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1 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation features ideal for white led driver low profile, inductorless regulator output current up to 200ma x1.5 and x2 modes for highest efficiency +2.7v to +5.5v input voltage range fast turn-on time, 175 s 1ma quiescent current <1.5 a shutdown current 600khz oscillator programmable output current or voltage pwm dimming control with enable pin shutdown to disconnect output from input soft start to eliminate in-rush current industry standard 10-pin msop package and small 10-pin dfn package applications next generation mobile phones pdas 3.3v to 5.0v conversion palmtop computers color lcd modules description the sp6682 is a current regulated charge pump ideal for converting a li-ion battery input for driving white leds used in backlighting color displays or cell phone camera flash applications. the charge pump automatically switches between x1.5 and x2 modes based on the program- mable v mode voltage, providing improved efficiency over traditional methods using charge pump doubler followed by ldo. this input voltage threshold can be externally programmed by a resistor divider network for optimized efficiency at specific output voltages and currents. the sp6682 operates with an internal 600khz clock, which reduces switching noise and improves v out ripple. output current or voltage can be accurately regulated by modulating the switcher between the charge pump and output capacitor. in shutdown mode, the ic disconnects the output from the input and draws less than 1.5 a current. the sp6682 is offered in a 10-pin msop package, and a small 10-pin dfn package. typical application schematic now available in lead free packaging sp6682 10 pin dfn 10 9 8 7 6 1 2 3 4 5 c2p c1n gnd c2n en/pwm v out c1p v in v mode fb lcd backlight application sp6682 v out c1p v in v mode fb ? c2p c1n gnd c2n en/pwm 1 2 3 4 5 10 9 8 7 6 c2 2.2 f c4 2.2 f c5 2.2 f r6 20 c1 2.2 f lithium-ion enable/pwm dimming white led r3 1m 20 20 20 2.7 - 4.2v c6 0.1 f sp6682 hi gh ef?ciency charge pump regulator for white leds
2 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation parameter min typ max units conditions input voltage 2.7 5.5 v quiescent current 1.2 3 ma v in = 4.2v, v out = 3.6v, i out = 100 a shutdown current 1.5 a en/pwm = 0.0v, v in = 5.5v oscillator frequency 0.42 0.60 0.78 mhz v in = 3.6v v fb reference voltage 0.275 0.306 0.337 v charge pump output 11 18 ?? fb = 0.0v, v in = 3.6v, resistance i out = 20ma, v mode = high v mode threshold voltage 1.15 1.25 1.35 v v in falling @ 25 c hysteresis for mode transition 30 mv pp v in = 3.6v @ 25 c voltage v mode pin current 0.01 0.5 a v mode = 1.25 en/pwm logic low 0.4 v en/pwm logic high 1.6 v en/pwm pin current 0.01 0.5 a v en/pwm = 4.2v fb pin current 0.5 a v fb = 1v v out turn-on time 175 500 s v in = 3.6v, fb within 90% regulation electrical characteristics unless otherwise specified: v in =+2.7v to +5.0v, c1=c2=c4=c5=2.2 f (ceramic, esr=0.03 ? ), c3=0.1 f (ceramic) and t amb =-40 c to +85 c unless otherwise noted. v in , v mode , v out and en/pwm ................. -0.3v to 6v v in - v out ........................................................... 0.7v output current (i out ) ...................................... 300ma power dissipation per package - 10-pin msop (derate 8.84mw/ c above +70 c) ................. 720mw junction temperature .................................... +125 c storage temperature ...................... -65 c to +150 c esd rating. ................................................ 2kv hbm these are stress ratings only and functional operation of the device at these ratings or any other above those indicated in the operation sections of the specifications below is not implied. exposure to absolute maximum rating conditions for extended periods of time may affect reliability. absolute maximum ratings typical application schematic camera flash application rf b 1. 5 oh m i out =2 00 ma fo r 1w le d en abl e/pw m le da c4 2. 2u f 1w le d c5 2. 2uf sp6 682 vout 1 c1 p 2 c2 n 7 en /pwm 6 fb 5 vm od e 4 vi n 3 gn d 8 c1 n 9 c2 p 10 vi n: 3. 0-4. 2v c1 2. 2u f r3 1. 0m le dk v fb=300m v
3 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation performance characteristics refer to the typical application circuit, t amb = 25 o c, i o = 60ma unless otherwise specified. en/pwm v out 5v/div 1v/div v in v out 50mv/div 50mv/div 0 10 20 30 40 50 60 70 80 90 2.7 3 3.3 3.6 3.9 4.2 input v oltage(v) e f f i c i e n c y ( % ) 0.26 0.27 0.28 0.29 0.3 0.31 0.32 0.33 0.34 2.7 3 3.3 3.6 3.9 4.2 v in (v) v f b ( v ) v out 50mv/div 50mv/div v in 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 2.7 3 3.3 3.6 3.9 4.2 v in (v) i s u p p l y ( m a ) figure 1. output voltage turn-on time figure 2. power efficiency vs. input voltage figure 3. x2 mode voltage ripple when v in = 2.7v figure 4. feedback pin voltage vs. input voltage figure 5. x1.5 mode voltage ripple when v in = 3.3v figure 6. quiescent current vs. input voltage
