mic2289 white led driver internal schottky diode and ovp mlf and micro leadframe are registered trademarks of amkor technology, inc. micrel inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? te l +1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.micre l.com july 2007 m9999-071007 general description the mic2289 is a pwm (pulse width modulated), boost- switching regulator that is optimized for constant-current white led driver applications . the mic2289 features an internal schottky diode and three levels of output overvoltage protection providi ng a small size and efficient dc/dc solution that requires only four external components. to optimize efficiency, the feedback voltage is set to only 95mv. this reduces power diss ipation in the current set resistor and allows the lowest total output voltage, hence minimal current draw from the battery. the mic2289 implements a constant frequency 1.2mhz pwm control scheme. the hi gh frequency, pwm operation saves board space by reducing external component sizes. the added bene t of the constant frequency pwm scheme in caparison to variable frequency is much lower noise and input ripple injected to the input power source. the mic2289 clamps the output voltage in case of open led conditions, protecting itself and the output capacitor. the mic2289 is available with three output ovp options of 15v, 24v, and 34v. the different ovp options allows the use of the smallest possible output capacitor with the appropriate voltage rating fo r a given application. the mic2289 is available in low profile 6-pin thin sot-23 and 8-pin 2mm 2mm mlf ? package options. the mic2289 has a junction temperature range of ?40c to +125c. data sheets and support doc umentation can be found on micrel?s web site at: www.micrel.com. features ? 2.5v to 10v input voltage ? output voltage up to 34v ? internal schottky diode ? 15v, 24v, 34v output ovp options ? 1.2 mhz pwm operation ? over 500ma switch current ? 95mv feedback voltage ? <1% line and load regulation ? <1a shutdown current ? overtemperature protection ? uvlo ? 2mm 2mm 8-pin mlf ? package ? ?40c to +125c junction temperature range applications ? white led driver for backlighting: ? cell phones ? pdas ? gps systems ? digital cameras ? mp3 players ? ip phones ? led ashlights ? constant current power supplies typical application 10h 0.22f/16v 95mv 1-cell li ion 1f mic2289-15bml vin en sw fb out gnd 3-series white led driver 70 72 74 76 78 80 82 0 5 10 15 20 25 efficiency (%) i out (ma) 3-series led efficienc y v in =3.6v
micrel, inc. mic2289 july 2007 2 m9999-071007 ordering information part number marking code overvoltage protection junction temp. range package lead finish mic2289-24yd6 sm 24 24v ?40c to +125c 6-pin thin sot-23 pb-free mic2289-15bml sna 15v ?40c to +125c 8-pin 2mm x 2mm mlf ? standard mic2289-15yml sna 15v ?40c to +125c 8-pin 2mm x 2mm mlf ? pb-free MIC2289-24BML snb 24v ?40c to +125c 8-pin 2mm x 2mm mlf ? standard mic2289-24yml snb 24v ?40c to +125c 8-pin 2mm x 2mm mlf ? pb-free mic2289-34bml snc 34v ?40c to +125c 8-pin 2mm x 2mm mlf ? standard mic2289-34yml snc 34v ?40c to +125c 8-pin 2mm x 2mm mlf ? pb-free note : marking bars may not be to scale. pin configuration vout vin en gnd sw fb 3 1 6 2 45 vout vin en a gnd pgnd sw fb nc 1 2 3 4 8 7 6 5 ep 6- pin thin sot-23 (d6) 8-pin mlf ? (ml) (top view) fused lead frame pin description pin number tsot-23-6 pin number mlf ? -8 pin name pin name 1 7 sw switch node (input): in ternal power bipolar collector. 2 D gnd ground (return): ground. 3 6 fb feedback (input): output v oltage sense node. connect the cathode of the led to this pin. a resistor from this pin to ground sets the led current. 4 3 en enable (input): logic high enables regulator. logic low shuts down regulator. 5 2 vin supply (input): 2.7v to 8v for internal circuitry. 6 1 vout output pin and overvoltage prot ection (output): connect to the output capacitor and leds. D 4 agnd analog ground. D 8 pgnd power ground. D 5 nc no connect (no internal connection to die). D ep gnd ground (return): exposed backside pad.
