1 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2004 sipex corporati on sp4446 features high output voltage: up to 30v high efficiency low quiescent current: ~20ua miniature package: (5-lead sot-23) single battery cell operation programmable output voltage 1 ? switch (150mv at 150ma) high output voltage boost regulator lcd bias regulator applications lcd bias tuner pin voltage white led driver high voltage bias description the sp4446 is a micro power boost regualtor in a 5-lead sot-23 package. it is a current limited, fixed off time regulator configured for use in boost mode applications. the operating voltage can be less than 3v and is capable of generating voltages as high as 30 volts. the sp4446 is to be supplied in a sot-23-5 and permits the construction of complete regulators that occupy < 0.2 square inches of board space. ? typical application schematic preliminary 54 123 sp4446 v in shdn sw gnd fb 5 pin sot-23 now available in lead free packaging v in sw gnd shdn fb 10 h d1 l1 r1 r2 c2 2.2 f high v oltage output v in 4.7 f c1 2 to 7v sp4446 digital cameras cell phone battery backup handheld computers
2 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2003 sipex corporati on pin description v in ....................................................................... 15v sw voltage .............................................. -0.4 to 34v fb voltage .......................................................... 2.5v all other pins .................................. -0.3 to v cc + 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 parameter symbol min typ max units conditions input voltage v in 1.0 8.0 v switch current limit = 150ma supply current i q 20 30 a ? no switching 0.01 1 a shdn = 0v 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 0.04 %/v 1.2 v in 8v switch off time t off 300 ns v fb > 1v 1200 ns v fb < 0.3v switch saturation voltage v cesat 50 mv ? i sw = 50ma 150 mv i sw = 150ma switch current limit i lim 100 150 200 ma ? shdn bias current i shdn 512 a ? v shdn = 5v shdn high threshold (on) v ih 0.9 v shdn low threshold (off) v il 0.25 v switch leakage current i swlk 25 a ? switch off, v sw = 5v electrical characteristics specifications are at v in = 3.3v, v shdn = v in , t a = 25 c, ? denotes the specifications which apply over the full operating temperature range, unless otherwise specified. absolute maximum ratings lead temperature (soldering, 10 sec) ............ 300 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. 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.
3 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2004 sipex corporati on functional diagram + - vi (external) (external) r1 r2 c1 shdn 4 q1 q2 r3 r4 r6 r5 x1 shutdown logic 300ns one-shot clear x2 + - set driver 52.5mv 0.35 gnd 2 1 5 3 l1 sw c2 d1 v out power transistor disable v in fb general overview: operation can be best understood by referring to the above block diagram. q1 and q2 along with r3 and r4 form a band gap reference. the input to this circuit completes a feedback path from the high voltage output through a voltage di- vider, 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 discharges 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 150ma, comparator x2 clears the latch, which turns off the driver tran- sistor for a preset 0.3 s. at the instant of shutoff, inductor current is diverted to the output through diode d1. during this 0.3 s time limit, inductor current decreases while its energy charges c2. theory of operation at the end of the 0.3 s time period, driver transistor is again allowed to turn on which ramps the current back up to the 150ma 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. the sp4446 contains circuitry to provide protection during start-up and while in short-circuit conditions. when fb pin volt- age is less than approximately 300mv, the switch off time is increased to about 1.2 s and the current limit is reduced to about 70% of its normal value. while in this mode, the average inductor current is reduced and helps minimize power dissipation in the sp4446, the external inductor and diode.
