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1 lt1932 1932f constant-current dc/dc led driver in thinsot the lt ? 1932 is a fixed frequency step-up dc/dc converter designed to operate as a constant-current source. be- cause it directly regulates output current, the lt1932 is ideal for driving light emitting diodes (leds) whose light intensity is proportional to the current passing through them, not the voltage across their terminals. with an input voltage range of 1v to 10v, the device works from a variety of input sources. the lt1932 accurately regulates led current even when the input voltage is higher than the led voltage, greatly simplifying battery- powered designs. a single external resistor sets led current between 5ma and 40ma, which can then be easily adjusted using either a dc voltage or a pulse width modulated (pwm) signal. when the lt1932 is placed in shutdown, the leds are disconnected from the output, ensuring a quiescent current of under 1 m a for the entire circuit. the devices 1.2mhz switching frequency permits the use of tiny, low profile chip inductors and capacitors to minimize footprint and cost in space-conscious portable applications. n up to 80% efficiency n inherently matched led current n adjustable control of led current n drives five white leds from 2v n drives six white leds from 2.7v n drives eight white leds from 3v n disconnects leds in shutdown n 1.2mhz fixed frequency switching n uses tiny ceramic capacitors n uses tiny 1mm-tall inductors n regulates current even when v in > v out n operates with v in as low as 1v n low profile (1mm) thinsot tm package n cellular telephones n handheld computers n digital cameras n portable mp3 players n pagers li-ion driver for four white leds efficiency , ltc and lt are registered trademarks of linear technology corporation. v in sw d1 15ma 1932 ta01 l1 6.8 h v in 2.7v to 4.2v lt1932 shdn c1: taiyo yuden jmk212bj475 c2: taiyo yuden emk212bj105 d1:zetex zhcs400 l1: sumida clq4d106r8 or panasonic eljea6r8 61 4 r set 1.50k pwm dimming control c1 4.7 f c2 1 f 2 3 5 led r set gnd led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta02 v in = 4.2v v in = 2.7v thinsot is a trademark of linear technology corporation. features descriptio u applicatio s u typical applicatio u
2 lt1932 1932f parameter conditions min typ max units minimum input voltage 1v quiescent current v rset = 0.2v 1.2 1.6 ma v shdn = 0v 0.1 1.0 m a r set pin voltage r set = 1.50k 100 mv led pin voltage r set = 1.50k, v in < v out (figure 1) 120 180 mv led pin current r set = 562 w , v in = 1.5v 33 38 45 ma r set = 750 w , v in = 1.2v 25 30 36 ma r set = 1.50k, v in = 1.2v 12.5 15 17.5 ma r set = 4.53k, v in = 1.2v 5 ma led pin current temperature coefficient i led = 15ma C 0.02 ma/ c switching frequency v in = 1v 0.8 1.2 1.6 mhz maximum switch duty cycle l 90 95 % switch current limit 400 550 780 ma switch v cesat i sw = 300ma 150 200 mv shdn pin current v shdn = 0v 0 0.1 m a v shdn = 2v 15 30 m a start-up threshold (shdn pin) 0.85 v shutdown threshold (shdn pin) 0.25 v switch leakage current switch off, v sw = 5v 0.01 5 m a (note 1) v in voltage ............................................................. 10v shdn voltage ......................................................... 10v sw voltage ............................................................. 36v led voltage ............................................................. 36v r set voltage ............................................................. 1v junction temperature .......................................... 125 c operating temperature range (note 2) .. C 40 c to 85 c storage temperature range ................. C 65 c to 150 c lead temperature (soldering, 10 sec).................. 300 c order part number lt1932es6 t jmax = 125 c, q ja = 250 c/ w the l denotes specifications that apply over the full operating temperature range, otherwise specifications are at t a = 25 c. v in = 1.2v, v shdn = 1.2v, unless otherwise noted. absolute axi u rati gs w ww u package/order i for atio uu w electrical characteristics s6 part marking ltst sw 1 gnd 2 led 3 6 v in 5 shdn 4 r set top view s6 package 6-lead plastic sot-23 note 1: absolute maximum ratings are those values beyond which the life of a device may be impaired. note 2: the lt1932e is guaranteed to meet specifications from 0 c to 70 c. specifications over the C 40 c to 85 c operating temperature range are assured by design, characterization and correlation with statistical process controls. consult ltc marketing for parts specified with wider operating temperature ranges.
