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3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 1 - htc features z 3.3v, 5.0v, 12v and adjustable output versions z adjustable version output voltage range, 1.23 to 37v +/- 4% ag10maximum over line and load conditions z guaranteed 3.0a output current z wide input voltage range z requires only 4 external components z 52khz fixed frequency internal oscillator z ttl shutdown capability, low power standby mode z high efficiency z uses readily available standard inductors z thermal shutdown and current limit protection z moisture sensitivity level 3 for smd packages application z simple high-efficiency step-down(buck) regulator z efficient pre-regulator for linear regulators z on-card switching regulators z positive to negative converter(buck-boost) z negative step-up converters z power supply for battery chargers sop8-pp pkg to-220 pkg to-263 pkg ordering information device marking package LM2576dp-x.x LM2576-x.x sop8-pp LM2576t-x.x LM2576-x.x to-220 LM2576r-x.x LM2576-x.x to-263 description the LM2576 series of regulators are monolithic int egrated circuits ideally suited for easy and convenient design of a step-down switching regulator (buck converter). all circuits of this series are capable of driving a 3.0a load with excellent line and load regulation. these devices are available in fixed output voltages of 3.3v, 5.0v, 12v and an adjustable output version. these regulators were designed to minimize the number of external components to simplify the power supply design. standard series of inductors optimized for use with the LM2576 are of fered by several different inductor manufacturers. since the LM2576 converter is a switch-mode power supply, its efficiency is significantly higher in comparison with popular three-terminal linear regulators, especially with higher input voltages. in many cases, the power dissipated is so low that no heatsink is required or its size could be reduced dramatically. a standard series of inductors optimiz ed for use with the LM2576 are available from several different manufacturers. this featur e greatly simplifies the design of switch-mode power supplies. the LM2576 features include a guaranteed +/- 4% tolerance on output voltage within specified input voltages and output load conditions, and +/-10% on the oscillator frequency (+/- 2% over 0 ? c to 125 ? c). external shutdown is included, featuring 80 ? (typical) standby current. the out put switch includes cycle- bycycle current limiting, as well as thermal shut down for full protection under fault conditions.
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 2 - htc ordering information v out package order no. description package marking status adj sop8-pp LM2576dp-adj 3a, adjustable, 52khz, on/off LM2576-adj contact us to220-5l LM2576t-adj 3a, adjustable, 52khz, on/off LM2576-adj active to263-5l LM2576r-adj 3a, adjustable, 52khz, on/off LM2576-adj active 3.3v sop8-pp LM2576dp-3.3 3a, fixed, 52khz, on/off LM2576-3.3 contact us to220-5l LM2576t-3.3 3a, fixed, 52khz, on/off LM2576-3.3 active to263-5l LM2576r-3.3 3a, fixed, 52khz, on/off LM2576-3.3 active 5.0v sop8-pp LM2576dp-5.0 3a, fixed, 52khz, on/off LM2576-5.0 contact us to220-5l LM2576t-5.0 3a, fixed, 52khz, on/off LM2576-5.0 active to263-5l LM2576r-5.0 3a, fixed, 52khz, on/off LM2576-5.0 active 12v sop8-pp LM2576dp-12 3a, fixed, 52khz, on/off LM2576-12 contact us to220-5l LM2576t-12 3a, fixed, 52khz, on/off LM2576-12 active to263-5l LM2576r-12 3a, fixed, 52khz, on/off LM2576-12 active root name product code lm 2576 package type dp : sop8-pp t : to220-5l r : to263-5l output voltage : adj / 3.3v / 5.0v /12v
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 3 - htc pin configuration sop8-pp to220-5l to263-5l pin description package symbol description to-220 5l to-263 5l sop8-pp 1 1 vin this pin is the positive input supply for the LM2576 step?down switching regulator. in order to minimize voltage transients and to supply the switching currents needed by the regulator, a suitable input bypass capacitor must be present. (cin in figure 1). 2 2 vout this is the emitter of the internal switch. the saturation voltage v sat of this output switch is typically 1.5v. it should be kept in mind that the pcb area connected to this pin should be kept to a minimum in order to minimize coupling to sensitive circuitry. 3 6 gnd circuit ground pin. see the in formation about the printed circuit board layout. 4 3 feedback this pin senses regulated output voltage to complete the feedback loop. the signal is divided by the internal resistor divider network r2, r1 and applied to the non?inverting input of the internal error amplifier. in the adjustable version of the LM2576 switching regulator this pin is the direct input of the error am plifier and the resistor network r2, r1 is connected externally to allow programming of the output voltage. 5 4 on/off it allows the switching regulator circuit to be shutdown using logic level signals, thus dropping the total input supply current to approximately 80ua. the threshold voltage is typically 1.4v. applying a voltage above this value (up to +vin) shuts the regulator off. if the voltage applied to this pin is lower than 1.4v or if this pin is left open, the regulator will be in the "on" condition - 5, 7, 8 n.c. no connect. * exposed pad of sop8-pp package should be externally connected to gnd. exposed pad vin 1 vout 2 feedback 3 on/off 4 8 n.c 7 n.c 6 gnd 5 n.c.
