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jan.2010 v1.2 1/11 AE2576 simple switcher 3a step-down voltage regulator features 3.3v, 5v, 12v, 15v and adjustable output versions adjustable version output voltage range, 1.23v to 30v 4% max over line and load conditions guaranteed 3a output current input voltage up to 45v requires only 4 external components 52khz fixed frequency internal oscillator ttl shutdown capability, low power standby mode high efficiency thermal shutdown and current limit protection applications simple high-efficiency step-down (buck) regulator efficient pre-regulator for linear regulators positive to negative converter (buck-boost) general description the AE2576 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator, capable of driving 3a load with excellent line and load regulation. these devices are available in fixed output voltages of 3.3v, 5v, 12v, 15v, and an adjustable output version. requiring a minimum number of external components, these regulators are simple to use and include internal frequency compensation and a fixed frequency oscillator. a standard series of inductors optimized for use with the AE2576 are available from several different manufacturers. this feature greatly simplifies the design of switch-mode power supplies. others features include a guaranteed 4% tolerance on output voltage within specified input voltages and output load conditions, and 10% on the oscillator frequency. external shutdown in included, featuring 50a (typical) standby current. the output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions. free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 2/11 typical application figure1: fixed output voltage versions block diagram 3.3v r2=1.7k 5v r2=3.1k 12v r2=8.4k 15v r2=11.3k for adjustable r2=0k r1=ope n connection diagrams 5-lead to-220 5-lead to-263 free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 3/11 pin functions: +vin this is the positive input supply for the ic switching regulator. a suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching currents needed by the regulator . ground circuit ground output internal switch, the voltage at this pin switches between (+vin vsat) and approximately -0.5v. to minimize coupling to sensitive circuitry, the pc board copper area connected to this pin should be kept to a minimum . feedback senses the regulated output voltage to complete the feedback loop . allows the switching regulator circuit to be shut down using logic level signals. pulling this pin below a threshold voltage of approximately 1.5v turns the regulator on, and pulling this pin above 1.51v (up to a maximum of 25v) shuts the regulator down. if this shutdown feature is not needed, the pin can be wired to the ground pin or it can be left open, in either case the regulator will be in the on condition absolute maximum ratings (note 1) parameter rating unit maximum supply voltage 45 v pin input voltage -0.3 + v in v output voltage to ground steady state) -1 v power dissipation internally limited -- storage temperature range -65 150 esd susceptibility (human body model) 2 kv maximum junction temperature 150 temperature range -40 125 conditions supply voltage 4.5~40 v electrical characteristics specifications with standard type face are for t j = 25 . AE2576-3.3v symbol parameter conditions min (note 2) typ max (note 2) units system parameters (note 3) test circuit figure 2 v out output voltage 6 v in 36v 0.5a i load 3a 3.168 3.3 3.432 v efficiency v in =12v i load =3a -- 75 -- % free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 4/11 AE2576-5v symbol parameter conditions min (note 2) typ max (note 2) units system parameters (note 3) test circuit figure 2 v out output voltage 8 v in 36v 0.5a i load 3a 4.800 5.0 5.20 v efficiency v in =12v i load =3a -- 77 -- % AE2576-12v symbol parameter conditions min (note 2) typ max (note 2) units system parameters (note 3) test circuit figure 2 v out output voltage 15v v in 36v 0.5a i load 3a 11.520 12 12.480 v efficiency v in =15v, i load =3a -- 88 --- % AE2576-15v symbol parameter conditions min (note 2) typ max (note 2) units system parameters (note 3) test circuit figure 2 v out output voltage 18v v in 36v 0.5a i load 3a 14.400 15 15.600 v efficiency v in =18v, i load =3a -- 88 --- % AE2576-adj symbol parameter conditions min (note 2) typ max (note 2) units system parameters (note 3) test circuit figure 2 v fb feedback voltage 8v v in 36v 0.5a i load 3a v out =5v 1.193 1.230 1.267 v free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 5/11 efficiency v in =12v i load =3a v out =5v -- 77 -- % all output voltage versions electrical characterist ics condition :t j = 25 ,otherwise specified, v in =12v for the 3.3v, 5v,and adjustable version, v in =25v for the 12v version, and v in =25v for the 12v version, and v in =30v for 15v version. i load =500ma AE2576xx symbol parameter conditions min (note 2) typ max (note2) units device parameters i b feedback bias current adjustable version only, v out =5v -- 50 100 na f o oscillator frequency (note 11) 47 52 58 khz v sat v sat saturation voltage i out =3a(note 4) -- 1.5 2.0 v dc max duty cycle (on) (note 5) 93 98 -- % i cl current limit (notes 4,11) 5.5 6.12 6.7 a output = 0v (notes 6, 7) -- 2..0 ma i l output leakage current output =-1v (notes 10) -- 7.5 30 ma i q quiescent current (note 6) -- 6 12 ma i stby standby quiescent current pin = 5v (off) -- 200 300 a ja t package, junction to ambient (note 8) -- 65 -- /w ja t package, junction to ambient (note 9) -- 45 -- /w jc t package, junction to case -- 2 -- /w ja thermal resistance s package, junction to ambient (note 10) -- 50 -- /w control v ih pin logic input level v out =0v 1.38 1.50 -- v free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 6/11 v il v out =nominal output voltage -- 1.36 1.43 v i h on/off pin =5v(off) -- 12 30 a i l pin input