micrel, inc. mic2289 july 2007 3 m9999-071007 absolute maximum ratings (1) supply voltage (v in ) .......................................................12v switch voltage (v sw )....................................... ?0.3v to 34v enable pin voltage (v en )................................... ?0.3v to v in fb voltage (v fb )...............................................................6v switch current (i sw ) .........................................................2a ambient storage temperature (t s ) ...........?65c to +150c schottky reverse voltage (v da ).....................................34v eds rating (3) .................................................................. 2kv operating ratings (2) supply voltage (v in ) ........................................ 2.5v to +10v output voltage (v in ) ............................................ v in to v ovp junction temperature (t j ) ........................ ?40c to +125c package thermal resistance 2mm x 2mm mlf ? ( ja ).....................................93c/w thin sot-23-6 ( ja ) ........................................177 c/w electrical characteristics (4) t a = 25c, v in = v en = 3.6v, v out = 10v, i out = 20ma, unless otherwise noted. bold values indicate ?40c< t j < +125c. symbol parameter condition min typ max units v in supply voltage range 2.5 10 v v uvlo under voltage lockout 1.8 2.1 2.4 v i vin quiescent current v fb > 200mv, (not switching) 2.5 5 ma i sd shutdown current v en = 0v (5) 0.1 1 a v fb feedback voltage (5%) 90 95 100 mv i fb feedback input current v fb = 95mv ?450 na line regulation (6) 3v v in 5v 0.5 1 % load regulation (6) 5ma i out 20ma 0.5 % d max maximum duty cycle 85 90 % i sw switch current limit 750 ma v sw switch saturation voltage i sw = 0.5a 450 mv i sw switch leakage current v en = 0v, v sw = 10v 0.01 5 a v en enable threshold turn on turn off 1.5 0.4 v v i en enable pin current v en = 10v 20 40 a f sw oscillator frequency 1.05 1.2 1.35 mhz v d schottky forward drop i d = 150ma 0.8 1 v i rd schottky leakage current v r = 30v 4 a v ovp overvoltage protection mic2289-15 mic2289-24 mic2289-34 13 21 30 14 22.5 32 16 24 34 v v v t j overtemperature threshold shutdown hysteresis 150 10 c c notes : 1. absolute maximum ratings indicate limits beyond wh ich damage to the component may occur. electrical speci cations do not apply when operating the device outside of its operating ratings. the maximum a llowable power dissipation is a f unction of the maximum junctio n temperature, t j(max) , the junction-to-ambient thermal resistance, ja , and the ambient temperature, t a . the maximum allowable power dissipation will result in excessive die temperature, and the regulator will go into thermal shutdown. 2. the device is not guaranteed to function outside its operating rating. 3. devices are esd sensitive. handli ng precautions recommended. human body model. 4. specification for packaged product only. 5. i sd = i vin . 6. guaranteed by design
micrel, inc. mic2289 july 2007 4 m9999-071007 typical characteristics 90 91 92 93 94 95 96 97 98 99 100 024681012 fb voltage (mv) v in (v) feedback voltage vs. input voltage 0 1 2 3 4 5 024681012 shutdown current (a) v in (v) shutdown voltage vs. input voltage 0 1 2 3 4 5 024681012 quiescent current (ma) v in (v) quiescent current vs. input current 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 -40 -20 0 20 40 60 80 100 switching frequency (mhz) temperature (c) switch frequenc y vs. temperature 0 5 10 15 20 25 30 35 40 45 50 -50 0 50 100 ienable (a) temperature (c) en pin bias current vs. temperature i en =4.2v i en =3.6v i en =3.0v i en =10v 0 100 200 300 400 500 600 700 450 550 650 750 850 950 1050 1150 schottky forward current (ma) schottky forward voltage drop (mv) schottky forward voltage drop 0 0.5 1 1.5 2 2.5 30 40 50 60 70 80 90 100 schottky leakage current (a) temperature (c) schottky reverse leakage current v r =25v v r = 10v v r = 16v 300 350 400 450 500 550 -40 0 40 80 120 saturation voltage (mv) temperature (c) saturation voltage vs. temperature i sw = 500ma 600 650 700 750 800 850 900 -40 0 40 80 120 current limit (ma) temperature (c) current limit vs. temperature v in =2.5v 0 100 200 300 400 500 600 0 100 200 300 400 500 saturation voltage (mv) i sw (ma) switch saturation voltag e vs. current v in =2.5v v in =5v
micrel, inc. mic2289 july 2007 5 m9999-071007 functional diagram gnd v ref pwm generator ramp generator 1.2mhz oscillator sw en fb out vin 95mv g m ovp s mic2289 block diagram functional description the mic2289 is a constant frequency, pwm current mode boost regulator. the block diagram is shown above. the mic2289 is composed of an oscillator, slope compensation ramp generator, current ampli er, g m error ampli er, pwm generator, 500ma bipolar output transistor, and schottky recti er diode. the oscillator generates a 1.2mhz clock. the clock?s two functions are to trigger the pwm generator that turns on the output transistor and to reset the slope compensation ramp generator. the current ampli er is used to measure the switch current by amplifying the voltage signal from the internal sense resistor. the output of the current ampli er is summed with the output of the slope compensation ramp generator. this summed current- loop signal is fed to one of the inputs of the pwm generator. the g m error ampli er measures the led current through the external sense resistor and ampli es the error between the detected signal and the 95mv reference voltage. the output of the gm error ampli er provides the voltage-loop signal that is f ed to the other input of the pwm generator. when the current-loop signal exceeds the voltage-loop signal, the pwm generator turns off the bipolar output transistor. the next clock period initiates the next switching cycle, maintaining the constant frequency current-mode pwm control. the led is set by the feedback resistor: fb led r 95mw i = the enable pin shuts down the output switching and disables control circuitry to reduce input current-to- leakage levels. enable pin input current is zero at zero volts.
