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1 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation sp6691 features drives up to 6 led's @ 25ma drives up to 8 led's @ 20ma high output voltage: up to 34v optimized for single supply, 2.7v - 4.2v applications operates down to 1v high efficiency: greater than 75% low quiescent current: 20 a ultra low shutdown current: 10na single battery cell operation programmable output voltage 1 ? switch (350mv at 350ma) available in 8 pin dfn, 5 pin tsot or 5 pin sot23 micro power boost regulator series white led driver applications white led driver high voltage bias digital cameras cell phone battery backup handheld computers description the sp6691 is a micro power boost regulator that is specifically designed for powering series configuration white led. the part utilizes fixed off time architecture and consumes only 10na quiescent current in shutdown. low voltage operation, down to 1v, fully utilizes maximal battery life. the sp6691 is offered in a 8 pin dfn, 5-pin sot-23 or 5 pin tsot package and enables the construction of a complete regulator occupying < 0.2 in 2 board space. typical application circuit v in sw gnd shdn fb 10 h 2.2 f 4.7 f 2.7 to 4.2v r b sp6691 d1 l1 c1 c2 now available in lead free packaging nc shdn v in gnd nc fb nc sw 8 7 6 5 1 2 3 4 sp6691 8 pin dfn
2 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation v in ....................................................................... 15v sw voltage .............................................. -0.4 to 34v fb voltage ......................................................... 2.5v all other pins ................................... -0.3 to v in + 0.3v current into fb ................................................. 1ma t j max ............................................................. 125 c operating temperature range ............ -40 c to 85 c peak output current < 10us sw .................... 500ma storage temperature ...................... -65 c to +150 c power dissipation. ......................................... 200mw 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. pin description electrical characteristics absolute maximum ratings specifications are at t a = 25 c, v in = 3.3, v shdn = v in , ? ? ? ? ? denotes the specifications which apply over the full operating temperature range, unless otherwise specified. pin number pin name 8 pin dfn description 1n c no connect. 2f b feedback. 3n c no connect. 3s w switch input to the internal power switch 5 gnd ground 6v in input voltage. bypass this pin with a capacitor as close to the device as possible. 7 shdn shutdown. pull high (on) to enable. pull low (off) for shutdown. 8n c no connect. parameter symbol min typ max units ? ? ? ? ? conditions input voltage v in 1.0 13.5 v supply current i q 20 30 a ? ? ? ? ? no switching 0.01 1 a ? ? ? ? ? shdn = 0v (off) reference voltage v fb 1.17 1.22 1.27 v ? ? ? ? ? fb hysteresis hyst 8 mv v fb input bias current i fb 15 80 na ? ? ? ? ? v fb = 1.22v line regulation ? v o / ? v i 0.1 0.3 %/v 1.2 v in 13.5v switch off time t off 250 ns switch saturation voltage v cesat 170 450 mv ? ? ? ? ? i sw = 325ma switch current limit i lim 325 450 575 ma ? ? ? ? ? shdn bias current i shdn 512 a ? ? ? ? ? v shdn = 3.3v shdn high threshold (on) v ih 0.9 v shdn low threshold (off) v il 0.25 v switch leakage current i swlk 0.01 5 a ? ? ? ? ? switch off, v sw = 5v
3 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation + - 4 q1 q2 r3 r4 r2 r1 x1 shutdown logic 250ns one-shot clear x2 + - set driver gnd 2 1 5 3 sw power transistor disable vin shdn fb functional diagram theory of operation operation can be best understood by referring to the functional diagram above and the typical application circuit in the front page. q1 and q2 along with r3 and r4 form a band gap refer- ence. the input to this circuit completes a feed- back path from the high voltage output through a voltage divider, and is used as the regulation control input. when the voltage at the fb pin is slightly above 1.22v, comparator x1 disables most of the internal circuitry. current is then provided by capacitor c2, which slowly dis- charges until the voltage at the fb pin drops below the lower hysteresis point of x1, about 6mv. x1 then enables the internal circuitry, turns on chip power, and the current in the inductor begins to ramp up. when the current through the driver transistor reaches about 450ma, comparator x2 clears the latch, which turns off the driver transistor for a preset 250ns. at the instant of shutoff, inductor current is diverted to the output through diode d1. during this 250ns time limit, inductor current decreases while its energy charges c2. at the end of the 250ns time period, driver transistor is again allowed to turn on which ramps the current back up to the 450ma level. comparator x2 clears the latch, it? output turns off the driver transistor, and this allows delivery of l1? stored kinetic energy to c2. this switch- ing action continues until the output capacitor voltage is charged to the point where fb is at band gap (1.22v). when this condition is reached, x1 turns off the internal circuitry and the cycle repeats. pin description pin number pin name description 1s w switch input to the internal power switch. 2 gnd ground 3f b feedback 4 shdn shutdown. pull high (on) to enable. pull low (off) for shutdown. 5v in input voltage. bypass this pin with a capacitor as close to the device as possible.
