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LM2596

SIMPLE SWITCHER

Power Converter 150 kHz

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

†

, and a fixed-frequency oscillator.

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

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 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.

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 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

typically 80 µA

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:

†

Patent Number 5,382,918.

Typical Application (Fixed Output Voltage

Versions)

01258301

SIMPLE SWITCHER

and

Switchers Made Simple

are registered trademarks of National Semiconductor Corporation.

May 2002

LM2596 SIMPLE SWITCHER Power Converter 150 kHz 3A Step-Down Voltage Regulator

Absolute Maximum Ratings (Note 1)

If Military/Aerospace specified devices are required,

please contact the National Semiconductor Sales Office/

Distributors for availability and specifications.

Maximum Supply Voltage 45V

ON /OFF Pin Input Voltage

−0.3 ≤ V ≤ +25V

Feedback Pin Voltage −0.3 ≤ V ≤+25V

Output Voltage to Ground

(Steady State) −1V

Power Dissipation Internally limited

Storage Temperature Range −65˚C to +150˚C

ESD Susceptibility

Human Body Model (Note 2) 2 kV

Lead Temperature

S Package

Vapor Phase (60 sec.) +215˚C

Infrared (10 sec.) +245˚C

T Package (Soldering, 10 sec.) +260˚C

Maximum Junction Temperature +150˚C

Operating Conditions

Temperature Range −40˚C ≤ T

≤ +125˚C

Supply Voltage 4.5V to 40V

LM2596-3.3

Electrical Characteristics

Specifications with standard type face are for T

= 25˚C, and those with boldface type apply over full Operating Tempera-

ture Range

Symbol Parameter Conditions

LM2596-3.3

Units

(Limits)

Typ

(Note 3)

Limit

(Note 4)

SYSTEM PARAMETERS (Note 5) Test Circuit

Figure 1

OUT

Output Voltage 4.75V ≤ V

≤ 40V, 0.2A ≤ I

LOAD

≤ 3A 3.3 V

3.168/3.135 V(min)

3.432/3.465 V(max)

η Efficiency V

= 12V, I

LOAD

=3A 73 %

LM2596-5.0

Electrical Characteristics

Specifications with standard type face are for T

= 25˚C, and those with boldface type apply over full Operating Tempera-

ture Range

Symbol Parameter Conditions

LM2596-5.0

Units

(Limits)

Typ

(Note 3)

Limit

(Note 4)

SYSTEM PARAMETERS (Note 5) Test Circuit

Figure 1

OUT

Output Voltage 7V ≤ V

≤ 40V, 0.2A ≤ I

LOAD

≤ 3A 5.0 V

4.800/4.750 V(min)

5.200/5.250 V(max)

η Efficiency V

= 12V, I

LOAD

=3A 80 %

LM2596-12

Electrical Characteristics

Specifications with standard type face are for T

= 25˚C, and those with boldface type apply over full Operating Tempera-

ture Range

Symbol Parameter Conditions

LM2596-12

Units

(Limits)

Typ

(Note 3)

Limit

(Note 4)

SYSTEM PARAMETERS (Note 5) Test Circuit

Figure 1

OUT

Output Voltage 15V ≤ V

≤ 40V, 0.2A ≤ I

LOAD

≤ 3A 12.0 V

11.52/11.40 V(min)

12.48/12.60 V(max)

η Efficiency V

= 25V, I

LOAD

=3A 90 %

LM2596

www.national.com3

All Output Voltage Versions

Electrical Characteristics

(Continued)

Specifications with standard type face are for T

= 25˚C, and those with boldface type apply over full Operating Tempera-

ture Range. Unless otherwise specified, V

= 12V for the 3.3V, 5V, and Adjustable version and V

= 24V for the 12V ver-

sion. I

LOAD

= 500 mA

Symbol Parameter Conditions

LM2596-XX

Units

(Limits)

Typ

(Note 3)

Limit

(Note 4)

ON /OFF Pin Input Current V

LOGIC

= 2.5V (Regulator OFF) 5 µA

15 µA(max)

LOGIC

= 0.5V (Regulator ON) 0.02 µA

5 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: The human body model is a 100 pF capacitor discharged through a 1.5k resistor into each pin.

Note 3: Typical numbers are at 25˚C and represent the most likely norm.

Note 4: 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. All limits are used to

calculate Average Outgoing Quality Level (AOQL).

Note 5: External components such as the catch diode, inductor, input and output capacitors, and voltage programming resistors can affect switching regulator

system performance. When the LM2596 is used as shown in the

Figure 1

test circuit, system performance will be as shown in system parameters section of Electrical

Characteristics.

Note 6: The switching frequency is reduced when the second stage current limit is activated.

Note 7: No diode, inductor or capacitor connected to output pin.

Note 8: Feedback pin removed from output and connected to 0V to force the output transistor switch ON.

Note 9: Feedback pin removed from output and connected to 12V for the 3.3V, 5V, and the ADJ. version, and 15V for the 12V version, to force the output transistor

switch OFF.

Note 10: V

= 40V.

Note 11: Junction to ambient thermal resistance (no external heat sink) for the TO-220 package mounted vertically, with the leads soldered to a printed circuit board

with (1 oz.) copper area of approximately 1 in