august 2005 1 m9999-082605-b lm2576 micrel, inc. lm2576 52khz simple 3a buck regulator general descriptionthe lm2576 series of monolithic integrated circuits provide all the active functions for a step-down (buck) switching regulator. fixed versions are available with a 3.3v, 5v, or 12v fixed output. adjustable versions have an output voltage range from 1.23v to 37v. both versions are capable of driving a 3a load with excellent line and load regulation. these regulators are simple to use because they require a minimum number of external components and include internal frequency compensation and a fixed-frequency oscillator. the lm2576 series offers a high efficiency replacement for popular three-terminal adjustable linear regulators. it substantially reduces the size of the heat sink, and in many cases no heat sink is required. a standard series of inductors available from several different manufacturers are ideal for use with the lm2576 series. this feature greatly simplifies the design of switch-mode power supplies. the feedback voltage is guaranteed to 2% tolerance for adjustable versions, and the output voltage is guaranteed to 3% for fixed versions, within specified input voltages and output load conditions. the oscillator frequency is guaranteedto 10%. external shutdown is included, featuring less than 200 a standby current. the output switch includes cycle-by- cycle current limiting and thermal shutdown for full protectionunder fault conditions. typical applications features ? 3.3v, 5v, 12v, and adjustable output versions ? voltage over specified line and load conditions: fixed version: 3% max. output voltage adjustable version: 2% max. feedback voltage ? guaranteed 3a output current ? wide input voltage range: 4v to 40v ? wide output voltage range 1.23v to 37v ? requires only 4 external components ? 52khz fixed frequency internal oscillator ? low power standby mode i q typically < 200 a ? 80% efficiency (adjustable version typically > 80%) ? uses readily available standard inductors ? thermal shutdown and current limit protection ? 100% electrical thermal limit burn-in applications ? simple high-efficiency step-down (buck) regulator ? efficient pre-regulator for linear regulators ? on-card switching regulators ? positive to negative converter (inverting buck-boost) ? isolated flyback converter using minimum number of external components ? negative boost converter r2r1 7v C 40v unregulated dc input lm2575 + c in 100f +v in 1 3 gnd 5 on/off 2 output 4 feedback l1 330h + d11n5822 c out 330f r2 3.09kr1 1k v out = 1.23 1 + ( ) +5v, 1a regulated output note: pin numbers are for to-220 package 7v C 40v unregulated dc input lm2575-5.0 + c in 100f +v in 1 3 gnd 5 on/off 2 output 4 feedback l1 330h + d11n5822 c out 330f +5v, 1a regulated output note: pin numbers are for to-220 package fixed regulator in typical application adjustable regulator in fixed output application micrel, inc. ? 2180 fortune drive ? san jose, ca 95131 ? usa ? tel + 1 (408) 944-0800 ? fax + 1 (408) 474-1000 ? http://www.mic rel.com downloaded from: http:///
m9999-082605-b 2 august 2005 lm2576 micrel, inc. part number ? temperature standard rohs compliant** range package lm2576bt* ? LM2576WT* ? C40 c to +85 c to-220-5 lm2576-3.3bt ? lm2576-3.3wt ? C40 c to +85 c to-220-5 lm2576-5.0bt ? lm2576-5.0wt ? C40 c to +85 c to-220-5 lm2576-12bt ? lm2576-12wt ? C40 c to +85 c to-220-5 lm2576bu* lm2576wu* C40 c to +85 c to-263-5 lm2576-3.3bu lm2576-3.3wu C40 c to +85 c to-263-5 lm2576-5.0bu lm2576-5.0wu C40 c to +85 c to-263-5 lm2576-12bu lm2576-12wu C40 c to +85 c to-263-5 * adjustable output regulators.**rohs compliant with "hot-melting solder" exemption. ? contact factory for bent or staggered leads option. pin configurations gnd 5- on/off4- feedback 3- ground 2- output 1- v in 5-lead to-263 (u) gnd 5- on/off4- feedback 3- ground 2- output 1- v in 5-lead to-220 (t) ordering information downloaded from: http:///
