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AP5725 white led step-up converter AP5725 rev. 1 1 of 16 june 2009 www.diodes.com ? diodes incorporated ? inherently matched led current ? high efficiency: 84% typical ? fast 1.2mhz switching frequency ? current limit and uvlo protections ? internal thermal shutdown ? internal over voltage protection ? integrated soft-start function ? sot26 and dfn2020c-6: available in ?green? molding compound (no br, sb) ? lead free finish/rohs compliant (note 1) the AP5725 is a step-up dc/dc converter specifically designed to drive white leds with a constant current. the device can drive 2~6 leds in series from a li-ion cell. series connection of the leds provides identical led currents resulting in uniform brightness and eliminates the need for ballast resistors. the AP5725 switches at 1.2mhz that allows the use of tiny external components. a low 0.25v feedback voltage minimizes power loss in the current setting resistor for better efficiency. ? cellular phones ? pdas, hand held computers ? digital cameras ? mp3 players ? gps receivers typical applicat ion circuit v in sw en gnd fb AP5725 c out 1uf r set 12 l1 22uh d1 v in c in 1uf ovp 2~6 leds pwm dimming offon figure 1. typical application circuit features general description applications
AP5725 white led step-up converter AP5725 rev. 1 2 of 16 june 2009 www.diodes.com ? diodes incorporated package ap 5725 xxx g - 7 packing 7 : tape & reel green g : green fdc : dfn2020c-6 w : sot26 device package code packaging (note 2) 13? tape and reel quantity part number suffix AP5725wg-7 w sot26 3000/tape & reel -7 AP5725fdcg-7 fdc dfn2020c-6 3000/tape & reel -7 notes: 1. eu directive 2002/95/ec (rohs). all applicable rohs exemptions applied. please visit our website at http://www.diodes.com/products/lead_free.html 2. pad layout as shown on diodes inc. suggested pad layout document ap02001, which can be found on our website at http://www.diodes.com/datasheets/ap02001.pdf. (1) sot26 (2) dfn2020c-6 1 2 3 7 4 6 ovp fb 5 en sw ( top view ) v in gnd sw v in ovp 1 2 3 6 5 4 gnd fb en ( top view ) pin name description sw switch pin. connect inductor/diode here. minimize trace area at this pin to reduce emi. gnd gnd pin. fb feedback pin. reference voltage is 0.25v. connect cathode of lowest led and resister here. calculate resistor value according to the formula: r set = 0.25v / iled en converter on/off control input. a high input at en turn on the converter, and a low input turns it off. when not used, connect en to the input source for automatic startup. the en pin cannot be left floating. ovp output volta g e detect pin for over volta g e protection. v in input supply pin. must be locally bypassed with 1 f or 2.2 f to reduce input noise. ordering information pin assignments pin descriptions
AP5725 white led step-up converter AP5725 rev. 1 3 of 16 june 2009 www.diodes.com ? diodes incorporated block diagram 1.2mhz oscillator ramp generator - + - + - + v ref 0.25v v in 3 fb rc cc comparator a2 control logic a1 1 driver sw q1 2 gnd 4 en enable 6 otp 5 ovp absolute maxi mum ratings symbol parameter rating unit v in vin pin voltage -0.3~7 v v sw sw voltage -0.3~34 v v ovp ovp pin voltage -0.3~35 v v fb feedback pin voltage -0.3~7 v en en -0.3~7 v t j(max) maximum junction temperature 150 o c t lead lead temperature 300 o c t st storage temperature range -65 to +150 o c caution: the absolute maximum ratings are rated values exceeding which the product could suffer physical damage. these values m ust therefore not be exceeded under any condition.
