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3.0a, 52khz, step-down switching regulator LM2576 features 3.3v, 5.0v, 12v, 15v, and adjustable output versions adjustable version output voltage range, 1.23 to 37v +/- 4% ag10maximum over line and load conditions guaranteed 3.0a output current wide input voltage range requires only 4 external components 52khz fixed frequency internal oscillator ttl shutdown capability, low power standby mode high efficiency uses readily available standard inductors thermal shutdown and current limit protection moisture sensitivity level 3 applications simple high-efficiency step-down(buck) regulator efficient pre-regulator for linear regulators on-card switching regulators positive to negative converter(buck-boost) negative step-up converters power supply for battery chargers description ordering information the LM2576 series of regulators are monolithic integrated 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, 15v, and an adjustable output version. these regulators were designed to minimize the number of extern al components to simplify the power supply design. standard series of inductors optimized fo r use with the LM2576 are offered 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, espec ially with higher input voltages. available from several different manufacturers. this feature g reatly simplifies the design of switch-mode power supplies. the LM2576 features include a guara nteed +/- 4% tolerance on output voltage within specified input voltages and output lo ad conditions, and +/-10% on the oscillator frequency (+/- 2% over 0oc to 125 oc). external shutdown is included, featuring 80 ?(typical) standby current. the output switch includes cycle-bycycle current limiting, as well as thermal shutdown for full protection under fault conditions. 2008 - ver. 1.0 htc - 1 - device marking package LM2576t-x.x LM2576t-x.x to-220 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 LM2576tv-x.x LM2576t-x.x LM2576r LM2576r-x.x to-263 to-220v 1. vin 2. output 3. ground 4. feedback 5. on/off 1 5 1 5 1 5 to-220 pkg to-263 pkg to-220v pkg
3.0a, 52khz, step-down switching regulator LM2576 absolute maximum ratings (absolute maximum ratings indicate limits beyond which damage t o the device may occur) maximum junction temperature t j 150 lead temperature (soldering,10seconds) - 260 minimum esd rating(human body model : - 2.0 kv c=100 pf, r=1.5?) storage temperature range t stg -60 to +150 thermal resistance, junction to case p jc 5.0 /w thermal resistance, junction to ambient p ja 70 /w p jc 5.0 /w to-263 5lead p d internally limited w w thermal resistance, junction to ambient p ja 65 /w - - 1.0 power dissipation to-220 5lead p d internally limited thermal resistance, junction to case rating symbol value unit maximum supply voltage vin 45 htc - 2 - v on/off pin input voltage - -0.3v v +vin v output voltage to ground (steady-state) v typical application (fixed output voltage versions) fi g ure 1. block dia g ram and t yp ical a pp lication
3.0a, 52khz, step-down switching regulator LM2576 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.) LM2576-3.3v ([note 1] test circuit figure 2) LM2576-5.0v ([note 1] test circuit figure 2) LM2576-12v ([note 1] test circuit figure 2) LM2576-adj ([note 1] test circuit figure 2) % - 1.28 - htc - 3 - t j = -40 ~ +125 1.18 feedback voltage(8.0vvin40v, 0.5ai load 3.0a, vout=5.0v) t j =25 1.193 efficiency (vin=12v, i load =3.0a, vout=5.0v) -77 1.23 1.267 vout % feedback voltage (vin=12v, i load =0.5a, t j =25) vout 1.217 1.23 1.243 v v - 12.6 efficiency (vin=25v, i load =3.0a) -88- vout v t j =25 11.52 12 12.48 t j = -40 ~ +125 11.4 output voltage (15vvin40v, 0.5ai load 3.0a % output voltage (vin = 25v, i load =0.5a, t j =25) vout 11.76 12 12.24 v - 5.25 efficiency (vin=12v, i load =3.0a) -77- vout v t j =25 4.8 5.0 5.2 t j = -40 ~ +125 4.75 output voltage (8.0vvin40v, 0.5ai load 3.0a % output voltage (vin = 12v, i load =0.5a, t j =25) vout 4.9 5.0 5.1 v - 3.465 efficiency (vin=12v, i load =3.0a) -75- vout v t j =25 3.168 3.3 3.432 t j = -40 ~ +125 3.135 output voltage (6.0vvin40v, 0.5ai load 3.0a 3.366 v characteristics symbol min output voltage (vin = 12v, i load =0.5a, t j =25) vout 3.234 3.3 typ supply voltage vin 40 max v unit operating junction temperature range t j -40 to +125 rating symbol value unit electrical characteristics / system parameters ([note 1] test circuit figure 15) (unless otherwise specified, vin = 12 v for the 3.3 v, 5.0 v, a nd adjustable version, vin = 25 v for the 12 v version, and vin = 30 v for the 15 v version. iload = 500 ma. for typical values tj = 25c, for min/max values tj is the operating junction temperature ran ge that applies [note 2], unless otherwise noted.) 1. external components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. when the LM2576 is used as shown in the figure 15 test circ uit, system performance will be as shown in system parameters section . 2. tested junction temperature range for the LM2576: tlow = C40 c thigh = +125c