4 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation 0 1 2 3 4 5 6 2.7 3 3.3 3.6 3.9 4.2 input v oltage (v) b r i g h t n e s s ( k c d / m 2 ) 4 led's @ 30ma 4 led's @ 15ma performance characteristics: continued refer to the typical application circuit, t amb = 25 c, i o = 60ma unless otherwise specified. 0 1 2 3 0 20 40 60 80 100 duty cycle,% b r i g t n e s s , k c d / m 2 100 hz 500 hz figure 7. brightness vs. input voltage figure 8. brightness vs. duty cycle figure 9. i out vs. v in sp 6682 i out vs v in 0 50 100 150 200 250 3. 0 3 .2 3. 4 3 .6 3. 8 4 .0 4. 2 v in (v ) i ou t (m a) sp6682 lux eon i, v f = 3. 2v
5 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation an input voltage to the mode comparator which sets the logic state of the mode selec- tion outputs to the x2 or x1.5 modes. v mode is compared to a 1.25v bandgap voltage. for example, if one makes a 158k ? /100k ?? divider, the mode will change at 2.58 x 1.25 v = 3.23v. a comparator-based cycle-by- cycle regulation ensures that no mode change occurs during cycles. 3) clock manager. an internal 600 khz clock is generated in this block. depending on the mode control, the appropriate clock phasing is generated here and sent to the start-up and charge-pump switches block. 4) start-up and charge pump switches. during start-up, until the reference is estab- lished, this block keeps the charge pump inactive. during this period the output stays floating, and by consequence the charge pump drivers are now referenced to v out . charging of the output will occur (e.g. when v in is ramped up to 4.2v, v out ramps only up to about 3v), but not to the value of v in , protecting the white leds from experienc- ing high input voltages. another important operation of this block is the pwm/en dim- ming control, which is implemented in the delay of each pump driver, so that the enable high pulse width is proportional to the delay of the individual pump switches. 5) v out comparator and output control. a 306mv reference voltage is compared to feedback output voltage to control the v out needed for the application. output current is set by a bias resistor from fb pin to gnd pin chosen by the relationship: i out = v fb r fb where v fb = 306mv. operation general overview the sp6682 is a current regulated charge pump ideal for converting a li-ion battery input for driving white leds used in back- lighting color displays, cell phone camera flash, pdas, digital cameras and mp3 play- ers. the sp6682?s proprietary autoboost feature enables the ic to automatically trans- ition from x1.5 boost mode to x2 boost mode based on battery input voltage for optimal efficiency and performance. the sp6682 is able to efficiently drive up to six 20ma white leds in parallel and maintain a constant brightness over a very wide operating voltage range (2.7v to 5.5v). the sp6682 operates with an internal 600khz clock, enabling the use of small external components. other features of sp6682 include pwm dimming control as well as complete input/out disconnect in shutdown. in shutdown mode the ic draws less than 1.5 a current. the output regulation is achieved by sensing the voltage at the feedback pin and modulating the switcher between the charge pump and output capacitor. theory of operation the sp6682 regulated charge pump block diagram consists of four main blocks (voltage reference, mode control, clock manager, start-up and charge-pump switches) and two comparators (v mode comparator and v out comparator). 1) voltage reference. this block provides the 306mv and 1.25v reference voltages needed for the two comparators. 2) mode control. an external voltage vider connected to the v mode pin will define di-
6 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation a 3-wire white led module with internal series resistors as shown in figure 11 can also be driven in this way. the current in one white led current is set by the ratio of the feedback pin voltage (306mv) and the bias resistor r b . to set the operating current, r b can be selected by: r b = v fb i led the current of the remaining white leds is set according to the similarity of the white leds. configuring the sp6682 as voltage or current source the white led load configuration used by customers can be discrete white leds or a white led module. inside the white led module, there may or may not be resistors in series with the white leds. according to the different application requirements, the sp6682 can be configured as either a voltage source or a current source to provide solutions for these different applications, as shown in figures 10-13. figure 10 shows a circuit using the sp6682 to drive discrete white leds as a current source. 1 8 5 rb sp6682 rb 2.2uf gnd fb v out figure 10. driving discrete white leds as current source 3-wire w-led module anode fb gnd fig 11. 3-wire white led module gnd v out anode 5 v fb rb sp6682 cathode 8 2-wire w-led module 1 figure 12. driving 2-wire white led module as current source in this application, the bias resistor can be selected by: r b = v fb i led (total) where i led(total) is the total operating cur- rent of all the white leds. application information in figure 12, the sp6682 was used to drive a 2-wire white led module without internal series resistors as a current source. the bias resistor r b is selected to regulate the total current of the white led module in- stead of the current of single led as in figure 10.
