LM2576T-ADJ National Semiconductor, LM2576T-ADJ Datasheet



Manufacturer Part Number
National Semiconductor

Specifications of LM2576T-ADJ

Primary Input Voltage
No. Of Outputs
Output Voltage
Output Current
Voltage Regulator Case Style
No. Of Pins
Operating Temperature Range
-40°C To +125°C
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
© 2004 National Semiconductor Corporation
LM2576/LM2576HV Series
General Description
The LM2576 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 avail-
able 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.
The LM2576 series offers a high-efficiency replacement for
popular three-terminal linear regulators. It substantially re-
duces 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
LM2576 are available from several different manufacturers.
This feature greatly simplifies the design of switch-mode
power supplies.
Other features include a guaranteed
put voltage within specified input voltages and output load
conditions, and
shutdown is included, featuring 50 µA (typical) standby cur-
rent. The output switch includes cycle-by-cycle current limit-
ing, as well as thermal shutdown for full protection under
fault conditions.
Typical Application
is a registered trademark of National Semiconductor Corporation.
10% on the oscillator frequency. External
(Fixed Output Voltage
4% tolerance on out-
3A Step-Down Voltage Regulator
n 3.3V, 5V, 12V, 15V, and adjustable output versions
n Adjustable version output voltage range,
n Guaranteed 3A output current
n Wide input voltage range, 40V up to 60V for
n Requires only 4 external components
n 52 kHz fixed frequency internal oscillator
n TTL shutdown capability, low power standby mode
n High efficiency
n Uses readily available standard inductors
n Thermal shutdown and current limit protection
n P+ Product Enhancement tested
n Simple high-efficiency step-down (buck) regulator
n Efficient pre-regulator for linear regulators
n On-card switching regulators
n Positive to negative converter (Buck-Boost)
1.23V to 37V (57V for HV version)
line and load conditions
HV version
4% max over
August 2004

Related parts for LM2576T-ADJ

LM2576T-ADJ Summary of contents

Page 1

... Typical Application (Fixed Output Voltage Versions) SIMPLE SWITCHER ® registered trademark of National Semiconductor Corporation. © 2004 National Semiconductor Corporation 3A Step-Down Voltage Regulator ® Features n 3.3V, 5V, 12V, 15V, and adjustable output versions n Adjustable version output voltage range, 1 ...

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... LM2576HVT-12 LM2576HVT-15 LM2576HVT-ADJ LM2576T-12 LM2576T-15 LM2576HVT-12 LM2576HVT-15 LM2576HVT-ADJ Flow LB03 Flow LB03 LM2576T-12 LM2576T-15 Flow LB03 Flow LB03 2 01147602 NS Package Package Type ADJ Number TS5B TO-263 LM2576S-ADJ TS5B Tape & Reel LM2576SX-ADJ T05A TO-220 LM2576T-ADJ T05D Flow LB03 LM2576T-ADJ Flow LB03 ...

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 LM2576 LM2576HV ON /OFF Pin Input Voltage Output Voltage to Ground (Steady State) Power Dissipation Storage Temperature Range Maximum Junction Temperature LM2576-3 ...

Page 4

LM2576-5.0, LM2576HV-5.0 Electrical Characteristics Specifications with standard type face are for T perature Range. Symbol Parameter SYSTEM PARAMETERS (Note 3) Test Circuit Figure 2 η Efficiency LM2576-12, LM2576HV-12 Electrical Characteristics Specifications with standard type face are for T Range. Symbol ...

Page 5

LM2576-ADJ, LM2576HV-ADJ Electrical Characteristics Specifications with standard type face are for T Range. Symbol Parameter SYSTEM PARAMETERS (Note 3) Test Circuit Figure 2 V Feedback Voltage OUT V Feedback Voltage OUT LM2576 V Feedback Voltage OUT LM2576HV η Efficiency All ...

Page 6

All Output Voltage Versions Electrical Characteristics Specifications with standard type face are for T Range. Unless otherwise specified 30V for the 15V version 500 mA. LOAD Symbol Parameter DEVICE PARAMETERS θ Thermal Resistance JA θ JA ...

Page 7

Typical Performance Characteristics Dropout Voltage Quiescent Current Oscillator Frequency (Circuit of Figure 2) (Continued) 01147629 01147631 01147633 7 Current Limit 01147630 Standby Quiescent Current 01147632 Switch Saturation Voltage 01147634 www.national.com ...

Page 8

Typical Performance Characteristics Efficiency Quiescent Current vs Duty Cycle Minimum Operating Voltage www.national.com (Circuit of Figure 2) (Continued) Minimum Operating Voltage 01147635 01147637 01147636 8 01147636 Feedback Voltage vs Duty Cycle 01147638 Quiescent Current vs Duty Cycle 01147637 ...

Page 9

Typical Performance Characteristics Feedback Voltage vs Duty Cycle Maximum Power Dissipation (TO-263) (See Note 10) Load Transient Response (Circuit of Figure 2) (Continued) 01147638 01147624 V = 15V OUT A: Output Pin Voltage, 50V/div B: Output Pin Current, 2A/div C: ...