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 4 - htc typical application (fixed output voltage versions) figure 1. block diagram and typical application
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 5 - htc absolute maximum ratings (absolute maximum ratings indicate limits beyond which damage to the device may occur) rating symbol value unit maximum supply voltage vin 45 v on/off pin input voltage - -0.3v v +vin v output voltage to ground (steady-state) - -1.0 v power dissipation sop8-pp 8lead thermal resistance, junction to ambient thermal resistance, junction to case p d ja jc internally limited contact us contact us w /w /w to-220 5lead p d internally limited w thermal resistance, junction to ambient j a 65 /w thermal resistance, junction to case jc 5 /w to-263 5lead p d internally limited w thermal resistance, junction to ambient j a 70 /w thermal resistance, junction to case jc 5 /w storage temperature range t stg -60 to +150 minimum esd rating(human body model: - 2.0 kv c=100 pf, r=1.5k ? lead temperature (soldering, 10seconds) - 260 maximum junction temperature t j 150 operating ratings (operating ratings indicate conditions for which the device is intended to be functional, but do not guarantee specific performance limits. for guaranteed specifications, see the electrical characteristics.) rating symbol value. unit operating junction temperature range t j -40 to +125 supply voltage vin 40 v
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 6 - htc electrical characteristics / system parameters ([note 1] test circuit figure 15) (unless otherwise specified, vin = 12v for the 3.3v, 5.0v, and adjustable version, vin = 25v for the 12v version. iload = 500 ma. for typical values tj = 25c, for min/max values tj is the operating junction temperature range that applies [note 2], unless otherwise noted.) characteristics symbol min typ max unit LM2576-3.3v ([note 1] test circuit figure 2) output voltage (vin = 12v, i load =0.5a, t j =25 ) vout 3.234 3.3 3.366 v output voltage (6.0v vin 40v, 0.5a i load 3.0a vout v t j =25 3.168 3.3 3.432 t j = -40 ~ +125 3.135 - 3.465 efficiency (vin=12v, i load =3.0a) - 75 - % LM2576-5.0v ([note 1] test circuit figure 2) output voltage (vin = 12v, i load =0.5a, t j =25 ) vout 4.9 5.0 5.1 v output voltage (8.0v vin 40v, 0.5a i load 3.0a vout v t j =25 4.8 5.0 5.2 t j = -40 ~ +125 4.75 - 5.25 efficiency (vin=12v, i load =3.0a) - 77 - % LM2576-12v ([note 1] test circuit figure 2) output voltage (vin = 25v, i load =0.5a, t j =25 ) vout 11.76 12 12.24 v output voltage (15v vin 40v, 0.5a i load 3.0a vout v t j =25 11.52 12 12.48 t j = -40 ~ +125 11.4 - 12.6 efficiency (vin=25v, i load =3.0a) - 88 - % LM2576-adj ([note 1] te st circuit figure 2) feedback voltage (vin=12v, i load =0.5a, t j =25 ) vout 1.217 1.23 1.243 v feedback voltage (8.0v vin 40v, 0.5a i load 3.0a, vout=5.0v) vout v t j =25 1.193 1.23 1.267 t j = -40 ~ +125 1.18 - 1.28 efficiency (vin=12v, i load =3.0a, vout=5.0v) - 77 - % 1. external components such as the catch diode, indu ctor, input and output capacitors can affect switching regulator system performance. when the LM2576 is used as shown in the figure 15 te st circuit, system performance will be as shown in system parameters section. 2. tested junction temperature range for the LM2576: tlow = ?40c thigh = +125c
