3.0a, 150khz, step-down switching regulator LM2596 features 3.3v, 5.0v, 12v, and adjustable output versions adjustable version output voltage range, 1.2 to 37v +/- 4%. maximum over line and load conditions guaranteed 3.0a output current wide input voltage range requires only 4 external components 150khz 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 LM2596 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, 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 LM2596 are offered by several different inductor manufacturers. since the LM2596 converter is a switch-mode power supply, its efficiency is significantly higher in comparison with popular three-terminal limear regulators, espec ially with higher input voltages. available from several different manufacturers. this feature gr eatly simplifies the design of switch-mode power supplies. the LM2596 features include a guara nteed +/- 4% tolerance on output voltage within specified input voltages and output lo ad conditions, and +/-15% on the oscillator frequency (+/- 2% over 0 to 125). external shutdown is included, featuring 80? (typical) standby current. self protection features include a two stage frequency reducing current limit for output switch and an over temperature shutdown for complete protection under fault conditions. dec. 2009 - rev.1.3.1 to-220v htc ? 1 ? device marking package LM2596t-x.x LM2596-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 tj2596 are LM2596tv-x.x LM2596-x.x LM2596r LM2596-x.x to-263 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, 150khz, step-down switching regulator LM2596 typical application (fixed output voltage versions) figure 1. block diagram and typical application absolute maximum ratings (absolute maximum ratings indicate limits beyond which damage to the device may occur.) v v v /w /w w /w /w w 150 kv 5.0 -60 to +150 2.0 260 65 5.0 internally limited 70 -0.3v v +vin - 1.0 internally limited t stg - - t j p jc p d p ja p jc maximum junction temperature symbol unit value vin 45 - - p d p ja storage temperature range minimum esd rating(human body model : c=100 pf, r=1.5?) lead temperature (soldering,10seconds) rating maximum supply voltage on/off pin input voltage output voltage to ground (steady-state) power dissipation to-220 5lead thermal resistance, juntion to ambient thermal resistance, juntion to case to-263 5lead htc ? 2 ? thermal resistance, juntion to ambient thermal resistance, juntion to case 680 uf 220 uf 1n5824 33 uh LM2596-5.0
3.0a, 150khz, step-down switching regulator LM2596 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 and test conditions, see the electrical characteristics.) electrical characteristics / system parameters ([note 1] test circuit figure 2) (unless otherwise specified, vin = 12v for the 3.3v, 5.0v, and adjustable version, vin = 25v for the 12v versi o 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.) LM2596-3.3v ([note 1] test circuit figure 2) LM2596-5.0v ([note 1] test circuit figure 2) LM2596-12v ([note 1] test circuit figure 2) LM2596-adj ([note 1] test circuit figure 2) efficiency (vin=12v, i load =3.0a, vout=5.0v) t j =25 t j = -40 ~ +125 efficiency (vin=12v, i load =3.0a) output voltage (vin = 25v, i load =0.5a, t j =25) efficiency (vin=12v, i load =3.0a) t j =25 -40 to +125 40 v operating junction temperature range supply voltage symbol t j vin rating value unit htc ? 3 ? output voltage (8.0vvin40v, 0.5ai load 3.0a vout output voltage (vin = 12v, i load =0.5a, t j =25) characteristics t j =25 t j = -40 ~ +125 t j = -40 ~ +125 efficiency (vin=12v, i load =3.0a) output voltage (vin = 12v, i load =0.5a, t j =25) output voltage (6.0vvin40v, 0.5ai load 3.0a vout unit symbol vout 3.234 3.3 3.366 v min typ max 3.432 3.465 v 3.168 3.135 3.3 - -73-% v 4.8 5.0 5.2 4.75 - 5.25 % vout 4.9 5.0 5.1 v -80- vout 11.76 12 12.24 v output voltage (15vvin40v, 0.5ai load 3.0a vout v t j =25 11.52 12 12.48 t j = -40 ~ +125 11.4 - 12.6 -90-% feedback voltage (vin=12v, i load =0.5a, t j =25) vout 1.217 1.23 1.243 v feedback voltage(8.0vvin40v, 0.5ai load 3.0a, vout=5.0v) vout v 1.193 1.23 1.267 1.18 - 1.28 % -73-