AP5725 white led step-up converter AP5725 rev. 1 4 of 16 june 2009 www.diodes.com ? diodes incorporated recommended oper ating conditions symbol parameter min max unit v in input voltage 2.7 5.5 v t j operating junction temperature -40 125 o c t a operating ambient temperature -40 85 o c electrical characteristics (v in =3.6v, t a =25 o c, unless otherwise specified.) symbol parameter conditions min typ. max unit system supply input v in operating input voltage 2.7 - 5.5 v uvlo under voltage lockout - 2.2 2.4 v under voltage lockout hysteretic - 85 - mv i q quiescent current fb=0.35v, no switching - 500 - a i sd shutdown current v en < 0.4v - 0.1 1 a oscillator f osc operation frequency 1 1.2 1.4 mhz dmax maximum duty cycle 86 90 - % reference voltage v fb feedback voltage 0.225 0.25 0.275 v i fb fb pin bias current 10 45 100 na mosfet rds(on) on resistance of mosfet 0.5 0.75 1.0 ? i ocp switching current limit normal operation - 750 - ma control and protection en voltage high on 1.5 - - v en voltage low off - - 0.4 v i en en pin pull low current - 4 6 a ovp ovp threshold 26 30 34 v ja thermal resistance junction-to-ambient sot26 (note 3) 162 o c/w dfn2020c-6 (note 3) 200 o c/w jc thermal resistance junction-to-case sot26 (note 3) 36 o c/w dfn2020c-6 ( note 3 ) 30 o c/w notes: 3. test condition for sot26 and dfn2020c-6: device mounted on fr-4 substrate, single-layer pc board, 2oz copper, with minimum recommended pad layout
AP5725 white led step-up converter AP5725 rev. 1 5 of 16 june 2009 www.diodes.com ? diodes incorporated typical performance characteristics (6 leds ; v in = 3.6v ; i out = 25ma) v in vs. shutdown current 0 0.2 0.4 0.6 0.8 1 2.5 3 3.5 4 4.5 5 5.5 v in (v) shutdown current(ua) v in vs. quiescent current 0 100 200 300 400 500 600 700 2.5 3 3.5 4 4.5 5 5.5 v in (v) quiescent current(ua) v in vs. frequency 1 1.05 1.1 1.15 1.2 1.25 2.5 3 3.5 4 4.5 5 5.5 v in (v) frequency(mhz) v in vs. max duty 80 85 90 95 100 2.5 3 3.5 4 4.5 5 5.5 v in (v) max duty(%) v in vs. feedback voltage 0.2 0.22 0.24 0.26 0.28 0.3 2.533.544.555.5 v in (v) feedback voltage(v) i out vs. feedback voltage 0.2 0.22 0.24 0.26 0.28 0.3 0 1020304050 i out (ma) feedback voltage(v)
AP5725 white led step-up converter AP5725 rev. 1 6 of 16 june 2009 www.diodes.com ? diodes incorporated typical performance characteristics (continued) v in vs. ovp threshold 25 27 29 31 33 35 2.5 3 3.5 4 4.5 5 5.5 v in (v) ovp threshold(v) temperature vs. shutdown current 0 0.2 0.4 0.6 0.8 1 -50 -25 0 25 50 75 100 125 shutdown current(ua) temperature ( ) temperature vs. ovp threshold 10 15 20 25 30 35 -50 -25 0 25 50 75 100 125 temperature ( ) ovp threshold(v) temperature vs. frequency 0.2 0.5 0.8 1.1 1.4 1.7 -50 -25 0 25 50 75 100 125 temperature ( ) frequency (mhz) v in = 3.6v v in = 4.2v temperature vs. feedback voltage 0.23 0.24 0.25 0.26 0.27 0.28 -50 -25 0 25 50 75 100 125 temperature( ) feedback voltage(v) v in = 3.6v v in = 4.2v
AP5725 white led step-up converter AP5725 rev. 1 7 of 16 june 2009 www.diodes.com ? diodes incorporated typical performance characteristics (continued) i out vs. efficiency 60 65 70 75 80 85 90 0 5 10 15 20 25 30 i out (ma) efficiency(%) 4 leds ; l = 22uh v in = 4.2v v in = 3.6v i out vs. efficiency 60 65 70 75 80 85 90 0 5 10 15 20 25 30 i out (ma) efficiency(%) 6 leds ; l = 22uh v in = 3.6v v in = 4.2v v in vs. efficiency 40 50 60 70 80 90 100 2.533.544.55 v in (v) efficiency(%) 3 leds 6 leds 4 leds
AP5725 white led step-up converter AP5725 rev. 1 8 of 16 june 2009 www.diodes.com ? diodes incorporated typical performance characteristics (continued) v out ripple v in = 3.6v; 4 leds ; i out = 30ma v out ripple v in = 3.6v; 6 leds ; i out = 30ma power on v in = 3.6v; 6 leds ; i out = 30ma power off v in = 3.6v; 6 leds ; i out = 30ma v en v en v out v out v out irushing irushing sw sw v out
AP5725 white led step-up converter AP5725 rev. 1 9 of 16 june 2009 www.diodes.com ? diodes incorporated inductor selection a 10 h~22 h inductor is recommended for most AP5725 applications. although small size and high efficiency are major concerns, the inductor should have low core losses at 1.2mhz and low dcr (copper wire resistance). capacitor selection the small size of ceramic capacitors are ideal for AP5725 applications. x5r and x7r types are recommended because they retain their capacitance over wider voltage and temperature ranges than other types such as y5v or z5u. a 1 f input capacitor and a 1 f output capacitor are sufficient for most AP5725 applications. diode selection schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for AP5725 applications. the forward voltage drop of a schottky