3.0a, 52khz, step-down switching regulator LM2576 all output voltage versions ? t j = 0 to +125 47 - 58 % a ma i cl i l na khz v ? 11 50 30 6.9 9 min typ 94 98 1.5 42 - -52 max duty cycle ("0") [note 5] dc ma - 7.5 - output = -1.0v - 2 feedback bias current (vout=5.0v [adjustable version only]) i b 1.8 - on/off pin = 0v (regulator on), tj=25 i il - 0 5.0 on/off pin = 5.0v (regulator off), tj=25 i ih -1530 on/off pin input current (test circuit figure 15) 1 t j = -40 to +125 - - 0.8 t j =25 - 1.2 - vout=nominal output voltage v ih v il - t j = -40 to +125 2.4 - t j =25 2.2 1.4 vout=0v 400 on/off pin logic input level (test circuit figure 15) t j = -40 to +125 -- t j =25 - 80 200 standby quiescent current (on/off pin = 5.0v ("off")) i stby t j = -40 to +125 -- t j =25 -5 quiescent current [note 6] i q 6 output = 0v - 0.8 output leakage current [note 6 and 7], t j =25 t j = -40 to +125 3.5 5.8 current limit (peak current [note 3 and 4]) t j =25 4.2 63 t j = -40 to +125 -- vsat t j =25 - saturation voltage (iout=3.0a [note 4]) t j = -40 to +125 -- fosc t j = -40 to +125 unit max characteristics symbol htc - 4 - t j =25 - 25 100 200 oscillator frequency [note 3] v t j =25 v electrical characteristics / device parameters (unless otherwise specified, vin = 12 v for the 3.3 v, 5.0 v, and adjustable version, vin = 25 v for the 12 v version, and vin = 30 v for the 15 v version. iload = 500 ma. for typical values tj = 25c, for min/ma x values tj is the operating junction temperature range that applies [note 2], unless otherwise noted.) 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 nominal output voltage. this self protection feature lowers the average dissipation of the ic by lowering the minimum duty cycle from 5% down to approximately 2%. 4. output (pin 2) sourcing current. no diode, inductor or capac itor connected to output pin. 5. feedback (pin 4) removed from output and connected to 0 v. 6. feedback (pin 4) removed from output and connected to +12 v for the adjustable, 3.3 v, and 5.0v ersions, and +25 v for the 12 v and15 v versions, to force the output transistor off. 7. vin = 40 v.
3.0a, 52khz, step-down switching regulator LM2576 htc - 5 - typical performance characteristics (circuit of figure 15) iq , quiescent current ( ma ) 20 18 16 14 12 10 8 6 4
3.0a, 52khz, step-down switching regulator LM2576 - 6 - htc typical performance characteristics (circuit of figure 15)
3.0a, 52khz, step-down switching regulator LM2576 - 7 - htc typical performance characteristics
3.0a, 52khz, step-down switching regulator LM2576 htc - 8 -
3.0a, 52khz, step-down switching regulator LM2576 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). this is the emitter of the internal switch. the saturation voltage vsat of this output switch is typically 1.5 v. 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. circuit ground pin. see the information about the printed circuit board layout. 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 amplifier and the resistor network r2, r1 is connected externally to allow programming of the output voltage. it allows the switching regulator circuit to be shut down using logic level signals, thus dropping the total input supply current to approximately 80 ma. the threshold voltage is typically 1.4 v. 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 feedback htc - 9 - symbol 1 vin output 4 5 on/off 2 gnd 3 description pin function description
3.0a, 52khz, step-down switching regulator LM2576 - 10 - htc
3.0a, 52khz, step-down switching regulator LM2576 htc - 11 -
3.0a, 52khz, step-down switching regulator LM2576 htc - 12 -
3.0a, 52khz, step-down switching regulator LM2576 htc - 13 -
3.0a, 52khz, step-down switching regulator LM2576 - 14 - htc

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