LM2576/LM2576HV Series 3A Step-Down Switching Regulator

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Melissa Norton
5 years ago
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1 /H /H Series 3A Step-Down Switching Regulator DESCRIPTION The 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 3.3, 5, 12, 15, 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. The series offers a high-efficiency replacement for popular three-terminal linear regulators. It substantially reduces the size of the heat sink, and in some cases no heat sink is required. A standard series of inductors optimized for use with the are available from several different manufacturers. This feature greatly simplifies the design of switch-mode power supplies. Other 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 is included, featuring 50 µa (typical) standby current. The output switch includes cycle-by-cycle current limiting, as well as thermal shutdown for full protection under fault conditions. FEATURES 3.3, 5, 12, 15, and adjustable output versions Adjustable version output voltage range, 1.23 to 37 (57 for H version) ±4% max over line and load conditions Guaranteed 3A output current Wide input voltage range, 40 up to 60 for H version Requires only 4 external components 52 khz fixed frequency internal oscillator TTL shutdown capability, low power standby mode High efficiency Uses readily available standard inductors Thermal shutdown and current limit protection 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 The pin-pin replacement of National Semi. and On Semi. Lm2576 ORDERING INFORMATION Output oltage ADJ Temperature S-3.3 S-5.0 S-12 S-15 S-ADJ Range HS-3.3 HS-5.0 HS-12 HS-15 HS-ADJ T-3.3 T-5.0 T-12 T-15 T-ADJ HT-3.3 HT-5.0 HT-12 HT-15 HT-ADJ Package TO-263 TO-220 PIN CONNECTION Straight Leads 5-Lead TO-220 (T) Top iew Bent, Staggered Leads 5-Lead TO-220 (T) Top iew TO-263 (S) 5-Lead Surface-Mount Package Top iew T-XX or HT-XX T-XX or HT-XX S-XX or HS-XX 1

2 /H TYPICAL APPLICATION (Fixed Output oltage ersions) FIGURE 1. BLOCK DIAGRAM 3.3 R2 = 1.7k 5, R2 = 3.1k 12, R2 = 8.84k 15, R2 = 11.3k For ADJ. ersion R1 = Open, R2 = 0Ω 2

3 /H ABSOLUTE MAXIMUM RATINGS (Note 1) Maximum Supply oltage 45 H 63 ON /OFF Pin Input oltage IN Output oltage to Ground (Steady State) -1 Power Dissipation Internally ed Storage Temperature Range -65 C to +150 C Maximum Junction Temperature 150 C Minimum ESD Rating (C = 100 pf, R = 1.5 k ) 2k Lead Temperature (Soldering, 10 Seconds) 260 C OPERATING RATINGS Temperature Range /H -40 C T J +125 C Supply oltage H , H-3.3 ELECTRICAL CHARACTERISTICS -3.3 OUT OUT OUT Output oltage Output oltage Output oltage H IN = 12, I LOAD = 0.5A 6 IN 40, 0.5A I LOAD 3A 6 IN 60, 0.5A I LOAD 3A H / / / /3.482 (s) (Min) (Max) (Min) (Max) (Min) (Max) Efficiency IN = 12, I LOAD = 3A 75 % -5.0, H-5.0 ELECTRICAL CHARACTERISTICS -5.0 OUT OUT OUT Output oltage Output oltage Output oltage H IN = 12, I LOAD = 0.5A 8 IN 40, 0.5A I LOAD 3A 8 IN 60, 0.5A I LOAD 3A H / / / /5.275 (s) (Min) (Max) (Min) (Max) (Min) (Max) Efficiency IN = 12, I LOAD = 3A 77 % 3

4 /H -12, H-12 ELECTRICAL CHARACTERISTICS -12 OUT OUT OUT Output oltage Output oltage Output oltage H IN = 25, I LOAD = 0.5A 15 IN 40, 0.5A I LOAD 3A 15 IN 60, 0.5A I LOAD 3A H / / / /12.66 (s) (Min) (Max) (Min) (Max) (Min) (Max) Efficiency IN = 15, I LOAD = 3A 88 % -15, H-15 ELECTRICAL CHARACTERISTICS -15 OUT OUT OUT Output oltage Output oltage Output oltage H IN = 25, I LOAD = 0.5A 18 IN 40, 0.5A I LOAD 3A 18 IN 60, 0.5A I LOAD 3A H / / / /15.83 (s) (Min) (Max) (Min) (Max) (Min) (Max) Efficiency IN = 18, I LOAD = 3A 88 % -ADJ, H-ADJ ELECTRICAL CHARACTERISTICS -ADJ IN = 12, I LOAD = 0.5A OUT Feedback oltage OUT = 5 OUT OUT Feedback oltage Feedback oltage H 8 IN 40, 0.5A I LOAD 3A OUT = 5 8 IN 60, 0.5A I LOAD 3A OUT = 5 H-ADJ / / / /1.286 (s) (Min) (Max) (Min) (Max) (Min) (Max) Efficiency IN = 12, I LOAD = 3A, OUT = 5 77 % 4