3 lt1932 1932f typical perfor a ce characteristics uw switch saturation voltage (v cesat ) switch current (ma) 0 switch saturation voltage (mv) 150 200 250 300 500 1932 g01 100 50 0 100 200 400 300 350 400 600 t j = 125 c t j = 50 c t j = 25 c temperature ( c) ?0 400 500 700 25 75 1932 g02 300 200 ?5 0 50 100 125 100 0 600 peak current (ma) v in = 1.2v v in = 10v temperature ( c) ?0 0 switching frequency (mhz) 0.2 0.6 0.8 1.0 2.0 1.4 0 50 75 1932 g03 0.4 1.6 1.8 1.2 ?5 25 100 125 v in = 1.2v v in = 10v switch current limit switching frequency led pin voltage led current led current (ma) 0 led pin voltage (mv) 150 200 250 15 25 1932 g04 100 50 0 510 20 300 350 400 40 30 35 t j = 125 c t j = 25 c t j = 50 c temperature ( c) ?0 led current (ma) 35 25 1932 g05 20 10 ?5 0 50 5 0 40 45 50 30 25 15 75 100 125 r set = 750 r set = 562 r set = 1.50k r set = 4.53k quiescent current shdn pin current led current input voltage (v) 0 led current (ma) 35 6 1932 g06 20 10 24 5 0 40 45 50 30 25 15 810 r set = 750 r set = 562 r set = 1.50k r set = 4.53k temperature ( c) ?0 quiescent current (ma) 1.75 25 1932 g07 1.00 0.50 ?5 0 50 0.25 0 2.00 1.50 1.25 0.75 75 100 125 v in = 1.2v v in = 10v shdn pin voltage (v) 0 shdn pin current 30 40 50 8 1932 g08 20 10 25 35 45 15 5 0 2 4 6 10 t j = 125 c t j = 25 c t j = 50 c switching waveforms v sw 10v/div i l1 200ma/div v out 20mv/div ac coupled i led 10ma/div v in = 3v 0.5 m s/div 1093 g09 4 white leds i led = 15ma circuit on first page of this data sheet
4 lt1932 1932f block diagra w + 1 3 s 5 1.2mhz oscillator driver s q r + a2 + a1 0.04 + + q1 q2 led sw d1 6 v in l1 5 shdn c1 c2 v out v in driver led current reference i led 4 r set 1932 f01 r set i set 2 gnd figure 1. lt1932 block diagram operatio u the lt1932 uses a constant frequency, current mode control scheme to regulate the output current, i led . operation can be best understood by referring to the block diagram in figure 1. at the start of each oscillator cycle, the sr latch is set, turning on power switch q1. the signal at the noninverting input of the pwm comparator a2 is proportional to the switch current, summed to- gether with a portion of the oscillator ramp. when this signal reaches the level set by the output of error amplifier a1, comparator a2 resets the latch and turns off the power switch. in this manner, a1 sets the correct peak current level to keep the led current in regulation. if a1s output increases, more current is delivered to the output; if it decreases, less current is delivered. a1 senses the led current in switch q2 and compares it to the current reference, which is programmed using resistor r set . the r set pin is regulated to 100mv and the output current, i led , is regulated to 225 ? i set . pulling the r set pin higher than 100mv will pull down the output of a1, turning off power switch q1 and led switch q2. uu u pi fu ctio s sw (pin 1): switch pin. this is the collector of the internal npn power switch. minimize the metal trace area con- nected to this pin to minimize emi. gnd (pin 2): ground pin. tie this pin directly to local ground plane. led (pin 3): led pin. this is the collector of the internal npn led switch. connect the cathode of the bottom led to this pin. r set (pin 4): a resistor between this pin and ground programs the led current (that flows into the led pin). this pin is also used to provide led dimming. shdn (pin 5): shutdown pin. tie this pin higher than 0.85v to turn on the lt1932; tie below 0.25v to turn it off. v in (pin 6): input supply pin. bypass this pin with a capacitor to ground as close to the device as possible.
