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ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 1 of 17 www.diodes.com july 2010 ? diodes incorporated description the ap5726 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 le ds provides identical led currents resulting in uniform brightness and eliminates the need for ballast resistors. for driving higher number of leds, ap5726 also supports a single feedback of parallel connected multiple strings of equal number of leds. the ap5726 switches at 1.2mhz t hat allows the use of tiny external components. a low 0.31v feedback voltage minimizes power loss in the current setting resistor for better efficiency. pin assignments 1 2 3 7 4 6 ovp fb 5 en sw (top view) v in gnd sot26 / tsot23-6 sw v in ovp 1 2 3 6 5 4 gnd fb en (top view) dfn2020c-6 features ? 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, tsot23-6 and dfn2020c-6: available in ?green? molding compound (no br, sb) ? lead free finish/ rohs compliant (note 1) applications ? cellular phones ? pdas, hand help computers ? digital cameras ? mp3 players ? gps receivers notes: 1. eu directive 2002/95/ec (rohs). all applicabl e rohs exemptions applied. please visit our website at http://www.diodes.com/products/lead_free.html . typical application circuit v in sw en gnd fb ap5726 c out 1uf r set 15 l1 22uh d1 v in c in 1uf ovp 2~6 leds pwm dimming off on figure 1. typical application circuit
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 2 of 17 www.diodes.com july 2010 ? diodes incorporated pin descriptions 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 0.31v. connect cathode of lowest led and a sense resister here. calculate resistor value according to the formula: r set = 0.31v / iled en converter on/off control input. a high input at en turns the converter on, and a low input turns it off. if on/off control is not needed, c onnect en to the input source for automatic startup. the en pin cannot be left floating. ovp output voltage detect pin for over voltage protection. v in input supply pin. must be locally bypassed with 1 f or 2.2 f to reduce input noise. functional block diagram 1.2mhz oscillator ramp generator - + - + - + v ref 0.31v v in 3 fb rc cc comparator a2 control logic a1 1 driver sw q1 2 gnd 4 en enable 6 otp 5 ovp
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 3 of 17 www.diodes.com july 2010 ? diodes incorporated absolute maximum ratings symbol parameter rating unit v in vin pin voltage -0.3~7 v vsw 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: operation above the absolute maxi mum ratings can cause device failure. these values, therefore, must not be exceeded under any condition. operation at the absolute maximum rating for extended periods, may reduce device reliability. recommended operating 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
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 4 of 17 www.diodes.com july 2010 ? diodes incorporated electrical characteristics (v in = 3.6v, t a = 25c, 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 hysteresis - 85 - mv i q quiescent current fb=0.41v, 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 0.279 0.31 0.341 v i fb fb pin bias current 10 45 100 na mosfet rds(on) on resistance of mosfet - 0.95 1.2 ? 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 2) 162 o c/w tsot23-6 (note 2) 152 dfn2020c-6 (note 2) 200 jc thermal resistance junction-to- case sot26 (note 2) 36 o c/w tsot23-6 (note 2) 32 dfn2020c-6 (note 2) 30 notes: 2. test condition for sot26, tsot23-6 and dfn2020c-6 : device mounted on fr-4 substrate, single-layer pc board, 2oz co pper, with minimum recommended pad layout
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 5 of 17 www.diodes.com july 2010 ? 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 2.533.544.555.5 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 2.533.544.555.5 v in (v) max duty(%) v in vs. feedback voltage 0.25 0.27 0.29 0.31 0.33 0.35 2.53 3.544.555.5 v in (v) feedback voltage(v) i out vs. feedback voltage 0.25 0.27 0.29 0.31 0.33 0.35 0 1020304050 i out (ma) feedback voltage(v)
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 6 of 17 www.diodes.com july 2010 ? 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 0.25 0.27 0.29 0.31 0.33 0.35 -50 -25 0 25 50 75 100 125 temperature( ) feedback voltage(v) v in = 4.2v v in = 3.6v
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 7 of 17 www.diodes.com july 2010 ? 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 2.5 3 3.5 4 4.5 5 v in (v) efficiency(%) 3 leds 6 leds 4 leds
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 8 of 17 www.diodes.com july 2010 ? diodes incorporated typical performance characteristics (continued) v out ripple v in = 3.6v; 4 leds ; iout = 30ma v out ripple v in = 3.6v; 6 leds ; iout = 30ma power on v in = 3.6v; 6 leds ; iout = 30ma power off v in = 3.6v; 6 leds ; iout = 30ma v en v en v out v out v out irushi irushin g sw sw v out
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 9 of 17 www.diodes.com july 2010 ? diodes incorporated applications information inductor selection a 10 h~22 h inductor is recommended for most ap5726 applicat ions. for high efficiency the inductor should have low core losses at 1.2mhz and low dcr (copper wi re resistance). the inductor saturation current rating should also exceed the peak input current, especially for high load current applications (like 3s8p). capacitor selection the small size of ceramic capacitors are ideal fo r ap5726 applications. x5r and x7r types are recommended because they retain their capacitance over wider volt age 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 ap5726 applications. for high output current applications like 3s8p, larger output capa citor of 2.2uf ~ 4.7uf is recommended to minimize output ripple. diode selection schottky diodes, with their low forward voltage drop and fast reverse recovery, are the ideal choices for ap5726 applications. the forward voltage drop of a schottky diode r epresents the conduction lo sses 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. larger schottky diode capacitance can cause significant switching losses at the 1.2mhz switching frequency of the ap5726. a schottky diode rated at 100ma to 200ma is sufficient for most ap5726 applications. led current control the led current is controll ed by the feedback resistor (r set in figure 1 ). the feedback reference is 0.31v. the led current is 0.31v/ 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 = 0.31v/i led (see table 1) table 1. r set resistor value selection i led (ma) r set ( ?) 5 62 10 31 15 20.6 20 15.5 30 10.3
