on the en pin (between 1.4v and 1.8v) after the device is enabled. in hybrid dimming mode, the led current is 25% of the full-scale current set by the resistor on the iset pin. the purpose of this hybrid dimming operation is to improve system efficiency by reducing the current in the leds, therefore reducing the forward drop in them. thermal shutdown the devices include a thermal-protection circuit. when the junction temperature exceeds t j = +160 n c (typ), a thermal sensor immediately activates the fault protection, which shuts down the step-up regulator and all current sources, allowing the devices to cool down. once the devices cool down by approximately 15 n c, the ics start up automatically. the thermal-overload protection pro - tects the devices in the event of fault conditions. for con - tinuous operation, do not exceed the absolute maximum junction temperature rating of t j = +150 nc. design procedure all the devices designs should be prototyped and tested prior to production. external component value choice is primarily dictated by the output voltage and the maximum load current, as well as maximum and minimum input voltages. begin by selecting an inductor value. once the inductor is known, choose the diode and capacitors. inductor selection the inductance, peak current rating, series resistance, and physical size should all be considered when select - ing an inductor. these factors affect the converters oper - ating mode, efficiency, maximum output load capability, transient response time, output voltage ripple, and cost. the maximum output current, input voltage, output voltage, and switching frequency determine the induc - tor value. very high inductance minimizes the current ripple, and therefore reduces the peak current, which decreases core losses in the inductor and i 2 r losses in the entire power path. however, large inductor values also require more energy storage and more turns of wire, which increase physical size and i 2 r copper losses. low inductor values decrease the physical size but increase the current ripple and peak current. finding the best inductor involves the compromises among circuit effi - ciency, inductor size, and cost. in choosing an inductor, the first step is to determine the operating mode: continuous-conduction mode (ccm) or discontinuous-conduction mode (dcm). when ccm mode is chosen, the ripple current and the peak current of the inductor can be minimized. if a small-size inductor is required, dcm mode can be chosen. in dcm mode, the inductor value and size can be minimized but the inductor ripple current and peak current are higher than those in ccm. the controller can be stable, but there is a maximum inductor value requirement to ensure the dcm operating mode. the equations used here include a con - stant lir, which is the ratio of the inductor peak-to-peak ripple current to the average dc inductor current at the full-load current. the controller operates in dcm mode www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 17 when lir is higher than 2.0, and it works in ccm mode when lir is lower than 2.0. the best trade-off between inductor size and converter efficiency for step-up regula - tors generally has an lir between 0.3 and 0.5. however, depending on the ac characteristics of the inductor core material and ratio of inductor resistance to other power- path resistances, the best lir can shift up or down. if the inductor resistance is relatively high, more ripples can be accepted to reduce the number of required turns and increase the wire diameter. if the inductor resistance is relatively low, increasing inductance to lower the peak current can reduce losses throughout the power path. if extremely thin high-resistance inductors are used, as is common for lcd panel applications, an lir higher than 2.0 can be chosen for dcm operating mode. once a physical inductor is chosen, higher and lower values of the inductor should be evaluated for efficiency improvements in typical operating regions. the detailed design procedure for ccm can be described as: calculate the approximate inductor value using the typical input voltage (v in ), the maximum output cur - rent (i out(max) ), the expected efficiency ( e typ ) taken from an appropriate curve in the typical operating characteristic s, and an estimate of lir based on the above discussion: out(max) out in(dc,max) in(min) min i v i v = choose an available inductor value from an appropriate inductor family. calculate the maximum dc input current at the minimum input voltage v in(min), using conserva - tion of energy and the expected efficiency at that operat - ing point ( e min ) taken from an appropriate curve in the typical operating characteristics : calculate the ripple current at that operating point and the peak current required for the inductor: ( ) in(min) out(max) in(min) ripple ccm out(max) sw v v v i l v f ? = ripple peak_ccm in(dc,max) i