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sgm3720 pwm dimming, 38v step- up led driver general description the sgm3720 is a versatile constant current led driver with a high efficiency step - up converter architecture. the low - side power mosfet is integrated in the device, significantly shrinking the overall pcb layout area and minimizing the total number of external components. unique technology and high 1. 6 a current limit allow sgm3720 to drive up to 38v output (10 leds in series). alternatively, sgm3720 can deliver 2 6 0ma total current with 3 series leds per string. it can also maximize the current capability while achieving high conversion efficiency. the optimized 60 0k hz switching frequency results in reduced conduction loss and small external component size. digital pwm dimming interface is integrated to adjust led current. the pwm frequency is in the range from 2k hz to 60khz. various protection features are built into the sgm3720 , including cycle - by - cycle input current limit protection, open led (output over - voltage) protection and thermal shutdown protection. the leakage current in shut down mode is less than 1a. the sgm3720 is available in green t sot - 23 - 6 package. it operates over an ambient temperature range of - 40 to +85 . features wide o utput r ange: up t o 10 series led s integrated 40v high current switch (1. 6 a limit) 2.7v to 5.5v input voltage range high efficiency pwm converter low 300 mv feedback voltage 500k pull - down resistor on ctrl pin 2khz to 60khz pwm dimming frequency 38v open led protection 600 khz switching frequency integrated soft -s tart function less than 1a shutdown current simple, small solution size - 40 t o +85 operating temperature range available in green t sot - 23 -6 package applications led b acklighting mobile phones handheld devices digital photo frames automotive navigation rev. a . 3 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3720 pwm dimming , 38v s tep - up led dri ver package/ordering inf ormati on model package description specified temperature range ordering number package marking pack ing option sgm3720 t sot -23 -6 -40 to +8 5 sgm3720ytn6g/tr -v1 smfxx tape and reel, 3000 note: xx = date code . green (rohs & hsf): sg micro corp defines "green" to mean pb - free (rohs compatible) and free of halogen substances. if you have additional comments or questions, please contact your sgmicro representative directly. marking information for example : s mff a ( 2015 , january ) smf x x date code - y ear ( "a" = 2010 , "b" = 2011 ) date code - month ("a" = jan . "b" = feb . "l" = dec .) chip i .d. absolute maximum rat ings input voltage, v in ................................................. - 0.3v to 6v high voltage nodes, sw, vout ....................... - 0.3v to 40v other pins , fb, ctrl ............................... - 0.3v to v in + 0.3v package thermal res istance tsot -23-6 , ja ........................................................ 120 /w junction temperature ................................................. + 150 storage temperature range ........................ -65 to +150 lead temperature (soldering, 10sec) ........................ + 260 esd susceptibility hbm ............................................................................. 4 000v mm ................................................................................. 200v recommended operatin g conditions input voltage range ........................................... 2.7v to 5.5v operating temperature range ....................... -40 to +85 overstress caution stresses beyond those listed may cause permanent damage to the device. functional operation of the device at these or any other conditions beyond those indicated in the operational section of the specification is not implied. exposure to absolute maximum rating conditions for extended periods may affect reliability. esd sensitivity caution this integrated circuit can be damaged by esd if you dont pay attention to esd protection. sgmicro recommends that all integrated circuits be handled with appropriate precautions. failure to observe proper handling and installation procedures can cause damage. esd damage can range from subtle performance degradation to complete device failure. precision integrated circuits may be more susceptible to damage because very small parametric changes could cause the device not to meet its published specifications. disclaimer sg micro corp reserves the right to make any change in circuit design, specification or other related thin gs if necessary without notice at any time. 2 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3720 pwm dimming , 38v s tep - up led dri ver pin configuration (top view) sw gnd fb 4 5 6 3 2 1 vin vout ctrl t sot - 23 - 6 pin description pin name function 1 sw converter switching node. 2 gnd ground. 3 fb output feedback pin regulated at 300mv. 4 ctrl control pin of the boost regulator. it is a multi - functional pin which can be used for enable control and digital pwm dimming. 