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? semiconductor components industries, llc, 2010 march, 2010 ? rev. 4 1 publication order number: cat32/d cat32 cmos white led driver description the cat32 is a dc/dc step up converter that delivers a regulated output current. operation at a constant switching frequency of 1.2 mhz allows the device to be used with very small value external inductor and ceramic capacitors. the cat32 is targeted to drive multiple white light ? emitting diodes (leds) connected in series and pr ovides the necessary regulated current to control the brightness and the co lor purity. an external resistor r set controls the output current level. led currents of up to 40 ma can be supported over a wide range of input supply voltages from 2 v to 7 v, making the device ideal for battery ? powered applications. a high voltage output stage allows up to 4 white leds to be driven in series. series drive provides inherent current matching. led dimming can be done by using a dc voltage, a logic signal, or a pulse width modulation (pwm) signal. the shutdown input pin allows the device to be placed in power ? down mode with ?near zero? quiescent current. in addition to overcurrent limiting protection, the device also includes detection circuitry to ensure protection against open ? circuit load fault conditions. the device is available in a low profile (1 mm max height) 6 ? lead tsot ? 23 package. features ? low quiescent ground current (0.5 ma typical) ? power efficiency over 80% ? compatible pinout with lt1932 ? adjustable output current (up to 40 ma) ? high frequency 1.2 mhz operation ? input voltage operation down to 2.0 v ? low resistance (0.5 ) high voltage power switch ? drives up to 4 white leds in series ? shutdown current less than 1 a ? load fault protection against open ? circuits ? low value external components ? low profile (1 mm) tsot ? 23 6 ? lead package ? these devices are pb ? free, halogen free/bfr free and are rohs compliant applications ? color lcd and keypad backlighting ? cellular phones ? handheld terminals ? digital cameras ? pdas/games ? portable mp3 players http://onsemi.com tsot ? 23 td suffix case 419af pin connections llym marking diagrams device package shipping ordering information cat32tdi ? t3 tsot ? 23 (pb ? free) 3,000/ tape & reel ll = cat32tdi ? t3 vf = cat32tdi ? gt3 y = production year (last digit) m = production month (1 ? 9, a, b, c) (top view) vin rset sw gnd led 1 shdn tsot ? 23 1 mm maximum height ja = 250 c/w (free air) vfym 1 cat32tdi ? gt3 tsot ? 23 (pb ? free) 3,000/ tape & reel
cat32 http://onsemi.com 2 typical application circuit figure 1. li ? ion driver for four high ? brightness white leds 15 ma 4 1.50 k tsot ? 23 pin numbers 6.8 h 2 3 1 6 5 sw vin rset d1 c2 1 f c1 4.7 f vin 2.7 v to 4.2 v pwm dimming control cat32 led gnd l 1 shdn c1: taiyo yuden jmk212bj475 c2: taiyo yuden emk212bj105 d1: zetez zhcs400 l1: sumida clq4d106r8 (panasonic eljea6r8) r set table 1. pin description pin number sot23 pin number tdfn name function 1 8 sw switch pin. this is the drain of the internal power switch. for minimum emi, min- imize the trace area connected to this pin. 2 5 gnd ground pin. connect pin 2 to ground. 3 6 led led (cathode) connection pin. 4 4 rset reset pin. a resistor connected from pin 4 to ground sets the led current. this pin is also used to dim the leds. 5 3 shdn shutdown pin. 6 2 vin input supply pin. this pin should be bypassed with a capacitor to ground. a 4.7 f capacitor mounted close to the pin is recommended. ? 1 power ground power ground
cat32 http://onsemi.com 3 table 2. absolute maximum ratings parameter rating unit v in , led, shdn voltage 8 v sw voltage 20 v rset voltage 1 v storage temperature range ? 65 to +150 c junction temperature 125 c lead soldering temperature (10 secs) 300 c esd rating ? human body model 2000 v stresses exceeding maximum ratings may damage the device. maximum ratings are stress ratings only. functional operation above t he recommended operating conditions is not implied. extended exposure to stresses above the recommended operating conditions may af fect device reliability. table 3. recommended operating conditions parameter range unit v in 2 to 7 v ambient temperature range ? 40 to +85 c inductor l1 6.8 20% typical h input capacitor c1 4.7 20% typical f output capacitor c2 1.0 20% typical f i led with 1 to 4 leds in series 0 to 20 ma note: typical application circuit with external components is shown on page 2. table 4. electrical operating characteristics (over recommended operating conditions unless otherwise specified. t a = 25 c, v in = 2 v and v shdn = 1.2 v.) symbol parameter conditions min typ max unit i q quiescent current v rset = 0.2 v 0.5 0.7 ma i gnd ground current in shutdown v shdn = 0 v 0.05 1 a v led led pin voltage v in < v out , i led = 15 ma 120 180 mv i led led current adjust range 5 40 ma i led programmed led current r set = 562 33 38 45 ma r set = 750 25 30 36 r set = 1.5 k 12.5 15 17.5 r set = 4.53 k 5 i led led pin current temperature coefficient i led = 15 ma ? 