4 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation performance characteristics refer to the typical application circuit, t amb = 25 c, unless otherwise specified. figure 1. 12v output efficiency figure 2. 12v output load regulation figure 3. 15v output efficiency figure 4. 15v output load regulation figure 5. 18v output efficiency figure 6. 18v output load regulation vout = 12v efficiency 50 60 70 80 90 020406 080 100 120 140 160 iout (ma) efficiency (%) vin = 5.0v vin = 4.2v vin = 33v vout = 12v load regulation 11.0 11.5 12.0 12.5 13.0 020406 080 100 120 140 160 iout (ma) vout (v) vin = 5.0v vin = 4.2v vin = 33v vout = 15v efficiency 50 60 70 80 90 020406 080 100 120 iout (ma) efficiency (%) vin = 5.0v vin = 4.2v vin = 3.3v vi vout = 15v load regulation 14.0 14.5 15.0 15.5 16.0 020406 080 100 120 iout (ma) vout (v) vin = 5.0v vin = 4.2v vin = 3.3v vin = 2.7v vout = 18v efficiency 50 60 70 80 90 020406 080 100 iout (ma) efficiency (%) vin = 5.0v vin = 4.2v vin = 33v vout = 18v load regulation 17.0 17.5 18.0 18.5 19.0 020406 080 100 iout (ma) vout (v) vin = 5.0v vin = 4.2v vin = 33v
5 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation performance characteristics refer to the typical application circuit, t amb = 25 c, unless otherwise specified. figure 7. 21v output efficiency figure 8. 21v output load regulation figure 9. 24v output efficiency figure 10. 24v output load regulation figure 11. 30v output efficiency figure 12. 30v output load regulation vout = 21v efficiency 50 60 70 80 90 010203 040 5060 70 iout (ma) efficiency (%) vin = 5.0v vin = 4.2v vin = 33v vout = 21v load regulation 20.0 20.5 21.0 21.5 22.0 010203 040506070 iout (ma) vout (v) vin = 5.0v vin = 4.2v vin = 33v vout = 24v efficiency 50 60 70 80 90 010203 0405060 iout (ma) efficiency (%) vin = 5.0v vin = 4.2v vin = 33v vout = 24v load regulation 23.0 23.5 24.0 24.5 25.0 010203 0405060 iout (ma) vout (v) vin = 5.0v vin = 4.2v vin = 33v vout = 30v efficiency 40 50 60 70 80 90 0510 15 20 25 30 iout (ma) efficiency (%) vin = 5.0v vin = 4.2v vin = 33v vout = 30v load regulation 29.0 29.5 30.0 30.5 31.0 0510 15 20 25 30 iout (ma) vout (v) vin = 5.0v vin = 4.2v vin = 33v
6 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation performance characteristics refer to the typical application circuit, t amb = 25 c, unless otherwise specified. figure 13. quiescent current i q vs. v in figure 14. shutdown pin current vs. v in figure 15. i pk current limit vs. v in figure 17. feedback voltage vs. temperature 0 5 10 15 20 25 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 input voltage (v) quiescent current (ua) tamb=-25c tamb=25c tamb=85c 0 2 4 6 8 10 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 input voltage (v) shutdown pin current (ua) 0 100 200 300 400 500 600 1.2 1.8 2.4 3 3.6 4.2 4.8 5.4 input voltage (v) current limit (ma) 1.20 1.21 1.22 1.23 1.24 1.25 -30 -10 10 30 50 70 90 temperature (c) feedback voltage (v) figure 16. switch saturation voltage v cesat vs. temperature (i sw = 450ma) figure 18. average i o vs. shdn duty cycle (v in =3.3v, standard 4x20ma wled evaluation board, pwm frequency 100hz 0 50 100 150 200 250 300 350 400 -30 -10 10 30 50 70 90 temperature (c) switch saturation voltage (mv) 0 4 8 12 16 20 0204 06080100 pwm duty cycle (%) iout/idc (%)
7 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation performance characteristics figure 19. startup waveform (v in =3.3v, v out =15v, i out =20ma) figure 20. typical switching waveforms (v in =3v, v out =15v, i out =20ma) figure 21. load step transient (v in =3v, v out =21v, 1 15ma load step refer to the typical application circuit, t amb = 25 c, unless otherwise specified. en v out i in (0.5a/div) v sw v out (ac) i l (0.5a/div) i l (0.5a/div) v out (ac) i out (100ma/div)
