lm2596sx-12 National Semiconductor Corporation, lm2596sx-12 Datasheet

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lm2596sx-12

Manufacturer Part Number
lm2596sx-12
Description
Simple Switcher Power Converter 150 Khz 3a Step-down Voltage Regulator
Manufacturer
National Semiconductor Corporation
Datasheet

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© 2002 National Semiconductor Corporation
LM2596
SIMPLE SWITCHER
3A Step-Down Voltage Regulator
General Description
The LM2596 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving a 3A load with
excellent line and load regulation. These devices are avail-
able in fixed output voltages of 3.3V, 5V, 12V, and an adjust-
able output version.
Requiring a minimum number of external components, these
regulators are simple to use and include internal frequency
compensation
The LM2596 series operates at a switching frequency of
150 kHz thus allowing smaller sized filter components than
what would be needed with lower frequency switching regu-
lators. Available in a standard 5-lead TO-220 package with
several different lead bend options, and a 5-lead TO-263
surface mount package.
A standard series of inductors are available from several
different manufacturers optimized for use with the LM2596
series. This feature greatly simplifies the design of
switch-mode power supplies.
Other features include a guaranteed
put voltage under specified input voltage and output load
conditions, and
shutdown is included, featuring typically 80 µA standby cur-
rent. Self protection features include a two stage frequency
reducing current limit for the output switch and an over
temperature shutdown for complete protection under fault
conditions.
Typical Application
Versions)
SIMPLE SWITCHER
®
, and a fixed-frequency oscillator.
and Switchers Made Simple
±
15% on the oscillator frequency. External
(Fixed Output Voltage
®
are registered trademarks of National Semiconductor Corporation.
±
4% tolerance on out-
DS012583
®
Power Converter 150 kHz
Features
n 3.3V, 5V, 12V, and adjustable output versions
n Adjustable version output voltage range, 1.2V to 37V
n Available in TO-220 and TO-263 packages
n Guaranteed 3A output load current
n Input voltage range up to 40V
n Requires only 4 external components
n Excellent line and load regulation specifications
n 150 kHz fixed frequency internal oscillator
n TTL shutdown capability
n Low power standby mode, I
n High efficiency
n Uses readily available standard inductors
n Thermal shutdown and current limit protection
Applications
n Simple high-efficiency step-down (buck) regulator
n On-card switching regulators
n Positive to negative converter
Note:
±
4% max over line and load conditions
Patent Number 5,382,918.
Q
typically 80 µA
01258301
www.national.com
May 2002

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lm2596sx-12 Summary of contents

Page 1

... Output Voltage Versions) SIMPLE SWITCHER ® and Switchers Made Simple ® are registered trademarks of National Semiconductor Corporation. © 2002 National Semiconductor Corporation Power Converter 150 kHz ® Features n 3.3V, 5V, 12V, and adjustable output versions n Adjustable version output voltage range, 1.2V to 37V ± ...

Page 2

Connection Diagrams and Ordering Information Bent and Staggered Leads, Through Hole Package 5-Lead TO-220 (T) Order Number LM2596T-3.3, LM2596T-5.0, LM2596T-12 or LM2596T-ADJ See NS Package Number T05D www.national.com Surface Mount Package 5-Lead TO-263 (S) 01258302 Order Number LM2596S-3.3, LM2596S-5.0, LM2596S-12 ...

Page 3

Absolute Maximum Ratings If Military/Aerospace specified devices are required, please contact the National Semiconductor Sales Office/ Distributors for availability and specifications. Maximum Supply Voltage ON /OFF Pin Input Voltage Feedback Pin Voltage Output Voltage to Ground (Steady State) Power Dissipation ...

Page 4

LM2596-ADJ Electrical Characteristics Specifications with standard type face are for T ture Range Symbol Parameter SYSTEM PARAMETERS (Note 5) Test Circuit Figure 1 V Feedback Voltage 4. OUT Efficiency V IN All Output Voltage Versions Electrical Characteristics Specifications ...