august 2005 3 m9999-082605-b lm2576 micrel, inc. electrical characteristics specifications with standard typeface are for t j = 25 c, and those with boldface type apply over full operating temperature range. unless otherwise specified, v in = 12v, and i load = 500ma. lm2576 symbol parameter conditions typ limit units (note 2) (limits) system parameters, adjustable regulators (note 3) test circuit figure 1 v out feedback voltage v in = 12v , i load = 0.5a 1.230 v v out = 5v 1.217 v(min) 1.243 v(max) v out feedback voltage 0.5a i load 3a, 8v v in 40v 1.230 v lm2576 v out = 5v 1.193/ 1.180 v(min) 1.267/ 1.280 v(max) efficiency v in = 12v, i load = 3a, v out = 5v 82 % system parameters, 3.3v regulators (note 3) test circuit figure 1 v out output voltage v in = 12v , i load = 0.5a 3.3 v v out = 3.3v 3.234 v(min) 3.366 v(max) v out output voltage 0.5a i load 3a, 6v v in 40v 3.3 v lm2576-3.3 v out = 3.3v 3.168/ 3.135 v(min) 3.432/ 3.465 v(max) efficiency v in = 12v, i load = 3a 75 % system parameters, 5v regulators (note 3) test circuit figure 1 v out output voltage v in = 12v , i load = 0.5a 5.0 v v out = 5v 4.900 v(min) 5.100 v(max) v out output voltage 0.5a i load 3a, 8v v in 40v 5.0 v lm2576-5.0 v out = 5v 4.800/ 4.750 v(min) 5.200/ 5.250 v(max) efficiency v in = 12v, i load = 3a 82 % system parameters, 12v regulators (note 3) test circuit figure 1 v out output voltage v in = 25v , i load = 0.5a 12 v v out = 12v 11.760 v(min) 12.240 v(max) v out output voltage 0.5a i load 3a, 15v v in 40v 12 v lmlm2576-12 v out = 12v 11.520/ 11.400 v(min) 12.480/ 12.600 v(max) efficiency v in = 25v, i load = 3a 88 % operating ratingstemperature range C40 c t j +125 c supply voltage 40v absolute maximum ratings (note 1) maximum supply voltage 45v on/off pin input voltage C0.3v v +40v output voltage to ground (steady state) C 1v power dissipation internally limited storage temperature range C65 c to +150 c minimum esd rating c = 100pf, r = 1.5k 2 kv fb pin 1 kv lead temperature (soldering, 10 sec.) 260 c maximum junction temperature 150 c downloaded from: http:///
m9999-082605-b 4 august 2005 lm2576 micrel, inc. electrical characteristics (continued) lm2576 units symbol parameter conditions typ limit (limits) (note 2) device parameters, adjustable regulator i b feedback bias current v out = 5v 50 100/ 500 na device parameters, fixed and adjustable regulatorsf o oscillator frequency 52 khz 47/ 42 khz (min) 58/ 63 khz (max) v sat saturation voltage i out = 3a (note 4) 1.4 v 1.8/ 2.0 v(max) dc max duty cycle (on) (note 5) 98 % 93 %(min) i cl current limit peak current, t on 3 s (note 4) 5.8 a 4.2/ 3.5 a(min) 6.9/ 7.5 a(max) i l output leakage current v in = 40v, (note 6), output = 0v 2 ma(max) output = C 1v 7.5 ma (note 6) output = C 1v 30 ma(max) i q quiescent current (note 6) 5 ma 10 ma(max) i stby standby quiescent on/off pin = 5v (off) 50 a current 200 a(max) ja thermal resistance t,u package, junction to ambient (note 7) 65 c/w ja t,u package, junction to ambient (note 8) 45 jc t,u package, junction to case 2 downloaded from: http:///
august 2005 5 m9999-082605-b lm2576 micrel, inc. electrical characteristics (continued) lm2576 units symbol parameter conditions typ limit (limits) (note 2) on/off control, fixed and adjustable regulators test circuit figure 1 v ih on/off pin logic v out = 0v 1.4 2.2/ 2.4 v(min) v il input level v out = 5v 1.2 1.0/ 0.8 v(max) i ih on /off pin logic on /off pin = 5v (off) 4 a current 30 a(max) i il on/off pin = 0v (on) 0.01 a 10 a(max) note 1: absolute maximum rating indicate limits beyond which damage to the device may occur. operating ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. for guaranteed specifications and test conditions, see the electrical characteristics. note 2: all limits guaranteed at room temperature (standard type face) and at temperature extremes (bold type face) . all