Page 10

Test Circuit and Layout Guidelines As in any switching regulator, layout is very important. Rap- idly switching currents associated with wiring inductance generate voltage transients which can cause problems. For minimal inductance and ground loops, the length of the leads ...

Page 11

LM2576 Series Buck Regulator Design Procedure PROCEDURE (Fixed Output Voltage Versions) Given Regulated Output Voltage (3.3V, 5V, 12V, OUT or 15V) V (Max) = Maximum Input Voltage I IN Maximum Load Current 1. Inductor Selection (L1) A. Select ...

Page 12

LM2576 Series Buck Regulator Design Procedure (Continued) INDUCTOR VALUE SELECTION GUIDES (For Continuous Mode Operation) FIGURE 3. LM2576(HV)-3.3 FIGURE 4. LM2576(HV)-5.0 www.national.com FIGURE 5. LM2576(HV)-12 01147609 FIGURE 6. LM2576(HV)-15 01147610 12 01147611 01147612 ...

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LM2576 Series Buck Regulator Design Procedure PROCEDURE (Adjustable Output Voltage Versions) Given Regulated Output Voltage V OUT Maximum Input Voltage I (Max) = Maximum Load LOAD Current F = Switching Frequency (Fixed at 52 kHz) 1. Programming Output ...

Page 14

... Schottky diode, or any of the suggested fast-recovery diodes in Figure 8. 5. Input Capacitor (C capacitor located near the input and ground pins provides sufficient bypassing. switching regulators. Switchers Made Simple (Version 3.3) is available ers from a National Semiconductor sales office in your area. 14 (Continued) (Max Inductance LOAD ) OUT = 680 µ ...

Page 15

V R 20V 1N5820 MBR320P SR302 30V 1N5821 MBR330 31DQ03 SR303 40V 1N5822 MBR340 31DQ04 SR304 50V MBR350 31DQ05 SR305 60V MBR360 DQ06 SR306 Inductor Inductor Code Value L47 L68 L100 L150 L220 L330 L470 L680 H150 H220 H330 H470 ...

Page 16

Application Hints (Continued) 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 drops to zero for ...

Page 17

Application Hints (Continued) CATCH DIODE Buck regulators require a diode to provide a return path for the inductor current when the switch is off. This diode should be located close to the LM2576 using short leads and short printed circuit ...

Page 18

Additional Applications The switch currents in this buck-boost configuration are higher than in the standard buck-mode design, thus lowering the available output current. Also, the start-up input current of the buck-boost converter is higher than the standard buck-mode regulator, and ...

Page 19

Additional Applications Note: Complete circuit not shown (see Figure 10). FIGURE 13. Undervoltage Lockout for Buck-Boost Circuit DELAYED STARTUP The ON /OFF pin can be used to provide a delayed startup feature as shown in Figure 14. With an input ...

Page 20

... TO-220 (T) Top View 01147621 LM2576T-XX or LM2576HVT-XX NS Package Number T05A TO-263 (S) 5-Lead Surface-Mount Package Top View 01147625 LM2576S-XX or LM2576HVS-XX NS Package Number TS5B LM2576SX-XX or LM2576HVSX-XX Bent, Staggered Leads 5-Lead TO-220 (T) Top View 01147622 LM2576T-XX Flow LB03 or LM2576HVT-XX Flow LB03 NS Package Number T05D ) op ...

Page 21

... Physical Dimensions inches (millimeters) unless otherwise noted 5-Lead TO-220 (T) Order Number LM2576T-3.3, LM2576HVT-3.3, LM2576T-5.0, LM2576HVT-5.0, LM2576T-12, LM2576HVT-12, LM2576T-15, LM2576HVT-15, LM2576T-ADJ or LM2576HVT-ADJ NS Package Number T05A 21 www.national.com ...

Page 22

... Physical Dimensions Order Number LM2576T-3.3 Flow LB03, LM2576T-XX Flow LB03, LM2576HVT-3.3 Flow LB03, LM2576T-5.0 Flow LB03, LM2576HVT-5.0 Flow LB03, LM2576T-ADJ Flow LB03 or LM2576HVT-ADJ Flow LB03 www.national.com inches (millimeters) unless otherwise noted (Continued) Bent, Staggered 5-Lead TO-220 (T) LM2576T-12 Flow LB03, LM2576HVT-12 Flow LB03, ...

Page 23

Physical Dimensions inches (millimeters) unless otherwise noted (Continued) LM2576HVS-3.3, LM2576HVS-5.0, LM2576HVS-12, LM2576HVSX-3.3, LM2576HVSX-5.0, LM2576HVSX-12, 5-Lead TO-263 (S) Order Number LM2576S-3.3, LM2576S-5.0, LM2576S-12,LM2576S-15, LM2576S-ADJ, LM2576HVS-15, or LM2576HVS-ADJ NS Package Number TS5B 5-Lead TO-263 in Tape & Reel (SX) Order Number LM2576SX-3.3, ...

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... BANNED SUBSTANCE COMPLIANCE National Semiconductor certifies that the products and packing materials meet the provisions of the Customer Products Stewardship Specification (CSP-9-111C2) and the Banned Substances and Materials of Interest Specification (CSP-9-111S2) and contain no ‘‘Banned Substances’’ as defined in CSP-9-111S2. ...

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