7 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation anode 5 8 sp6682 cathode v out r6 1 r5 2.2uf v fb 2-wire w-led module gnd figure 13. driving 2-wire white led module as voltage source v in v in c2 gnd 4 v mode r1 sp6682 8 r2 3 figure 14. programming the vmode resistors the output voltage is set by the ratio of the two resistors and the feedback control volt- age as shown by: v out = ( 1 + r 5 ) ? v fb r 6 programming the operating mode sp6682 can automatically change from x1.5 mode to x2 mode for highest efficiency. to use this feature, divider resistors should be chosen according to the specific applica- tion, as shown in figure 14. the guideline for divider resistor selections is as follows: for high input voltage, the sp6682 will work in x1.5 mode. when the input voltage drops to the v th threshold voltage, it will switch to x2 mode automati- cally. the v th threshold voltage for mode change can be calculated by: v th = (v f + 0.306 + m ? i led ? r out )/1.5 where v f and m are the forward voltage and number of the white leds, r out is the output resistance of the sp6682. the equation for the voltage divider r 1 and r 2 with v mode = 1.25v is: v th = 1.25v ? (1+r 1 /r 2 ) which can be expressed as r1: r 1 = (v th / 1.25 -1) ? r 2 for the typical sp6682 application, using v f =3.6v, m=4, i led =15ma, r out =16 ? , the v th will be 3.24v. select r 2 =100k ? , then r 1 =158k ? . capacitor selection ceramic capacitors are recommended for their inherently low esr, which will help produce low peak to peak output ripple, and reduce high frequency spikes. the fly capacitor controls the strength of the charge pump. selection of the fly capacitor is a trade-off between the output voltage ripple and the output current capability. decreasing the fly capacitor will reduce the output voltage ripple because less charge will be delivered to the output capacitor. however, smaller fly capacitors lead to larger output resistance, thus decreasing the out- t o use the sp6682 as a voltage source for fixed voltage applications, a voltage divider is needed to program the ouput voltage, as shown in figure 13. application information: continued
8 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation application information: continued brightness control using pwm dimming control can be achieved by applying a pwm control signal to the en/pwm pin. the brightness of the white leds is con- trolled by increasing and decreasing the duty cycle of the pwm signal. while the operating frequency range of the pwm control is from 60hz to 700hz, the recommended maxim- um brightness frequency range of the pwm signal is from 60hz to 200hz. a repetition rate of at least 60hz is required to prevent flicker. brightness matching for white leds, the forward voltage drop is a function of the operating current. however, for a given current, the forward voltage drops do not always match due to normal man- ufacturing tolerances, thus causing uneven brightness of the white leds. in figure 15, assume high-precision bias resistors were used, the operating current ratio of two different branches can be easily derived as shown by: put current capability and the circuit effi- ciency. place all the capacitors as close to the sp6682 as possible for layout. increas- ing the value of the input and output capaci- tors could further reduce the input and out- put ripple. refer to table 1 for some suggested low esr capacitors. manufacturer part number capacitance/ capacitor/ esr voltage size/type at 100khz tdk c2012x5r1a225k 2.2 f/10v 0805/x5r 0.030 ? tdk c2012x5r0j475k 4.7 f/6.3v 0805/x5r 0.020 ? murata grm188r60j225ke01d 2.2 f/6.3v 0603/x5r 0.030 ? murata grm219r60j475ke01d 4.7 f/6.3v 0805/x5r 0.020 ? table 1: suggested low esr capacitors i 