5 lt1932 1932f applicatio s i for atio wu uu inductor selection several inductors that work well with the lt1932 are listed in table 1. many different sizes and shapes are available. consult each manufacturer for more detailed information and for their entire selection of related parts. as core losses at 1.2mhz are much lower for ferrite cores that for the cheaper powdered-iron ones, ferrite core inductors should be used to obtain the best efficiency. choose an inductor that can handle at least 0.5a and ensure that the inductor has a low dcr (copper wire resistance) to mini- mize i 2 r power losses. a 4.7 m h or 6.8 m h inductor will be a good choice for most lt1932 designs. table 1. recommended inductors max max l dcr height part ( m h) (m w ) (mm) vendor eljea4r7 4.7 180 2.2 panasonic eljea6r8 6.8 250 2.2 (714) 373-7334 www.panasonic.com lqh3c4r7m24 4.7 260 2.2 murata lqh3c100m24 10 300 2.2 (814) 237-1431 www.murata.com lb2016b4r7 4.7 250 1.6 taiyo yuden lb2016b100 6.8 350 1.6 (408) 573-4150 www.t-yuden.com cmd4d06-4r7 4.7 216 0.8 sumida cmd4d06-6r8 6.8 296 0.8 (847) 956-0666 clq4d10-4r7 4.7 162 1.2 www.sumida.com clq4d10-6r8 6.8 195 1.2 inductor efficiency considerations many applications have thickness requirements that re- strict component heights to 1mm or 2mm. there are 2mm tall inductors currently available that provide a low dcr and low core losses that help provide good overall effi- ciency. inductors with a height of 1mm (and less) are becoming more common, and a few companies have introduced chip inductors that are not only thin, but have a very small footprint as well. while these smaller induc- tors will be a necessity in some designs, their smaller size gives higher dcr and core losses, resulting in lower efficiencies. figure 2 shows efficiency for the typical application circuit on the front page of this data sheet, with several different inductors. the larger devices improve efficiency by up to 12% over the smaller, thinner ones. keep this in mind when choosing an inductor. the value of inductance also plays an important role in the overall system efficiency. while a 1 m h inductor will have a lower dcr and a higher current rating than the 6.8 m h version of the same part, lower inductance will result in higher peak currents in the switch, inductor and diode. efficiency will suffer if inductance is too small. figure 3 shows the efficiency of the typical application on the front page of this data sheet, with several different values of the same type of inductor (panasonic eljea). the smaller values give an efficiency 3% to 5% lower than the 6.8 m h value. figure 2. efficiency for several different inductor types figure 3. efficiency for several different inductor values led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 f02 v in = 3.6v 4 white leds all are 10 h inductors taiyo yuden lb2016b6r8 taiyo yuden lb2012b6r8 sumida cmd4d06-6r8 panasonic eljea6r8 sumida clq4d10-6r8 led current (ma) 0 55 efficiency (%) 60 65 70 75 2.2 h 80 85 5101520 1932 f03 v in = 3.6v 4 white leds panasonic eljea inductors 6.8 h 22 h 4.7 h
6 lt1932 1932f applicatio s i for atio wu uu capacitor selection low esr (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. because they have an extremely low esr and are available in very small packages, multilayer ceramic ca- pacitors are an excellent choice. x5r and x7r type capacitors are preferred because they retain their capaci- tance over wider voltage and temperature ranges than other types such as y5v or z5u. a 1 m f or 2.2 m f output capacitor is sufficient for most applications. always use a capacitor with a sufficient voltage rating. ceramic capaci- tors do not need to be derated (do not buy a capacitor with a rating twice what your application needs). a 16v ce- ramic capacitor is good to more than 16v, unlike a 16v tantalum, which may be good to only 8v when used in certain applications. low profile ceramic capacitors with a 1mm maximum thickness are available for designs having strict height requirements. ceramic capacitors also make a good choice