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sgm37 25 38v step- up led driver general description the sgm3725 is a versatile constant current led driver with a high efficiency step - up converter architecture. unique technology and high 1.35a current limit allow sgm3725 to drive up to 38v output (10 leds in series) . alternatively, s gm3725 can deliver 26 0ma total current with 3 series leds per string. it can also maximize the current capability while achieving high conversion efficiency. the optimized 1. 1 mhz switching frequency results in reduced conduction loss and small external component size. a single wire interface is integrated to adjust the fb voltage in 32 steps, which can overcome audible noise and inrush current issues in normal pwm dimming schemes. various protection features are built into the sgm3725 , including cycle - by -c ycle input current limit protection, open led (output over - voltage) protection and thermal shutdown protection. the leakage current in shutdown mode is less than 1a. the sgm3725 is available in green tsot - 23 - 6 package. it operates over an ambient tempera ture range of - 40 to +85 . features wide output range: u p to 10 series leds integrated 40v high current switch ( 1.35a limit) 2.7v to 5.5v input voltage range high efficiency pwm converter low 200mv feedback voltage 500k pull - down resistor on ctrl pin single wire dimming interface 38v open led protection 1. 1 mhz switching frequency integrated soft -s tart function less than 1a shutdown current simple, small solution size available in green tsot - 23 - 6 package - 40 to +85 operating temperature range applic ations led backlighting mobile phones handheld devices digital photo frames automotive navigation rev. a . 3 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver package/ordering inf ormation model package description specified temperature range ordering number package marking pack ing option sgm3725 tsot -23 -6 -40 to +85 sgm3725ytn6g/tr -v1 sk9xx 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 : sk9fa ( 2015 , january ) sk 9 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 in put 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 resistance 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 spe cifications. disclaimer sg micro corp reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. 2 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver 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 200m v. 4 ctrl control p in of the b oost r egulator. can be used to enable/disable the ic, as well as to program the output current at 32 levels. 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 3725 l sw white leds up to 10 in series or up to 10 s4p up to 38 v output 1 6 2 5 3 4 r set brightness control 1k figure 1 . typical application circuit 3 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver electrical character istics (1) (v in = 3.6v, l = 10 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 risin g 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 0.72 1.5 ma vin pin shutdown current i shdn v en = 0v +25 0.1 1 a step- up conv erter voltage feedback regulation voltage v ref full 192 2 00 212.5 mv 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 1.35 a oscillator frequency f s full 0.9 0 1. 10 1. 4 mhz 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 minimum logic high pulse width timing t high_mi n +25 0.4 s logic low pulse width timing t low +25 0.4 750 s minimum shut d own pulse width timing t off +25 3 ms junction thermal shutdown threshold 150 junction thermal shutdown hysteresis 15 note: 1. the sgm3725 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
sgm3725 38v s tep - up led driver recommended componen ts of test circuits component component inductor 22h/cd75np -2 20kc capacitor 10f/c2012x7r1h106kt 10h / cd75np - 100kc 0.47f/c2012x7r1h474kt diode mbr0540 typical performance characteristics t a = + 25 , l = 10 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) start -up v en v out i l 2v/div 10v/div 200ma/div time (1 ms/div) v in = 3.6v , i l ed = 20ma, l = 10 h , 8 leds ac coupled v in = 3.6v , i l ed = 20ma, l = 10 h , 8 leds v in = 3.6v , i l ed = 20ma, l = 10 h , 8 leds 5 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver typical performance characteristics t a = + 25 , l = 10 h, c in = 10f, c out = 0.47 f , unless otherwise noted. feedback voltage vs. temperature feedback voltage vs. input voltage 185 190 195 200 205 210 215 -50 -25 0 25 50 75 100 temperature ( ) feedback voltage (mv) v in =3. 