1 = v out - v f1 i 2 v out - v f2 where i 1 , i 2 are the operating current of the white leds andv f1 ,v f2 are the forward volt- age of the white leds. since the brightness of the white led is proportional to the operating current, for better brightness matching, a higher output voltage could be used. this could be done by using a larger resistor, as shown in figure 15. r b2 is used to bias the operating current of the white led, r b1 is used to increase the output voltage. better bright- ness matching was achieved at the cost of the power wasted on the bias resistor. rb1 8 v fb d1 rb dn gnd vfn vf1 v out 1 rb2 rb vf2 rb 5 d2 sp6682 i 1 i 2 i n figure 15. increasing brightness matching
9 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation 70 75 80 85 90 95 100 2.7 3.0 3.3 3.6 3.9 4.2 v in (v) e f f i c i e n c y ( % ) d11 x5r ceramic d3 sot23 r2 15 25v l1 lqh32cn4r7m11 4.7uh d12 d8 ds schottky mbr0530 d4 q1 ceramic en/pwm r1 15 d6 c1 10uf d9 d7 c3 x5r 2.2uf 25v d10 d2 r3 1m iled = vfb/r1 = 20ma sp6682 1 2 7 6 5 4 3 8 9 10 v out c1p c2n en/pwm fb v mode v in gnd c1n c2p d1 si1304 d5 vin: 2.7-4.2v figure 16. using sp6682 as a high voltage white led driver pinouts sp6682 10 pin dfn 10 9 8 7 6 1 2 3 4 5 c2p c1n gnd c2n en/pwm v out c1p v in v mode fb v out c1p v in v mode fb sp6682 10 pin msop 1 2 3 4 5 10 9 8 7 6 c2p c1n gnd c2n en power efficiency the efficiency of driving the white leds can be calculated by: ? = v f ? i f = v f ? i f ? v f v i ? i i v i ? (n ? i f + i q ) v i ? n where v i , i i are input voltage and current v f , i f are the forward voltage and operating current of white leds; i q is quiescent cur- application information: continued rent, which is considered small compared with i f ; n is the boost ratio (x1.5 or x2). sp6682 high voltage white led driver the sp6682 can also be configured as a high voltage boost converter to drive more than 10 white leds. figure 16 shows the schematic of this application as well as actual data showing efficiency of > 85%. by using an external inductor, mosfet and diode, high output voltages can be generated to drive 12 white leds (2 branches -- each branch has 6 white leds in series). the current through the white leds is determined by: i led = v fb r 1
10 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation pin #1 designator to be within this index area (d/2 * e1/2) front view l gauge plane seating plane l2 c ? ?1 ?1 r1 r e1 e e/2 e1 e d 1 2 top view (l1) 1 2 3 4 5 10 9 8 7 6 d/2 min nom max min nom max a1 0.00 - 0.15 0.000 - 0.006 c 0.08 - 0.23 0.004 - 0.009 r 0.07 - - 0.003 - - r1 0.07 - - 0.003 - - ? 0o - 8o 0o - 8o ?1 5o - 15o 5o - 15o a - - 1.10 - 0.043 a2 0.75 0.85 0.95 0.030 0.034 0.038 b 0.17 - 0.33 0.007 - 0.013 d e e1 e e1 l 0.40 0.60 0.80 0.016 0.024 0.032 l1 l2 symbol 0.118 bsc 0.193 bsc 0.118 bsc 0.079 bsc 0.037 ref 0.010 bsc 0.020 bsc sipex pkg signoff date/rev: jl aug09-05 reva 0.50 bsc 2.00 bsc 0.95 ref 0.25 bsc 3.00 bsc 4.90 bsc 3.00 bsc 10 pin msop jedec mo-187 variation ba dimensions in millimeters: controlling dimension dimensions in inches conversion factor: 1 inch = 25.40 mm side view a a2 a1 seating plane b package: 10 pin msop
11 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation package: 10 pin d fn min nom max min nom max a 0.80 0.90 1.00 0.032 0.036 0.039 a1 0.00 0.02 0.05 0.000 0.001 0.002 a3 k 0.20 - - 0.008 - - ? 0o - 14o 0o - 14o b 0.18 0.25 0.30 0.008 0.010 0.012 d d2 2.20 - 2.70 0.087 - 0.106 e e2 1.40 - 1.75 0.056 - 0.069 e l 0.30 0.40 0.50 0.012 0.016 0.020 3x3 10 pin dfn jedec mo-229 variation veed-5 dimensions in millimeters: controlling dimension dimensions in inches conversion factor: 1 inch = 25.40 mm 3.00 bsc 0.119 bsc symbol sipex pkg signoff date/rev: jl aug09-05 / reva 0.20 ref 0.008 ref 0.119 bsc 3.00 bsc 0.020 bsc 0.50 bsc ? (a3) a1 a seating plane side view 1 0 1 2 3 4 5 9 8 7 6 index area (d/2 x e/2) bottom view b e l k d2 e2 e2/2 d2/2 pin1 designator to be within this index area (d/2 x e/2) top view d e e/2 d/2