diode represents the conduction losses in the diode, while the diode capacitance (c t or c d ) represents the switching losses. for diode selection, both forward voltage drop and diode capacitance need to be considered. schottky diodes with higher current ratings usually have lower forward voltage drop and larger diode capacitance, which can cause significant switching losses at the 1.2mhz switching frequency of the AP5725. a schottky diode rated at 100ma to 200ma is sufficient for most AP5725 applications. led current control the led current is controlled by the feedback resistor (r set in figure 1 ). the feedback reference is 0.25v. the led current is 0.25v/ r set . in order to have accurate led current, precision resistors are preferred (1% is recommended). the formula and table for r set selection are shown below. r set = 0.25v/i led (see table 1 ) table 1. r set resistor value selection i led (ma) r set ( ? ) 5 50 10 25 15 16.6 20 12.5 30 8.3 application information
AP5725 white led step-up converter AP5725 rev. 1 10 of 16 june 2009 www.diodes.com ? diodes incorporated open-circuit protection in the cases of output open circuit, when the leds are disconnected from the circuit or the leds fail, the feedback voltage will be zero. the AP5725 will then switch at a high duty cycle resulting in a high output voltage, which may cause the sw pin voltage to exceed the level of the over voltage protect function. the ovp pin can detect the output voltage and monitor if the output voltage reach to the protect voltage level ( figure 2 ). once ovp is activated, sw pin stops switching. v in sw en gnd fb AP5725 c out 1uf r set 12 l1 22uh d1 v in c in 1uf ovp x x figure 2. led driver with open-circuit protection dimming control there are four different types of dimming control circuits: 1. using a pwm signal to en pin with the pwm signal applied to the en pin, the AP5725 is turned on or off by the pwm signal. the leds operate at either zero or full current. the average led current increases proportionally with the duty cycle of the pwm signal. a 0% duty cycle will turn off the AP5725 and corresponds to zero led current. a 100% duty cycle corresponds to full current. the typical frequency range of the pwm signal is below 2khz. application information (continued)
AP5725 white led step-up converter AP5725 rev. 1 11 of 16 june 2009 www.diodes.com ? diodes incorporated 2. using a dc voltage for some applications, the preferred method of brightness control is a variable dc voltage to adjust the led current. the dimming control using a dc voltage is shown in figure 3 . as the dc voltage increases, the voltage drop on r2 increases and the voltage drop on r set decreases. thus, the led current decreases. the selection of r2 and r3 will make the current from th e variable dc source much smaller than the led current and much larger than the fb pin bias current. for v dc range from 0v to 2v, the selection of resistors in figure 3 gives dimming control of led current from 0ma to 20ma. 3. using a filtered pwm signal the filtered pwm signal can be considered as an adjusta ble dc voltage. it can be used to replace the variable dc voltage source in dimming control. AP5725 fb r set 12 r2 5k r3 100k v dc figure 3. dimming control using a dc voltage 4. using a logic signal for applications that need to adjust the led current in discrete steps, a logic signal can be used as shown in figure 4 . r set sets the minimum led current (when the nmos is off). r set sets how much the led current increases when the nmos is turned on. AP5725 fb r set r inc logic signal figure 4. dimming control using a logic signal application information (continued)
AP5725 white led step-up converter AP5725 rev. 1 12 of 16 june 2009 www.diodes.com ? diodes incorporated application circuit on off d4 led vin c1 1uf d7 led r1 12ohm d3 led vout d2 led d6 led d5 led u1 AP5725 1 2 3 6 4 5 sw gnd fb vin en ovp c2 1uf l1 22uh d1 b0540ws table 2. suggested inductors vendor inductors (uh) current rating (a) type dimensions (mm) series wurth electronics 22 0.51a smd 3.8x 3.8 x 1.6 744031220 gotrend 22 0.56a smd 3.8 x 3.8 x 1.05 glp3810ph220n taiyo yudrn 22 0.51a smd 4.0 x 4.0 x 1.25 nr4012 table 3. suggested capacitors for c in and c out vendor capacitance type series taiyo yuden 1uf smd tmk212 b7105mg-t table 4. suggested diodes vendor rating type series zetex 40v/0.5a sod323 zlls400 diodes 40v/0.5a sod323 b0540ws diodes 40v/0.25a sod523 sdm20u40 table 5. suggested resistor vendor type series yageo smd fr-sk table 6. suggested w-led vendor type series liteon smd ltw-c1911uc5