i i 2 = + when dcm operating mode is chosen to minimize the inductor value, the calculations are different from those above in ccm mode. the maximum inductor value for dcm mode (or the minimum inductor value for ccm mode) is calculated with the following equation: in(min) dcm(max) out(max) 2 in(min) sw out(max) out(max) v l 1 v v 2 f v i ? ? = ? ? ? ? ? ? ? the peak inductor current in dcm is calculated with the following equation: ( ) out(max) out(max) in(min) peak_dcm dcm sw i 2 v v i l f ? = the inductors saturation current rating should exceed i peak and the inductors dc current rating should exceed i in(dc,max) . for good efficiency, choose an inductor with less than 0.1 i series resistance. considering the circuit with six 10-led strings and 20ma led full-scale current, the maximum load current (i out(max) ) is 120ma with a 32v output and a minimal input voltage of 7v. choosing a ccm operating mode with lir = 0.8 at 1mhz and estimating efficiency of 85% at this operating point: 2 ccm 7v 32v 7v 0.85 l 10.59 h 32v 120ma 1mhz 0.8 ? ? ? ? ?? ? = = ? ? ? ?? ? ? ? ? ?? ? a 10 f h inductor is chosen and the peak inductor current at minimum input voltage is calculated as follows: ( ) peak_ccm 7v 32v 7v 120ma 32v i 7v 0.85 2 10 h 32v 1mhz 0.92a ? = + = alternatively, choose a dcm operating mode by using lower inductance and estimating efficiency of 85% at this operating point. since dcm has higher peak inductor current at lower input, it causes current limit when the parameters are not chosen properly. considering the case with six 10-led strings and 20ma led full-scale current to prevent excessive switch current from causing current limit: 2 dcm(max) 7v (7v) 0.85 l 1 32v 2 1mhz 32v 120ma 4.24 h ? ? = ? ? ? ? ? = www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 18 a 3.3 f h inductor is chosen. the peak inductor current at minimum input voltage is calculated as follows: ( ) ( ) peak_dcm 120ma 2 32v 32v 7v i 1.46a 3.3uh 1mhz 0.85 32v ? = = output capacitor selection the total output-voltage ripple has two components: the capacitive ripple caused by the charging and discharging on the output capacitor, and the ohmic ripple due to the capacitors equivalent series resistance (esr): v ripple = v ripple(c) + v ripple(esr) out(max) out(max) in(min) ripple(c) out out(max) sw i v v v c v f ? ? ? ? ? ? ? ? ? and: v ripple(esr) i peak x r esr(cout) where i peak is the peak inductor current (see the inductor selection section). the output-voltage ripple voltage should be low enough for the fb_ current-source regulation. the ripple voltage should be less than 200mv p-p . for ceramic capaci - tors, the output-voltage ripple is typically dominated by v ripple(c) . the voltage rating and temperature charac - teristics of the output capacitor must also be considered. rectifier diode selection the devices high switching frequency demands a high- speed rectifier. schottky diodes are recommended for most applications because of their fast recovery time and low forward voltage. the diode should be rated to handle the output voltage and the peak switch current. make sure that the diodes peak current rating is at least i peak calculated in the inductor selection section and that its breakdown voltage exceeds the output voltage. input capacitor selection the input capacitor (c in ) filters the current peaks drawn from the input supply and reduces noise injection into the ics. a 4.7 f f ceramic capacitor is used in the typical operating circuit (figure 1) because of the high source impedance seen in typical lab setups. actual applica - tions usually have much lower source impedance since the step-up regulator often runs directly from the output of another regulated supply. in some applications, c in can be reduced below the values used in the typical operating circuit . ensure a low-noise supply at in by using adequate c in , especially when running at low in voltage. alternatively, greater voltage variation can be tolerated on c in if in is decoupled from c in using an rc lowpass filter. led selection and bias the series/parallel configuration of the led load and the full-scale bias current has a significant effect or regula - tor performance. led characteristics vary significantly from manufacturer to manufacturer. consult the respec - tive led data sheets to determine the range of output voltages for a given brightness and led current. in general, brightness increases as a function of bias cur - rent. this suggests that the number of leds could be decreased if higher bias current is chosen; however, a high current increases led temperature and reduces operating life. improvements in led technology are resulting in devices with lower forward voltage while increasing the bias current and light output. led manufacturers specify the led color at a given led current. with lower led current, the color of the emitted light tends to shift toward the blue range of the