for the input decoupling capacitor, which should be placed as close as possible to the lt1932. a 2.2 m f or 4.7 m f input capacitor is sufficient for most applications. table 2 shows a list of several ceramic capacitor manufacturers. consult the manufacturers for detailed information on their entire selection of ceramic parts. table 2. recommended ceramic capacitor manufacturers vendor phone url taiyo yuden (408) 573-4150 www.t-yuden.com murata (814) 237-1431 www.murata.com kemet (408) 986-0424 www.kemet.com diode selection schottky diodes, with their low forward voltage drop and fast switching speed, are the ideal choice for lt1932 applications. table 3 shows several different schottky diodes that work well with the lt1932. make sure that the diode has a voltage rating greater than the output voltage. the diode conducts current only when the power switch is turned off (typically less than one-third the time), so a 0.4a or 0.5a diode will be sufficient for most designs. table 3. recommended schottky diodes part vendor mbr0520 on semiconductor mbr0530 (800) 282-9855 mbr0540 www.onsemi.com zhcs400 zetex zhcs500 (631) 543-7100 www.zetex.com programming led current the led current is programmed with a single resistor connected to the r set pin (see figure 1). the r set pin is internally regulated to 100mv, which sets the current flowing out of this pin, i set , equal to 100mv/r set . the lt1932 regulates the current into the led pin, i led , to 225 times the value of i set . for the best accuracy, a 1% (or better) resistor value should be used. table 4 shows several typical 1% r set values. for other led current values, use the following equation to choose r set . r v i set led = ? ? ? ? 225 01 . table 4. r set resistor values i led (ma) r set value 40 562 w 30 750 w 20 1.13k 15 1.50k 10 2.26k 5 4.53k most white leds are driven at maximum currents of 15ma to 20ma. some higher power designs will use two parallel strings of leds for greater light output, resulting in 30ma to 40ma (two strings of 15ma to 20ma) flowing into the led pin.
7 lt1932 1932f open-circuit protection for applications where the string of leds can be discon- nected or could potentially become an open circuit, a zener diode can be added across the leds to protect the lt1932 (see figure 4). if the device is turned on without the leds present, no current feedback signal is provided to the led pin. the lt1932 will then switch at its maximum duty cycle, generating an output voltage 10 to 15 times greater than the input voltage. without the zener, the sw pin could see more than 36v and exceed its maximum rating. the zener voltage should be larger than the maximum forward voltage of the led string. if the r set pin is used, increasing the duty cycle will decrease the brightness. using this method, the leds are dimmed using r set and turned off completely using shdn. if the r set pin is used to provide pwm dimming, the approximate value of r pwm should be (where v max is the high value of the pwm signal): rr v v pwm set max = ? ? ? ? . 015 1 in addition to providing the widest dimming range, pwm brightness control also ensures the purest white led color over the entire dimming range. the true color of a white led changes with operating current, and is the purest white at a specific forward current, usually 15ma or 20ma. if the led current is less than or more than this value, the emitted light becomes more blue. for color lcds, this often results in a noticeable and undesirable blue tint to the display. when a pwm control signal is used to drive the shdn pin of the lt1932 (see figure 6), the leds are turned off and on at the pwm frequency. the current through them alternates between full current and zero current, so the average current changes with duty cycle. this ensures that when the leds are on, they can be driven at the appropriate current to give the purest white light. figure 5 shows the led current when a 5khz pwm dimming control signal is used with the lt1932. the led current waveform cleanly tracks the pwm control signal with no delays, so