lm2595sx-adj

Manufacturer Part Numberlm2595sx-adj
DescriptionSimple Switcher Power Converter 150 Khz 1a Step-down Voltage Regulator
ManufacturerNational Semiconductor Corporation
lm2595sx-adj datasheet
 


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LM2595
SIMPLE SWITCHER
1A Step-Down Voltage Regulator
General Description
The LM2595 series of regulators are monolithic integrated
circuits that provide all the active functions for a step-down
(buck) switching regulator, capable of driving a 1A 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
, and a fixed-frequency oscillator.
The LM2595 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. Typically, for output voltages less
than 12V, and ambient temperatures less than 50˚C, no heat
sink is required.
A standard series of inductors are available from several dif-
ferent manufacturers optimized for use with the LM2595 se-
ries. This
feature
greatly
simplifies
switch-mode power supplies.
±
Other features include a guaranteed
4% tolerance on out-
put voltage under specified input voltage and output load
±
conditions, and
15% on the oscillator frequency. External
shutdown is included, featuring typically 85 µA stand-by cur-
rent. Self protection features include a two stage frequency
reducing current limit for the output switch and an over tem-
perature shutdown for complete protection under fault condi-
tions.
Typical Application
(Fixed Output Voltage Versions)
SIMPLE SWITCHER
®
and Switchers Made Simple
®
are registered trademarks of National Semiconductor Corporation.
© 1999 National Semiconductor Corporation
DS012565
Power Converter 150 kHz
®
Features
n 3.3V, 5V, 12V, and adjustable output versions
n Adjustable version output voltage range, 1.2V to 37V
±
4% max over line and load conditions
n Available in TO-220 and TO-263 (surface mount)
packages
n Guaranteed 1A 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
the
design
of
n Efficient pre-regulator for linear regulators
n On-card switching regulators
n Positive to negative converter
Note:
Patent Number 5,382,918.
May 1999
typically 85 µA
Q
DS012565-1
www.national.com

lm2595sx-adj Summary of contents

  • Page 1

    ... Typical Application (Fixed Output Voltage Versions) SIMPLE SWITCHER ® and Switchers Made Simple ® are registered trademarks of National Semiconductor Corporation. © 1999 National Semiconductor Corporation DS012565 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 LM2595T-3.3, LM2595T-5.0, LM2595T-12 or LM2595T-ADJ See NS Package Number T05D Order Number LM2595J-3.3-QML (5962-9687901QEA), For specifications and information about Military-Aerospace products, please see ...

  • 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

    LM2595-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 4.5V FB programmed for 3V. Circuit of Figure 1 V OUT = 12V, V ...

  • Page 5

    All Output Voltage Versions Electrical Characteristics Specifications with standard type face are for T ture Range. Unless otherwise specified 200 mA. sion. I LOAD Symbol Parameter ON/OFF CONTROL Test Circuit Figure 1 I ON/OFF Pin V H LOGIC ...

  • Page 6

    Typical Performance Characteristics Switch Saturation Voltage DS012565-14 Operating Quiescent Current DS012565-4 ON /OFF Threshold Voltage DS012565-7 www.national.com (Circuit of Figure 1 ) (Continued) Switch Current Limit DS012565-15 Shutdown Quiescent Current DS012565-5 ON /OFF Pin Current (Sinking) DS012565-8 6 Dropout Voltage ...

  • Page 7

    Typical Performance Characteristics Feedback Pin Bias Current DS012565-10 Continuous Mode Switching Waveforms = 20V 5V OUT LOAD µ 120 µF, C ESR = 100 m OUT OUT A: ...

  • Page 8

    Test Circuit and Layout Guidelines C — 120 µF, 50V, Aluminum Electrolytic Nichicon “PL Series” — 120 µF, 25V Aluminum Electrolytic, Nichicon “PL Series” OUT D1 — 3A, 40V Schottky Rectifier, 1N5822 L1 — 100 µH, L29 C ...

  • Page 9

    LM2595 Series Buck Regulator Design Procedure (Fixed Output) PROCEDURE (Fixed Output Voltage Version) Given: = Regulated Output Voltage (3.3V 12V) V OUT (max) = Maximum DC Input Voltage V IN (max) = Maximum Load Current I LOAD 1. ...

  • Page 10

    LM2595 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 11

    LM2595 Series Buck Regulator Design Procedure (Fixed Output) Conditions Output Load Max Input Inductance Voltage Current Voltage (µH) (V) ( 100 8 33 ...