5 vout output and over - voltage protection pin. 6 vin ic supply. connect vin to a supply voltage between 2.7v and 5.5v. typical application vin ctrl gnd fb vout d1 c out input range 2.7v~5.5v c in sgm 3720 l sw white leds up to 10 in series or up to 10 s4p up to 38 v output pwm dimming 1 6 2 5 3 4 1k r set figure 1 . typical application circuit 3 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3720 pwm dimming , 38v s tep - up led dri ver electrical character istics (1) (v in = 3.6v, l = 22 h, c in = 10f, c out = 0.47f , full = - 40 to +85 , typical values are at t a = +25 , unless otherwise noted.) parameter symbol conditions temp min typ max units ic supply input voltage range v in full 2.7 5.5 v input u nder - voltage lockout uvlo ris ing edge +25 2.5 2.6 v uvlo hysteresis v hys +25 0.1 5 v quiescent current (non switching) i q v fb = 0.4v +25 0.2 0 0.35 ma operating current (switching) v fb = 0v +25 0. 5 0.9 ma vin pin shutdown current i shdn v en = 0v +25 0.1 1 a step- up con verter voltage feedback regulation voltage v ref full 289 300 311 mv voltage feedback regulation voltage under brightness control v ref_pwm f pwm = 10khz, duty cycle = 3% +25 6.5 9 11.5 mv v ref f ilter 3db f requency f ref (3db) +25 600 hz voltage feedback input bias current i fb full 0.001 0.3 a sw pin leakage current i sw +25 0. 01 1 a peak nmos current limit i lim +25 1.6 a oscillator frequency f s full 480 600 750 khz over - voltage threshold v ovp measured at vout pin full 35.5 38.0 40.5 v start- up time t s +25 800 s control logic low threshold v il full 0.35 v logic high threshold v ih full 1. 5 v pwm dimming frequency range dfr +25 2 60 khz minimum shut d own pulse width timing t off +25 3 ms junction thermal shutdown thre shold 150 junction thermal shutdown hysteresis 15 note: 1. the sgm3720 is guaranteed to meet performance specifications over the -40 to +85 operating temperature range by design, characterization and correlation with statistical process controls. 4 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3720 pwm dimming , 38v s tep - up led dri ver recommended components of test circuits component component inductor 22h / cd75np - 220kc capacitor 10f/c2012x7r1h106kt diode mbr0540 0.47f/c2012x7r1h474kt typical performance characteristics t a = + 25 , l = 22 h, c in = 10f, c out = 0.47 f , unless otherwise noted. switching waveform open led protection v sw v out i l 20 v/div 2 00m v/div 200ma /div v fb v out i l 200mv/div 10v/div 500ma/div time (1 s/div) time (100 s/div) sta rt -up output ripple at pwm dimming v en v out i l 2v/div 10v/div 500ma/div pwm v out i led 2v/div 200mv/div 10ma/div time (1 ms/div) time (100 s/div) v in = 3.6v, i l ed = 20ma, l = 22 h , 8 leds ac coupled v in = 3.6v , i l ed = 20ma, l = 22 h , 8 leds v in = 3.6v , i l ed = 2 0ma, f pwm = 10 khz, l = 22 h , 8 leds ac coupled v in = 3.6v , i l ed = 20ma, l = 22 h , 8 leds 5 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3720 pwm dimming , 38v s tep - up led dri ver typical performance characteristics t a = + 25 , l = 22 h, c in = 10f, c out = 0.47 f , unless otherwise noted. feedback voltage vs. temperature efficiency vs. input voltage 285 290 295 300 305 310 315 -50 -25 0 25 50 75 100 temperature ( ) feedback voltage (mv ) v in =3.6v, d pwm = 100% 80 82 84 86 88 90 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) efficiency (%) 10 leds (32v) i led = 20ma, l = 22h efficiency vs. output current oscillator frequency vs. input voltage 70 74 78 82 86 90 0 5 10 15 20 25 30 output current (ma) efficiency (%) 10 leds (32v) v in = 3.6v, l = 22h 450 500 550 600 650 700 750 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) oscillator frequency (khz) led current vs. pwm duty cycle 0 3 6 9 12 15 18 21 24 0 20 40 60 80 100 pwm duty cycle (%) led current (ma) f pwm = 2khz v in = 3.6v, i led = 20ma, l = 22 h , 6 leds f pwm = 20khz 6 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3720 pwm dimming , 38v s tep - up led dri ver function al block diagram voltage reference and pwm dimming control pwm control and gate drive thermal shutdown over - voltage protection ramp generator oscillator current limit input logic and dac current sense fb ctrl gnd sw vout vin v in current sense sgm 3720 500 k pull - down resistor v ref led current control comp gm figure 2 . sgm37 20 block diagram functional descripti on the sgm3720 uses a constant - frequency current - mode boost converter architecture to c ontrol the led current by regulating the feedback voltage. please refer to the functional block dia gram above for an explanation of sgm3720 operation. the beginning of each cycle turns on the power mosfet. a slope compensation ramp is added to the output o f the current sense amplifier and the result is fed into the positive input of the comparator (comp). when this voltage goes above the output voltage of the error amplifier (gm), the power mosfet is turned off. the voltage at the output of the gm block amp lifies the difference between the reference voltage and the feedback voltage (fb), so that fb voltage can be regulated to the reference