the led brightness varies linearly with the pwm duty cycle. v in sw d1 15ma 1932 f04 l1 6.8 h v in lt1932 shdn 61 4 r set 1.50k c1 4.7 f c2 1 f 24v 2 3 5 led r set gnd figure 4. led driver with open-circuit protection dimming using a pwm signal pwm brightness control provides the widest dimming range (greater than 20:1) by pulsing the leds on and off using the control signal. the leds operate at either zero or full current, but their average current changes with the pwm signal duty cycle. typically, a 5khz to 40khz pwm signal is used. pwm dimming with the lt1932 can be accomplished two different ways (see figure 6). the shdn pin can be driven directly or a resistor can be added to drive the r set pin. if the shdn pin is used, increasing the duty cycle will increase the led brightness. using this method, the leds can be dimmed and turned off completely using the same control signal. a 0% duty cycle signal will turn off the lt1932, reducing the total quiescent current to zero. v pwm 2v/div i led 10ma/div 50 m s/div 1932 f05 figure 5. pwm dimming using the shdn pin applicatio s i for atio wu uu
8 lt1932 1932f dimming using a filtered pwm signal while the direct pwm method provides the widest dim- ming range and the purest white light output, it causes the lt1932 to enter into burst mode ? operation. this opera- tion may be undesirable for some systems, as it may reflect some noise to the input source at the pwm fre- quency. the solution is to filter the control signal by adding a 10k resistor and a 0.1 m f capacitor as shown in figure 6, converting the pwm to a dc level before it reaches the r set pin. the 10k resistor minimizes the capacitance seen by the r set pin. dimming using a logic signal for applications that need to adjust the led brightness in discrete steps, a logic signal can be used as shown in figure 6. r min sets the minimum led current value (when the nmos is off): r v i min led min = ? ? ? ? 225 01 . () r incr sets how much the led current is increased when the nmos is turned on: r v i incr led increase = ? ? ? ? 225 01 . () dimming using a dc voltage for some applications, the preferred method of brightness control uses a variable dc voltage to adjust the led current. as the dc voltage is increased, current flows through r adj into r set , reducing the current flowing out applicatio s i for atio wu uu figure 6. five methods of led dimming of the r set pin, thus reducing the led current. choose the r adj value as shown below where v max is the maximum dc control voltage, i led(max) is the current programmed by r set , and i led(min) is the minimum value of i led (when the dc control voltage is at v max ). r vv ii adj max led max led min = ? ? ? ? 225 01 . () () regulating led current when v in > v out the lt1932 contains special circuitry that enables it to regulate the led current even when the input voltage is higher than the output voltage. when v in is less than v out , the internal npn led switch (transistor q2 in figure 1) is saturated to provide a lower power loss. when v in is greater than v out , the npn led switch comes out of saturation to keep the led current in regulation. soft-start/controlling inrush current for many applications, it is necessary to minimize the inrush current at start-up. when first turned on and the led current is zero, the lt1932 will initially command the maximum switch current of 500ma to 600ma, which may give an inrush current too high for some applications. a soft-start circuit (figure 7) can be added to significantly reduce the start-up current spike. figure 8 shows that without soft-start the input current reaches almost 600ma. figure 9 shows that when the soft-start circuit is added, the input current has only a brief 300ma spike, and on average does not exceed 100ma. lt1932 r set v dc r set 4 1932 f06 r adj lt1932 r set pwm lt1932 pwm filtered pwm dc voltage logic r set pwm r set 4 r pwm lt1932 pwm shdn pwm 5 r set 0.1 f 4 10k r pwm lt1932 r set r min logic signal 4 r incr burst mode is a registered trademark of linear technology corporation.