0.01 ma/ c v rset rset pin voltage r set = 1.5 k 100 mv shutdown pin logic high level 0.85 v shutdown pin logic low level 0.25 v f sw boost converter frequency 0.8 1.2 1.6 mhz i swl switch current limit 400 550 780 ma r sw switch resistance v in = 2 v, i sw = 100 ma 0.7 1.2 v in = 3 v, i sw = 100 ma 0.5 0.9 switch leakage current switch off, v sw = 5 v 0.01 5 a efficiency components shown on figure 1 83 %
cat32 http://onsemi.com 4 typical characteristics (v in = 3.6 v, t amb = 25 c, c in = 4.7 f, c out = 1 f, l = 6.8 h, unless otherwise specified.) figure 2. quiescent current vs. input voltage figure 3. quiescent current vs. temperature input voltage (v) temperature ( c) 7 6 5 4 3 2 200 300 400 500 600 125 100 75 50 25 0 ? 25 ? 50 200 300 400 500 600 figure 4. switching frequency vs. input voltage figure 5. switching frequency vs. temperature input voltage (v) temperature ( c) 7 6 5 4 3 2 0 0.4 0.8 1.2 1.6 2.0 100 125 75 50 25 0 ? 25 ? 50 0 0.4 0.8 1.2 1.6 2.0 figure 6. led current vs. input voltage figure 7. led current vs. temperature input voltage (v) temperature ( c) 7 6 5 4 3 2 0 5 10 15 20 25 30 35 125 100 75 50 25 0 ? 25 ? 50 0 5 10 15 20 quiescent current ( a) quiescent current ( a) switch frequency (mhz) switch frequency (mhz) led current (ma) led current (ma) vin = 2 v vin = 7 v r set = 750 r set = 1.13 k r set = 1.50 k r set = 2.26 k
cat32 http://onsemi.com 5 typical characteristics (v in = 3.6 v, t amb = 25 c, c in = 4.7 f, c out = 1 f, l = 6.8 h, unless otherwise specified.) figure 8. switch resistance vs. input voltage figure 9. switch resistance vs. temperature input voltage (v) temperature ( c) 6 5 4 3 2 0 0.2 0.4 0.6 0.8 1.0 125 100 75 50 25 0 ? 25 ? 50 0 0.2 0.4 0.6 0.8 1.0 figure 10. led pin voltage vs. led current figure 11. v sw , i l , & v out signal waveforms led current (ma) 40 32 24 16 8 0 0 50 100 150 200 250 300 figure 12. efficiency vs. input voltage figure 13. pwm on shdn pin waveform input voltage (v) 6 5 4 3 2 60 65 70 75 80 85 switch resistance ( ) switch resistance ( ) led pin voltage (mv) efficiency (%) v in = 3 v 4 leds at 15 ma v out = 13 v
cat32 http://onsemi.com 6 operation the cat32 device is a high efficiency, constant frequency, current regulating boost converter. the device includes a switch and an internally compensated loop for the regulation of the led current. operation can be best understood by examining the block diagram. the rset pin is regulated at 100 mv and the current through the external resistor will set the regulated current in the leds (from 5 ma to 40 ma) with a multiplication factor of 225. while maintaining led current regulation, the cat32 automatically adjusts the led pin voltage to be as low as possible. a low led pin voltage ensures high efficiency. current through the internal power switch is continuously monitored cycle ? by ? cycle. if the current limit is exceeded, the switch is immediately turned off, protecting the device, for the remainder of the cycle. pwm dimming operation can be achieved by switching the shdn pin or by pulling the rset pin higher than 0.1 v. block diagram figure 14. cat32 block diagram current sense amp cat32 pwm & logic current control 1.2 mhz oscillator 100 mv gnd rset sw led over voltage protection (22 v) 225x c 1 6 3 4 2 1 5 v in v in shdn c 2 d 1 + ? + ? i led = 225 x i s l 1 r set i s i led
cat32 http://onsemi.com 7 application information inductor selection and efficiency inductor vendors are shown below. contact the manufacturer for detailed technical data and new product information. table 5. inductor manufacturers inductor l ( h) maximum dcr (m ) maximum height (mm) vendor web eljea4r7 4.7 180 2.2 panasonic 714.373.7334 www.panasonic.com eljea6r8 6.8 250 2.2 LQH3C4R7M24, 4.7 260 2.2 murata 770.436.1300 www.murata.com lqh32cn4r7m11 lqh3c100k24, 10 300 2.2 lqh32cn100k11 lb2016b4r7 4.7 250 2.0 taiyo yuden 408.573.4150 www.t ? yuden.com lb2016b100 3.8 350 2.0 cmd4d06 ? 4r7 4.7 216 0.8 sumida 847.956.0666 www.sumida.com cmd4d06 ? 6r8 6.8 296 0.8 clq4d10 ? 4r7 4.7 162 1.2 clq4d10 ? 