8 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation inductor selection for sp6691, the internal switch will be turned off only after the inductor current reaches the typical dc current limit (i lim =450ma). how- ever, there is typically propagation delay of 200ns between the time when the current limit is reached and when the switch is actually turned off. during this 200ns delay, the peak inductor current will increase, exceeding the current limit by a small amount. the peak inductor current can be estimated by: i pk = i lim + v in(max) ?200ns l the larger the input voltage and the lower the inductor value, the greater the peak current. in selecting an inductor, the saturation current specified for the inductor needs to be greater than the sp6691 peak current to avoid saturating the inductor, which would result in a loss in efficiency and could damage the inductor. choosing an inductor with low dcr decreases power losses and increase efficiency. refer to table 1 for some suggested low esr inductors. table 1. suggested low esr inductor manuf. part number dcr current ( ? ) rating (ma) murata lqh32cn100k11 0.3 450 770-436-1300 (10 h) tdk nlc453232t-100k 0.55 500 847-803-6100 (10 h) diode selection a schottky diode with a low forward drop and fast switching speed is ideally used here to achieve high efficiency. in selecting a schottky diode, the current rating of the schottky diode should be larger than the peak inductor current. moreover, the reverse breakdown voltage of the schottky diode should be larger than the output voltage. 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. for the typical application, 4.7 f input capaci- tor and 2.2 f output capacitor are sufficient. the input and output ripple could be further reduced by increasing the value of the input and output capacitors. place all the capacitors as close to the sp6691 as possible for layout. for use as a voltage source, to reduce the output ripple, a small feedforward (47pf) across the top feedback resistor can be used to provide sufficient overdrive for the error comparator, thus reduce the output ripple. refer to table 2 for some suggested low esr capacitors. table 2. suggested low esr capacitor manuf. part number cap size /voltage /type murata grm32rr71e 2.2 f 1210 770-436-1300 225kc01b /25v /x5r murata grm31cr61a 4.7 f 1206 770-436-1300 475ka01b /10v /x5r tdk c3225x7r1e 2.2 f 1210 847-803-6100 225m /25v /x7r tdk c3216x5r1a 4.7 f 1206 847-803-6100 475k /10v /x5r led current program in the white leds application, the sp6691 is generally programmed as a current source. the bias resistor r b , as shown in the typical applica- tion circuit is used to set the operating current of the white led using the equation: r b = v fb i f where v fb is the feedback pin voltage (1.22v), i f is the operating current of the white leds. in order to achieve accurate led current, 1% application information
9 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation preci sion resistors are recommended. table 3 below shows the r b selection for different white led currents. for example, to set the operating current to be 20ma, r b is selected as 60.4 ? , as shown in the schematic. table 3. bias resistor selection i f (ma) r b ( ? ) 5 243 10 121 12 102 15 80.6 20 60.4 output voltage program the sp6691 can be programmed as either a voltage source or a current source. to program the sp6691 as voltage source, the sp6691 re- quires 2 feedback resistors r 1 & r 2 to control the output voltage. as shown in figure 22. table 4. divider resistor selection v out (v) r 1 ( ? )r 2 ( ? ) 12 1m 113k 15 1m 88.7k 18 1m 73.2k 21 1m 61.9k 30 1m 42.2k brightness control dimming