Page 5

All Output Voltage Versions Electrical Characteristics Specifications with standard type face are for T ture Range. Unless otherwise specified, V sion 500 mA LOAD Symbol Parameter I ON /OFF Pin Input Current Note 1: Absolute ...

Page 6

Typical Performance Characteristics Switch Saturation Voltage 01258307 Operating Quiescent Current 01258310 ON /OFF Threshold Voltage 01258313 www.national.com (Circuit of Figure 1 ) (Continued) Switch Current Limit 01258308 Shutdown Quiescent Current 01258311 ON /OFF Pin Current (Sinking) 01258314 6 Dropout Voltage ...

Page 7

Typical Performance Characteristics Feedback Pin Bias Current 01258316 (Circuit of Figure 1 ) (Continued) 7 www.national.com ...

Page 8

Typical Performance Characteristics Continuous Mode Switching Waveforms V = 20V 5V OUT µ 220 µF, C OUT Horizontal Time Base: 2 µs/div. A: Output Pin Voltage, 10V/div. B: Inductor Current 1A/div. ...

Page 9

Test Circuit and Layout Guidelines where V = 1.23V REF Select approximately use a 1% resistor for best stability — 470 µF, 50V, Aluminum Electrolytic Nichicon “PL Series” — 220 ...

Page 10

LM2596 Series Buck Regulator Design Procedure (Fixed Output) PROCEDURE (Fixed Output Voltage Version) Given Regulated Output Voltage (3.3V 12V) OUT V (max) = Maximum DC Input Voltage IN I (max) = Maximum Load Current LOAD 1. ...

Page 11

LM2596 Series Buck Regulator Design Procedure (Fixed Output) PROCEDURE (Fixed Output Voltage Version) 3. Catch Diode Selection (D1) A. The catch diode current rating must be at least 1.3 times greater than the maximum load current. Also, if the power ...

Page 12

LM2596 Series Buck Regulator Design Procedure (Fixed Output) Conditions Output Load Max Input Voltage Current Voltage (V) (A) (V) 3 ...

Page 13

LM2596 Series Buck Regulator Design Procedure (Adjustable Output) PROCEDURE (Adjustable Output Voltage Version) Given Regulated Output Voltage OUT V (max) = Maximum Input Voltage IN I (max) = Maximum Load Current LOAD F = Switching Frequency (Fixed at ...

Page 14

LM2596 Series Buck Regulator Design Procedure (Adjustable Output) (Continued) PROCEDURE (Adjustable Output Voltage Version) 3. Output Capacitor Selection (C OUT A. In the majority of applications, low ESR electrolytic or solid tantalum capacitors between 82 µF and 820 µF provide ...

Page 15

LM2596 Series Buck Regulator Design Procedure (Adjustable Output) (Continued) PROCEDURE (Adjustable Output Voltage Version) 5. Catch Diode Selection (D1) A. The catch diode current rating must be at least 1.3 times greater than the maximum load current. Also, if the ...

Page 16

LM2596 Series Buck Regulator Design Procedure (Adjustable Output) Output Through Hole Output Capacitor Voltage Panasonic Nichicon PL (V) HFQ Series (µF/V) 2 820/35 4 560/35 6 470/25 9 330/ 330/ 220/ 220/ ...

Page 17

LM2596 Series Buck Regulator Design Procedure Inductance Current Schott (µH) (A) Through Hole L15 22 0.99 67148350 67148460 RL-1284-22-43 RL1500-22 L21 68 0.99 67144070 67144450 RL-5471-5 L22 47 1.17 67144080 67144460 RL-5471-6 L23 33 1.40 67144090 67144470 RL-5471-7 L24 22 ...

Page 18

LM2596 Series Buck Regulator Design Procedure Nichicon Corp. Panasonic AVX Corp. Sprague/Vishay FIGURE 10. Capacitor Manufacturers Phone Numbers VR 3A Diodes Surface Mount Schottky Ultra Fast Recovery 20V All of these SK32 diodes are 30V 30WQ03 rated to SK33 at ...