room temperature limits are 100% production tested. all limits at temperature extreme are guaranteed via testing. note 3: external components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. when the lm2576/lm1576 is used as shown in figure 1 test circuit, system performance will be shown in system parameters section of electrical characteristics. note 4: output (pin 2) sourcing current. no diode, inductor or capacitor connected to output. note 5: feedback (pin 4) removed from output and connected to 0v. note 6: feedback (pin 4) removed from output and connected to 12v to force the output transistor off. note 7: junction to ambient thermal resistance (no external heat sink) for the 5-lead to-220 package mounted vertically, with 1/2" leads in a socket, or on pc board with minimum copper area. note 8: junction to ambient thermal resistance (no external heat sink) for the 5-lead to-220 package mounted vertically, with 1/4" leads soldered to pc board containing approximately 4 square inches of copper area surrounding the leads. note 9: junction to ambient thermal resistance with approximately 1 square inch of pc board copper surrounding the leads. additional copper will lower thermal resistance further. typical performance characteristics normalizedfeedback voltage* junction temperature ( ? c) normalized feedback voltage (mv) 25 20 15 10 5 0 -5 -10 -15 -20 -25 -75 -50 -25 0 25 50 75 100 125 150 v in = 12v i load = 200ma normalized to t j = 25?c feedback voltagevs duty cycle* duty cycle (%) feedback voltage change (mv) 20 15 10 5 0 -5 -10 -15 -20 iload = 200 ma vin = 40v vin = 7v 0 20 40 60 80 100 * adjustable version only downloaded from: http:///
m9999-082605-b 6 august 2005 lm2576 micrel, inc. typical performance characteristics (continued) (circuit of figure 1 ) supply current input voltage (v) supply current (ma) 20 measured at ground pin t j = 25 ?c v out = 5v 1816 14 12 10 86 4 0 102030405060 i load to 1a supply currentvs. duty cycle duty cycle (%) 20.017.5 15.0 12.5 10.0 7.55.0 2.5 0 0 20 40 60 80 100 v in from 7v to 40v i load = 200 ma supply current (ma) junction temperature ( ? c) 200150 100 50 0-75 v in = 12v standby quiescent current (a) standbyquiescent current v in = 40v -50 -25 0 25 50 75 100 125 150 current limit junction temperature ( ? c) 32 1 0 -75 vi n = 25v output current (a) input voltage (v) 100 efficiency (%) efficiency v out = 12v -50 -25 0 25 50 75 100 125 150 9590 85 80 75 70 65 60 200 ma 200 ma v out = 3v 1a 0 5 10 15 20 25 30 35 40 minimum operatingvoltage junction temperature ( ? c) 5.0 i load = 200 ma input voltage (v) line regulation input voltage (v) 14 0 normalized feedback voltage (mv) junction temperature ( ? c) 100 -100 -75 standby quiescent current (a) feedback pin current -50 -25 0 25 50 75 100 125 150 v out = 1.23v 4.54.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 -75 -50 -25 0 25 50 75 100 125 150 1210 86 4 2 0 -2-4 -6 5 1015202530 7550 25 0 -25-50 -75 junction temperature ( ? c) +8 -8 -75 normalized frequency (%) oscillator frequency -50 -25 0 25 50 75 100 125 150 +6+4 +2 0 -2-4 --6 v in = 12v v in = 40v normalized at 25?c normalized to v in = 10v v out = 5v i load = 500ma t j = 25 v on/off = 5v switchsaturation voltage switch current (a) 1.2 -55 ?c 1.00.8 0.6 0.4 0 saturation voltage (v) 0.2 0.4 0.6 0.8 1.0 25 ?c 125 ?c 150 ?c -40 ?c dropout voltage junction temperature ( ? c) input-output differential (v) 2.0 -75 -50 -25 0 25 50 75 100 125 150 ? v out = 5% r ind = 0.2 i load = 1a i load = 200 ma 1.5 1.0 0.5 0 normalizedoutput voltage junction temperature ( ? c) output voltage change (mv) 100 75 50 25 0 -25 -50 -75 -100 -75 -50 -25 0 25 50 75 100 125 150 v in = 12v i load = 200ma normalized to t j = 25 ?c 1a downloaded from: http:///