9 lt1932 1932f applicatio s i for atio wu uu figure 10. recommended component placement board layout considerations as with all switching regulators, careful attention must be paid to the pcb board layout and component placement. to maximize efficiency, switch rise and fall times are made as short as possible. to prevent radiation and high fre- quency resonance problems, proper layout of the high frequency switching path is essential. minimize the length and area of all traces connected to the sw pin and always use a ground plane under the switching regulator to minimize interplane coupling. the signal path including the switch, output diode d1 and output capacitor c2, contains nanosecond rise and fall times and should be kept as short as possible. in addition, the ground connec- tion for the r set resistor should be tied directly to the gnd pin and not be shared with any other component, ensuring a clean, noise-free connection. recommended compo- nent placement is shown in figure 10. v in sw d1 soft-start circuit 1932 f07 l1 6.8 h v in i in v out lt1932 shdn 61 4 r set 1.50k c1 4.7 f c2 1 f 2 3 5 led q1 2n3904 r set gnd c3 0.047 f r1 1.5k figure 7. soft-start circuit for the lt1932 v out 5v/div i in 200ma/div 100 m s/div 1932 f08 figure 8. input current at start-up without soft-start v out 5v/div i in 200ma/div 100 m s/div 1932 f09 figure 9. input current at start-up with soft-start c1 l1 d1 gnd c2 r set 1932 f10 1 2 3 6 5 4 dimming control shdn v in
10 lt1932 1932f v in sw d1 15ma 1932 ta03a l1 4.7 h v in 1v to 1.5v lt1932 shdn c1, c2: taiyo yuden jmk212bj475 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 61 4 r set 1.50k 2.5v pwm dimming control c1 4.7 f c2 4.7 f 24.9k 2 3 5 led r set gnd single cell driver for one white led v in sw d1 15ma 1932 ta04a l1 4.7 h v in 1v to 1.5v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden lmk212bj225 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 61 4 r set 1.50k 2.5v pwm dimming control c1 4.7 f c2 2.2 f 24.9k 2 3 5 led r set gnd single cell driver for two white leds efficiency efficiency led current (ma) 0 50 efficiency (%) 55 60 65 70 75 80 51015 2.5 7.5 12.5 1932 ta03b v in = 1.5v v in = 1.1v led current (ma) 0 55 50 efficiency (%) 60 65 70 75 80 51015 2.5 7.5 12.5 1932 ta04b v in = 1.5v v in = 1.1v typical applicatio s u
11 lt1932 1932f typical applicatio s u v in sw d1 15ma 1932 ta06a l1 4.7 h v in 1.8v to 3v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden emk316bj225 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 61 4 r set 1.50k 2.5v dc dimming control c1 4.7 f c2 2.2 f 60.4k 2 3 5 led r set gnd 2-cell driver for three white leds efficiency led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta06b v in = 3v v in = 1.8v 2-cell driver for two white leds v in sw d1 15ma 1932 ta15a l1 4.7 h v in 1.8v to 3v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden lmk212bj225 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 61 4 r set 1.50k 2.5v dc dimming control c1 4.7 f c2 2.2 f 60.4k 2 3 5 led r set gnd led current (ma) 0 efficiency (%) 55 60 65 70 75 80 85 10 20 515 1932 ta15b v in = 3v v in = 1.8v efficiency
12 lt1932 1932f 2-cell driver for five white leds v in sw d1 15ma 1932 ta05a l1 4.7 h v in 2v to 3v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden tmk316bj105 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 61 4 r set 1.50k pwm dimming control c1 4.7 f c2 1 f 2 3 5 led r set gnd efficiency v in sw d1 15ma 1932 ta07a l1 4.7 h v in 1.8v to 3v lt1932 shdn 61 4 r set 1.50k pwm dimming control c1 4.7 f c2 1 f 2 3 5 led r set gnd c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden emk212bj105 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 2-cell driver for four white leds efficiency led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta05b v in = 3v v in = 2v led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta07b v in = 3v v in = 1.8v typical applicatio s u