micrel, inc. mic2289 july 2007 6 m9999-071007 external component selection the mic2289 can be used across a wide rage of applications. the table below shows recommended inductor and output capacitor values for various series- led applications. series leds l manufacturer min c out manufacturer lqh32cn220k21 (murata) 0805zd225kat(avx) 22h nlc453232t-220k(tdk) 2.2f grm40x5r225k10(murata) lqh32cn150k21 (murata) 0805zd105kat(avx) 15h nlc453232t-150k(tdk) 1f grm40x5r105k10(murata) lqh32cn100k21 (murata) 0805zd224kat(avx) 10h nlc453232t-100k(tdk) 0.22f grm40x5r224k10(murata) lqh32cn6r8k21 (murat a) 0805zd225kat(avx) 6.8h nlc453232t-6r8k(tdk) 0.22f grm40x5r225k10(murata) lqh32cn4r7k21 (murat a) 0805zd224kat(avx) 2 4.7h nlc453232t-4r7k(tdk) 0.22f grm40x5r224k10(murata) lqh43mn220k21 (murata) 0805yd225mat(avx) 22h nlc453232t-220k(tdk) 2.2f grm40x5r225k16(murata) lqh43mn 150k21 (murat a) 0805yd105mat(avx) 15h nlc453232t-150k(tdk) 1f grm40x5r105k16(murata) lqh43mn 100k21 (murat a) 0805yd224mat(avx) 10h nlc453232t-100k(tdk) 0.22f grm40x5r224k16(murata) lqh43mn 6r8k21 (murat a) 0805yd224mat(avx) 6.8h nlc453232t-6r8k(tdk) 0.22f grm40x5r224k16(murata) lqh43mn 4r7k21 (murat a) 0805yd274mat(avx) 3 4.7h nlc453232t-4r7k(tdk) 0.27f grm40x5r224k16(murata) lqh43mn220k21 (murata) 0805yd105mat(avx) 22h nlc453232t-220k(tdk) 1f grm40x5r105k25(murata) lqh43mn 150k21 (murat a) 0805yd105mat(avx) 15h nlc453232t-150k(tdk) 1f grm40x5r105k25(murata) lqh43mn 100k21 (murat a) 0805yd274mat(avx) 10h nlc453232t-100k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn 6r8k21 (murat a) 0805yd274mat(avx) 6.8h nlc453232t-6r8k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn 4r7k21 (murat a) 0805yd274mat(avx) 4 4.7h nlc453232t-4r7k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn220k21 (murata) 08053d224mat(avx) 22h nlc453232t-220k(tdk) 0.22f grm40x5r224k25(murata) lqh43mn 150k21 (murata) 08053d224mat(avx) 15h nlc453232t-150k(tdk) 0.22f grm40x5r224k25(murata) lqh43mn 100k21 (murata) 08053d274mat(avx) 10h nlc453232t-100k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn 6r8k21 (murata) 08053d274mat(avx) 6.8h nlc453232t-6r8k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn 4r7k21 (murata) 08053d274mat(avx) 5, 6 4.7h nlc453232t-4r7k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn220k21 (murata) 08053d224mat(avx) 22h nlc453232t-220k(tdk) 0.22f grm40x5r224k25(murata) lqh43mn 150k21 (murata) 08053d224mat(avx) 15h nlc453232t-150k(tdk) 0.22f grm40x5r224k25(murata) lqh43mn 100k21 (murata) 08053d274mat(avx) 10h nlc453232t-100k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn 6r8k21 (murata) 08053d274mat(avx) 6.8h nlc453232t-6r8k(tdk) 0.27f grm40x5r274k25(murata) lqh43mn 4r7k21 (murata) 08053d274mat(avx) 7, 8 4.7h nlc453232t-4r7k(tdk) 0.27f grm40x5r274k25(murata)
micrel, inc. mic2289 july 2007 7 m9999-071007 dimming control there are two techniques for dimming control. one is pwm dimming, and the other is continuous dimming. 1. pwm dimming control is implemented by applying a pwm signal on en pin as shown in figure 1. the mic2289 is turned on and off by the pwm signal. with this method, the leds operate with either zero or full current. the average led current is increased proportionally to the duty-cycle of the pwm signal. this technique has high-ef ciency because the ic and the leds consume no current during the off cycle of the pwm signal. typical frequency should be between 100hz and 10khz. 2. continuous dimming cont rol is implemented by applying a dc control voltage to the fb pin of the mic2289 through a series resistor as shown in figure 2. the led current is decreased proportionally with the amplitude of the control voltage. the led