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SGM3127 white led driver with low dropout current source general description the SGM3127 low-dropout bias supply for white leds is a high-performance alternative to the simple ballast resistors used in conventional white led designs. it is optimized for low power keypad and portable backlighting applications. the SGM3127 uses an internal resistor to set the bias current for four leds, which are matched to 5%. the SGM3127's advantages over ballast resistors include much lower bias variation with supply voltage variation, significantly lower dropou t voltage, and in some applications, significantly improved efficiency. the SGM3127 requires only a 50mv dropout voltage at a 30ma load on each output to match the led brightness. the SGM3127 is available in green sot-23-6 package. it operates over an ambient temperature range of -40 to +85 . features support up to 4 leds low 50mv dropout at 30ma less than 5% led current matching simple led brightness control low shutdown current 2.5v to 5.5v supply voltage range thermal shutdown protection operating temperature range: -40 to +85 available in green sot-23-6 package applications wireless handsets mp3, mp4, and pmp cellular phones portable communication devices digital cameras, camcorders pdas, palmtops, and handy terminals led/display back light driver leds for camera flash battery-powered equipment rev. a. 3 sg micro corp www.sg-micro.com
white led driver with low dropout current source 2 SGM3127 sg micro corp www.sg-micro.com package/ordering information model order number package description specified temperature range package option marking information SGM3127 SGM3127yn6g/tr sot-23-6 -40 to +85 tape and reel, 3000 s01xx note: order number and package mark ing are defined as the follow: order number SGM3127 x x g / tr package type green product tape and reel n6 sot-23-6 operating temperature range y -40 to +85 marking information for example: s019a (2009 year, the 1st month) s01 x x year assembled ("9" = 2009, "a" = 2010 ) month assembled ("a" = jan. "b" = feb. "l" = dec.) absolute maximum ratings v in to gnd?????.??...??.. ..????.-0.3v to 6v the other pins to gnd?????.????...-0.3v to 6v storage temperature range..??.??...-65 to +150 junction temperature???????.?????...150 operating temperature range????? -40 to +85 power dissipation, p d @ t a = 25 sot-23-6???????????.??.?????..0.5w package thermal resistance sot-23-6, ja ??????????.?????.250 /w lead temperature range (soldering 10 sec) ?????????????..??.??.????.. 260 esd susceptibility hbm????????????????.??.??4000v mm????????????????.??.???400v note: stresses beyond those list ed 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 sp ecifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. caution this integrated circuit can be damaged by esd if you don?t pay attention to esd protecti on. 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. sgmicro reserves the right to make any change in circuit design, specification or other related things if necessary without notice at any time. pl ease contact sgmicro sales office to get the last datasheet.
white led driver with low dropout current source 3 SGM3127 sg micro corp www.sg-micro.com pin configuration (top view) 1 3 2 6 4 5 led1 led2 led3 en gnd led4 s01xx sot-23-6 pin description pin name function 1 en enable input/power input. (active high). when disabled, led1, led2, led3 and led4 are high impedance. when enabled, en is the power input for the SGM3127. 2 gnd ground. 3 led4 led4 output pin. connect to led4?s cathode. 30ma constant current output. led4 is high impedance when en is low. 4 led3 led3 output pin. connect to led3?s cathode. 30ma constant current output. led3 is high impedance when en is low. 5 led2 led2 output pin. connect to led2?s cathode. 30ma constant current output. led2 is high impedance when en is low. 6 led1 led1 output pin. connect to led1?s cathode. 30ma constant current output. led1 is high impedance when en is low.