13 lt1932 1932f typical applicatio s u li-ion driver for two white leds efficiency li-ion driver for three white leds efficiency v in sw d1 15ma 1932 ta08a l1 6.8 h v in 2.7v to 4.2v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden lmk212bj225 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: panasonic eljea6r8 (714) 373-7334 61 4 r set 1.50k 3.3v pwm dimming control c1 4.7 f c2 2.2 f 31.6k 2 3 5 led r set gnd v in sw d1 15ma 1932 ta09a l1 6.8 h v in 2.7v to 4.2v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden emk316bj225 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: panasonic eljea6r8 (714) 373-7334 61 4 r set 1.50k 3.3v pwm dimming control c1 4.7 f c2 2.2 f 31.6k 2 3 5 led r set gnd led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta08b v in = 4.2v v in = 2.7v led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta09b v in = 4.2v v in = 2.7v
14 lt1932 1932f typical applicatio s u li-ion driver for four white leds efficiency v in sw d1 15ma 1932 ta10a l1 6.8 h v in 2.7v to 4.2v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden emk212bj105 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: panasonic eljea6r8 (714) 373-7334 61 4 r set 1.50k pwm dimming control c1 4.7 f c2 1 f 2 3 5 led r set gnd led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta10b v in = 4.2v v in = 2.7v li-ion driver for five white leds efficiency v in sw d1 15ma 1932 ta11a l1 4.7 h v in 2.7v to 4.2v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden tmk316bj105 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 61 4 r set 1.50k pwm dimming control c1 4.7 f c2 1 f 2 3 5 led r set gnd led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta11b v in = 4.2v v in = 2.7v
15 lt1932 1932f typical applicatio s u li-ion driver for eight white leds efficiency v in sw d1 1932 ta13a l1 4.7 h v in 3v to 4.2v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden gmk316bj105 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 61 4 r set 1.50k 3.3v dc dimming control c1 4.7 f c2 1 f 80.6k 2 3 5 led r set gnd 15ma led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta13b v in = 4.2v v in = 3v u package descriptio s6 package 6-lead plastic sot-23 (ltc dwg # 05-08-1634) (ltc dwg # 05-08-1636) l datum ? .09 ?.20 (.004 ?.008) (note 2)
16 lt1932 1932f ? linear technology corporation 2001 lt/tp 1201 2k ? printed in usa linear technology corporation 1630 mccarthy blvd., milpitas, ca 95035-7417 (408) 432-1900 l fax: (408) 434-0507 l www.linear.com related parts part number description comments lt1615 micropower dc/dc converter in 5-lead thinsot 20v at 12ma from 2.5v input, thinsot package lt1617 micropower inverting dc/dc converter in 5-lead thinsot C15v at 12ma from 2.5v input, thinsot package lt1618 constant-current/constant-voltage dc/dc converter drives 20 white leds from li-ion, ms10 package ltc1682 doubler charge pump with low noise linear regulator 3.3v and 5v outputs with 60 m v rms noise, up to 80ma output lt1930 1.4mhz switching regulator in 5-lead thinsot 5v at 480ma from 3.3v input, thinsot package lt1931 inverting 1.2mhz switching regulator in 5-lead thinsot C 5v at 350ma from 5v input, thinsot package ltc3200 low noise regulated charge pump 5v output with up to 100ma output ltc3201 ultralow noise, charge pump 100ma, integrated lp filter, msop8 ltc3202 high efficiency, fractional charge pump 125ma, integrated 2-bit dac u typical applicatio li-ion driver for ten white leds efficiency v in sw d1 30ma 1932 ta16a l1 10 h v in 2.7v to 4.2v lt1932 shdn c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden tmk325bj475 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c100m24 (814) 237-1431 61 4 r set 750 c1 4.7 f c2 4.7 f 2 3 100 5 led r set gnd 100 total led current (ma) 0 50 efficiency (%) 55 60 65 70 75 80 10 20 30 51525 1932 ta16b v in = 4.2v v in = 2.7v efficiency li-ion driver for six white leds v in sw d1 15ma 1932 ta12a l1 4.7 h v in 2.7v to 4.2v lt1932 shdn 61 4 r set 1.50k 3.3v dc dimming control c1 4.7 f c2 1 f 80.6k 2 3 5 led r set gnd c1: taiyo yuden jmk212bj475 (408) 573-4150 c2: taiyo yuden tmk316bj105 (408) 573-4150 d1: zetex zhcs400 (631) 543-7100 l1: murata lqh3c4r7m24 (814) 237-1431 led current (ma) 0 55 efficiency (%) 60 65 70 75 80 85 5101520 1932 ta12b v in = 4.2v v in = 2.7v

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