voltage. the sgm3720 has built - in soft - start to limit the inrush current during start - up and to limit the amount of ove rshoot on the output. protection features in the sgm3720 include over - voltage protection (ovp), cycle - by - cycle current limit protection and thermal shutdown. ovp protects in the event where an led fails open, which forces the feedback voltage to zero. this causes the boost converter to operate in maximum duty cycle mode, ramping up the output voltage. switching will stop when the output reaches the ovp threshold. the ovp feature protects the ic from damaging itself by exceeding the voltage rating on sw/vout pins. for the brightness dimming control of the sgm3720 , the ic provides typically 300mv feedback voltage when the ctrl pin is pulled constantly high. however, ctrl pin allows a pwm signal to reduce this regulation voltage by changing the pwm duty cycle to achieve led brightness dimming control. an internal low pass filter ( 6 00hz) is used to filter the pulse signal. the relationship between the duty cycle and fb voltage can be calculated as following equation. v fb = duty 300mv where: duty = duty cycle of the pwm signal 300mv = internal reference voltage the pwm frequency is in the range from 2khz to 60khz, and the recommended minimum pwm duty cycle is 3 % for no blind dimming. 7 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3720 pwm dimming , 38v s tep - up led dri ver application informat ion inductor selection a 10 h to 22h inductor is re commended for 10/8/6 s eries led applications and 10s4p led applications. if high efficiency is a critical requirement, a low dcr inductor should be selected. the inductors saturation current rating should also exceed the peak input current, especially for high load current application (like 10s4p). capacitor selection small size ceramic capacitors are ideal for sgm3720 application. a n input capacitor in the range of 1f to 22f and a 0.47f output capacitor are suggested for 10/8/6 s eries led applications . for higher output current applications like 10s4p, larger value output capacitors like 2.2f are recommended to minimize output ripple. diode selection the current rating of the s chottky diode should exceed the peak current of the boost converter. the v oltage rating should also exceed the target output voltage. led maximum current setting led maximum current setting, i max , is determined by the feedback resistor (r set in figure 3 ). the feedback voltage is interna lly set at 300 mv when the pwm dimming duty cycle = 100%. the led current is programmed according to the formula i max = 300 mv/r set . for accurate led current settings, precision 1% resistors are recommended. the formula and table for r set selection are shown below. r set = 300 mv/i max table 1. current setting resistor r set () i max current (ma) 300 1 60.4 5 30. 0 10 20.0 15 15.0 20 10.0 30 3.00 100 layout considerations pcb layout is very important for high frequency switching regulators in order to keep the loop stable and minimize noise. the input capacitor should be very close to the ic to get the best decoupling. the path of the inductor and output capacitor should be kept as short as possible to minimize noise and ringing. 20 ma 10 - series white leds gnd vout d1 c out 0. 47 f sgm 3720 l sw 1 2 5 input power 2.7v~ 30 v c in 22 f 22 h r set 15 vin 6 bias voltage 2.7v~5.5v c 1 0.1 f ctrl 4 pwm dimming 1k fb 3 figure 3. application circuit for 10 leds in series with 20ma current (v in can be tied to input power rail if less than 5.5v) 8 sg micro corp www.sg - micro.com a ll data sheet.com
package informatio n package outline dimensions tsot - 23 -6 e e1 e b d 0.99 0.95 0.69 recommended land pattern (unit: mm) 2.59 c a2 a1 0.25 l a symbol dimensions in millimeters dimensions in inches min max min max a 1.000 0.043 a1 0.000 0.100 0.000 0.004 a2 0.700 0. 9 00 0.028 0.03 9 b 0.3 00 0.500 0.01 2 0.020 c 0.080 0.200 0.003 0.008 d 2.8 50 2.950 0.112 0.116 e 1.550 1.650 0.061 0.065 e1 2.650 2.950 0.104 0.116 e 0.95 0 bsc 0.037 bsc l 0.300 0.600 0.012 0.024 0 8 0 8 tx00038.00 1 sg micro corp www.sg - micro.com a ll data sheet.com
package informatio n tape and reel information note: the picture is only for reference. please make the object as the standard. key parameter list of tape and reel package type reel diameter reel width w1 (mm) a0 (mm) b0 (mm) k0 (mm) p0 (mm) p1 (mm) p2 (mm) w (mm) pin1 quadrant dd0001 tsot -23 -6 7 9.5 3. 2 3.1 1.1 4.0 4.0 2.0 8.0 q3 reel width (w1) reel diameter reel dimensions tape dimensions direction of feed p2 p0 w p1 a0 k0 b0 q1 q2 q4 q3 q3 q4 q2 q1 q3 q4 q2 q1 tx10 0 00 .000 sg micro corp www.sg - micro.com a ll data sheet.com
package informatio n carton box dimensions note: the picture is only for reference. please make the object as the standard. key parameter list of carton box reel type length (mm) width (mm) height (mm) pizza/carton dd000 2 7 (option) 368 227 224 8 7 44 2 410 224 18 tx20 0 00 .000 sg micro corp www.sg - micro.com a ll data sheet.com

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