white led driver with low dropout current source 4 SGM3127 sg micro corp www.sg-micro.com electrical characteristics (v in = 3.7v, t a = +25 , unless otherwise noted.) parameter symbol conditions min typ max units operation voltage range v en 2.5 5.5 v under-voltage lockout v uvlo falling 2.1 v uvlo hysteresis 110 mv led sink current i led 27 30 33 ma quiescent power supply current i en i led = 0 240 a led dropout voltage i led = 30ma, v led @ i ledn = 90% i led 50 mv shutdown supply current i shdn v en < 0.4v 1 a led current deviation matching d led -5 +5 % opt 150 opt hysteresis 10 input high voltage at en v ih 2.5 v input low voltage at en v il 0.7 v
white led driver with low dropout current source 5 SGM3127 sg micro corp www.sg-micro.com typical performance characteristics led current vs. input voltage 0 10 20 30 40 50 22.533.544.555.5 input voltage (v) led current (ma) led1 led2 led3 led4 en current vs. en supply voltage 0 50 100 150 200 250 300 1.5 2.5 3.5 4.5 5.5 en supply voltage (v) en current ( a) led current vs. en voltage 0 10 20 30 40 50 1.5 2.5 3.5 4.5 5.5 en voltage (v) led current (ma) led current vs. temperature 25 27 29 31 33 35 -40 -15 10 35 60 85 temperature ( ) led current (ma)
white led driver with low dropout current source 6 SGM3127 sg micro corp www.sg-micro.com typical performance characteristics
white led driver with low dropout current source 7 SGM3127 sg micro corp www.sg-micro.com typical application led1 led2 led3 led4 gnd en v in c in 0.1f SGM3127 pwm figure 1. application circuit for backlight
white led driver with low dropout current source 8 SGM3127 sg micro corp www.sg-micro.com application information the SGM3127 is a 4-channel current source driver for white leds. enable input en powers the input of the SGM3127. this ic provides an under-voltage lockout (uvlo) function to prevent it from unstable issue when startup. the uvlo threshold of input falling voltage is set at 2.1v typically with a hysteresis 0.11v. drive en high to enable the device; drive en low to disable the device. when driven high, en draws 240 a to power the ic. driving en low forces led1, led2, led3, and led4 into a high-impedance state. led current SGM3127 provides a constant current for white led. figure 1 shows a typical application circuit for 4 white leds. each channel supports up to 30ma current and regulates a constant current for uniform intensity. for keypad led application, the all channels must be connected to led as shown in figure 2. in order to maintain led constant current, the input voltage must provide the required led forward voltage and current source dropout voltage. if the forward voltage of white leds is 3.3v, the input voltage should be higher than 3.4v to provide enough voltage headroom for maintaining constant brightness. led1 led2 led3 led4 gnd en v in c in 0.1f SGM3127 pwm keypad led figure 2. application circuit for keypad led brightness dimming control for controlling the led brightness, the SGM3127 can perform the dimming control by applying a pwm signal to en pin. when an external pwm signal is connected to the en pin, brightness of white led is adjusted by the duty cycle. the average led current is proportional to the pwm signal duty cycle. the magnitude of the pwm signal must be higher than the minimum level of enable input high level, in order to let the dimming control perform correctly, the suggested pwm frequency range is 10khz to 200hz. thermal considerations for continuous operation, do not exceed absolute maximum operation junction temperature 150 . the maximum power dissipation depends on the thermal resistance of ic package, pcb layout, the rate of surroundings airflow and temperature difference between junctions and ambient. the maximum power dissipation can be calculated by following formula: p d(max) = ( t j(max) - t a ) / ja where t j(max) is the maximum operation junction temperature 150 , t a is the ambient temperature and the ja is the junction to ambient thermal resistance. for recommended operating conditions specification of SGM3127, where t j(max) is the maximum junction temperature of the die (150c) and t a is the maximum ambient temperature. the junction to ambient thermal resistance ja is layout dependent. for sot-23-6 package, the thermal resistance ja is 250 /w. the maximum power dissipation at t a = 25 can be calculated by following formula: p d(max) = (150 - 25 ) / (250 /w) = 0.5w
white led driver with low dropout current source 9 SGM3127 sg micro corp www.sg-micro.com package outline dimensions sot-23-6 e e1 e e1 b d a1 a2 a c l 0.2 2.59 0.99 0.95 0.69 recommended land pattern (unit: mm) dimensions in millimeters dimensions in inches symbol min max min max a 1.050 1.250 0.041 0.049 a1 0.000 0.100 0.000 0.004 a2 1.050 1.150 0.041 0.045 b 0.300 0.500 0.012 0.020 c 0.100 0.200 0.004 0.008 d 2.820 3.020 0.111 0.119 e 1.500 1.700 0.059 0.067 e1 2.650 2.950 0.104 0.116 e 0.950 bsc 0.037 bsc e1 1.900 bsc 0.075 bsc l 0.300 0.600 0.012 0.024 0 8 0 8
white led driver with low dropout current source 10 SGM3127 sg micro corp www.sg-micro.com 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 sot-23-6 7 9.5 3.17 3.23 1.37 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
white led driver with low dropout current source 11 SGM3127 sg micro corp www.sg-micro.com 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 7 (option) 368 227 224 8 7 442 410 224 18

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