6r8 6.8 195 1.2 capacitor selection low esr (equivalent series resistance) capacitors should be used at the output to minimize the output ripple voltage. the low esr and small package options available with multilayer ceramic capacitors make them excellent choices. the x5r and x7r capacitor types are preferred because they retain their capacitance over wider voltage and temperature ranges than the y5v or z5u types. a 1.0 f or 2.2 f output capacitor is recommended for most applications. the voltage rating of the output capacitor c2 depends on the number of leds driven in series. a 10 v ceramic capacitor is recommended when driving two leds. a 16 v ceramic capacitor is recommended when driving 3 or 4 leds. table 6. ceramic capacitor manufacturers supplier phone web taiyo yuden 408.573.4150 www.t ? yuden.com murata 814.237.1431 www.murata.com kemet 408.986.0424 www.kemet.com low profile ceramic capacitors with a 1 mm maximum height/thickness are available for designs height requirements. ceramic capacitors also make a good choice for the input capacitor, which should be mounted as close as possible to the cat32. a 2.2 f or 4.7 f input capacitor is recommended. table 6 shows a list of several ceramic capacitor manufacturers. consult the manufacturers for detailed information as new products and package options are introduced regularly. diode selection schottky diodes, with their low forward voltage drop and fast switching speed, are the ideal choice for high ef ficiency applications. table 7 shows several different schottky diodes that work well with the cat32. 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 of f (typically less than one ? third the time), so a 0.4 a or 0.5 a diode will be sufficient for most designs. table 7. schottky diode suppliers part supplier mbr0520 on semiconductor www.onsemi.com 800.282.9855 mbr0530 s mbr0540 zhcs400 zetex led current programming the led current is programmed with a single resistor connected to the rset pin. the rset pin is internally regulated to 100 mv, which sets the current flowing out of this pin, iset, equal to 100 mv/rset. the ca t32 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 is recommended. table 8 shows several typical 1% r set values.
cat32 http://onsemi.com 8 table 8. r set resistor values i led (ma) r set 40 562 30 750 25 909 20 1.13 k 15 1.50 k 10 2.26 k 5 4.53 k for other led current values, use the following equation to choose r set . r set 255 0.1 v i led most white leds are driven at maximum currents of 15 ma to 20 ma. some higher power designs will use two parallel strings of leds for greater light output, resulting in 30 ma to 40 ma (two strings of 15 ma to 20 ma) flowing into the led pin. led dimming with pwm signal pwm brightness control provides the widest dimming range (greater than 20:1). by turning 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. t ypically, a 5 khz to 40 khz pwm signal is used. pwm dimming with the cat32 can be accomplished two different ways. the shdn pin can be driven directly or a resistor can be added to drive the rset pin. if the shdn pin is used, increasing the duty cycle will increase the led brightness. using th is method, the leds can be dimmed and turned off completely using the same control signal. a 0% duty cycle signal will turn off the cat32, reducing the total quiescent current to near zero. if the rset pin is used, increasing the duty cycle will decrease the brightness. using this method, the leds are dimmed using rset and turned off completely using shdn . if the rset pin is used to provide pwm dimming, the approximate value of r pwm should be calculated (where v max is the ?high? value of the pwm signal): r pwm r set v max 0.15 v 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 15 ma or 20 ma. if the led current is less than or more than this value, the emitted light becomes more blue. applications involving color lcds can find the blue tint objectionable. when a pwm control signal is used to drive the shdn pin of the cat32, 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. led brightness varies linearly with the pwm duty cycle. led dimming with a logic signal for applications that need to adjust the led brightness in discrete steps, a logic signal can be used. rmin sets the minimum led current value (when the nmos is off): r min 255 0.1 v i led(min) r incr determines how much led current increases when the external nmos switch is turned on. r incr 255 0.1 v i led(increase) led dimming with a dc voltage r adj 225 v max 0.1 v i led(max) i lead(min) pcb layout guidelines the cat32 is a high ? frequency switching regulator and therefore proper pcb board layout and component placement can minimize noise and radiation and increase efficiency. to maximize efficiency, the cat32 design has fast switch rise and fall times. to prevent radiation and high frequency resonance problems minimize the length and area of all traces connected to the sw pin and use a ground plane under the switching regulator. the switch, schottky output diode and output capacitor signal path should be kept as short as possible. the ground connection for the r set resistor should be tied directly to the gnd pin and not be shared with other components. figure 15. led dimming circuits cat32 5 pwm cat32 rset 4 pwm cat32 rset 4 cat32 rset pwm 10 k 0.1 f 4 cat32 rset logic signal 4 shdn r set r set r pwm r pwm r set r adj v dc r min r incr