intensity (current) can be dynamically varied applying a dc voltage to the fb pin. the dc voltage can come from a dac signal, or a ltered pwm signal. the advantage of this approach is that a high frequency pwm signal (>10khz) can be used to control led intensity. pwm vin en sw fb out gnd v in figure 1. pwm dimming method vin en sw fb out 5.11k 49.9k gnd dc v in equivalent figure 2. continuous dimming open-circuit protection if the leds are disconnected from the circuit, or in case an led fails open, the sense re sistor will pull the fb pin to ground. this will cause t he mic2289 to switch with a high duty-cycle, resulting in output overvoltage. this may cause the sw pin voltage to exceed its maximum voltage rating, possibly damaging the ic and the external components. to ensure the highest level of protection, the mic2289 has 3 product options in the 2mm 2mm mlf ? -8 with overvoltage protection, ovp. the extra pins of the 2mm 2mm mlf ? -8 package allow a dedicated ovp monitor with options for 15v, 24v, or 34v (see figure 3). the reason for the three ovp levels is to let users choose the suitable level of ovp for their application. for example, a 3-led application would typically see an output voltage of no more than 12v, so a 15v ovp option would offer a suitable level of protection. this allows the user to select the output diode and capacitor with the lowest voltage ratings, therefore smallest size and lowest cost. the ovp will clamp the output vo ltage to within the speci ed limits. vin en gnd sw fb out v in figure 3. ovp circuit start-up and inrush current during start-up, inrush curre nt of approximately double the nominal current ows to set up the inductor current and the voltage on the output capacitor. if the inrush current needs to be limited, a soft-start circuit similar to figure 4 could be implemented. the soft-start capacitor, css, provides over-drive to the fb pin at start-up, resulting in gradual increase of switch duty cycle and limited inrush current. vin en 10k 2200pf sw out fb c ss r gnd v in figure 4. one of soft-start circuit
micrel, inc. mic2289 july 2007 8 m9999-071007 6-series led circuit without external soft-start time (100s/di v.) enable (2v/div) input curren t (200ma/div) output voltage l = 10h c in = 1f c out = 0.22f v in = 3.6v i out = 20ma 6 leds 6-series led circuit with external soft-start time (100s/di v.) enable (2v/div) input curren t (200ma/div) output voltage l = 10h c in = 1f c out = 0.22f v in = 3.6v i out = 20ma 6 leds c ss = 2200pf figure 5. 6-series led circuit without external soft start figure 6. 6-series led circuit with external soft start
micrel, inc. mic2289 july 2007 9 m9999-071007 package information 6-pin thin sot-23 (d6) 8-pin mlf ? (ml)
micrel, inc. mic2289 july 2007 10 m9999-071007 micrel, inc. 2180 fortune drive san jose, ca 95131 usa tel +1 (408) 944-0800 fax +1 (408) 474-1000 web http:/www.micrel.com the information furnished by micrel in this data sheet is belie ved to be accurate and reliable. however, no responsibility is a ssumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authori zed for use as components in life support app liances, devices or systems where malfu nction of a product can reasonably be expected to result in personal injury. life suppo rt devices or systems are devices or systems that (a) are in tended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significan t injury to the user. a purchaser?s use or sale of micrel produc ts for use in life support app liances, devices or systems is a purchaser?s own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2004 micrel, incorporated.
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