6v, not dimmed 185 190 195 200 205 210 215 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) feedback voltage (mv) not dimmed efficiency vs. input voltage efficiency vs. input vol tage 70 74 78 82 86 90 2.5 3 3.5 4 4.5 5 5.5 input voltage (v) efficiency (%) 10 leds (32v) i led = 20ma, l = 10h 70 74 78 82 86 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 curre nt 60 65 70 75 80 85 90 0 5 10 15 20 25 30 output current (ma) efficiency (%) 10 leds (32v) v in = 3.6v, l = 10h 6 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver function al block diagram voltage reference and 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 3725 500 k pull- down resistor v ref led current control comp gm figure 2 . sgm3725 block diagram 7 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver functional descripti on the sgm3725 uses a constant - frequency current - mode boost converter architecture to control the led current by regulating the feedback voltage. please refer to the f unctional b lock d iagram above for an explanation of sgm3725 operation. the beginning of each cyc le turns on the power mosfet. a slope compensation ramp is added to the output of 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 amplifies the difference between the reference voltage and the feedback voltage (fb), so that fb voltage can be regulated to the reference voltage. the sgm3725 has built - in soft - start to limit the inrush current during start - up and to limit the amount of overshoot on the output. protection features in the sgm3725 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. the single wire control interface accepts a series of pulses into the ctrl pin to program the reference voltage. the number of rising edges is detected internally and decoded as illustrated in table 1 . the register contains 5 - bits, yielding 32 different current levels. using the simplest control method, output current can be toggled on and off between i max and 0ma, by pulling the ctrl pin high or low. i max is programmed by the resistor connected between fb and gnd. please see led maximum current setting section in this document to determine the proper resistor value. the next level of control is achieved by injecting a series of pulses into the ctrl pin to program the reference voltage at 32 levels. the number of rising edges is detected internally and decoded to the current level as illustrated in table 1 . the reference voltage levels are evenly spaced among these 32 steps. the first rising edge on the ctrl pin takes the current level to maximum of 100% of i max . then the current will be changed with each additional qualified pulse. the current stays uncha nged as long as the ctrl pin stays h igh. table 1. current setting data led current ratio data led current ratio data led current ratio data led current ratio 1 32/32 9 24/32 17 16/32 25 8/32 2 31/32 10 23/32 18 15/32 26 7/32 3 30/32 11 22/32 19 14/32 27 6/32 4 29/32 12 21/32 20 13/32 28 5/32 5 28/32 13 20/32 21 12/32 29 4/32 6 27/32 14 19/32 22 11/32 30 3/32 7 26/32 15 18/32 23 10/32 31 2/32 8 25/32 16 17/32 24 9/32 32 1/32 8 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver application informat ion inductor selectio n a 6.8 h to 22h inductor is recommended 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 pe ak input current, especially for high load current application (like 10s4p ). capacitor selection small size ceramic capacitors are ideal for sgm3725 application. a n input capacitor in the range of 1f to 22f and a 0.47f output capacitor are suggested fo r 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 voltage 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 internally set at 200mv when the data = 1. the led current is programmed according to the formula i max = 200mv/r set . for accurate led current settings, precision 1% resistors are recommended. the formula and table for r set selecti on are shown below. r set = 200mv/i max table 2. current setting resistor r set () i max current (ma) 200 1 40.2 5 20.0 10 13.3 15 10.0 20 6.65 30 2.00 100 vin gnd vout d1 c out 0. 47 f input power 2.7v~ 30v c in 22 f sgm 3725 l sw 20 ma 10- series white leds r set 10 1 6 2 5 10 h bias voltage 2.7v~5.5v c 1 0.1 f ctrl 4 brightness control 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) 9 sg micro corp www.sg - micro.com a ll data sheet.com
sgm3725 38v s tep - up led driver application information current setting at ctrl pin current control can be as simple as a bi - level signal at the ctrl pin, resulting in leds on at 100% i max or led off state. however, more sophisticated control techni ques can be achieved by pulsing the ctrl pin. an example for programming the output current is shown in figure 4 . there are two ways to adjust the channels on/off state or current level. the first way is by simply adding the number of pulses according to table 2 . for example, we will use r set = 10 to program 20ma i max . in this example, the user can add 12 more pulses when changing from 14/32 (8.75ma when i max = 20ma) to 2 /32 (1.25ma when i max = 20ma). however, increasing the current level can be accomplished by two ways, allowing for more flexible programming. since the data in table 1 automatically circles around after 32 pulses, adding 32 - 8 = 24 pulses changes from 6/32 (data 27) to 14/32 (data 19). the second way is to reset the ic by pulling ctrl pin low for 3ms (guaranteed shutdown), and then inputting the desired number of pulses. example: going from 6/32 (data 27) to 14/32 (data 19) option 1: send in 24 pulses (19+32 - 27 = 24); option 2: pull low for 3ms and then send in 19 pulses. 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. please see the sgm3725 evaluation document for detailed pcb lay out guidelines. t high > 0.4s ctrl i_ led 0.4s < t low < 750 s t off > 3 ms off off 100 % 31 / 32 30 / 32 4/ 32 3/ 32 2/ 32 1/ 32 t s = 800 s ( typ ) figure 4 . output current programming via ctrl pin 10 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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