AP5725 white led step-up converter AP5725 rev. 1 13 of 16 june 2009 www.diodes.com ? diodes incorporated marking information (1) sot26 1 2 3 6 7 4 xx y wx xx : identification code y : year 0~9 x : a~z : green ( top view ) 5 w : week : a~z : 1~26 week; a~z : 27~52 week; z represents 52 and 53 week part number package identification code AP5725 sot26 fc (2) dfn2020c-6 ( top view ) xx y : year : 0~9 x : a~z : green xx : identification code w : week : a~z : 1~26 week; a~z : 27~52 week; z represents 52 and 53 week y w x part number package identification code AP5725 dfn2020c-6 gc
AP5725 white led step-up converter AP5725 rev. 1 14 of 16 june 2009 www.diodes.com ? diodes incorporated package information (all dimensions in mm) (1) package type: sot26 (2) package type: dfn2020c-6 0.10 m c a b b 0.25 bottom view a a 0/0.05 0.57/0.63 0.15max. c 0.25 b 2x- 2x 0.08 c 0.10 c seating plane 1.55/1.75 1.95/2.075 0.25/0.35 0.25/0.35 0.65nom. 0.86/1.06 1.95/2.075 pin#1 id r 0. 1 marking 0.43mon. (active area depth) r 0 . 1 5
AP5725 white led step-up converter AP5725 rev. 1 15 of 16 june 2009 www.diodes.com ? diodes incorporated (1) dfn2020c-6 notes: 4. the taping orientation of the other package type can be found on our website at http://www.diodes.com/datasheets/a p02007.pdf. taping orientation
AP5725 white led step-up converter AP5725 rev. 1 16 of 16 june 2009 www.diodes.com ? diodes incorporated important notice diodes incorporated makes no warranty of any kind, express or implied, with regards to this document, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose (and their equivalents under the laws of any jurisdiction). diodes incorporated and its subsidiaries reserve the right to make modifications, enhancements, improvements, corrections or ot her changes without further notice to this document and any product described herein. diodes incorporated does not assume any liabi lity arising out of the application or use of this document or any product described herein; neither does diodes incorporated convey any license under its patent or trademark rights, nor the rights of others. any customer or user of this document or products desc ribed herein in such applications shall assume all risks of such use and will agree to hold diodes incorporated and all the companies whose products are represented on diodes incorporated website, harmless against all damages. diodes incorporated does not warrant or accept any liability whatsoever in respect of any products purchased through unauthoriz ed sales channel. should customers purchase or use diodes incorporated products for any unintended or unauthorized application, customers shall indemnify and hold diodes incorporated and its representatives harmless against all claims, damages, expenses, and attorney fee s arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized a pplication. products described herein may be covered by one or more united states, international or foreign patents pending. product names and markings noted herein may also be covered by one or more united states, international or foreign trademarks. life support diodes incorporated products are specifically not authorized for use as critical components in life support devices or systems without the express written approval of the chief executive officer of diodes incorporated. as used herein: a. life support devices or systems are devices or systems which: 1. are intended to implant into the body, or 2. support or sustain life and whose failure to perform when properly used in accordance with instructions for use provided in the labeling can be reasonably expected to result in significant injury to the user. b. a critical component is any component in a life support device or system whose failure to perform can be reasonably expected to cause the failure of the life support device or to affect its safety or effectiveness. customers represent that they have all necessary expertise in the safety and regulatory ramifications of their life support dev ices or systems, and acknowledge and agree that they are solely responsible for all legal, regulatory and safety-related requirements concerning their products and any use of diodes incorporated products in such safety-critical, life support devices or systems, notwithstanding any devices- or systems-related information or support that may be provided by diodes incorporated. further, customers must fully indemnify diodes incorporated and its representatives against any damages arising out of the use of diodes incorporated products in such safety-critical, life support devices or systems. copyright ? 2009, diodes incorporated www.diodes.com

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