control can be achieved by applying a pwm control signal to the shdn pin. the brightness of the white leds is controlled by increasing and decreasing the duty cycle of the pwm signal. a 0% duty cycle corresponds to zero led current and a 100% duty cycle corre- sponds to full load current. while the operating frequency range of the pwm control is from 60hz to 700hz, the recommended maximum brightness frequency range of the pwm signal is from 60hz to 200hz. a repetition rate of at least 60hz is required to prevent flicker. the magnitude of the pwm signal should be higher than the minimum shdn voltage high. open circuit protection when any white led inside the white led module fails or the led module is disconnected from the circuit, the output and the feedback control will be open, thus resulting in a high output voltage, which may cause the sw pin voltage to exceed it maximum rating. in this case, a zener diode can be used at the output to limit the voltage on the sw pin and protect the part. the zener voltage should be larger than the maximum forward voltage of the white led module. application information: continued l1 1.22v r2 d1 c1 c2 r1 vout u1 sp6691 1 2 3 4 5 s w g n d fb shdn v i n vin figure 22. using sp6691 as voltage source the formula and table for the resistor selection are shown below: r 1 = ( v out - 1 ) ?r 2 1.22
10 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation layout consideration both the input capacitor and the output capacitor should be placed as close as possible to the ic. this can reduce the copper trace resistance which directly effects the input and output ripples. the feedback resistor network should be kept close to the fb pin to minimize copper trace connections that can inject noise into the system. the ground connection for the feedback resistor network should connect directly to the gnd pin or to an analog ground plane that is tied directly to the gnd pin. the inductor and the schottky diode should be placed as close as possible to the switch pin to minimize the noise coupling to the other circuits, especially the feedback network. power efficiency for the typical application circuit, the output efficiency of the circuit is expressed by = v out ?i out v in ?i in where v in , i in , v out , i out are the input and output voltage and current respectively. while the white led efficiency is expressed by = (v out - 1.22) ?i out v in ? i in this equation indicates that the white led efficiency will be much smaller than the output efficiency of the circuit when v out is not very large, compared to the feedback voltage (1.22v). the other power is consumed by the bias resis- tor. to reduce this power loss, two circuits can be used, as shown in figure 23 and figure 24. in figure 23, a general-purpose diode (for ex- ample, 1n4148) is used to bring the voltage across the bias resistor to be around 0.7v. r 1 is used to create a loop that provides around 100 a operating current for the diode. 3% efficiency improvement can be achieved by using this method. application information figure 23. improve efficiency with diode in feedback loop to further improve the efficiency and reduce the effects of the ambient temperature on the diode d1 used in method 1, an op amp circuit can be used as shown in figure 24. the gain of the op amp circuit can be calculated by: av = r 1 + r 2 r 1 if the voltage across the bias resistor is set to be 0.1v the current through r 1 and r 2 to be around 100 a, r 1 and r 2 can be selected as 1k and 11.2k respectively. lmv341 can be used be- cause of its small supply current, offset voltage and minimum supply voltage. by using this method, the efficiency can be increased around 7%. vin wled module c1 4.7uf murata lqh32cn100k11 ds mbr0530 d1 diode 34.8ohm rb c2 2.2uf r1 150kohm l1 10uh 0.45a 1.22v 2.7-4.2v 0.7v u1 sp6691 1 2 3 4 5 s w gnd fb shdn v in lmv341 1 3 4 + - out 2 6 0.1v c2 2.2uf 2.7-4.2v l1 10uh 0.45a 1.22v vbattery u1 sp6691 1 2 3 4 5 s w g n d fb shdn v in 5 ds mbr0530 r1 1k wled module c1 4.7uf r2 1 1.2k vbattery murata lqh32cn100k11 rb 5.1? figure 24. improve efficiency with op amp in feedback loop