  • Page 12

    LM2595 Series Buck Regulator Design Procedure (Adjustable Output) (Continued) PROCEDURE (Adjustable Output Voltage Version) 2. Inductor Selection (L1) A. Calculate the inductor Volt • microsecond constant E • • µs), from the following formula: = internal switch saturation ...

  • Page 13

    LM2595 Series Buck Regulator Design Procedure (Adjustable Output) (Continued) PROCEDURE (Adjustable Output Voltage Version) Procedure continued on next page. 5. Catch Diode Selection (D1) A. The catch diode current rating must be at least 1.3 times greater than the maximum ...

  • Page 14

    LM2595 Series Buck Regulator Design Procedure (Adjustable Output) (Continued) Output Through Hole Electrolytic Output Capacitor Voltage Panasonic Nichicon PL (V) HFQ Series Series (µF/V) (µF/V) 1.2 330/50 330/50 4 220/25 220/25 6 220/25 220/25 9 180/25 180/ 120/25 ...

  • Page 15

    LM2595 Series Buck Regulator Design Procedure Inductance Current (µH) (A) Through Hole L4 68 0.32 RL-1284-68- 0.37 RL-1284-47- 0.44 RL-1284-33-43 L9 220 0.32 RL-5470-3 L10 150 0.39 RL-5470-4 L11 100 0.48 RL-5470-5 L12 68 0.58 RL-5470-6 ...

  • Page 16

    LM2595 Series Buck Regulator Design Procedure Nichicon Corp. Panasonic AVX Corp. Sprague/Vishay FIGURE 10. Capacitor Manufacturers Phone Numbers VR 1A Diodes Surface Mount Schottky Ultra Fast Recovery SK12 All of these 20V diodes are SK13 rated to 30V MBRS130 at ...

  • Page 17

    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 18

    Application Information lytic capacitors designed for switching regulator applications. Other capacitor manufacturers offer similar types of capaci- tors, but always check the capacitor data sheet. “Standard” electrolytic capacitors typically have much higher ESR numbers, lower RMS current ratings and typically ...

  • Page 19

    Application Information (Continued) FIGURE 15. Capacitor ESR Change vs Temperature INDUCTOR SELECTION 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, ...

  • Page 20

    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 21

    Application Information (Continued) eters such as, peak inductor or peak switch current, mini- mum load current before the circuit becomes discontinuous, output ripple voltage and output capacitor ESR can all be calculated from the peak-to-peak I . When the inductor ...

  • Page 22

    Application Information but with copper areas greater than approximately 3 in small improvements in heat dissipation are realized. If fur- ther thermal improvements are needed, double sided or mul- tilayer PC-board with large copper areas are recommended. The curves shown ...

  • Page 23

    Application Information (Continued) DS012565-36 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 ...

  • Page 24

    Application Information This circuit has hysteresis = 13V Regulator starts switching Regulator stops switching FIGURE 24. Undervoltage Lockout with Hysteresis for Inverting Regulator C : — 220 µF/25V Tant. Sprague 595D IN ...

  • Page 25

    Application Information (Continued) FIGURE 27. Inverting Regulator Ground Referenced Shutdown FIGURE 28. Inverting Regulator Ground Referenced Shutdown using Opto Device DS012565-42 DS012565-43 25 www.national.com ...

  • Page 26

    Application Information TYPICAL THROUGH HOLE PC BOARD LAYOUT, FIXED OUTPUT (1X SIZE 150 µF, 50V, Aluminium Electrolytic Nichicon, “PL series” 120 µF, 25V Aluminium Electrolytic Nichicon, “PL series” OUT D1 - 3A, 40V Schottky Rectifier, ...

  • Page 27

    Physical Dimensions inches (millimeters) unless otherwise noted Order Number LM2595T-3.3, LM2595T-5.0, 5-Lead TO-220 (T) LM2595T-12 or LM2595T-ADJ NS Package Number T05D 27 www.national.com ...

  • Page 28

    Physical Dimensions inches (millimeters) unless otherwise noted (Continued) www.national.com 5-Lead TO-263 Surface Mount Package (S) Order Number LM2595S-3.3, LM2595S-5.0, LM2595S-12 or LM2595S-ADJ NS Package Number TS5B 28 ...

  • Page 29

    ... 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 ...