spectrum. a blue bias is often acceptable for business applications but not for high-image-quality applications such as dvd players. dpwm dimming is a viable solution for reducing power dissipation while maintaining led color integrity. careful attention should be paid to switching noise to avoid other display quality problems. using fewer leds in a string improves step-up converter efficiency, and lowers breakdown voltage requirements of the external mosfet and diode. the minimum num - ber of leds in series should always be greater than max - imum input voltage. if the diode voltage drop is lower than maximum input voltage, the voltage drop across the current-sense inputs (fb_) increases and causes excess heating in the ic. between 8 and 12 leds in series are ideal for input voltages up to 20v. www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 19 applications information led v fb_ variation the forward voltage of each white led may vary up to 25% from part to part and the accumulated voltage dif - ference in each string equates to additional power loss within the devices. for the best efficiency, the voltage difference between strings should be minimized. the difference between lowest voltage string and highest voltage string should be less than 8v (typ). otherwise, the internal led short-protection circuit disables the high fb voltage string. fb pin maximum voltage the current through each fb_ pin is controlled only during the step-up converters on-time. during the converter off- time the current sources are turned off. the output voltage does not discharge and stays high. the devices disable the fb current source, which string shorts. in this case, the step-up converters output voltage is always applied to the disabled fb pin. fb_ pin can withstand 48v. pcb layout guidelines careful pcb layout is important for proper operation. use the following guidelines for good pcb layout: 1) minimize the area of high current-switching loop of the rectifier diode, internal mosfet, and output capacitor to avoid excessive switching noise. 2) connect high-current input and output components with short and wide connections. the high-current input loop goes from the positive terminal of the input capacitor to the inductor, to the internal mosfet, then to the input capacitors negative terminal. the high-current output loop is from the positive terminal of the input capacitor to the inductor, to the rectifier diode, to the positive terminal of the output capaci - tors, reconnecting between the output capacitor and input capacitor ground terminals. avoid using vias in the high-current paths. if vias are unavoidable, use multiple vias in parallel to reduce resistance and inductance. 3) create a ground island (pgnd) consisting of the input and output capacitor ground. connect all these together with short, wide traces or a small ground plane. maximizing the width of the power ground traces improves efficiency and reduces out - put-voltage ripple and noise spikes. create an analog ground island (gnd) consisting of iset, in, v cc con - nections, and the devices exposed backside pad. connect the gnd and pgnd islands by connecting the gnd pins directly to the exposed backside pad. make no other connections between these separate ground planes. 4) place the in pin and v cc pin bypass capacitors as close to the device as possible. the ground connec - tion of the bypass capacitors should be connected directly to the gnd pins with a wide trace. 5) minimize the size of the lx node while keeping it wide and short. if possible, avoid running the lx node from one side of the pcb to the other. use dc traces as shield if necessary. refer to the MAX17129/max17149 evaluation kit for an example of proper board layout. www.datasheet.co.kr datasheet pdf - http://www..net/
MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter 20 simplified operating circuit chip information process: bicmos package information for the latest package outline information and land pat terns (footprints), go to www.maxim-ic.com/packages . note that a +, #, or - in the package code indicates rohs status only. package drawings may show a different suf fix character, but the drawing pertains to the package regardless of rohs status. lx pgnd ovp fb1 fb2 fb3 fb4 fb5 fb6 in v cc iset en brt gnd fsel ep MAX17129 package type package code outline no. land pattern no. 16 tqfn-ep t1633+5 21-0136 90-0032 www.datasheet.co.kr datasheet pdf - http://www..net/
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 21 ? 2011 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. MAX17129/max17149 low-cost, 6-string wled drivers with quick-pwm step-up converter revision history revision number revision date description pages changed 0 12/10 initial release 1 9/11 updated die specifications 1C6, 8, 9, 12C15, 17 www.datasheet.co.kr datasheet pdf - http://www..net/

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