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 10 of 17 www.diodes.com july 2010 ? diodes incorporated applications information (continued) 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 ap5726 will then switch at a high duty cycle resulting in a high output voltage, which may cause the sw and ovp pin voltage to exceed the voltage rating of these pins. the ovp pin monitors the output voltage. if the output volt age reaches the over voltage protection threshold at the ovp pin ( figure 2 ), the over voltage protection is activated and sw pin stops switching. v in sw en gnd fb ap5726 c out 1uf r set 15 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 ap5726 is turned on or off by the pwm signal. the leds operate at either zero or full current. the average led current in creases proportionally with the duty cycle of the pwm signal. a 0% duty cycle will turn off the ap5726 and co rresponds to zero led current. a 100% duty cycle corresponds to full current. the typical frequency range of the pwm signal is below 2khz.
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 11 of 17 www.diodes.com july 2010 ? diodes incorporated applications information (continued) 2. using a dc voltage for some applications, the preferre d 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 the va riable 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. ap5726 fb r set 15 r2 5k r3 100k v dc figure 3. dimming control using a dc voltage 3. using a filtered pwm signal the filtered pwm signal can be considered as an adjustab le dc voltage. it can be used to replace the variable dc voltage source in dimming control. 4. using a logic signal for applications that need to adjust the led current in di screte 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. ap5726 fb r set r inc logic signal figure 4. dimming control using a logic signal
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 12 of 17 www.diodes.com july 2010 ? diodes incorporated applications information (continued) d4 led d3 led vout d5 led d2 led c2 1uf l1 22uh c1 1uf r1 15ohm vin d7 led on off u1 ap5726 1 2 3 6 4 5 sw gnd fb vin en ovp d6 led 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
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 13 of 17 www.diodes.com july 2010 ? diodes incorporated ordering information package ap 5726 xxx g - 7 packing 7 : tape & reel green g : green fdc : dfn2020c-6 w : sot26 wu : tsot23-6 device package code packaging (note 3) 7? tape and reel quantity part number suffix ap5726wg-7 w sot26 3000/tape & reel -7 ap5726wug-7 wu tsot23-6 3000/tape & reel -7 ap5726fdcg-7 fdc dfn2020c-6 3000/tape & reel -7 notes: 3. 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. marking information (1) sot26 and tsot23-6 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 ap5726wg-7 sot26 fd ap5726wug-7 tsot23-6 gd (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 ap5726fdcg-7 dfn2020c-6 gd
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 14 of 17 www.diodes.com july 2010 ? diodes incorporated package outline dimensions (all dimensions in mm) (1) package type: sot26 (2) package type: tsot23-6
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 15 of 17 www.diodes.com july 2010 ? diodes incorporated package outline dimensions (continued) (3) 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 land pattern recommendation (unit:mm) top view 0.65 0.45 0.37 1.59 0.9
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 16 of 17 www.diodes.com july 2010 ? diodes incorporated taping orientation for dfn2020c-6 notes: 4. the taping orientation of the other package ty pe can be found on our website at http://www.diodes.com/datasheets/a p02007.pdf.
ap5726 white led step-up converter ap5726 document number: ds31845 rev. 3 - 2 17 of 17 www.diodes.com july 2010 ? 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 rese rve the right to make modifications, enhanc ements, 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 an y product described herein; neither does diodes incorporated convey any license under its patent or trademark rights, nor the rights of othe rs. 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 incorp orated website, harmless against all damages. diodes incorporated does not warrant or accept any liability what soever in respect of any prod ucts purchased through unauthoriz ed sales channel. should customers purchase or use diodes in corporated products for any unintended or unauthorized application, customers shall indemnify and hold diodes incorporated and its representatives har mless against all claims, damages, expenses, and attorney fee s arising out of, directly or indirectly, any claim of personal injury or death a ssociated 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 specifica lly not authorized for use as critical co mponents 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 pr operly used in accordance with instructions for use provided in the labeling can be reasonably expected to re sult 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 t he safety and regulatory ramifications of their life support dev ices or systems, and acknowledge and agree that they are solely responsi ble for all legal, regulatory and safety-related requirements concerning their products and any use of diode s incorporated products in such safety-cri tical, 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 repr esentatives against any damages ar ising out of the use of diodes incorporated products in such safety-c ritical, life support devices or systems. copyright ? 2010, diodes incorporated www.diodes.com

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