11 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation package: pinouts 54 123 sp6691 5 pin tsot v in shdn sw gnd fb nc shdn v in gnd nc fb nc sw 8 7 6 5 1 2 3 4 sp6691 8 pin dfn 54 123 sp6691 5 pin sot-23 v in shdn sw gnd fb
12 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation package: 8 pin dfn note: dimensions in (mm) symbol min nom max a 0.8 0.9 1 a1 0 0.02 0.05 a3 b 0.18 0.25 0.3 d d2 1.5 1.75 e- 0.5 - e e2 1.6 - 1.9 k 0.2 - - l 0.3 0.4 0.5 2x3 8 pin dfn jedec mo-229 (vced-2) variation 0.20 ref 2.00 bsc 3.00 bsc t op view a a3 a1 d e e/2 d/2 bottom view b e l k d2 e2 1 2 side view
13 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation package: 5 pin sot-23 d e e/2 e1 n/2 2 1 b e e1 e1/2 n n/2 +1 l1 l l seating plane gauge plane view c see view c b b c with plating base metal b section b-b seating plane view a-a side view symbol min nom max a- - 1.45 a1 0 - 0.15 a2 0.9 1.15 1.3 b 0.3 - 0.5 c 0.08 - 0.22 d e e1 e e1 l 0.3 0.45 0.6 l1 l2 ?0o4 o8o ?5o 10o 15o note: dimensions in (mm) 5 pin sot-23 jedec mo-178 (aa) variation 2.80 bsc 1.60 bsc 2.90 bsc 0.95 bsc 1.90 bsc 0.60 ref 0.25 bsc a a2 a1
14 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation package: 5 pin tsot l1 l ? 1 gauge plane view c c with plating base metal b d e e/2 e1 n/2 2 1 b e e1 e1/2 n n/2 +1 index area (d/2 x e1/2) b-b section seating plane see view c b b view a-a side view seating plane c a a1 a2 symbol min nom max a-- 1.1 a1 0 - 0.1 a2 0.7 0.9 1 b 0.3 - 0.5 c 0.08 - 0.2 d e e1 e e1 l 0.3 0.45 0.6 l1 l2 ?0o4 o8o ?1 4o 10o 12o note: dimensions in (mm) 1.60 bsc 0.60 ref 0.25 bsc 5 pin tsot jedec mo-193 (ab) variation 2.90 bsc 0.95 bsc 1.90 bsc 2.80 bsc
15 date: 01/26/05 sp6691 micro power boost regulator, series white led driver ?copyright 2005 sipex corporation corporation analog excellence sipex corporation reserves the right to make changes to any products described herein. sipex does not assume any liability aris ing out of the application or use of any product or circuit described herein; neither does it convey any license under its patent rights nor t he rights of others. sipex corporation headquarters and sales office 233 south hillview drive milpitas, ca 95035 tel: (408) 934-7500 fax: (408) 935-7600 /tr = tape and reel pack quantity is 2,500 for tsot or sot-23 and 3,000 for dfn. available in lead free packaging. to order add "-l" suffix to part number. example: sp6691er/tr = standard; sp6691er-l/tr = lead free ordering information part number temperature range package type sp6691ek1 .......................................................... -40?c to +85?c ............................. 5 pin tsot sp6691ek1/tr ..................................................... -40?c to +85?c ............................ 5 pin tsot sp6691ek ............................................................ -40?c to +85?c .......................... 5 pin sot-23 sp6691ek/tr ....................................................... -40?c to +85?c ......................... 5 pin sot-23 sp6691er ............................................................ -40?c to +85?c ............................... 8 pin dfn sp6691er/tr ...................................................... -40?c to +85?c .............................. 8 pin dfn click here to order samples

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