august 2005 7 m9999-082605-b lm2576 micrel, inc. 100 s/div. load transient response +100mv 0 -100mv output voltagechange 3a2a 1a 0 output current 50v 0 4a2a 0 4a2a 0 a bc d 5 s/div. switching waveforms a: output pin voltage 50v/divb: output pin current 2a/div c: inductor current 2a/div d: output ripple voltage 50 mv/div., ac coupled horizontal time base: 5s/div v out = 5v v in = 45v typical performance characteristics (circuit of figure 1 ) downloaded from: http:///
m9999-082605-b 8 august 2005 lm2576 micrel, inc. lm2575 + 100 f +v in 1 3 gnd 5 on/off 2 output 4 feedback l1 330 h + d1mbr360 c out 470f r2 r1 v out 5.00v 7v - 40v unregulated dc input c in lo a d c in 100f, 75v aluminum electrolytic c out 470f, 15v aluminum electrolytic d1 schottky, mbr360 l1 330h, 415-0926 (aie) r1 1k, 0.01% r2 3.065k, 0.01% 5-pin to-220 socket2936 (loranger mfg. co.) 4-pin to-3 socket8112-ag7 (augat inc.) lm2575-5.0 + 100 f +v in 1 3 gnd 5 on/off 2 output 4 feedback l1 330 h + d111dq06 c out 220f v out 5.00v note : pin numbers are for to-220 package 7v - 40v unregulated dc input c in c in 100f, 75v aluminum electrolytic c out 330f, 15v aluminum electrolytic d1 schottky, 11dq06 l1 100h, 415-0926 (aie) 5-pin to-220 socket 2936 (loranger mfg. co.) 4-pin to-3 socket8112-ag7 (augat inc.) lo a d on/off comparator fixed gainerror amp 3 ampswitch output driver + - +- v in feed-back 1.23v band-gap reference 52 khz oscillator reset thermal shutdown current limit 52 3 1 note: pin numbers are for the to-220 package internal regulator on/off gnd on/off comparator fixed gainerror amp 3 ampswitch output driver + - +- v in feed-back 1.23v band-gap reference 52 khz oscillator reset thermal shutdown current limit 52 3 14 internal regulator on/off gnd 3.1k1.0k 4 block diagrams as in any switching regulator, layout is very important. rapidly switching currents associated with wiring inductance generate voltage transients which can cause problems. for minimal stray inductance and ground loops, the length of the leads indicated by heavy lines should be kept as short as possible. single-point grounding (as indicated) or ground plane construction should be used for best results. fixed regulator adjustable regulator test circuits and layout guidelines figure 1. downloaded from: http:///
august 2005 9 m9999-082605-b lm2576 micrel, inc. package information 0.018 0.008 (0.46 0.20) 0.268 ref (6.81 ref) 0.032 0.005 (0.81 0.13) 0.550 0.010 (13.97 0.25) 7 typ. seatingplane 0.578 0.018 (14.68 0.46) 0.108 0.005 (2.74 0.13) 0.050 0.005 (1.27 0.13) 0.150 d 0.005 (3.81 d 0.13) 0.400 0.015 (10.16 0.38) 0.177 0.008 (4.50 0.20) 0.103 0.013 (2.62 0.33) 0.241 0.017 (6.12 0.43) 0.067 0.005 (1.70 0.127) inch (mm) dimensions: 5-lead to-220 (t) 0.067 0.005 0.032 0.003 0.360 0.005 0.600 0.025 0.405 0.005 0.060 0.005 0.176 0.005 8 max 0.100 0.01 0.050 0.005 0.015 0.002 0.004 +0.004 C 0.008 seating plane 0.065 0.010 20 2 dim. = inch 5-lead to-263 (u) micrel inc. 2180 fortune drive san jose, ca 95131 usa tel + 1 (408) 944-0800 fax + 1 (408) 474-1000 web http://www.micrel.com this information furnished by micrel in this data sheet is believed to be accurate and reliable. however no responsibility is assumed by micrel for its use. micrel reserves the right to change circuitry and specifications at any time without notification to the customer. micrel products are not designed or authorized for use as components in life support appliances, devices or systems where malfunction of a product can reasonably be expected to result in personal injury. life support devices or systems are devices or systems that (a) are intended for surgical implant into the body or (b) support or sustain life, and whose failure to perform can be reasonably expected to result in a significant injury to the user. a purchaser s use or sale of micrel products for use in life support appliances, devices or systems is a purchaser s own risk and purchaser agrees to fully indemnify micrel for any damages resulting from such use or sale. ? 2005 micrel, incorporated. downloaded from: http:///
|