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 7 - htc electrical characteristics / device parameters (unless otherwise specified, vin = 12v for the 3.3v, 5.0v, and adjustable version, vin = 25v for the 12v version. iload = 500 ma. for typical values tj = 25c, for min/max values tj is the operating junction temperature range that applies [note 2], unless otherwise noted.) characteristics symbol min. typ. max. unit all output voltage versions feedback bias current (vout=5.0v [adjustable version only]) t j =25 t j = -40 to +125 i b - - 25 - 100 200 na oscillator frequency [note 3] t j =25 t j = 0 to +125 t j = -40 to +125 f osc - 47 42 52 - - - 58 63 khz saturation voltage (iout=3.0a [note 4]) t j = 25 t j = -40 to +125 v sat - - 1.5 - 1.8 2 v max duty cycle (?0?) [note 5] dc 94 98 - % current limit (peak current [note 3 and 4]) t j = 25 t j = -40 to +125 i cl 4.2 3.5 5.8 - 6.9 7.5 a output leakage current [note 6 and 7], t j =25 output = 0v output = -1.0v i l - - 0.8 6 50 30 ma quiescent current [note 6] t j = 25 t j = -40 to +125 i q - - 5 - 9 11 ma standby quiescent current (on/off pin = 5.0v ("off")) t j =25 t j = -40 to +125 i stby - - 80 - 200 400 a on/off pin logic input level (test circuit figure 15) vout=0v t j =25 t j = -40 to +125 v ih 2.2 2.4 1.4 - - - v vout=nominal output voltage t j =25 t j = -40 to +125 v il - - 1.2 - 1 0.8 v on/off pin input current (test circuit figure 15) on/off pin = 5.0v (regulator off), t j =25 on/off pin = 0v (regulator on), t j =25 i ih i il - - 15 0 30 0.5 a 3. the oscillator frequency reduces to approximately 18 khz in the event of an output short or an overload which causes the regulated output voltage to drop approximately 40% from the no minal voltage. this self protection feature lowers the average dissipation of the ic by lowering the mini mum duty cycle from 5% down to approximately 2% 4. output sourcing current. no diode, inducto r or capacitor connected to output pin. 5. feedback removed from output and connected to 0v. 6. feedback removed from output and connected to +12v for t he adjustable, 3.3v, and 5.0v versions, and +25v for the 12v version, to force the output transistor ?off?. 7. vin = 40v.
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 8 - htc typical performance characteristics (circuit of figure 15) figure 2. normalized output voltage figure 3. line regulation figure 4. dropout voltage figure 5. current limit figure 6. quiescent current figure 7. standby quiescent current
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 9 - htc typical performance characteristics (circuit of figure 15) figure 8. standby quiescent current figure 9. switch saturation voltage figure 10. oscillator frequency figur e 11. minimum operating voltage figure 12. feedback pin current
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 10 - htc typical performanc e characteristics vout = 15v a : output pin voltage, 10v/div b: inductor current, 2.0a/div c: inductor current, 2.0a/div d: output ripple voltage, 50mv/ddiv, ac-coupled horizontal time base : 5.0 s/div figure 13. switching waveforms figure 14. load transient response
3a, 52khz, step-down switching regulator LM2576 dec 2011 ? rev. 1.3 - 11 - htc cin - 100f, 75v, aluminium electrolytic cout - 1000f, 25v, aluminium electrolytic d1 - schottky, mbr360 l1 -100 h, pulse eng. pe-92108 r1 - 2.0 k, 0.1% r2 - 6.12 k, 0.1% ) 0 . 1 v v ( 1 r = 2 r ref out - where v ref = 1.23v, r1 between 1.0k and 5.0k ) 1 r 2 r + 0 . 1 ( v = v ref out figure 15. typical test circuit

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