4 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2003 sipex corporati on capacitor selection ceramic capacitors are recommended for their inherently low esr, which will help produce low peak to peak output ripple, and reduce high fre- quency spikes. for the typical application, 4.7 f input capacitor 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 capaci- tors. place all the capacitors as close to the sp4446 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 com- parator, thus reduce the output ripple. refer to table 2 for some suggested low esr capacitors. table 2. suggested low esr capacitor manuf. part cap/ size/ number voltage type murata grm32rr71e 2.2 f/25v 1210/x5r 770-436-1300 225kc01b murata grm31cr61a 4.7 f/10v 1206/x5r 770-436-1300 475ka01b tdk c3225x7r1e 2.2 f/25v 1206/x7r 847-803-6100 225m tdk c3216x5r1a 4.7 f/10v 1206/x5r 847-803-6100 475k application informamtion inductor selection for sp4446, the internal switch will be turned off only after the inductor current reaches the typical dc current limit (i lim =150ma). however, 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 sp4446 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 lqh32cn100k21 0.44 300 770-436-1300 (10 h) murata lqh32cn220k21 0.71 250 770-436-1300 (22 h) tdk nlfc453232t-100k 847-803-6100 (10 h) 0.273 250 tdk nlc453232t-100k 0.9 370 847-803-6100 (22 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. output voltage program the sp4446 can be programmed as voltage source, the sp4446 requires 2 feedback resistors r 1 & r 2 to control the output voltage. as shown in fig. 19. l1 1.22v r2 d1 c1 c2 r1 vout u1 sp4446 1 2 3 4 5 s w g n d fb shdn v i n vin figure 19. using sp4446 as voltage source
5 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2004 sipex corporati on application informamtion: continued the formula and table for the resistor selection are shown below: r 1 = ( v out - 1 ) ?r 2 1.22 table 3. divider resistor selection v out (v) r 1 ( ? )r 2 ( ? ) 12 1m 113k 15 1m 88.7k 18 1m 73.2k 20 1m 64.9k 30 1m 42.2k 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. 3.3v or 5v r1 1m c1 4.7uf 30v r2 42.2k u1 sp4446 1 2 3 4 5 shdn murata lqh32cn100k21 3 to 5 ma ds mbr0530 c2 47pf 1.22v l1 10uh 0.3a c3 2.2uf 3.3v or 5v r1 1m c1 4.7uf 30v r2 42.2k u1 sp4446 1 2 3 4 s w gnd fb shdn v in murata lqh32cn100k21 v in 3 to 5 ma ds mbr0530 v out c2 47pf 1.22v l1 10uh 0.3a c3 2.2uf v in ds c1 4.7uf q1 mmbt2907a r1 1m r3 154k 20v 1.22v c2 47pf r2 64.9k u1 sp4446 1 2 3 4 5 sw gnd fb shdn v in v out l1 10uh c3 2.2uf load disconnect in shutdown when sp4446 was shut down, the load is still connected to the input. in applications that re- quire output isolation during shutdown, an ex- ternal pnp transistor (for example mmbt2907a) can be added as shown in figure 20. when the sp4446 is active, the voltage set at the emitter of the transistor exceeds the input voltage, forcing the transistor into the saturation region. when the sp4446 is shut down, the input voltage exceeds the emitter voltage, thus the transistor becomes inactive and provides high-impedance isolation between the input and load. efficiency will be slightly sacrificed because of the satura- tion voltage and base current of the pnp transistor. fig. 20. load disconnect in shutdown pin diode driver the sp4446 can be used as pin diode driver as shown in fig. 21. two resistors (r 1 =1m ? , r 2 =42.2k ? ) are used to program the output volt- age to be 30v. when input voltage is 3.3v or 5v, it can supply a maximum current of 3ma and 5ma to the load. fig. 21. pin diode driver