12 date: 7/19/06 rev d sp6682 hi gh ef?ciency charge pump regulator for white leds ? 2006 sipex corporation application information: continued brightness control using pwm dimming control can be achieved by applying a pwm control signal to the en/pwm pin. the brightness of the white leds is con- trolled by increasing and decreasing the duty cycle of the pwm signal. while the operating frequency range of the pwm control is from 60hz to 700hz, the recommended maxim- um brightness frequency range of the pwm signal is from 60hz to 200hz. a repetition rate of at least 60hz is required to prevent flicker. brightness matching for white leds, the forward voltage drop is a function of the operating current. however, for a given current, the forward voltage drops do not always match due to normal man- ufacturing tolerances, thus causing uneven brightness of the white leds. in figure 15, assume high-precision bias resistors were used, the operating current ratio of two different branches can be easily derived as shown by: put current capability and the circuit effi- ciency. place all the capacitors as close to the sp6682 as possible for layout. increas- ing the value of the input and output capaci- tors could further reduce the input and out- put ripple. refer to table 1 for some suggested low esr capacitors. manufacturer part number capacitance/ capacitor/ esr voltage size/type at 100khz tdk c2012x5r1a225k 2.2 f/10v 0805/x5r 0.030 ? tdk c2012x5r0j475k 4.7 f/6.3v 0805/x5r 0.020 ? murata grm188r60j225ke01d 2.2 f/6.3v 0603/x5r 0.030 ? murata grm219r60j475ke01d 4.7 f/6.3v 0805/x5r 0.020 ? table 1: suggested low esr capacitors i 1 = v out - v f1 i 2 v out - v f2 where i 1 , i 2 are the operating current of the white leds andv f1 ,v f2 are the forward volt- age of the white leds. since the brightness of the white led is proportional to the operating current, for better brightness matching, a higher output voltage could be used. this could be done by using a larger resistor, as shown in figure 15. r b2 is used to bias the operating current of the white led, r b1 is used to increase the output voltage. better bright- ness matching was achieved at the cost of the power wasted on the bias resistor. rb1 8 v fb d1 rb dn gnd vfn vf1 v out 1 rb2 rb vf2 rb 5 d2 sp6682 i 1 i 2 i n figure 15. increasing brightness matching vlshfrusrudwlr hdgtduwhuvdg vdohvrifh 233 south hillview drive milpitas, ca 95035 tel: (408) 934-7500 fax: (408) 935-7600 sipex corporation reserves the right to make changes to any products described herein. sipex does not assume any liability arising out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor the rights of others. ordering information part number top mark operating temperature range package type sp6682eu ....................... sp6682eu....................................-40 c to +85 c ............................ 10 pin msop sp6682eu/tr ................. sp6682eu....................................-40 c to +85 c ............................ 10 pin msop sp6682er ........................ sp6682eryww.........................-40 c to +85 c ................................ 10 pin dfn sp6682er/tr ................. sp6682eryww...........................-40 c to +85 c ............................... 10 pin dfn /tr = tape and reel pack quantity is 2,500 for msop and 3,000 for dfn. available in lead free packaging. to order add "-l" suffix to part number. example: sp6682er/tr = standard; sp6682er-l/tr = lead free

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