3.0a, 150khz, step-down switching regulator LM2596 electrical characteristics / device parameters (unless otherwise specified, vin = 12v for the 3.3v, 5.0v, and adjustable version, vin = 25v for the 12v versi o iload = 500 ma. for typical values tj = 25c, for min/max values tj is the operating junction temperature ran that applies [note 2], unless otherwise noted.) all output voltage versions 1. external components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. when the LM2596 is used as shown in the figure 1 test circuit, system performance will be as shown in system paramete rs section . 2. tested junction temperature range for the tj2596 : t low = C40c t high = +125c 3. the oscillator frequency reduces to approximately 18khz in t he event of an output short or an overload which causes the regulated output voltage to drop appr oximately 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 +12v f or the adjustable, 3.3v, and 5.0v versions, and '+25 v for the 12v versions, to force the output transistor off.c195 7. vin = 40 v. 11.4 - 12.6 11.52 12 12.48 t j = 0 ~ +125 i b max unit feedback bias current (vout=5.0v [adjustable version only]) t j =25 characteristics symbol min typ htc ? 4 ? t j =25 127 150 173 oscillator frequency [note 3] fosc 173 saturation voltage (iout=3.0a [note 4]) vsat t j = 0 ~ +125 110 - 1.4 t j = 0 ~ +125 - - 1.5 t j =25 - 1.16 t j =25 3.6 4.5 6.9 current limit (peak current [note 3 and 4]) i cl t j = 0 ~ +125 3.4 - 7.5 quiescent current [note 6] i q output = 0v -- t j =25 -5 t j = 0 ~ +125 -- standby quiescent current (on/off pin = 5.0v ("off")) i stby t j =25 -80 t j = 0 ~ +125 -- vout=0v t j =25 on/off pin logic input level (test circuit figure 2) v ih 0.6 vout=nominal ouput voltage t j = 0 ~ +125 2.0 - t j =25 - 1.3 t j = 0 ~ +125 - - 0.6 na khz v % a ma ma ? - - output leakage current [note 6 and 7], t j =25 i l max duty cycle ("0") [note 5] dc - 100 output = -1.0v -2 50 30 250 200 - 10 - 2.0 1.3 v il v on/off pin input current (test circuit figure 2) ? v logic = 2.5v (regulator off) i ih -515 v logic = 0.5v (regulator on) i il - 0.02 5.0
3.0a, 150khz, step-down switching regulator LM2596 htc ? 5 ? typical performance characteristics (circuit of figure 2)
3.0a, 150khz, step-down switching regulator LM2596 htc ? 6 ? typical performance characteristics (circuit of figure 2) feedback pin bias current
3.0a, 150khz, step-down switching regulator LM2596 cin = 470?, 50v, cout = 220?, 25v (aluminum electrilytic nichic on "pl series" d1 = 5a, 40v schottky rectifier, in5825 l1 = 68uh, l38 cin = 470?, 50v, cout = 220?, 35v (aluminum electrilytic nichic on "pl series" d1 = 5a, 40v schottky rectifier, in5825 l1 = 68uh, r 1 = 1?, 1% r2 = r1 x (vout / vref - 1) figure 2. typical test circuits and layout guide as in any switching regulator, layout is very important. rapidl y switching currents associated with wiring inductance can generate voltage transients which can cause prob lems. for minimal inductance and ground loops, the wires indicated by heavy lines should be wide printed circuit traces and should be kept as short as possible. for best results, external component s should be located as close to the switching lc as possible using ground plane construction or si ngle point grounding. if open core inductors are used, special care must be taken as to the locat ion and positioning of this type of inductor. allowing the inductor flux to intersect sensitive fe edback, lc groundpath and c out wiring can cause problems. when using the adjustable version, special care must be taken as to the location of the feedback resistors and the associated wiring. physically locate both resistors near the ic, and route the wiring away from the inductor, especially an open cor e type of inductor. ? 7 ? htc test circuit and layout guidelines
3.0a, 150khz, step-down switching regulator LM2596 pin function description this pin is the positive input supply for the LM2596 stepCdown switching regulator.in order to minimize voltage transients and to supply the switching currents needed by the regulator, a suitable input bypass capac itor must be present .(cin in figure 1). this is the emitter of the internal switch. the saturation volt age vsat of this output switch is typically 1.5 v. it should be kept in mind tha t the pcb area connected to this pin should be kept to a minimum in order to m inimize coupling to sensitive circuitry. circuit ground pin. see the information about the printed circu it board layout. this pin senses regulated output voltage to complete the feedba ck loop. the signal is divided by the internal resistor divider network r2, r1 and applied to the nonCinverting input of the internal error amplif ier. in the adjustable version of the LM2596 switching regulator this pin i s 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 approx imately 80ma. the threshold voltage is typically 1.4v. applying a voltage abo ve 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 3 htc 4 5 on/off ? 8 ? symbol 1 vin output 2 gnd description feedback
|