5 /H ALL OUTPUT OLTAGE ERSIONS ELECTRICAL CHARACTERISTICS Specifications with standard type face are for T J = 25 C, and those with boldface type apply over full Operating Temperature Range. Unless otherwise specified, IN = 12 for the 3.3, 5, and Adjustable version, IN = 25 for the 12 version, and IN = 30 for the 15 version. I LOAD = 500 ma. -XX H-XX (s) DEICE PARAMETERS I b Feedback Bias Current OUT = 5 (Adjustable ersion Only) /500 na 52 khz f O Oscillator Frequency (Note 11) 47/42 58/63 khz(min) khz(max) SAT Saturation oltage I OUT = 3A (Note 4) /2.0 (Max) DC Max Duty Cycle (ON) (Note 5) 98 % 93 %(Min) 5.8 A I CL Current (Notes 4, 11) 4.2/ /7.5 A(Min) A(Max) (Notes 6, 7): Output = 0 2 ma(max) I L Output Leakage Current Output = ma Output = ma(max) I Q Quiescent Current (Note 6) 5 ma 10 ma(max) I STBY Standby Quiescent Current ON /OFF Pin = 5 (OFF) 50 µa 200 µa(max) JA T Package, Junction to Ambient (Note 8) 65 JA T Package, Junction to Ambient (Note 9) 45 Thermal Resistance JC T Package, Junction to Case 2 C/W JA S Package, Junction to Ambient (Note 10) 50 ON /OFF CONTROL Test Circuit Figure 2 IH ON /OFF Pin OUT = /2.4 (Min) IL Logic Input Level OUT = Nominal Output oltage /0.8 (Max) I IH 12 µa ON /OFF Pin = 5 (OFF) ON /OFF Pin Input 30 µa(max) I IL Current 0 µa ON /OFF Pin = 0 (ON) 10 µa(max) Note 1: Absolute Maximum Ratings 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). Note 3: External components such as the catch diode, inductor, input and output capacitors can affect switching regulator system performance. When the / H is used as shown in the Figure 2 test circuit, system performance will be as shown in system parameters section of Electrical Characteristics. Note 4: Output pin sourcing current. No diode, inductor or capacitor connected to output. Note 5: Feedback pin removed from output and connected to 0. Note 6: Feedback pin removed from output and connected to +12 for the Adjustable, 3.3, and 5 versions, and +25 for the 12 and 15 versions, to force the output transistor OFF. Note 7: IN = 40 (60 for high voltage version). 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 4 square 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 connected to the package. Using 0.5 square inches of copper area, JA is 50 C/W, with 1 square inch of copper area, JA is 37 C/W, and with 1.6 or more square inches of copper area, JA is 32 C/W. Note 11: The oscillator frequency reduces to approximately 11 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 power dissipation of the IC by lowering the minimum duty cycle from 5% down to approximately 2%. 5

6 TYPICAL PERFORMANCE CHARACTERISTICS () Normalized Output oltage Line Regulation Dropout oltage /H OUTPUT OLTAGE CHANGE (%) IN =20 Normalized at TJ =25 C OUTPUT OLTAGE CHANGE (%) TJ =25 C 3.3, 5 & ADJ 12 & 15 I LOAD = 3A I LOAD = 200mA JUNCTION TEMPERATURE ( C) INPUT OLTAGE () JUNCTION TEMPERATURE ( C) INPUT-OUTPUT DIFFERENTIAL () L1 = 150 I LOAD = 1A RIND = 0.1 H Standby Quiescent Current STANDBY QUIESCENT CURRENT ( A) IN = 40 ON/OFF = 5 IN =12 Quiescent Current QUIESCENT CURRENT (ma) ILOAD = 200mA OUT = 5 Measured at Ground Pin TJ =25 C ILOAD = 3A Current JUNCTION TEMPERATURE ( C) INPUT OLTAGE () JUNCTION TEMPERATURE ( C) OUTPUT CURRENT (A) IN = 25 Switch Saturation oltage Efficiency Oscillator Frequency Normalized at 25 C SATURATION OLTAGE CHANGE () -55 C 25 C 150 C EFFICIENCY (%) I LOAD = 3A TJ =25 C I LOAD = 200mA 15 OUT 5 ILOAD = 3A ILOAD = 200mA NORMALIZED FREQUENCY (%) IN = 40 IN = 12 SWITCH CURRENT (A) INPUT OLTAGE () JUNCTION TEMPERATURE ( C) Minimum Operating oltage INPUT OLTAGE () Adjustable ersion Only OUT 1.23 JUNCTION TEMPERATURE ( C) Quiescent Current vs Duty Cycle QUIESCENT CURRENT (ma) Adjustable ersion Only IN = 7 IN = 40 DUTY CYCLE (%) FEEDBACK OLTAGE CHANGE (m) Feedback oltage vs Duty Cycle Adjustable ersion Only IN = 40 IN = 7 DUTY CYCLE (%) 6

7 /H Maximum Power Dissipation (TO-263) (See Note 10) Feedback Pin Current Adjustable ersion Only POWER DISSIPATION (W) JA = 32 C/W JA = 37 C/W JA = 50 C/W JA = 73 C/W FEEDBACK PIN CURRENT (na) AMBIENT TEMPERATURE ( C) JUNCTION TEMPERATURE ( C) Switching Waveforms Load Transient Response A B Output oltage Change C Load Current D 5 s/div 100 s/div OUT =15 A: Output Pin oltage, 50/div B: Output Pin Current, 2A/div C: Inductor Current, 2A/div D: Output Ripple oltage, 50m/div, AC-Coupled Horizontal Time Base: 5 s/div 7

8 /H TEST CIRCUIT AND LAYOUT GUIDELINES 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 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. When using the Adjustable version, physically locate the programming resistors near the regulator, to keep the sensitive feedback wiring short. Fixed Output oltage ersions C IN 100 µf, 75, Aluminum Electrolytic C OUT 1000 µf, 25, Aluminum Electrolytic D 1 Schottky, MBR360 L µh, Pulse Eng. PE R 1 2k, 0.1% R k, 0.1% Adjustable Output oltage ersion where REF = 1.23, R1 between 1k and 5k. FIGURE 2. 8

LM2596 3A Step-Down Voltage Regulator

LM2596 3A Step-Down Voltage Regulator LM296 3A Step-Down oltage Regulator GENARAL DESCRIPTION The LM296 series of regulators are monolithic integrated circuits that provide all the active functions for a step-down (buck) switching regulator,