6 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2003 sipex corporati on figure 5. 18v output efficiency (v in =3.3v) figure 6. 18v output efficiency (v in =5v) figure 3. 15v output efficiency (v in =3.3v) figure 4. 15v output efficiency (v in =5v) v in=3.3v; vout = 18v efficiency 40 45 50 55 60 65 70 75 80 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 iout (ma) efficiency (%) 10 uh 22 uh vi n=5.0v; vout = 18v efficiency 40 45 50 55 60 65 70 75 80 0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 iout (ma) efficiency (%) 10 uh 22 uh performance characteristics refer to the typical application circuit, t amb = 25 c, unless otherwise specified. figure 1. 12v output efficiency (v in =3.3v) figure 2. 12v output efficiency (v in =5v) vi n=3.3v;vout =12v efficiency 50 55 60 65 70 75 80 85 0369121518 iout (ma) efficiency (%) 10 uh 22 uh vi n=5.0v;vout =12v efficiency 50 55 60 65 70 75 80 85 0510 15 20 25 30 iout (ma) efficiency (%) 10 uh 22 uh vi n=3.3v;vout =15v efficiency 50 55 60 65 70 75 80 024681012 iout (ma) efficiency (%) 10 uh 22 uh vi n=5.0v;vout =15v efficiency 50 55 60 65 70 75 80 0369121518 iout (ma) efficiency (%) 10 uh 22 uh
7 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2004 sipex corporati on vi n=3.3v;vout = 20v efficiency 30 35 40 45 50 55 60 65 70 75 01234567 iout (ma) efficiency (%) 10 uh 22 uh vi n=5v;vout = 20v efficiency 35 40 45 50 55 60 65 70 75 024681012 iout (ma) efficiency (%) 10 uh 22 uh performance characteristics refer to the typical application circuit, t amb = 25 c, unless otherwise specified. figure 7. 20v output efficiency (v in =3.3v) figure 8. 20v output efficiency (v in =5v) figure 9. maximum output current vs. v in (v out =20v) figure 10. maximum output current vs. v in (v out =30v) 0 2 4 6 8 10 12 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1 input voltage (v) maximum output current (ma) 10uh 22uh 0 1 2 3 4 5 6 2.7 3 3.3 3.6 3.9 4.2 4.5 4.8 5.1 input voltage (v) maximum output current (ma) 10uh 22uh 0 5 10 15 20 25 30 12345678 input voltage (v) quiescent current (ua) ta mb=-40c ta mb=25c ta mb=85c 0 2 4 6 8 10 12345678 input voltage (v) shutdown pin current (ua) figure 11. quiescent current i q vs. v in figure 12. shutdown pin current vs. v in
8 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2003 sipex corporati on v out (ac) i out (5ma/div) v sw v out (ac) i l (0.1a/div) v sw v in v out i in (100ma/div) figure 16. startup waveform (v in =3.3v, v out =20v, i out =2ma) figure 17. typical switching waveforms (v in =3.3v, v out =20v, i out =5ma) figure 18. load step transient (v in =3.3v, v out =20v, 1 o =100 a 5ma) figure 13. i pk current limit vs. v in figure 14. feedback voltage vs. temperature 0 50 100 150 200 250 12345678 input voltage (v) ipk current limit (ma) 1.18 1.19 1.20 1.21 1.22 1.23 1.24 1.25 -40 -15 10 35 60 85 te mperature (c) feedback voltage (v) performance characteristics refer to the typical application circuit, t amb = 25 c, unless otherwise specified. figure 15. switch saturation voltage v cesat vs. temperature (i sw =50ma) 0 10 20 30 40 50 60 -40 -15 10 35 60 85 te mperature (c) switch saturation voltage (mv)
9 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2004 sipex corporati on 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 b0.3 -0.5 c0.08- 0.22 d e e1 e e1 l0.30. 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
10 date: 11/29/04 sp4446 high output voltage boost regualtor, lcd bias regulator ? copyright 2003 sipex corporati on 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 ordering information part number operating temperature range package type sp4446ek .................................................. -40 c to +85 c ........................................................ 5 pin sot-23 sp4446ek/tr ............................................ -40 c to +85 c ........................................................ 5 pin sot-23 available in lead free packaging. to order add "-l" suffix to part number. example: sp4446ek/tr = standard; SP4446EK-L/tr = lead free /tr = tape and reel pack quantity is 2,500 for sot-23. click here to order samples
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