current on/off pin =0v(on) -- 0 10 a note 1: absolute maximum ratings indicates limits beyond which damage to the device may occur. operating ratings indicate conditions for which the device is intended to be functional, but specific performance is not guaranteed. for guaranteed specifications and the best 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 extremes are guaranteed via correlation using standard statistical quality control (sqc) methods. note 3: external components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator system performance. note 4: output pin sourcing current. no diode, inductor or capacitor connected to output pin. note 5: feedback pin removed from output and connected to 0v. note 6: feedback pin removed from output and connected to +12v for the 3.3v, 5v, and the adj. version, and +25v for the 12v and 15v version, to force the output transistor switch off. note 7: v in =36v. note 8: junction to ambient thermal resistance (no external heat sink) for the 5 lead to-220 package mounted vertically, with 1/2 inch leads in a socket, or on a pc board with minimum copper area. note 9: junction to ambient thermal resistance (no external heat sink) for the 5 lead to-220 package mounted vertically, with 1/4 inch leads soldered to a pc board containing approximately 4spuare inches of copper area surrounding the leads. note 10: if the to-263 package is used, the thermal resistance can be reduced by increasing the pc board copper area thermally to the package.using 0.5spuare inches of copper area ja 50 /w, with 1square inch of copper area, ja 37 /w, and with 1.6 or more square inches of copper area ja 32 /w. free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 7/11 typical performance characteristics free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 8/11 testing circuit fixed output voltage version s adjustable output voltage version s figure2 fixed and adjustable output voltage c in 100 f, 50v, aluminum electrolytic nichicon pl s eries c out 1000 f, 50v aluminum electrolytic, nichicon pl series d1 5a, 40v schottky rectifier, 1n5822 l1 100h note : keep feedback wiring away from inductor flux and heavy line must be kept short and use ground plane construction or best results. application note free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 9/11 input capacitor c in a low esr aluminum or tantalum bypass capacitor is needed between the input pin and ground pin . it must be located near the regulator using short leads. this capacitor prevents large voltage transients from appearing at the input, and provides the instantaneous current needed each time the switch turns on. selecting an input capacitor requires consulting the manufacturers data sheet for maximum allowable rms ripple current. for a maximum ambient temperature of 40c, a general guideline would be to select a capacitor with a ripple current rating of approximately 50% of the dc load current. for ambient temperatures up to 70c, a current rating of 75% of the dc load current would be a good choice for a conservative design. the capacitor voltage rating must be at least 1.25 times greater than the maximum input voltage, and often a much higher voltage capacitor is needed to satisfy the rms current requirements. output capacitor c out -an output capacitor is required to filter the output and provide regulator loop stability. low impedance or low esr electrolytic or solid tantalum capacitors designed for switching regulator applications must be used. when selecting an output capacitor, the important capacitor parameters are; the 100 khz equivalent series resistance (esr), the rms ripples current rating, voltage rating, and capacitance value. for the output capacitor, the esr value is the most important parameter. the output capacitor requires an esr value that has an upper and lower limit. for low output ripple voltage, a low esr value is needed. this value is determined by the maximum allow able output ripple voltage, typically 1% to 2% of the output voltage. but if the selected capacitors esr is extremely low, there is a possibility of an unstable feedback loop, resulting in an oscillation at the output. catch diode d -buck regulators require a diode to provide a return path for the inductor current when the switch turns off. this must be a fast diode and must be located close to the AE2576 using short leads and short printed circuit traces. because of their very fast switching speed and low forward voltage drop, schottky diodes provide the best performance, especially in low output voltage applications (5v and lower). ultra fast recovery, or high-efficiency rectifiers are also a good choice, but some types with an abrupt turnoff characteristic may cause instability or emi problems. inductor selection l -all switching regulators have two basic modes of operation; continuous and discontinuous. the difference between the two types relates to the inductor current, whether it is flowing continuously, or if it drops to zero for a period of time in the normal switching cycle. each mode has distinctively different operating characteristics, which can affect the regulators performance and requirements. most switcher designs will operate in the discontinuous mode when the load current is low. the AE2576 (or any of the simple switcher family) can be used for both continuous and discontinuous modes of operation. there is a formula for general applications: l =(5 10) (1- v v in o )mh note the unit of voltage is v the unit of current is a) free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 10/11 physical dimensions inches (millimeters) 5-lead to-220 free datasheet http:///
AE2576 simple switcher 3a step-down v oltage regulator jan.2010 v1.2 11/11 physical dimensions (continued) 5-lead to-263 surface mount package free datasheet http:///

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