Page 19

Block Diagram Application Information PIN FUNCTIONS +V — This is the positive input supply for the IC switching IN regulator. A suitable input bypass capacitor must be present at this pin to minimize voltage transients and to supply the switching ...

Page 20

Application Information A graph shown in Figure 13 shows the relationship between an electrolytic capacitor value, its voltage rating, and the RMS current it is rated for. These curves were obtained from the Nichicon “PL” series of low ESR, high ...

Page 21

Application Information good choice, but some types with an abrupt turnoff charac- teristic may cause instability or EMI problems. Ultra-fast recovery diodes typically have reverse recovery times less. Rectifiers such as the 1N5400 series are much ...

Page 22

Application Information DISCONTINUOUS MODE OPERATION The selection guide chooses inductor values suitable for continuous mode operation, but for low current applications and/or high input voltages, a discontinuous mode design may be a better choice. It would use an inductor that ...

Page 23

Application Information FIGURE 18. Peak-to-Peak Inductor Ripple Current vs Load Current In a switching regulator design, knowing the value of the peak-to-peak inductor ripple current ( I determining a number of other circuit parameters. Param- eters such as, peak inductor ...

Page 24

Application Information THERMAL CONSIDERATIONS The LM2596 is available in two packages, a 5-pin TO-220 (T) and a 5-pin surface mount TO-263 (S). The TO-220 package needs a heat sink under most condi- tions. The size of the heatsink depends on ...

Page 25

Application Information FIGURE 21. Delayed Startup FIGURE 22. Undervoltage Lockout for Buck Regulator DELAYED STARTUP The circuit in Figure 21 uses the the ON /OFF pin to provide a time delay between the time the input voltage is applied and ...

Page 26

Application Information This circuit has hysteresis Regulator starts switching 13V IN Regulator stops switching FIGURE 24. Undervoltage Lockout with Hysteresis for Inverting Regulator C — 68 µF/25V Tant. Sprague 595D IN 470 ...

Page 27

Application Information INVERTING REGULATOR SHUTDOWN METHODS To use the ON /OFF pin in a standard buck configuration is simple, pull it below 1. 25˚C, referenced to ground) to turn regulator ON, pull it above 1.3V to shut the ...

Page 28

Application Information TYPICAL THROUGH HOLE PC BOARD LAYOUT, FIXED OUTPUT (1X SIZE), DOUBLE SIDED C — 470 µF, 50V, Aluminum Electrolytic Panasonic, “HFQ Series” — 330 µF, 35V, Aluminum Electrolytic Panasonic, “HFQ Series” OUT D1 — 5A, 40V ...

Page 29

Application Information TYPICAL THROUGH HOLE PC BOARD LAYOUT, ADJUSTABLE OUTPUT (1X SIZE), DOUBLE SIDED C — 470 µF, 50V, Aluminum Electrolytic Panasonic, “HFQ Series” — 220 µF, 35V Aluminum Electrolytic Panasonic, “HFQ Series” OUT D1 — 5A, 40V ...

Page 30

Physical Dimensions unless otherwise noted www.national.com inches (millimeters) 5-Lead TO-220 (T) Order Number LM2596T-3.3, LM2596T-5.0, LM2596T-12 or LM2596T-ADJ NS Package Number T05D 30 ...

Page 31

... NATIONAL’S PRODUCTS ARE NOT AUTHORIZED FOR USE AS CRITICAL COMPONENTS IN LIFE SUPPORT DEVICES OR SYSTEMS WITHOUT THE EXPRESS WRITTEN APPROVAL OF THE PRESIDENT AND GENERAL COUNSEL OF NATIONAL SEMICONDUCTOR CORPORATION. As used herein: 1. Life support devices or systems are devices or systems which, (a) are intended for surgical implant ...

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