cat32 http://onsemi.com 9 typical application circuits (the application diagrams below are shown for the tsot ? 23 packages.) figure 16. two leds with dc level dimming control 2.5 v dc dimming control 15 ma 4 1.50 k 60.40 k 6.8 h 2 3 1 6 5 sw vin rset d1 c2 2.2 f c1 4.7 f vin cat32 led gnd 2.5 v dc dimming control 15 ma 4 1.50 k 60.40 k 6.8 h 2 3 1 6 5 sw vin rset d1 c2 1 f c1 4.7 f vin cat32 led gnd figure 17. three leds with dc level dimming control 15 ma 4 1.50 k 6.8 h 2 3 1 6 5 sw vin rset d1 c2 1 f c1 4.7 f vin pwm dimming control cat32 led gnd figure 18. efficiency ? three leds led current (ma) 20 15 10 5 0 60 65 70 75 80 85 led current (ma) efficiency (%) figure 19. four leds with pwm dimming control figure 20. efficiency ? four leds shdn l 1 r set v in = 4.2 v v in = 3.0 v 20 15 10 5 0 60 65 70 75 80 85 efficiency (%) v in = 4.2 v v in = 3.0 v l 1 shdn r set shdn r set l 1
cat32 http://onsemi.com 10 package dimensions tsot ? 23, 6 lead case 419af ? 01 issue o e1 e a2 a1 e b d c a top view side view end view l1 l l2 notes: (1) all dimensions are in millimeters. angles in degrees. (2) complies with jedec mo-193. symbol min nom max a a1 a2 b c d e e1 e l 0o 8o l1 l2 0.01 0.80 0.30 0.12 0.30 0.05 0.87 0.15 2.90 bsc 2.80 bsc 1.60 bsc 0.95 typ 0.40 0.60 ref 0.25 bsc 1.00 0.10 0.90 0.45 0.20 0.50
cat32 http://onsemi.com 11 example of ordering information (note 3) prefix device # suffix company id cat 32 product number 32 t3 t: tape & reel 3: 3,000 / reel tape & reel (note 5) (optional) td package i i = industrial ( ? 40 c to +85 c) temperature range td: tsot ? 23 ? g g: nipdau lead finish 1. all packages are rohs ? compliant (lead ? free, halogen ? free). 2. the standard lead finish is nipdau. 3. the device used in the above example is a cat32tdi ? gt3 (tsot ? 23, industrial temperature range, nipdau, tape & reel, 3,000 / reel). 4. for additional package and temperature options, please contact your nearest on semiconductor sales office. 5. for information on tape and reel specifications, including part orientation and tape sizes, please refer to our tape and reel packaging specifications brochure, brd8011/d. on semiconductor and are registered trademarks of semiconductor components industries, llc (scillc). scillc reserves the right to mak e changes without further notice to any products herein. scillc makes no warranty, representation or guarantee regarding the suitability of its products for an y particular purpose, nor does scillc assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including wi thout limitation special, consequential or incidental damages. ?typical? parameters which may be provided in scillc data sheets and/or specifications can and do vary in different application s and actual performance may vary over time. all operating parameters, including ?typicals? must be validated for each customer application by customer?s technical experts. scillc does not convey any license under its patent rights nor the rights of others. scillc products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the scillc product could create a sit uation where personal injury or death may occur. should buyer purchase or use scillc products for any such unintended or unauthorized application, buyer shall indemnify and hold scillc and its of ficers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, direct ly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that scillc was negligent regarding the design or manufacture of the part. scillc is an equal opportunity/affirmative action employer. this literature is subject to all applicable copyright laws and is not for resale in any manner. cat32/d publication ordering information n. american technical support : 800 ? 282 ? 9855 toll free usa/canada europe, middle east and africa technical support: phone: 421 33 790 2910 japan customer focus center phone: 81 ? 3 ? 5773 ? 3850 literature fulfillment : literature distribution center for on semiconductor p.o. box 5163, denver, colorado 80217 usa phone : 303 ? 675 ? 2175 or 800 ? 344 ? 3860 toll free usa/canada fax : 303 ? 675 ? 2176 or 800 ? 344 ? 3867 toll free usa/canada email : orderlit@onsemi.com on semiconductor website : www.onsemi.com order literature : http://www.onsemi.com/orderlit for additional information, please contact your local sales representative

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